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Thread: Strange cooling Question !

  1. 21st January 2008, 09:01 PM #1
    Jezzaol's Avatar
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    Strange cooling Question !

    HI All,

    I have a interesting question relating to my cooling system on my D1 3.9 V8i Auto.

    For the past few months or so I have noticed that the Disco temp would slightly climb when im at lights or stopped for longer periods. I removed the engine fan last year and fitted twin thermo fans ! Now from everthing I read and followed up on I needed fan cowlings (which I had not done) and when I drove quicker and had the Air flow up the temp always went back down. Confirming that I needed fan cowling.
    I got around to making a alloy cowling and fitting it up on the weekend, this is where it gets odd. Straight away when I drove it in the hottest part of the day it stayed nice and cool, even sitting in a take away drive through for 15 mins..........Did'nt budge..........Normal operating temp. So I decided to go for a extended drive, about 160km round trip and see how she went. Well after about 30mins of stop start type city driving my temp rose a bit, I kept going and just kept my eye on it........... Well First shock was the temp would rise when the engine was under load and then go down while at the stop lights The opposite to what was happening ?? so I got on the freeway thinking at least the air flow at 100km would help it come back down.......... Hmmmmmmmmmmm NO..............it kept going up and down depending on the load OK........ SO Im starting to think I have a biger problem, I slow down and do some stop start driving again and the temp goes back down, get back on the open road doing 100km and up she goes again (always not going over that 3/4 temp) hmmmmmmmm drove for another 10 mins ambient temp still the same and all of a sudden the temp goes back to its normal just under half temp drove fast, slow whatever it didnt budge ?????? OK maybe Im going mad, take it for a drive in the sand......... still no budge temp all good ????? Its seems to be all good now

    Thermostat ?? Air block in the system ??? Head gasket ???Any Idea's ???

    Cheers and thanks in advance !
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  2. 21st January 2008, 09:42 PM #2
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    Blknight.aus
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    its possable that your reaching a balance point for the airflow through the radiator...

    try removing the shroud...

    when you load the engine up at speed the shroud might actually be restricting the flow that used to go past the edges of the fans. When your loading it at a lower speed the additional air movement provided by the shroud through the fans will be enough to deal with the engines cooling requirements..


    Just a guess so far.
    Dave

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  3. 21st January 2008, 09:50 PM #3
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    Maybe the thermo fans are rotating the wrong way and blowing air back out through the radiator. This works at low speeds but at higher speed the air coming in balances out the air being pushed backwards - you you get hot.

    Just a thought - might be worth checking the wiring is not reversed. It HAS been done before.....
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  4. 21st January 2008, 10:07 PM #4
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    Checked the direction ........... Thats OK.


    Quote Originally Posted by spudboy View Post
    Maybe the thermo fans are rotating the wrong way and blowing air back out through the radiator. This works at low speeds but at higher speed the air coming in balances out the air being pushed backwards - you you get hot.

    Just a thought - might be worth checking the wiring is not reversed. It HAS been done before.....
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  5. 21st January 2008, 10:09 PM #5
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    Thought had crossed my mind as well................ But does not explain why the temp went back to normal after a while ??

    Quote Originally Posted by Blknight.aus View Post
    its possable that your reaching a balance point for the airflow through the radiator...

    try removing the shroud...

    when you load the engine up at speed the shroud might actually be restricting the flow that used to go past the edges of the fans. When your loading it at a lower speed the additional air movement provided by the shroud through the fans will be enough to deal with the engines cooling requirements..


    Just a guess so far.
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  6. 22nd January 2008, 06:58 AM #6
    RonMcGr Guest
    For starters, I'd get the radiator flushed.
    Secondly, I'd remove the water pump and have a look at the impeller. Murray from Jag/Rover spares tells me the impeller had a bad habit of rusting away the vanes.

    So if you have a partially blocked radiator, plus an ineffecient water pump, you will have an overheating problem

    My 97 3.9 V8, never gets hot, even towing a caravan up a steep hill with the aircon running. I have never seen the guage even rise further than half way, and I live in Brisbane.

    Cheers
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  7. 22nd January 2008, 08:38 AM #7
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    I think we have the same problem Jezzaol

    Last week going home on the tonkin highway when it was a cool 42deg with my aircon on the temp got just above half way.

    So I turned off the aircon and the temp went down to between 1/4 and 1/2 way. The next day coming home from work my temp was just past halfway again but this time I did not have the aircon on??????

    But since then my temp without the air-con on is between 1/4 and 1/2 and with the air-con on its just below 1/2.

    Difference is mine is diesel ans still running the clutch fan but I think my thermostat sticks sometimes and thats what sounds like yours is doing


    Adam
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  8. 22nd January 2008, 09:57 PM #8
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    Thermo fan size ?

    Hi again, I want to put bigger thermo fans on my radiator.

    Can anyone tell me how many 2750cfm's are required ? And what other prople use ?

    I have found the following on Ebay !


    16" S BLADE STYLE ELECTRIC FAN
    2750cfm - DRAWING ONLY 13.2 AMPS

    Cheers

    Jeremy
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