Ok, I have been searching the internet for months and asking everybody with any motor knowledge that I know and still can not figure out what is going on with my 02 Firehawks coolant system.

The coolant seems to be going into the overflow tank when car is warm but when car cools it does not return to the radiator. Every time I check coolant level after I drive car it is low in radiator but overfilled in overflow.

I have tried two new radiator caps with no luck.
I tried the block leak test kit with the blue liquid and it didnt show any combustion gasses in system.
No coolant in oil or oil in coolant
No white smoke in exhaust
Car runs good
Did pressure test on system and it held 18psi (although I didnt really know how long to leave it on, instructions with gauge said 2 min)
Let car run with pressure gauge on system, gauge needle held still with no shaking
Replaced overflow tank and tube
Tried bleeding coolant system multiple times
No visible leaks, except before I realized what was happening and let the overflow get to full it would eventually shoot out overflow tank under hard acceleration

Only thing I havent done is pull plugs to look at them, and pressure test each cylinder, but every other test I tried for head gasket came up fine.

I am stumped and dont know what to try from here.

I would greatly appreciate any help or tips

Thanks

 

Check that the vent line coming from the heads to the radiator is not switched from the overflow line. Look at the PS of the radiator and there you will see 2 hoses. Which one is on top? That may have been switched on installation and will cause overflow of the tank

 

Thanks for reply,

The overflow tube is on the top

 

??anyone have any other ideas or tips??

 

bump??

 

This is just a shot in the dark but maybe you have a slight head gasket leak thats letting the cylinder push air into the system? Good luck with it. I would try a leakdown test. Its the only thing I can figure is happening.

 

That is what I was thinking too, I just wish I could find a way to confirm that's what is happening before I pull heads.
Thanks for response

 

I did try another pressure test on coolant system, I pumped 20psi into it and within first couple min it dropped to 17psi, but after that it held 17psi for at least an hour.

Also if i can keep my foot off the gas pedal when driving it will maintain correct fluid levels. It only seems to give me problems when I have been letting it hit some higher rpms?

 

Does the coolant have a slight smell like Exhaust ? If so, head gasket.
+ if you say it's fine until you get on it, that may be head gaskets .

What if you have the cap off and radiator almost full. Rev the engine up. Does the coolant want to come out? Do you see Bubbles in the coolant ?

You could take it to a shop with an exhaust sniffer and put it right at the radiator opening. If there are any Hydrocarbon exiting the radiator, the exhaust sniffer will find it.

 

Didn't see it listed in your description.....

Did you replace the thermostat?

 

No have not replaced thermostat because it never overheats, I have been thinking about changing it anyways.

I have tried the block leak test that is supposed to detect the exhaust gasses in system and it came up fine.

When i rev engine with cap off fluid does want to come out overflow, but no noticeable bubbling.

Thanks for replys

 

Check the hose from overflow to reservoir and make sure it is not kinked or pinched. You can get coolent through a pinched hose at pressure but it won't go the other way.

 

Thanks for reply
I will look at it again but I am pretty sure it isnt pinched or kinked.
Thanks for time!!

 

I've been trying to tell people for 10 years on this site that coolant won't go back into the radiator after it has gone into the over-flow tank. Its a bullshit system. The pull of vacuum from the radiator when its cooling down will just pull harder on the radiator cap seal and make it tighter, so coolant cannot get sucked in.
It doesn't happen on mine, and it does not happen on a few other F-Body's that I know who have over-pressurized from over-heating and their coolant never went back into the radiator either......But I'm sure theirs people who will say it has, and maybe it did. These cars are all different, they act different, the PCM's act different, clearances in places are different, etc....

So, stop worrying about the coolant staying in the over-flow tank...its normal.

Concentrate on the reason the coolant is being "pushed" into the tank. If you tried two radiator caps already, I would try a third.....allot of them are duds. If it still happens then you have a blown head gasket. It might not show on a coolant system pressure check and possibly will not show on a leakdown check either. Depends on how tiny the leak is. PSI in the combustion chamber with a running engine will over-come any sized leak, those pressure tests might not.

The other way is from a small leak somewhere in the system. Maybe in a hose or the water pump or a gasket.......when you get the engine up to operating temp and its normal ~18 psi......it might not leak coolant out that little tiny leak. But when you shut an engine down the pressure and the temp RISE for about 30 minutes to 1 hour. This could be when the coolant it getting pushed past the radiator cap or out that tiny leak somewhere. Then when it cools........air will get sucked into that leak. Unlike the radiator cap, which will be sucked tighter to seal it off from air getting in, there is no seal to get tighter with a tiny leak somewhere.

***The way to find such a leak.....get the engine hot....put the front up on ramps, wait about 20 minutes. Then come back with a flashlight and look for a slow drip or tiny stream of coolant leaking out everywhere underneath the car and from the top too.....shine the light all over the rubber hoses, plastic areas of the tanks on the radiator, the radiator itself front and back, etc....

Now, I personally think you have a blown head gasket....since you said it shoots out of the over-flow tank on hard acceleration. Thats the #1 symptom of a blown head gasket.

...oh, and you do have your coolant cross-over tube attached to the lower port under the radiator cap....right?

Good luck.

.

 

Oh....and try going for a drive with the t-stat removed. See if it still pushes coolant into the over-flow tank under hard acceleration.....or at all. Just remove it and bolt the housing back on. Even if you have a "one piece t-stat", which it is not, its a two piece also. The t-stat pushes down, push down on the two little wings, and twists and it pops out of the metal housing. "Watch your eyes if it goes flying under that spring pressure when taking it out and putting it back in". Bolt the housing back on.....top off coolant in the radiator.....go drive.

See what happens. If it still blows coolant into the over-flow tank....you have a blown head gasket.

If it doesn't I'd say the t-stat is not opening fully, you are getting hot, your temp gauge isn't showing it properly, you are over-pressurizing and blowing coolant into the over-flow tank.

.

 

That's my assumption, personally. Not a STUCK T-Stat, but a sticking one on it's way out.

 

Thanks for your time!!

I always wondered how the coolant was supposed to get back past the radiator cap? But if the coolant isnt supposed to go back to radiator why does the overflow tank dip stick have a full cold and full hot level? Also what would even be the point of the overflow tank if not to have a place to push fluid to so it could bring it back later? Not trying to disagree with you, just trying to learn so I can have better understanding to try to fix my problem.

I will try another radiator cap, probably a different brand this time.

I will also try another thermostat.

Thanks again for your time, I really appreciate the help

 

Its supposed to work that way....but there is no question about it.....it DOES NOT work as advertised in every car. It does not work in mine and I know a handful of others who have removed it because it does not work in theirs either.
And yes....they have factory stock radiator caps or other 18psi caps. It just makes no sense that it should work as they say, but I guess some people get coolant defying physics......

The only time coolant ever went into my over-flow tank is when I lost my serpentine belt 2 different times while doing a hard top end run. I overheated into the red and coolant blew into the tank. It never returned to the radiator......lol

I'll probably remove my tank next time my battery is out...its completely useless......

.

 

Look at how the system works ,,,,,as the coolant and engine cool they contract creating a vecuum in the system which in turn pulls coolant from overflow so an air leak anywhere in the system will ,,,,,,,I would bet the cap is not sealing properly as the radiator neck wears over time ,,,,,try using some needle nose and bend the tabs on the cap upward so the cap is tighter when closed on the radiator

To answer You're question about coolant going back into rad ,,,,,,,,look at the cap under-neath the spring actually on the bottom sealing side in the middle of the seal and You will see a piece of brass alloy just about an inch in diameter ,,,,,if You get You're nail or something under it that is a valve

 

That reminds me, there was a TSB years back stating something to the effects of what you are experiencing. I think LS6427 knows what I'm talking about....

Anyway, even GM recommend that their techs rub down the top of the radiator neck, where the cap seals, with a bit of emmery cloth to smooth it out.

Someone chime in here if you remember what I'm talking about.