GS#0677

hi guy's
i just blow up my second cooling radiator (both were aluminium core with plastic tank). the problem is the aluminium hooks that support the core to the plastic box get loose and it is leaking when the car don't run and a lots of coolant is spread in the engine bay when i run hard like track day or fast ( around 120mph). when i cruise,no problems. The car don't get hot , i've got an 160 thermostat and an oil cooler in the front .

The first time i thought it was a head gasket problem. so i change it but it wasn't the problem (no problem on the heads and a perfect gasket). i talked with a guy who fix radiators and i remember that i changed the surge tank cap 6 month ago. it looks too hard (21/26 lbs) and thought it was the reason why i blow up the radiator . i was confiant, i changed the cap and put the same kind of radiator.

6 month later , still the same problem. the radiator is in the same shape and i don't understand why?
i want to upgrade with a Dewitt direct fit radiator (ordered) but if there is a big pressure like in the other radiators what is this going to happen? i'll put a new surge tank cap too.
Why the radiators fails ? i look at the surge tank when i'm idling and there is no bubles so how can i have a back pressure in the system?

Maybe someone already have the same problem ?
Thanks for your help.

racebum

head gaskets were my first guess as well, if it isn't that have you checked your cap and overflow? when you run the track temps get nuts quick and your radiator will pop if there is no relief for it.

Aurora40

Is the thermostat the correct one? If I recall, the LT4 has some sort of radiator bypass to prevent overpressure of the radiator? Some people have blown out LT5 radiators for a similar reason, the thermostat was wrong and the bypass feature didn't work right.

_twisted_

do a search for some of Tom Dewtitts posts - there was another guy with a gs that buldged his alum rad - I dont think it was a DeWtts but the thread was a good one.

If you cant find it call Tom

GS#0677

thanks for the answers

i'm going to get a new GM stock cap
About the thermostat, i baught a hypertech 160° when i changed the head gasket. for the moment the fans stills run at the factory statement but on the road i'm at 160°.
Where is located this bypass ?

aminnich

Surge tank cap should be 17 psi max. Not the 21/26 lbs you mentioned in the initial post.

REDC4CORVETTE

I was going to say the same thing
I run a 7 lb cap but a 26 lb no way.I have blown 3 radiators and the core is weak ,they make one with bigger rungs that go into the tanks but they will be alum.Your radiator cap is to high a presure and will not allow the cap to release the presure into the surge tank.

MK 82

Your Grand Sport deserves a DeWitt! Problem solved.

GS#0677

Who make this one with a bigger rung ? Dewitt ? What are you talking about the cap or radiator ?
Yes i know that 26 lbs was too high, i change it after the first radiator blow up.
Where did you found a 7 lbs REDC4CORVETTE ??? i'm interested in ?

Yes my GS deserve a DEWITT radiator but i'm not pretty shure that the problem is solved, i doesn't want to blow it !!!!

REDC4CORVETTE

I got my 7 lb cap at NAPA.The radiator place sells radiators on E-bay.
1-800-223-2501 Dean.
I blew up the cheap one they first sent me and Dean the owner had to look around for a few weeks to find a radiator with the heavier rungs in it.
I was going with the dewitt but I was not sure if I could have a radiator that would serve me any better than just any alum radiator.
Next time I will go with the dewitts.I blew up 2 plastic tank ones and one alum one so far.
I had him find me one that could take 150 mph and he said the first one was not designed for that kinda of speed.

Quiktrp94

What does speed have to do with the radiator?

REDC4CORVETTE

The only thing he said was the point of acceloration was in 1320 ft and the stress was to much for the radiator.All I told him what ever excuse you come up with, I just don't want to lose my 14k motor to a junk radiator that is 2 mths old.

jcb5565

The stock radiator has been known to blow off the plastic ends. Go with a Dewtitt radiator, the tanks are aluminum and welded on. The cap should be 15lbs, make sure the the blow off tube is clear and check your radiator hoses. Good luck to you.

GS#0677

thanks guy's
I have already ordered a dewitt rad and i'm going to change hoses and the cap (between 7 and 15 lbs)
I hope not to have problems anymore.
i'll keep you informed cause i've got a track day on the 24 of mars so i'll see if the radiator is fine .

Gary04Z06

You might be thinking of me. My orginal blew the passenger side tank, no biggie it was 10+ years old I figured. Then ordered a new DeWitts, and it blew, but not the tanks, the vented part expanded and the walls of the tanks buldged a little. I ran a compression and leak down test figuring that a cylinder was the only thing that could create enough pressure to blow the new radiator. THose came out fine, even had a shop do it just to be sure. The heater core was also buldged. Water pump was fine, I went ahead and ordered a second DeWitts, I kept in contact with Tom DeWitt through the process, after the second one was in, no real problems. It got a little warm at the track, but I noticed the oil temp was high. So soon I will finaly get the built in oil cooler hooked up and hopefully that will take care of the oil temp issue.
Never really found what blew the first alum. radiator.

Gary04Z06

I think part of the problem is the design from GM. The remote cap has all the fluid going through small 1/4" or 3/8" hose, not very big so might not be ableto handle the pressure. My cap was the original and it did not hold pressue when tested. I did not replace it until I added the second radiator, don't know if that was the issue or not, hard to say, everything else tested ok.

0Tom@Dewitt

Gary,

I was thinking of you and when I read more and more of the C4 2nd design blown radiators, I'm convinced it is a design problem. Obviously if the heater core was puffed up, it wasn't just the radiator but rather the whole cooling system that saw a pressure spike.
Until someone comes up with a better solution, I think it has something to do with overfilling.
I say this because there is only two ways to produce the kind of force necessary to expand the metal parts the way it does. One way is a compression leak, which many people did not have, or simply fluid expansion. Think about what happens to a pop can when you forget it in the freezer, that's the same fluid force when fluid heats up. If the system is overfilled and the fluid has no place to go, it will still expand. Why the cap does not relieve this pressure is the million dollar question. Maybe it has something to do with remote location of the cap vs the early C4 (84-89) which has the cap directly on the radiator.
I appreciate the suggestions by members to get one our radiators, and while I believe they are a much more rugged design, it will not stop this problem from happening and we will not warranty a radiator that is ballooned. Be careful not to over fill the system and make sure the cap is functioning correctly.

Gary04Z06

Hard to say, I really don't think I had the system "overfilled", but strange that the second one was fine.

GS#0677

Thanks for your help

Tom Dewitt spoke about overfilling so i look at my manuel and here is what they say

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They said that the level coolant in the high fill reservoir must arrives at the base of the filler neck Of course, you can't put more so is it overfilled ????
And i think that it is important to install a new original cap on the tank.

I'm going to replace hoses, cap , radiator (of course a Dewitt) and i'll see

93 ragtop

How could you overfill the system? There are air bleeds on top of the thermostat to get all the air out of the system. I didn't think there was supposed to be any air pocket in the system for expansion. It totally depends on the cap for pressure relief.
Personally, I would think that as someone stated above, there is a problem with the hose going to the fill tank. Unless, somehow there is a leak in the heads or head gasket that has not been found yet.