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Well the Vette lasted all this time with new rad and electric derale 17” fan without an issue. Now it’s overheating after driving for about an hour either at stops or highway. The overflow tank never goes over it’s level (I have it filled to half) when it should be filling up when hot. I made sure there is no obstruction in the tank. I got it with an air compressor from the rad to the tank and it leaks all over the back of it but not the actual tank filling up or spilling over the back. Is this why? Does the overflow tank need be sealed completely so it overflows? Is it the rad cap 16 psi not allowing the hot water to escape?
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
What is your temp gauge reading adn do you know if its accurate. If the the cap is bad, as it heats it builds pressure, so if the cap is bad it can overflow even if your temp isnt into the red.
Spring in lower hose?? Waterpump circulating the coolant?? All seals around the Radiator?
All this, first. What is the temperature of the upper radiator hose, using your IR gun?
If coolant isn't being released into your overflow tank, then the rad cap is not opening at 15 PSI. Either it has failed closed (unlikely), or the system isn't getting up to that pressure. Either the coolant is low, or there is a leak somewhere. If you don't have a puddle on the floor, it is possible that the leak is internal to the engine.
These Stant caps look like garbage in a clean, stock engine compartment, but they do work, and they let you release pressure safely (into the coolant overflow tube), which can help diagnose issues. If you come back from a run, release the red lever, and there is no pressure change, your system isn't getting up to pressure.
Last edited by Bikespace; Dec 27, 2020 at 06:58 PM.
If it is really overheating and nothing has changed, check your thermostat. they can fail and stick shut
The op recently replaced the radiator and I believe the rest of the cooling system completely from hoses to pump to stat and electric fans..
I had to replace my thermostat 3 times before I got a reliable one in my 74. if it worked ok for a couple weeks prior to now, My guess would also be thats your issue.
Last edited by augiedoggy; Dec 27, 2020 at 06:43 PM.
What is your temp gauge reading adn do you know if its accurate. If the the cap is bad, as it heats it builds pressure, so if the cap is bad it can overflow even if your temp isnt into the red.
temp gauge is accurate. the temp gun shows it's working well. the mishimoto controller is working. i set it lower to turn on at 165 and it turns off at 185 just to keep it low. it never overflows, it simply doesn't let hot water to get to the overflow container, so it builds up hot steam. at that point my gauge goes over 200. when i stop and check you can hear it gurgle below the cap. a good cap would have the steam push the spring in and let the steam go to the overflow wouldn't it? cap came with rad.
Spring in lower hose?? Waterpump circulating the coolant?? All seals around the Radiator?
hi 4-vettes. spring is in there. waterpump is circulating. all sealed up no leaks. bad cap not retractin to let steam out? the overflow container doesn't change it's level at all.
All this, first. What is the temperature of the upper radiator hose, using your IR gun?
If coolant isn't being released into your overflow tank, then the rad cap is not opening at 15 PSI. Either it has failed closed (unlikely), or the system isn't getting up to that pressure. Either the coolant is low, or there is a leak somewhere. If you don't have a puddle on the floor, it is possible that the leak is internal to the engine.
These Stant caps look like garbage in a clean, stock engine compartment, but they do work, and they let you release pressure safely (into the coolant overflow tube), which can help diagnose issues. If you come back from a run, release the red lever, and there is no pressure change, your system isn't getting up to pressure.
when i open the cap very slowly, it definitely boils out. my cap is 16psi. what you're saying is, try the cap. run it till it's over 200, release lever to see if steam releases. what kills me is the overflow tank never ever changes the amount of coolant. it's at the middle between cold and hot (i filled it there). unless i'm crazy it should get to the hot line.
The op recently replaced the radiator and I believe the rest of the cooling system completely from hoses to pump to stat and electric fans..
I had to replace my thermostat 3 times before I got a reliable one in my 74. if it worked ok for a couple weeks prior to now, My guess would also be thats your issue.
removed it altogether to see if it's the issue. not that.
when i open the cap very slowly, it definitely boils out. my cap is 16psi. what you're saying is, try the cap. run it till it's over 200, release lever to see if steam releases. what kills me is the overflow tank never ever changes the amount of coolant. it's at the middle between cold and hot (i filled it there). unless i'm crazy it should get to the hot line.
Yes, if the system is full (no trapped air), the rad cap should release coolant into your overflow tank. If it isn't doing that, either the cap isn't working, or coolant is low. A good parts place should be able to test it, or you could try a Stant cap for testing without burning yourself.
Yes, if the system is full (no trapped air), the rad cap should release coolant into your overflow tank. If it isn't doing that, either the cap isn't working, or coolant is low. A good parts place should be able to test it, or you could try a Stant cap for testing without burning yourself.
i burped the system for about 25 min. removed all the bubbles. definitely full. ordered the cap just now arriving tuesday. it lasted all this time. this just happened now. i'm hoping bad cap.
awesome by the way that most of you remember me rebuilding this thing. feels good. everything is working great by the way (except this that just cropped up)
Can you pan back and take a wider photo? Do you have the foam pieces installed around your radiator? Your car would have come with a dual-snorkel intake over the radiator. You'll need to fill that gap, too, to force air through the radiator (if that's the problem).
in your photo I can see you still have the factory upper Rad seal, which is cut out in the center for the air intake duct. which you no longer have. although I really don't think this is the main problem. (Really does sound like a bad cap). every little bit helps with these old cars. You can get that upper seal for a earlier year car.
photo of my 77
full length seal keeps air from going over the top of the Rad.
in your photo I can see you still have the factory upper Rad seal, which is cut out in the center for the air intake duct. which you no longer have. although I really don't think this is the main problem. (Really does sound like a bad cap). every little bit helps with these old cars. You can get that upper seal for a earlier year car.
photo of my 77
full length seal keeps air from going over the top of the Rad.
You can also use a pool noodle for a quick test. As @4-vettes said, I don't think it is your main problem, but every bit helps.
actually was thinking the foam insulators they use for the copper pipes from the a/c compressors. i can slit it in the middle and put it in and around the other sections.
C3 overheating
All this, first. What is the temperature of the upper radiator hose, using your IR gun?
