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  1. #1
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    Default Trailblazer cooling

    Having a digital readout available for engine coolant temperature as well as transmission oil temperature is very informative and I'm happy to have it at my disposal. But, it comes at a strange price. Now I know that pulling my Echo Chobe up a long incline in summer heat will result in the coolant temperature rising to 100C from the normal 79-80C. There is clearly a heat exchange happening between the coolant and the tranny oil, because the tranny temperature follows suit. The car didn't complain and has never required a drop of coolant. I also checked the coolant level on the expansion tank, when the engine was hot, and the level didn't even rise by 1mm.
    I'm thus not creating this post in panic, but out of curiosity. The attached pic shows the grill layout and important to take note that only the top half of the grill is open. That broad "grill" running between the fog lights is just a decoration. On closer inspection it becomes clear that only the top half of the radiator is exposed to direct airflow from grill openings.
    Now for my questions:
    Has anybody bothered to open that dummy grill?
    What could be the negative impact of creating slots in that dummy grill?
    Last edited by RoelfleRoux; 2020/01/12 at 06:26 AM.

  2. #2
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    Default Re: Trailblazer cooling

    Roelf, very valid observation. I am of the school of thought that believe you can never have enough potential cooling capacity. Rather that and let the thermostat do its job. Nothing spoils my day like a temp gauge that starts creeping upwards.

    I recall many, many years ago Mercedes Benz (going on raw memory here) were running 2.3 16 e (or was 2.5's) Mercs at the Nardo facilty - continous flat out running in a 24 / 48 hour attempt at absolute distance covered. During night they had to shutter part of the grilles on these cars as they were getting too much cooling. Winter in Italy. So I suppose too much cooling is possible.

    I am also always amazed when watching programmes like, especially Diesel Brothers, where they swop out radiators on their builds according to requirements. How do they calc this requirement? And it always works - on tv at least.

    Back to your question. Why not try and find a piece from a scrapped TB, and do your experiment on this. Leave yours pristine and able to refit?

    The radiator in the TB certainly drops low enough in the engine bay to get potential airflow from this area being opened. Only downside I can imagine is picking up debris from traffic in front of you that could damage the radiator. Easily prevented with a bit of mesh over the opened areas.

  3. #3
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    Default Re: Trailblazer cooling

    Yip, my thoughts also lean towards mesh. If I pull the trigger I'll get it done by a pro to make sure it is a neat job. The number plate actually takes up quite a bit of real estate in the centre of that dummy gril. Not too worried about reselling the old Chev, we are both in this relationship 'till death do us part.

  4. #4
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    Default Re: Trailblazer cooling

    I'm basically considering a smallish slot each side of the number plate.

  5. #5
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    Default Re: Trailblazer cooling

    Its an interesting subject with some counter-intuitive dynamics at play such as increasing air volume could have the opposite effect.

    As an example, the old air cooled Beetle would be prone to over heating if the plates sealing the engine bay from the cylinders were removed. However, if a Baja Bug (remember them) chop was done exposing the whole engine, it was fine.

    Those of you familiar with the old Deutz 3 cylinder air-cooled engines will know that removing the plates encasing the engine, to expose the cylinders in the engine bay to get ''more'' air, would result in an increase in engine temp, not a decrease.

    In both of these examples, air flow and rate of flow between the plates and cylinder head was the critical aspect, not the volume of air available.

    In this instance, upgrading the fan diameter and or speed might have the desired effect as opposed to opening more slots in the grill.

    I an not a Thermodynamacist, the above is based on my own experience and interactions with Engineers so take it at face value
    Estee = S T = Sean Towlson

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  6. #6
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    Default Re: Trailblazer cooling

    Estee,
    I was hoping some of the tech fundies on the forum would find this thread. I'll respond later when I have some time available.
    Last edited by RoelfleRoux; 2019/08/25 at 06:07 AM.

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  8. #7
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    Default Re: Trailblazer cooling

    Some interesting forum chat in this link. Seems I was correct in assuming that there is a heat exchange between the coolant and the transmission oil. https://www.coloradodiesel.org/threa...s-cooler.3425/
    I can also confirm that the fan cowling covers the complete radiator area (which a pic in the attached link confirms).
    Estee, your point about getting more suck for your buck from the fan seems very valid, considering the effort Chev went to with the cowling design. I do however still believe that allowing more air into the front of the radiator, will allow the fan to get more air through the system. Also keep in mind that 3 "radiators" are stacked one in front of the other - coolant, air con and intercooler.
    I include 2 pics I took yesterday which gives a view of the cowling setup and the coolant level after 60k km (the car was parked nose down, hense the "scew" level).
    Last edited by RoelfleRoux; 2019/08/25 at 06:02 AM.

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  10. #8
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    Default Re: Trailblazer cooling

    I found this which might assist in answering your questions. It pertains to both flow and volume but also includes impedence and its affect on these.

    At the very least, a possible interesting read:

    http://www.comairrotron.com/establis...ow-vs-pressure
    Estee = S T = Sean Towlson

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  11. #9
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    Default Re: Trailblazer cooling

    Thanks for the info.
    Intuitively, one would accept that higher fan speed will have the biggest effect to dissipate heat. Your supplied info corroborates it and actually shows that it happens to the square of fan speed.
    The thing with car cooling that isn't addressed in your link, is the speed with which the radiator is pushed through the air (ignoring fan speed), think transverse engine with electric fan that only kicks in when required.
    Once again intuition is that at a constant speed, the larger the area of air intake, the bigger effect it will have on heat dissipation.
    We know that car designers are under immense pressure to reduce fuel consumption, yet increase power at the same time. Yes, they do their magic with fuel pressure and incredibly fancy injectors, but aerodynamics must also be important. One of the aero aspects to consider is obviously the grill size. The smaller the better.
    I am happy to accept that GM got it right with my Chevy, because it doesn't overheat, but I would have been happier if more radiator was exposed to direct airflow at speed.
    Last edited by RoelfleRoux; 2020/01/05 at 03:49 AM.

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  13. #10
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    Default Re: Trailblazer cooling

    No arguments from my side Roelf.

    Out of all of the automotive systems, the one which appears to be the most straight forward is actually very complex to a degree, I think particularly in more recent times where aesthetics and aerodynamics are important. In earlier years, it wasnt as complex, a slab grill on the front end covering a radiator of almost the same size with a belt driven fan behind and very little impedance to air flow. (Except the first series Minis where the radiator was mounted sideways in a wheel arch area with the resultant overheating problems)
    Estee = S T = Sean Towlson

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    ''Nothing makes the Earth seem so spacious as to have friends at a distance; they make the latitudes and longitudes''. H.D. Thoreau.

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  14. #11
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    Default Re: Trailblazer cooling

    Estee,
    Thanks for your input and sharing your knowledge.
    Those early transverse engine cars from Leyland... oh dear! I was blessed with an old Austin 1100 as a student. Very quickly learned that the rubber cowling between radiator and the body was all important. The radiator was fixed to the engine, so the rubber strip sealing the gap to the body had to take up quite a bit of movement and it was all that prevented recirculation of the hot air.
    I eventually solved the two biggest issues (overheating when the sun shined and wet distributer when the sun didn't shine) with a single fix. I installed a plate behind the grill that sloped towards the radiator. This helped to channel the air towards the radiator and shielded the distributer from rain.

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  16. #12
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    Default Re: Trailblazer cooling

    It is happening

  17. #13
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    Default Re: Trailblazer cooling

    Quote Originally Posted by RoelfleRoux View Post
    It is happening
    Is that a grinder ??
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  18. #14
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    Default Re: Trailblazer cooling

    Net n vraag, ek het nou nie die hele thread gelees nie.

    Is daar n probleem met die vekoeling op daai voertuie dat julle vents in sny om met die verkoeling te help of vind julle net dat dit beter werk?

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  19. #15
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    Default Re: Trailblazer cooling

    Ja...nee
    Lees die thread. Alles is daar.
    Quote Originally Posted by Chris8d View Post
    Net n vraag, ek het nou nie die hele thread gelees nie.

    Is daar n probleem met die vekoeling op daai voertuie dat julle vents in sny om met die verkoeling te help of vind julle net dat dit beter werk?
    2004 Defender 110 Td5


  20. #16
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    Default Re: Trailblazer cooling

    Quote Originally Posted by globaljaco View Post
    Is that a grinder ??
    Nope...
    It is a very clever looking piece of equipment with many different interchangeable bits. This one actually belongs to his wife who uses it in her reupholster business.
    Now I'll just live with this for a while and see how I find it. The slots aren't really obtrusive, so maybe I won't be ordering a new panel anytime soon... maybe.

  21. #17
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    Default Re: Trailblazer cooling

    I like your logical honesty Roelf Looking forward to the temperature readings as a result of this.
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  22. #18
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    Default Re: Trailblazer cooling

    Dremel tool?
    Always think: Could this be sarcasm?

    Andr Opperman

  23. #19
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    Default Re: Trailblazer cooling

    Quote Originally Posted by Oppies3800 View Post
    Dremel tool?
    That looks like a reciprocating multi-purpose tool, like this:
    https://www.loot.co.za/product/bosch...iABEgIQS_D_BwE

  24. #20
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    Default Re: Trailblazer cooling

    Amazing difference after 1st test. The car cruises 2C cooler at 77-78C. The climb from Badplaas towards Barberton, with cruise set to the speed limit, used to push the temperature up to 90C from 79C. Today it only went as high as 82C.
    And all that from those two small square openings next to the number plate.
    Last edited by RoelfleRoux; 2020/01/12 at 02:13 PM.

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