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Thread: DIABLO Overheating - HELP!

  1. #1

    DIABLO Overheating - HELP!



    I am having trouble figuring why my car keeps overheating. It has a 350 with a Porsche 930 5 speed transaxle, After about 15 minutes, it continues to rise in temperature til I turn it off.
    I have 4 electric fans, a huge aluminum 4 core radiator, tried every temperature thermostat, removed thermostat, water flow from pump is going the right direction, tested exhaust gasses in the radiator fluid and it's clear, not loosing water and nothing coming out the exhaust. Radiator has been flushed and is cleaned, there is nothing in the vents of the radiator.

    If I can't figure it out, I may consider selling it here.

    Please let me know if you have any ideas.
    Thanks.
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    Last edited by txumbro; 09-23-2015 at 01:45 AM.

  2. #2
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    Is it a front mount radiator? Does it get cool off when car is moving? Do you have fan shrouds? Could it be air pockets in your system?
    Last edited by notnilc20; 09-23-2015 at 02:11 AM.

  3. #3
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    Poor radiator placement and shrouding

  4. #4
    Senior Member murcie-me's Avatar
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    4 fans on one radiator? Are they mounted on shrouds?
    Without talent experience is worthless

  5. #5
    Senior Member ITALIANKNIGHTRIDER's Avatar
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    did you jack the rear of the car up to make sure it has no trapped air in the system while filling it up with coolant , or the lines under the car bent or kinked that take coolant to and from the radiator ,what is the timing on the 350 engine set at , is their a corvette or caddy V8 coolant catch can ,that sit above the heads in the rear engine bay to fill the coolant system ,and last do you have a rubber air divertor under the car to force the air up and through the radiator while moving / driving
    In the USA if you pay a company / person to start a plug, then it,s your plug and work ,it is not theirs to sell or trade !!

  6. #6
    Yes, it is a front mount radiator. It has two puller fans mounted in a shroud, one large pusher fan on the bottom side, and one exhaust fan pulling the hot air out of the hood area.
    Nope, when the car is moving it heats up just as fast.
    The only thing I haven't done is jack up the back of the car, start it, and then check for air. I'll do that tomorrow and let you know here.

    Thank you so much for your time and suggestions

  7. #7
    It's mounted in the same place as most, in the front, just like a Fiero would be mounted. It does have shrouds.

    Thanks for the feedback and ideas.

  8. #8
    ItalianKnightRider,
    You've given this a lot of thought. You must be really familiar with these setups.
    Per your first suggestion, the only thing I haven't done is jack up the back of the car, start it, and then check for air. I'll do that tomorrow and let you know here.
    Lines are straight.
    Not sure what the timing is set at, but it runs really well. Do you think that's a possibility?
    No coolant catch can, just an overflow attached to a pressure vented radiator neck/cap.
    It heats up at the same rate, running or sitting.

    Thanks so much for the detailed ideas and suggestion. I'll try jacking it up tomorrow and let you know what happens.


    Thank you so much for your time and suggestions

  9. #9
    Quote Originally Posted by ITALIANKNIGHTRIDER View Post
    did you jack the rear of the car up to make sure it has no trapped air in the system while filling it up with coolant , or the lines under the car bent or kinked that take coolant to and from the radiator ,what is the timing on the 350 engine set at , is their a corvette or caddy V8 coolant catch can ,that sit above the heads in the rear engine bay to fill the coolant system ,and last do you have a rubber air divertor under the car to force the air up and through the radiator while moving / driving
    Great info IKR!
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  10. #10
    Although not the same car I had overheating issues as well in very similar setup (rear engine, front radiator, small vents)

    * As mentioned I filled up the system with the rear of the car jacked up, ran it with no cap on whilst filling up the last bit to get as much air out as possible. Check after first few drives as they normally need a small top up.

    * The first thing I did was let it idle on the drive to till the fans kicked in, as id fitted the temperature switch for the fan circuit I knew when they should kick in, then if they cut back out I knew it was dropping the temperature as designed. It does run a little hotter when at stand still but most OEM cars do as it happens, its just the needle on the temp guages are not designed to move with every degree or they'd have cars coming in all the time. they generally have a 10 - 15c operating range. Id let it idle for 45minutes

    Once this test was complete I took it for a drive and was still overheating. I had an ally radiator and 2 powerful; spal fans. I actually did 3 things to help the temps but I know which one fixed it.

    1. moved a return coolant pipe to a cooler part of the engine bay it was too close to the exhaust
    2. in my case i fitted a turbo blanket

    3. I ducted the front radiator. At first I just ducted the scoops to the side not selling the top and bottom of the radiator and it still ran hot. I then ducted the bottom of the radiator as well and had a 40f straight away and then running as designed.

    I then added some 'water wetter' this basically breaks surface tension on the water so more water is touching the cylinder walls etc... as an extra measure for getting heat away. The car now gets up to temperature quicker as well and is I'm sure is helping.

    Been fine ever since.
    So basically:

    check air bubbles
    duct the front radiator
    water wetter additive

    Hope this helps.

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