Discovery 1 300 Tdi coolant temp sensor relocation





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  1. #1
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    Default 300 Tdi coolant temp sensor relocation

    One of the benefits of stripping a Tdi is that you get much more acquainted with the layout of the whole thing. Even if you've done lots of work on it already, there's nothing like taking it apart piece by piece to get an idea of exactly what sits where (and sometimes wonder what on earth LR was thinking!).

    I've been thinking about this for a while now. Spurred into action by experiencing my first ever water loss situation with my Tdi. The small bleed hose on top of the thermostat housing ruptured. I stopped before the Madman beeped (low coolant level detector) because I smelt coolant and the water temp on the Madman went down. When I topped up after the repair, I'd already lost 5 litres!

    With that hose right at the top going, things could have been a lot worse on the highway at speed, or climbing Magoebaskloof pass. You don't lose enough coolant to trigger the level, yet it's not being pumped any more due to the location of the water pump.

    On my old Tdi, I monitored coolant temp (Madman, at the top of the thermostat housing). This is standard location for Madman monitoring on all Tdi's I've seen. I also monitored cylinder head temp on the side of the head, with a separate gauge (the previous owner convinced me about how important this is!).

    When my dad drove my old Tdi(with me in the passenger seat almost passed out from a stomach bug due to some infected water!) he STILL managed to overheat it with all those gauges! (I woke up when the Madman went off for EGT and water temp simultaneously!) - up a mountain pass in Lesotho. He was very surprised that I was so worried - after all the stock temperature gauge had not moved! No matter how much you try to "educate" normal, non-Landy owners, they still rely on the gauges in the instrument panel and don't know how to analyse the Madman figures properly.

    This blurb turned out longer than I thought. Will continue later, sorry for the verbosity, just putting the problem properly in context. My solution? Watch this space a bit later...

  2. #2
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    Default Re: 300 Tdi coolant temp sensor relocation

    Antz

    On my recent trip to Nam the following happend which I think is one reason to keep the madman temp sensor where it is

    In the mornings the thermostat wouldn't open - happened about 3 times over a 3 week period before I replaced it on the side of the road near Kunene lodge

    So my madman went off as temp got above 94 - would dought its authenticity - so felt top radiator hose and it was cold and not full of water

    Luckily was always in the bush so 20 kph stuff and it was a LR part that was less than 2 years old so put my old britpart one back and all still OK

  3. #3
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    Default Re: 300 Tdi coolant temp sensor relocation

    Quote Originally Posted by RossJ View Post
    Antz

    On my recent trip to Nam the following happend which I think is one reason to keep the madman temp sensor where it is

    In the mornings the thermostat wouldn't open - happened about 3 times over a 3 week period before I replaced it on the side of the road near Kunene lodge

    So my madman went off as temp got above 94 - would dought its authenticity - so felt top radiator hose and it was cold and not full of water

    Luckily was always in the bush so 20 kph stuff and it was a LR part that was less than 2 years old so put my old britpart one back and all still OK
    ok i concur fit the temp gauge on top. i normally drill and tap the brass plug and then screw the sensor in there. be careful on the Disco 1 that the bonnet does not short out on top of the sensor. could not figure why the temp gauge was waving erratically till i figured it is shorting to earth against the bonnet. as far as the coolant level is concerned i always mount it in the expansion tank as that spot is the most reliable. the thermo housing and the radiator return dump excess air in there so you will typically get a reliable level indication. as far as the thermostat is concerned, always drill a 2.5 or 3mm hole in the rim of the thermostat and locate the hole at the 12 o clock position. this will ensure that no airlock can form behind the thermostat but also so small that it cannot have any effect on cooling.

    Land Rovers never die, they simply become organ donors!

  4. #4
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    Default Re: 300 Tdi coolant temp sensor relocation

    Quote Originally Posted by antvz View Post
    One of the benefits of stripping a Tdi is that you get much more acquainted with the layout of the whole thing. Even if you've done lots of work on it already, there's nothing like taking it apart piece by piece to get an idea of exactly what sits where (and sometimes wonder what on earth LR was thinking!).

    I've been thinking about this for a while now. Spurred into action by experiencing my first ever water loss situation with my Tdi. The small bleed hose on top of the thermostat housing ruptured. I stopped before the Madman beeped (low coolant level detector) because I smelt coolant and the water temp on the Madman went down. When I topped up after the repair, I'd already lost 5 litres!

    With that hose right at the top going, things could have been a lot worse on the highway at speed, or climbing Magoebaskloof pass. You don't lose enough coolant to trigger the level, yet it's not being pumped any more due to the location of the water pump.

    On my old Tdi, I monitored coolant temp (Madman, at the top of the thermostat housing). This is standard location for Madman monitoring on all Tdi's I've seen. I also monitored cylinder head temp on the side of the head, with a separate gauge (the previous owner convinced me about how important this is!).

    When my dad drove my old Tdi(with me in the passenger seat almost passed out from a stomach bug due to some infected water!) he STILL managed to overheat it with all those gauges! (I woke up when the Madman went off for EGT and water temp simultaneously!) - up a mountain pass in Lesotho. He was very surprised that I was so worried - after all the stock temperature gauge had not moved! No matter how much you try to "educate" normal, non-Landy owners, they still rely on the gauges in the instrument panel and don't know how to analyse the Madman figures properly.

    This blurb turned out longer than I thought. Will continue later, sorry for the verbosity, just putting the problem properly in context. My solution? Watch this space a bit later...
    That is why I removed the original temp gauge and installed the Madman in it's place.
    '07 Land Rover Defender 110 TDI 300 Kalahari (Meisiekind˛)

    84' Land Rover Defender 110 V8 4-speed Hardtop (Meisiekind) Sold after 12 years of fun and hard work




    The only thing needed for evil to triumph is for a good man to do nothing.

  5. #5
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    Default Re: 300 Tdi coolant temp sensor relocation

    This is the typical setup in a 300 Tdi. It's what I had on my old Tdi and also have on the new one. The first pic is the location of the Madman temp sensor. The second is the location of the temp sensor that goes to the gauge in the instrument panel.

  6. #6
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    Default Re: 300 Tdi coolant temp sensor relocation

    I had a sensor on the side of the head, installed with some heat sink paste, to measure the actual head temperature. This was typically around 90 deg C, going up to 100-110 deg C on a hot day with aircon on.

  7. #7
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    Default Re: 300 Tdi coolant temp sensor relocation

    I am going to move the Madman sensor to the location of the sensor for the original temperature gauge in the instrument panel. At this level, it will be properly immersed in water, unlike in the original position where there can sometimes be air bubbles since it's the highest point.

    The sensor for the original gauge in the instrument panel will be moved to the position on the side of the head where the old cylinder head temp sensor was located. Therefore, the needle on the dash will now measure "head temperature" and not "water temperature". I've been told by most people that their gauge starts moving upwards from the middle, after the temperature exceeds about 105 deg C. Anyone driving the car will see it begin to overheat, irrespective of whether there's water in or not (or what the water temp is). By 110 deg C, which is my danger zone for the cylinder head, the gauge will be in the red. (I'll take some experimental readings to verify these figures).

    For now, the plug on top of the thermostat housing will be blanked off. Later, I might play around with fitting a second water level sensor in here, or even a pressure sensor!

    That's the plan. Will report back on how this goes.

  8. #8
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    Default Re: 300 Tdi coolant temp sensor relocation

    Incidentally, the pipe bursting incident made me realise again how important it is to renew these things regularly. The enemy is the extreme heat under that bonnet. I will be installing a complete set of new hoses (the whole lot, not one single one left unchanged). When doing this, remember about the two heater hoses, and beware - they like to chafe against the back of the rocker cover. I always install a section of bigger pipe (slit lengthwise down the middle) whenever two pipes touch or when a pipe touches something else. This is especially important with the vibrations of the Tdi motor, and more so if you drive gravel regularly.

  9. #9
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    Default Re: 300 Tdi coolant temp sensor relocation

    Would a VDO water temp gauge (with VDO sender) in standard location not work better than the standard gauge? In other words, would the VDO accurately display water temps as they fluctuate?

  10. #10
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    Default Re: 300 Tdi coolant temp sensor relocation

    It is a VDO guage.

    I think.
    '07 Land Rover Defender 110 TDI 300 Kalahari (Meisiekind˛)

    84' Land Rover Defender 110 V8 4-speed Hardtop (Meisiekind) Sold after 12 years of fun and hard work




    The only thing needed for evil to triumph is for a good man to do nothing.

  11. #11
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    Default Re: 300 Tdi coolant temp sensor relocation

    Quote Originally Posted by thujack View Post
    Would a VDO water temp gauge (with VDO sender) in standard location not work better than the standard gauge? In other words, would the VDO accurately display water temps as they fluctuate?
    This would be absolute tops, IMO. It's just that mine is a Discovery, not a Defender, so I can't chop and change inside the instrument panel. I have to put up a gauge next to the panel, which I know to look at, but others don't always. That's why I'm going to exploit the features of the existing gauge in a better way rather than rendering it useless.

  12. #12
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    Default Re: 300 Tdi coolant temp sensor relocation

    Quote Originally Posted by thujack View Post
    Would a VDO water temp gauge (with VDO sender) in standard location not work better than the standard gauge? In other words, would the VDO accurately display water temps as they fluctuate?
    Yes, that's what I did. The standard gauge only starts moving from the normal position at 98 deg C.


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