Slight engine temperature rise on inclines





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  1. #1
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    Default Slight engine temperature rise on inclines

    Solution:
    The original replacement radiator was insufficient for my bakkie model (it was presumably for a smaller petrol model). After replacing that with an OEM part, the issue resolved itself.
    Known good radiators for the KB5 (Go Big; 2007-2012 model):
    • Isuzu (OEM): 93613216
    • Behr: 4701252 (This is what Silverton Radiators supply)


    The radiator core needs to be at least 32mm wide. Anything less than that is probably for a smaller petrol engine.
    There is another OEM radiator that is significantly more expensive, but that appears to be an imported radiator that was replaced by the one mentioned above ~2010.

    Original post:
    Hi everyone, instead of hijacking yet another thread, I thought I'd start a new one for my current issue. I also apologise for the long post, but I would like to give as much information as possible in order to get an accurate as possible reason for the issue.

    I have an Isuzu KB300LX D-TEQ DC MT 4x4 (late 2012 model). Mid-November, during an outing at Atlantis dunes, I hit a dune a bit too hard, and managed to crack my radiator at the top (right by the mounting bracket). I kept an eye on the temperature
    and stopped and refilled with water each time the temp reached about halfway between 1/2 and 3/4 on the temp gauge. First chance I got, I made a quick repair with Pratley Putty before driving home without any overheating issues. That same week, I had the radiator and OEM sump guard plate replaced via my insurance.

    About a week after that, I noticed the temperature going just over the halfway mark while cresting an incline, and immediately dropping to normal again on the down hill side. Upon getting home, after an inspection, I noticed the following:
    • the overflow reservoir was empty, and the radiator was not filled to the top,
    • the small tap on the radiator draining pipe at the back of the engine bay on the passenger side was not fully closed, and some coolant seemed to have been leaking there.

    I filled the reservoir tank and radiator (about 300ml to go in the radiator) and closed the drainage tap. After driving again the next day, I double checked the coolant levels and noticed that whatever was in the overflow tank was still clear, instead of the expected red colour. I could also not smell nor taste any indication of coolant, even in the radiator itself, leading me to believe that the panel beaters did not add any coolant.

    I took the vehicle in to Goch & Cooper, and asked them to make sure all fittings were done correctly, add coolant, and "burp" the radiator (as I understand air in the system can cause the symptoms I experienced). We then drove from Cape Town to East London, towing a Venter trailer without any issues. The temperature stayed just below the halfway mark on the temperature gauge, as expected. On the way back though, on the longer uphills, I noticed the temperature climbing to about a third of the way between 1/2 and 3/4 on the temperature gauge, but it always dropped to just below 1/2 upon cresting the hill. The one major difference I can think of, is that on the outbound trip, the average ambient temperature was around 25'C, whereas on the way back it was just over 30'C.

    I once again checked all fluid levels and all seemed fine. I'm not losing coolant. The next few days was cool once again, and I didn't experience any temperature rise for a few days.
    On a Saturday drive though, completely unloaded, on a fairly long incline the engine temperature rose just over the halfway mark again. This time however:
    • with ambient temperature at 26'C,
    • speed was about 60km/h (so not putting the engine under excessive stress), and
    • wind was from behind (possibly assisting the engine, but at the same time reducing airflow from the front).


    After this I went to Silverton Radiators in Parow, as they seem to be the go-to guys for this kind of issue on this forum. I forgot the name of the older gentleman I spoke with there, unfortunately.
    The initial reaction was that I might have damaged the head gasket due to the initial rise in temperature, but the bakkie does not exhibit any of the symptoms for this. They also "tested" the viscous clutch (albeit in a way that their own website claims is inconclusive) and declared this to be fine. The guy also said that it should be OK to expect the engine temperature to rise when under load on inclines (though this doesn't seem right to me, as this never happened before). So I left it at that.

    Yesterday, we went out for lunch and on the way back, the engine temperature rose again, though only to right on the halfway mark. This time however, it's a longish (but not that long), yet relatively easy incline on the way home, that I have NEVER had issues with. The only thing that was different, is that the ambient temperature was once again over 30'C.

    So my question is, what could it be? So far I have the following possibilities:
    • damaged head gasket - I have none of the symptoms; I'm not losing coolant or oil, my oil isn't milky, I don't have discoloured smoke coming from the exhaust (I haven't done a test for exhaust gasses in the coolant yet),
    • faulty thermostat - as far as I understand the symptoms is different from what I see; the engine reaches operating temperature in the same time as it always has, and usually the engine temperature stays constant, just not on uphills,
    • faulty water pump - same argument as for thermostat
    • insufficient/incorrect coolant - possible, though unlikely
    • air in the cooling system - I haven't redone any "burping" of the radiator so might be this,
    • failing viscous clutch - Silverton Radiators seemed to think the fan clutch is fine, though from what I understand from the workshop manual I found on the internet, at operating temperature, after switching the engine off, the fan should take considerable effort to turn, while in my case it seems to turn just as easily as when the engine is cool.


    Once again, sorry for the long post, but I'm planning 2 trips up to Gauteng and beyond in the next three months, and at this stage I'm not convinced my cooling system can survive the trip through the Karoo. Any input is appreciated.
    Last edited by Pienats; 2019/03/26 at 10:10 AM. Reason: Added solution to original issue
    2012 Isuzu KB300LX D-TEQ D/C 4x4 MT
    Modifications:
    • Unichip
    • DIY Overhead Console

    2015 Infanta 4x4 Offroad trailer (Bessie die Boskampwa)

  2. #2
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    Default Re: Slight engine temperature rise on inclines

    Quote Originally Posted by Pienats View Post
    Hi everyone, instead of hijacking yet another thread, I thought I'd start a new one for my current issue. I also apologise for the long post, but I would like to give as much information as possible in order to get an accurate as possible reason for the issue.

    I have an Isuzu KB300LX DC MT 4x4 (late 2012 model). Mid-November, during an outing at Atlantis dunes, I hit a dune a bit too hard, and managed to crack my radiator at the top (right by the mounting bracket). I kept an eye on the temperature
    and stopped and refilled with water each time the temp reached about halfway between 1/2 and 3/4 on the temp gauge. First chance I got, I made a quick repair with Pratley Putty before driving home without any overheating issues. That same week, I had the radiator and OEM sump guard plate replaced via my insurance.

    About a week after that, I noticed the temperature going just over the halfway mark while cresting an incline, and immediately dropping to normal again on the down hill side. Upon getting home, after an inspection, I noticed the following:
    • the overflow reservoir was empty, and the radiator was not filled to the top,
    • the small tap on the radiator draining pipe at the back of the engine bay on the passenger side was not fully closed, and some coolant seemed to have been leaking there.

    I filled the reservoir tank and radiator (about 300ml to go in the radiator) and closed the drainage tap. After driving again the next day, I double checked the coolant levels and noticed that whatever was in the overflow tank was still clear, instead of the expected red colour. I could also not smell nor taste any indication of coolant, even in the radiator itself, leading me to believe that the panel beaters did not add any coolant.

    I took the vehicle in to Goch & Cooper, and asked them to make sure all fittings were done correctly, add coolant, and "burp" the radiator (as I understand air in the system can cause the symptoms I experienced). We then drove from Cape Town to East London, towing a Venter trailer without any issues. The temperature stayed just below the halfway mark on the temperature gauge, as expected. On the way back though, on the longer uphills, I noticed the temperature climbing to about a third of the way between 1/2 and 3/4 on the temperature gauge, but it always dropped to just below 1/2 upon cresting the hill. The one major difference I can think of, is that on the outbound trip, the average ambient temperature was around 25'C, whereas on the way back it was just over 30'C.

    I once again checked all fluid levels and all seemed fine. I'm not losing coolant. The next few days was cool once again, and I didn't experience any temperature rise for a few days.
    On a Saturday drive though, completely unloaded, on a fairly long incline the engine temperature rose just over the halfway mark again. This time however:
    • with ambient temperature at 26'C,
    • speed was about 60km/h (so not putting the engine under excessive stress), and
    • wind was from behind (possibly assisting the engine, but at the same time reducing airflow from the front).


    After this I went to Silverton Radiators in Parow, as they seem to be the go-to guys for this kind of issue on this forum. I forgot the name of the older gentleman I spoke with there, unfortunately.
    The initial reaction was that I might have damaged the head gasket due to the initial rise in temperature, but the bakkie does not exhibit any of the symptoms for this. They also "tested" the viscous clutch (albeit in a way that their own website claims is inconclusive) and declared this to be fine. The guy also said that it should be OK to expect the engine temperature to rise when under load on inclines (though this doesn't seem right to me, as this never happened before). So I left it at that.

    Yesterday, we went out for lunch and on the way back, the engine temperature rose again, though only to right on the halfway mark. This time however, it's a longish (but not that long), yet relatively easy incline on the way home, that I have NEVER had issues with. The only thing that was different, is that the ambient temperature was once again over 30'C.

    So my question is, what could it be? So far I have the following possibilities:
    • damaged head gasket - I have none of the symptoms; I'm not losing coolant or oil, my oil isn't milky, I don't have discoloured smoke coming from the exhaust (I haven't done a test for exhaust gasses in the coolant yet),
    • faulty thermostat - as far as I understand the symptoms is different from what I see; the engine reaches operating temperature in the same time as it always has, and usually the engine temperature stays constant, just not on uphills,
    • faulty water pump - same argument as for thermostat
    • insufficient/incorrect coolant - possible, though unlikely
    • air in the cooling system - I haven't redone any "burping" of the radiator so might be this,
    • failing viscous clutch - Silverton Radiators seemed to think the fan clutch is fine, though from what I understand from the workshop manual I found on the internet, at operating temperature, after switching the engine off, the fan should take considerable effort to turn, while in my case it seems to turn just as easily as when the engine is cool.


    Once again, sorry for the long post, but I'm planning 2 trips up to Gauteng and beyond in the next three months, and at this stage I'm not convinced my cooling system can survive the trip through the Karoo. Any input is appreciated.
    Just a quick one... My fathers 300tdi with unichip used to do this under load, always on the long constant climbs. Consider removing the chip with the bridging plug to do a test?
    My 300Dteq did this when loaded - no chip.
    My 360 V6 also did this when worked hard, but quickly came down again.

    I just think that the cooling systems are inadequate for harder applications. Mine never overheated, but did as you explained... Went up just about half and sometimes a bit higher, but tap off and it nearly instantly comes down.
    Current: Toyota FJ Sport Cruiser

    Previous: VW Amarok ULTIMATE 4motion (auto)
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  3. #3
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    Default Re: Slight engine temperature rise on inclines

    Quote Originally Posted by jonoB View Post
    Just a quick one... My fathers 300tdi with unichip used to do this under load, always on the long constant climbs. Consider removing the chip with the bridging plug to do a test?
    My 300Dteq did this when loaded - no chip.
    My 360 V6 also did this when worked hard, but quickly came down again.

    I just think that the cooling systems are inadequate for harder applications. Mine never overheated, but did as you explained... Went up just about half and sometimes a bit higher, but tap off and it nearly instantly comes down.
    I do actually want to try with the chip bypassed, but we're having a relatively cool summer in Cape Town this year, and so far the easiest way to replicate is if the ambient temperature is over 30'C. If I have time on a hot day, I'll definitely do the bypass and see what it does. However, shortly after I had the chip installed we did a trip to Tankwa while towing the offroad trailer (much higher load) and also to Simonskloof in the Montague area, with no engine temperature rise at all. This issue only started after I had the radiator replaced.

    I'm starting to wonder if the know that bent the protective plate and pushed the radiator up didn't somehow damage the fan clutch in a way that's difficult to notice.
    Last edited by Pienats; 2019/01/21 at 12:06 PM.
    2012 Isuzu KB300LX D-TEQ D/C 4x4 MT
    Modifications:
    • Unichip
    • DIY Overhead Console

    2015 Infanta 4x4 Offroad trailer (Bessie die Boskampwa)

  4. #4
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    Default Re: Slight engine temperature rise on inclines

    Remove the chip and replace the radiator cap.

    Replace the viscous coupling.

    IF it still overheats, it might be headgasket.

    Have you checked the waterflow in the radiator? Waterpump working correctly?

    Thermostat blocked will have you overheat quickly.
    Always think: Could this be sarcasm?

  5. #5
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    Default Re: Slight engine temperature rise on inclines

    Was the correct radiator fitted? I had a 2.8 ages ago that had to get some work done - later figured out that a smaller radiator (think it was from the old 2.5) was fitted.

    Have you seen the fan come on after the vehicle was fixed?

  6. #6
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    Default Re: Slight engine temperature rise on inclines

    Quote Originally Posted by Pienats View Post
    That same week, I had the radiator and OEM sump guard plate replaced via my insurance.

    About a week after that, I noticed the temperature going just over the halfway mark while cresting an incline, and immediately dropping to normal again on the down hill side. Upon getting home, after an inspection, I noticed the following:
    • the overflow reservoir was empty, and the radiator was not filled to the top,
    • the small tap on the radiator draining pipe at the back of the engine bay on the passenger side was not fully closed, and some coolant seemed to have been leaking there.

    I filled the reservoir tank and radiator (about 300ml to go in the radiator) and closed the drainage tap. After driving again the next day, I double checked the coolant levels and noticed that whatever was in the overflow tank was still clear, instead of the expected red colour. I could also not smell nor taste any indication of coolant, even in the radiator itself, leading me to believe that the panel beaters did not add any coolant.

    .
    With this sort of work they probably just added water to the system or the incorrect type and ratio of coolant.

    I would drain the radiator system and add the correct type and mix of coolant.

    Make sure there is no airlock.

    Test again.

    The coolant and mix ratio is very important.
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    Default Re: Slight engine temperature rise on inclines

    Is the coolant of the right mix with anti freeze? Should be a 50/50 mix ratio and if not sorrect can also affect cooling efficiency.

  8. #8
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    Default Re: Slight engine temperature rise on inclines

    Quote Originally Posted by Oppies3800 View Post
    Remove the chip and replace the radiator cap.

    Replace the viscous coupling.

    IF it still overheats, it might be headgasket.

    Have you checked the waterflow in the radiator? Waterpump working correctly?

    Thermostat blocked will have you overheat quickly.
    Radiator cap is brand new and seems to have the correct pressure rating.
    Radiator itself is brand new, so I would expect that it's not blocked (though anything is possible).

    As to the waterpump and thermostat, as far as I can tell without actually trying to test anything, all should be fine as under "normal" conditions everything seems fine: correct temperature reached within the usual time and maintained there. The exception seems to be uphills on hotter days.

    On the next hot day we have, I'll bypass the unichip and try again.
    2012 Isuzu KB300LX D-TEQ D/C 4x4 MT
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    Default Re: Slight engine temperature rise on inclines

    Quote Originally Posted by SAND View Post
    Was the correct radiator fitted? I had a 2.8 ages ago that had to get some work done - later figured out that a smaller radiator (think it was from the old 2.5) was fitted.

    Have you seen the fan come on after the vehicle was fixed?
    I have considered that the incorrect radiator might have been fitted, but finding it difficult to figure out if that's the case. I'm planning to take the bakkie in again to try and have this sorted (this post is mostly to try and get ideas as to what needs to be looked at), and this is one of the things I'm planning on having checked out. The only number I've been able to find on the radiator turned out to be the code for the plastic it was made out of and not the radiator model number...

    When the bakkie is started the fan turns fine and seems to move the air quite easily. Assuming it is the viscous clutch, it won't be able to move enough air at the top end of it's requirements, hence the engine temp rise.
    2012 Isuzu KB300LX D-TEQ D/C 4x4 MT
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    2015 Infanta 4x4 Offroad trailer (Bessie die Boskampwa)

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    Default Re: Slight engine temperature rise on inclines

    Quote Originally Posted by DC Polokwane View Post
    With this sort of work they probably just added water to the system or the incorrect type and ratio of coolant.

    I would drain the radiator system and add the correct type and mix of coolant.

    Make sure there is no airlock.

    Test again.

    The coolant and mix ratio is very important.
    Quote Originally Posted by Mariuslg View Post
    Is the coolant of the right mix with anti freeze? Should be a 50/50 mix ratio and if not sorrect can also affect cooling efficiency.
    I had Goch and Cooper top up the coolant, but without a radiator flush and starting from scratch it's likely that the ratio is not correct. Unless someone can with a high likelihood suggest another cause, my current plan is to have the viscous fan replaced and the radiator flushed and drained and topped up again.
    Silverton Radiators indicated they typically only put 3l of coolant into the system, which is a ~9l system in my case. I'm also not sure if it's the same quality as what Isuzu would put in, but I've lost faith in the local Isuzu garage, so unlikely to take it back there.
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    Default Re: Slight engine temperature rise on inclines

    I have some general comments as I have not specific knowledge of the Isuzu under discussion.

    In general engine temp indicators are close to useless and by the time there is any deviation from normal, the motor is often cooked. Turbo Diesels seem to be very sensitive to this, more-so than petrol vehicles. It only takes seconds to destroy a diesel through overtemp. A lot of vehicles have the temp sensor pretty high on the engine, so you can easily be loosing fluid, and nothing is making contact the the temp sender, and then the engine just stops.

    I had something very similar to what you describe on my old Disco Tdi. It was basically down to very small cracks in the cylinder head, which were welded following an earlier issue. it would pass a pressure test, but only under load etc it would end up going overtemp and then cool down quickly as soon as you went downhill. (Exhaust gases getting into the cooling system and raising the temp.)

    The fact that you are loosing water indicates to me that you have a knackered head/head gasket or similar. It is unlikely that anything else would cause the symptoms you describe. The next thing you will probably be in for is a dash removal to replace the heater matrix. Happened to me in the D1 since the exhaust gas overpressure the cooling system and the heater matrix was the weak point in the system.

    I would investigate sooner rather than later and assume you are in for a head off job. perhaps you will be lucky and just need a new head gasket? I hope you are.

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    Default Re: Slight engine temperature rise on inclines

    Quote Originally Posted by stephenplumb View Post
    I have some general comments as I have not specific knowledge of the Isuzu under discussion.

    In general engine temp indicators are close to useless and by the time there is any deviation from normal, the motor is often cooked. Turbo Diesels seem to be very sensitive to this, more-so than petrol vehicles. It only takes seconds to destroy a diesel through overtemp. A lot of vehicles have the temp sensor pretty high on the engine, so you can easily be loosing fluid, and nothing is making contact the the temp sender, and then the engine just stops.

    I had something very similar to what you describe on my old Disco Tdi. It was basically down to very small cracks in the cylinder head, which were welded following an earlier issue. it would pass a pressure test, but only under load etc it would end up going overtemp and then cool down quickly as soon as you went downhill. (Exhaust gases getting into the cooling system and raising the temp.)

    The fact that you are loosing water indicates to me that you have a knackered head/head gasket or similar. It is unlikely that anything else would cause the symptoms you describe. The next thing you will probably be in for is a dash removal to replace the heater matrix. Happened to me in the D1 since the exhaust gas overpressure the cooling system and the heater matrix was the weak point in the system.

    I would investigate sooner rather than later and assume you are in for a head off job. perhaps you will be lucky and just need a new head gasket? I hope you are.
    Hi Stephen, I am NOT loosing any water. I don't have any of the obvious symptoms of a cracked head or gasket.
    2012 Isuzu KB300LX D-TEQ D/C 4x4 MT
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    Default Re: Slight engine temperature rise on inclines

    Quote Originally Posted by Pienats View Post
    Hi Stephen, I am NOT loosing any water. I don't have any of the obvious symptoms of a cracked head or gasket.
    I hope you are right. I had similar with my amarock when very nearly new. Heating on inclines. They diagnosed it as a faulty thermostat and since then the temp never moves over normal, no matter what the outside temp and how hard I am pulling.

    I still think some damage was done to the engine when it overheated the first time. As mentioned, I don't know the Isuzu, but most temp senders stick around "normal" until the engine is very hot, and then by the time they start indicating something, the engine has already run away and boiled.

    I hope you are lucky, but it sounds to me like combustion gases getting into the water jacket and delivering all the signs you are seeing, then as soon as the engine is not working too hard, then it all calms down again. I did the exhaust gas tests with my Disco and they came back clean, but then on hot days, i noticed small bubbles in the water and the pipes getting hard. With the head off it became apparent, why.

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    Default Re: Slight engine temperature rise on inclines

    Fill the viscous fan coupling with more oil and test run , won't cost you a arm and a leg .
    Had the same problem , ok it was on a Cruiser but the basic's is the same .
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    Default Re: Slight engine temperature rise on inclines

    Thanks guys, think for now I'll have the viscous replaced and the cooling system completely drained and started from scratch.
    As most of the components will be off already, I'll ask them to check the thermostat and water pump as well.
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    Default Re: Slight engine temperature rise on inclines

    Sorry, slightly off subject...why do some vehicles heat up in traffic (slightly hotter but not overheating) and others don't?

    I know the science behind air going through the radiator. But my Corsa and Mercedes, increase heat slightly, while the Sedona indicates operating temp, the whole time in standstill traffic...
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    Default Re: Slight engine temperature rise on inclines

    If you had a blown head gasket you would have known it. You would be losing coolant.

    Over time the components on the cooling system deteriorate ever so slightly. The thermostat does not open completely, the radiator has collects debris slightly reducing airflow through it, the viscous fan slightly loses friction, the water pump impellers can corrode (but only if it was driven for an extended period without anti-freeze), etc.

    I like to replace a car's thermostat once it is 5 years old although I have seen much older cars with good thermostats.

    On my Hilux I was surprised to see how much insect remains and other particles were stuck in the radiator, particularly directly behind the radiator after about 10 years driving 90%+ tarred roads.

    If I were you I would replace the thermostat (they are cheap enough) and would remove the radiator and make sure that it is clean. Be very careful if you are going to clean it yourself, especially with a pressure washer as you can bugger up those thin fins very quickly if the pressure is too high.

    I would also make sure that it has the right amount of a good quality anti-freeze/coolant in.

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    Default Re: Slight engine temperature rise on inclines

    Best anti-freeze is the Toyota pink ones.

    Cheap enough and they are already diluted.

    Can get them in 1lt or 5lt containers.

    I take it as you are in Northern Suburbs?
    Always think: Could this be sarcasm?

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    Default Re: Slight engine temperature rise on inclines

    Quote Originally Posted by Mars67 View Post
    If you had a blown head gasket you would have known it. You would be losing coolant.

    Over time the components on the cooling system deteriorate ever so slightly. The thermostat does not open completely, the radiator has collects debris slightly reducing airflow through it, the viscous fan slightly loses friction, the water pump impellers can corrode (but only if it was driven for an extended period without anti-freeze), etc.

    I like to replace a car's thermostat once it is 5 years old although I have seen much older cars with good thermostats.

    On my Hilux I was surprised to see how much insect remains and other particles were stuck in the radiator, particularly directly behind the radiator after about 10 years driving 90%+ tarred roads.

    If I were you I would replace the thermostat (they are cheap enough) and would remove the radiator and make sure that it is clean. Be very careful if you are going to clean it yourself, especially with a pressure washer as you can bugger up those thin fins very quickly if the pressure is too high.

    I would also make sure that it has the right amount of a good quality anti-freeze/coolant in.
    Yes, I'm optimistic at this stage that my head gasket is OK. As I said I've not observed any of the obvious symptoms of a blown gasket.
    Most likely causes as far as I can tell at this stage, are:
    1. Incorrect coolant type or ratio
    2. Viscous fan failing
    3. Thermostat failing
    4. Water pump failing
    5. Too small radiator


    This all started with a radiator replacement, it's quite within the realm of possibility that the panel beaters sourced an inadequate size.
    2012 Isuzu KB300LX D-TEQ D/C 4x4 MT
    Modifications:
    • Unichip
    • DIY Overhead Console

    2015 Infanta 4x4 Offroad trailer (Bessie die Boskampwa)

  20. #20
    Join Date
    Sep 2018
    Location
    Cape Town
    Age
    39
    Posts
    90

    Default Re: Slight engine temperature rise on inclines

    Quote Originally Posted by Oppies3800 View Post
    Best anti-freeze is the Toyota pink ones.

    Cheap enough and they are already diluted.

    Can get them in 1lt or 5lt containers.

    I take it as you are in Northern Suburbs?
    I am indeed in the Northern Suburbs.
    I am toying with the idea of buying the coolant straight from Isuzu. In the 6 years I've had the bakkie, I have had no issue with the standard coolant. This all only started after I had to have the radiator replaced.
    2012 Isuzu KB300LX D-TEQ D/C 4x4 MT
    Modifications:
    • Unichip
    • DIY Overhead Console

    2015 Infanta 4x4 Offroad trailer (Bessie die Boskampwa)

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