cooling issue [Archive] - Forum


View Full Version : cooling issue

05-08-2010, 09:06 PM
hey guys im new to this site. just picked up a 99 ga gt 4 door for a dd so i can give my z06 a rest. i got the car for $750 bucks. replaced the wheel bearings, did my normal tune up stuff and its running good except for a cooling issue.

got home the other day and noticed the coolant was boiling in the reservoir tank, i could hear the coolant boiling in the upper and lower radiator hoses and it was boiling out of the overflow tube. i figured the t stat was locked so i replaced it and its still doing the same thing.

i did notice the middle air dam was missing so i am going to pick that up asap but the cooling fans are also not coming on with or without the ac running. any help will be greatly appreciated.

05-08-2010, 10:12 PM
ACCORDING TO YOUR INFO> First, I wouldn't worry about the air dam right now unless you planned on getting it anyway. One of the first things you might want to try is a new reservoir cap. If your cap is bad it will let fluid purge through at low psi and maybe take on air(you have to have air in the system for it to boil vigorously). I had this problem myself and have resolved it to my knowledge.

If you don't know the process.

Wait til the car is cold fill up your reservoir tank. Start the car and purge the system of air (left side of pipe in front of manifold) before it warms up really good. It should drain down the water in your reservoir after that so add some more.

05-09-2010, 08:38 AM
Yeah, I'd replace the pressure cap on the reservoir first and see what that does. If it's not holding pressure it will let the coolant boil at a lower temp than it should. Raise the pressure and the boiling point should go up. Other thing that would cause it to boil is an improper ratio of water and antifreeze, or if there was a bad head gasket. These cars normally run in the 200-220 range and they shouldn't boil and vent from the reservoir until you get up in the red zone around 240-260. Did you happen to notice what the temp gauge was reading?

05-09-2010, 08:51 PM
many updates: i replaced all fan relays with new ones and tested the fan via running a jumper and the fans DO work. the coolant is a 50/50 mix so that should be fine. i replaced the coolant temp sensor with a new one to eliminate that variable. the system has been "burped" properly to get all of the air out. my guage reads right at 200 and will not exceed 215.

i do not think its a head gasket. i checked the oil on the dipstick and there is no water/coolant mixing in with the oil.

i do have a new cap but i think the overflow tank may be warped or something like that cause the new cap is hard to screw on (i got a new one because the old one was hard to screw on as well) however its not leaking from anywhere but the overflow tube. the cap does seal and the tank itself does not leak. im beginning to think the ecm may be bad as that is looking to be the only variable left...

05-09-2010, 09:23 PM
You did use Dexcool right? Also maybe you can try flushing out your radiator. Just drain all the coolant, Undo the upper and lower rad hoses. Put a Hose in the upper rad hose inlet on the rad and turn it on. Do this until the watter comming out of the lower outlet gets clean.

05-09-2010, 11:35 PM
i did use the dexcool. i can flush the fluid out and clean the lines but that still leaves me with the fans not running. any other suggestions?

05-09-2010, 11:55 PM
IIRC, there's a fan switch in the radiator, looks very similar to the CTS on the thermostat housing. I've seen those go, and cause the fans to never turn on.

Did you apply power directly to the fans at all, to see if they work?

05-10-2010, 01:44 AM
yeah, i ran a jumper wire to the fans and got them to kick on but other than that no luck

05-10-2010, 05:27 AM
Aaron said that the normal operating temp for this car is 200-220.
You said that you are running 200 and not exceeding 215.
At what temp are the fans supposed to come on?
This tells me that you are running normal temps and that your fans are not going to turn on.

05-10-2010, 01:10 PM
^^ Yea i thought the fans don't turn on until a higher tempature like 230 or something. There is a post arround here that has all that information on it but you would have to search for it to get the exact numbers.

Edit: I found the post and here is the link:

05-10-2010, 06:34 PM
Yeah, the low speed fans aren't even supposed to come on until over 220 so I'd say you don't really know if they are working properly or not yet. Try and get your temps over that and see if they come on, or see if it will get to that temp at idle sitting still and turn your A/C. And sometimes even if they don't come on right away with the A/C they still will come on if they reach the temp threshold.

If that doesn't work and they definitely aren't coming on, then it could be the fan circuit in the pcm is bad or a break in the wire harness somewhere. Try and get a wiring diagram and using a multi-tester to check for continuity on all the wires (pcm to relay, relay to fans, etc). If that's not it then try replacing the pcm.

As for the boiling though, if the tank isn't warped and the cap is good and sealing properly, you shouldn't get any venting out the cap with the temp only at 215 if the coolant mixture is correct.

05-11-2010, 04:12 PM
well today i flushed the cooling system again and checked the water pump, t stat, and made sure the radiator wasnt clogged. all parts are in good condition. well after doing all that i drove home and the car tried to overheat. the guage climbed to about 250 and when the red warning light came on i pulled over and let it cool off. i had to refill all of the collant that boiled out and the fans never came on. im probably going to just bring the car to pontiac tomorrow and let them do a diagnostics on it so i can stop pissing in the wind. this is really starting to get aggrivating now lol

05-11-2010, 06:15 PM
I've seen this before. A Malibu owner with the LG8, same issues with the coolant boiling out of the bottle, and he tried everything you did. Turned out, the block was warped in the end.

05-11-2010, 09:23 PM
yeah, that would be my next guess.... quick over heat and boiling is a good sign of a head gasket sealing problem.

05-11-2010, 09:29 PM
im pretty certain its not head gaskets, the oil looks fine and i dont see any other signs that they could be bad. im really lost on this one lol

05-11-2010, 09:37 PM
im pretty certain its not head gaskets, the oil looks fine and i dont see any other signs that they could be bad. im really lost on this one lol

Just because there's no coolant in the oil doesn't mean the headgaskets are properly sealed. The head gasket will usually form leaks to the coolant passages before it'll find an oil drain back passage.

The quick boiling over and overheating to 250 makes me think its a headgasket as well. While boiling over can be caused by pockets of steam in the engine, the fact that it overheats in addition to that screams headgasket.

Another thing about the cooling fans. If you're driving faster than around 40 mph there should be enough airflow across the radiator that the fans aren't needed. Check the front of the condensor for plastic bags and such.

05-12-2010, 03:30 PM
Exactly. Coolant in the oil can be head gasket also, but more often it is from bad LIM gaskets than head gaskets. Head gaskets can make you burn coolant and/or over heat without any oil contamination at all. There are all kinds of coolant passages in the block that go through the gasket into the head. There are no oil passages. ;)

05-12-2010, 03:35 PM
turns out its the heads. dealer said it/they are cracked. game over car for sale....