andystaiger

I've got a mild built 12 sec camaro.
It's my daily driver, got the A/C charged in it again after putting the motor back in. For a couple days ran fine with A/c blasting.
BUT one day after shutting off the car i heard water boiling looked under the hood and it just started pouring out of the top of the overflow (not the radiator).

I've changed:
PS pump (not that it has anything to do with my problem)
Thermostat
Radiator cap
And also checked to see if both my fans were operating..
Recently I was driving down the highway and had the a/c on and my car just got hotter than hell (maxed out the temp gauge)
THAT was the only time it actually overheated, the other times just boiled water out.. And yes after it boiled out i put more antifreeze and water in it..

Last night my buddy and I were troubleshooting and noticed the relay box says under the hood; Fan 1 Fan 2 and Fan 3..
Where is fan 3?
I only have the 2 between the radiator and motor..

killagt

iTrader: (3)

head gasket ?

andystaiger

Nope.. Head gaskets are good..
And if it were wouldn't it do it all the time? Not just when the A/C is on?

1 FMF

iTrader: (1)

you (a) have less than a 50/50 mixture, (b)and/or the radiator cap (cooling system) isn't holding to 15-18psi, (c) and/or there is air in the cooling system.

water boils at 212F at atmospheric pressure,
50/50 antifreeze/water at atmospheric pressure also boils at 212F or not very far above 212F. Stock radiator fan settings come on at low speed at 226F and high speed at 234F. a 50/50 dexcool mix should not boil until 265F with a cooling system able to hold pressure up to 15psi. a 70/30 mix af/water shouldn't boil till something like 280F under pressure. The fact it's only happening, or happens mostly, when you run the AC tells me the extra heat dumped into the cooling system is exceeding it's capacity, because of the 3 reasons I said above. And when you shut the engine off, if coolant temp is already at 220F, will heat soak and get a little hotter and boil over.

if you have flushed your cooling system with water, then you have less than a 50/50 mixture if you refilled with 50/50 because there was water left in the block.

There are only 2 electric radiator fans, a left and a right, but it takes 3 relays to operate both fans on either low speed or high speed. If a relay were bad you would get a check engine light, the computer can tell whether the fans are running or not.

if you're not confident the new radiator cap is holding pressure, get a coolant system pressure tester thingamajig and pressurize your coolant system 20psi and see if it holds.
and you can pick up a freeze/boil coolant mixture tester for like $5 and see what your coolant mixture boiling point is

andystaiger

I guess I'm leaning more towards C..
I've got 50-50 af and water..
And I've tried 3 different radiator caps..

How would I solve that little problem to see if that helps it?

1 FMF

iTrader: (1)

wait till the car gets cold to undo the radiator cap, or don't if you're rambo and can ignore pain, and keep topping off the radiator (not the overflow tank) after every cool down cycle. The air will work it's way out as long as you get the engine to operating temp for a little while, such as a 20 minute drive. Make sure the overflow tank is at least half full, the radiator will expel some coolant to it when hot but suck back when cooling down, you don't want the radiator sucking back air from an empty overflow tank. Make sure the overflow tank hose is clean and not leaking anywhere.

the best thing to do when filling the radiator is undo the throttle body coolant hose, air will purge out there as you fill the radiator. When coolant comes out throttle body hose, reconnect and top off radiator, that should get you 95% there, enough to where what little air is in the system will not cause a problem and work it's way out.

and unless you know you're mix is not less than 50/50, I would get a coolant tester and check the boiling point. If it's less than 50/50 you're wasting your time with everything else. if you've flushed the system with water, get the tester.

bjamick

iTrader: (31)

Just get the system pressure tested.

andystaiger

Alrighty I'll see what I can do about that..
But if something else comes to mind that hasn't been above mentioned, then by all means update..

00pooterSS

iTrader: (40)

1 FMF posted a lot of great info, what I would like to add is...

Too much pressure in the system or lack of ability to hold in the acceptable pressure causes it. If it does it when you turn off the car try the radiator cap, yes I read that you put one on it. Go to the dealership and get one there, not the parts store, and this is why... I replaced a cap once on an Acura I had just because the original one was old and I was doing a new radiator. I blew up two radiators in a row then a radiator hose, then a TB coolant hose, all at different times, and all after the new cap and radiator. I had bought the car with a cracked radiator so I put in a new radiator and cap. So I naturally assumed I must have a blown head gasket. I ended up finding the old cap I threw away in the parking lot at work and put it on the car and never had a problem again, the NEW cap from the parts strore was not releasing pressure and things blew up.

On your car most likely the cap is slightly weak and when everything is running and the fans come on it keeps the pressure right under that threshold where the cap lets go, then when you turn it off and it heat soaks and builds pressure there are no fans to come on and cool the coolant and bring the pressure down.

andystaiger

That helps alot too..
BUT two of those radiator caps that I talked about were from the dealership..
I did double check just in case the 1st one they sent me was faulty..

LS6427

iTrader: (2)

You need to lean a different way....air just doesn't appear out of nowhere. If your engine wasn't doing this a month ago and now it is boiling over....something has failed or you sprung a tiny leak somewhere.

I have about 15% Dexcool and the rest water in HOT *** south Florida with my 427ci.....it runs cool as hell all the time....so thats not it. I know people that run 100% water and they are fine.

If you already tried BRAND NEW caps, you can be pretty sure its not the cap than.

Failed/stuck closed t-stat....will not cause the coolant to boil over....it will go into the red and get up to 260* and beyond before it overpressurizes and starts pushing coolant out through the cap.
Same with failed fans......it'll get hot as hell before coolant gets pushed out, like buried into the red on the guage.

You have a blown head gasket......or a tiny leak that might only leak 15-20 minutes AFTER you shut the engine off. The engine gets hotter for a little while and the pressure rises before it falls. Thats why we have overflow tanks, overpressure. If you have a tiny leak it will **** out when you're not there...then when it starts to cool, it sucks in air.

SO....get the engine up to operating temp by driving it so you heat soak it good. Not just a 15-20 drive. Good and HOT. Drive home where you have ramps waiting. Put the front end up there and shut it off...then watch and wait to see if you see a leak. Wait 15-20 minutes. Hopefully you find one. maybe you'll see it ever so slightly leaking from the weep hole in the water pump.

If not.......head gasket.

***Important*** If you decide to do a pressure test, which is a great idea. If you do get a drop in pressure...BUT you don't see externally where the coolant is going.......You MUST remove all 8 spark plugs to see if the coolant went into a cylinder through a blown head gasket.....BEFORE YOU TRY TO TURN THE ENGINE OVER AGAIN.....If you don't and you start the engine with coolant in a cylinder...you could completely trash your engine depending on how much coolant is in there.

.

jrpimp00

iTrader: (17)

^^ He beat me to it^^

Exact same thing happening to my 98 T/A. Changed caps 3 times, thermostat twice, and checked the water pump. Today, after 3 weeks I finaly saw water pooring out from the heater hoses around the firewall. I guess I had a little leak that turned into a bigger leak, that was messing up my pressure causing it to boil over after i cut it off. I will try and change the hose tomorrow and see if it is fixed

00pooterSS

iTrader: (40)

I completely missed where you said you tried 3 caps, is the sealing area on the radiator in good condition where the cap goes on?


A good way to see if you do have a bad headgasket or head etc to where you are getting bypass from the combustion chamber to the cooling system is to go to NAPA and get a block test kit and some of the color changing block test fluid. You put fluid in a tube with a squeeze pump on one end and a nozzle on the other end and you hold it over the radiator and pump it. It pulls air in through the fluid and if and hydrocarbons are present the fluid changes from blue to yellow. So if you take the cap off and hold the tester in there and pump it with the engine running you can test for hydrocarbons and rule that out.

I cant post the link because its a non sponsor but if you search "NAPA block test" on google there is an article on it by a place called arrowheadradiator, should be the first link that pops up. It describes the kit a little better, it also shows it to be vacuum operated instead of a hand pump

andystaiger

A buddy of mine has that kit and we ran the test..
So I can rule that out for sure..