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DIABLO Overheating - HELP!

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  • 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.
    Attached Files
    Last edited by txumbro; 09-23-2015, 01:45 AM.

  • #2
    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, 02:11 AM.

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    • #3
      Poor radiator placement and shrouding

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      • #4
        4 fans on one radiator? Are they mounted on shrouds?
        Without talent experience is worthless

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        • #5
          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 !!

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          • #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

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            • #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.

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              • #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

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                • #9
                  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!
                  Yellow Vetter Carrera Gt-boxter based
                  White Vetter Murcielago-boxter based
                  White Gagliardi Vendetta
                  Gemballa avalanche 911

                  Team Mad Mechanics 2016

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                  • #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.

                    Comment


                    • #11
                      hi Txumbro, I had a friend that built a Countach a few years ago with a jag v12 and had the same problem as you describe, he had radiators modelled on the oem Countach and he had pusher and puller fans back to back and that was causing his issue as one fan fights the other I would suggest trying it without the pusher fan but actually remove it otherwise it will spin with the puller fans sucking through it, also make sure your fans are true puller by design , he also found that some fans although it was claimed you could turn the blades over to be push or pull your better to get fans designed to be one mode only, this post on KC will help as Jim Dinner had issues with his bmw powered Diablo if you do a search for OVERHEATING and JDINNER there is some good info over there
                      http://www.kitcentral.com/index.php?...c6c14b9f71ad85

                      and also make sure you fit a proper header tank, and raising the rear to bleed the car is critical, I just spent 3 months working on rover mgfs in a rover specialist workshop they are a mid engine car and we resolved heaps of over heating issues with them, we had to raise the rear at least 3 ft in the air to get all the air out,they even have a heater nipple under the hood to bleed the heater core
                      Last edited by Lambolex; 09-24-2015, 08:39 AM.

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                      • #12
                        Very good info on here. Interesting about the fans fighting each other. Makes total sense.
                        Yellow Vetter Carrera Gt-boxter based
                        White Vetter Murcielago-boxter based
                        White Gagliardi Vendetta
                        Gemballa avalanche 911

                        Team Mad Mechanics 2016

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                        • #13
                          Thanks for all the ideas.
                          UPDATE:
                          Today, I tilted the car (see pic). A lot of bubbles came out, but still overheating. Do you think I need to jack it up higher than this steep incline?
                          Tomorrow I'll be checking the timing and putting exhaust pipe tape on all the pipes and see if it helps.
                          I've tried the Water Wetter, to no avail. Maybe I have to I have to sold the bigger problem first.
                          The radiator and fans are ducted.

                          Thanks. again.
                          Attached Files

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                          • #14
                            That is the one thing I don't have and didn't even know about, the HEADER TANK. Is that like an overflow on steroids?

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                            • #15
                              Just email Jim dinner he will know exactly what to do

                              jim@kwikercars.com

                              You need to post some pics of your engine compartment and radiator location too

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