Problem!! Coolant Boils In Radiator!! HELP!!!

**L3THAL_Z28** · 05-07-2007, 10:14 AM

I have a 2000 Z28 and it runs at about 205-210 in the city. I live in LA so im stuck in traffic often. The car is not overheating, however after I turn the engine off I can hear the coolant boiling inside the radiator and can smell the coolant. My fans never go on (havent checked if they go on when the AC is on but I will check today) My guess is that my thermostat is not working. Anybody out there that has any suggestions?? Thanx this is driving me nuts!!

**96z28** · 05-07-2007, 10:26 AM

if your thermostat did not open then you would overheat. I would flush the cooling system and get some new one in there

**L3THAL_Z28** · 05-07-2007, 10:29 AM

I replaced the coolant after i heard it boiling the first time but that didnt help. Any other idea of what the problem may be?

**jigger1166** · 05-07-2007, 10:44 AM

your radiator cap may have gone bad and isn't holding the pressure. Try replacing it.The boiling you hear, might be the coolant flowing from the rad. into the resevoir, giving the smell you mentioned.

**L3THAL_Z28** · 05-07-2007, 10:53 AM

I'm gonna try and replace the radiator cap and see if that solves the problem. Thanx and I'll keep u guys posted. Hopefully this solves the problem.

**Danger731** · 05-07-2007, 10:59 AM

thermostat

**L3THAL_Z28** · 05-07-2007, 11:01 AM

I was thinking about getting a 160 tstat anyway, should i just replace the cap n tstat altogether??

**67CamaroRSSS** · 05-07-2007, 11:27 AM

IMHO, the factory water pumps and thermostats used for these cars is crap. Remember, they get parts from the LOWEST bidder. 39,xxx miles and I've already had to replace both. I vote for a thermostat that's stuck open in your case. Have you checked the weep hole on the water pump?

**L3THAL_Z28** · 05-07-2007, 12:25 PM

actually no i havent checked it...so i should change the thermostat and the water pump as well?

**2001NBMZ28** · 05-07-2007, 12:44 PM

I'd do the cap first, make sure all the air is out of the system from the coolant change, and you should be getting at least low speed fans in traffic in LA this time of year - especially with the AC on. Next on my list would be the thermostat.

**L3THAL_Z28** · 05-07-2007, 01:03 PM

alrite well i changed the cap today...my fans dont go on in traffic...y is dat?? the car is always running just below 210 degrees at about 206 or 207 (GM gauges suck so the reading could be wrong)...is it normal for the fans to never go on at around this temperature??...Im going to run my car witht he AC on in a little bit and see if the fans go on...oh yeah how do get all the air out of the cooling system?? sorry fellas im new to all of this...thanx

**2001NBMZ28** · 05-07-2007, 01:34 PM

To check for air in the system run the car at idle with the radiator cap off until the thermostat opens, if the level drops keeps adding fluid. Your low speed fans may be coming on and just not hearing it, mine for low speed are set at 184/175 so they come on sooner - plus I have LEDs for high/low and can see them cycle on and off. Stock settings are much higher. Do some "spirited" driving with the AC on and see if you have the same sound/smell.

**L3THAL_Z28** · 05-07-2007, 01:36 PM

I idled the car for a bout 10 min after replacing the cap and its all working fine now. The fans kick in at slow speeds at around 210 degrees and run at high speed when the AC is one. After i turned the car off i couldnt hear the boiling noise or smell the coolant anymore...thanx for ur help guys.

**L3THAL_Z28** · 05-07-2007, 01:41 PM

One last question...i plan on switching to a 160 degree thermostat...should i reprogram the ecu to start the fans sooner or should i have a shop do it?? how hard is this to do??

**Y2KPewterSS** · 05-07-2007, 02:43 PM

Originally Posted by Assassin66

One last question...i plan on switching to a 160 degree thermostat...should i reprogram the ecu to start the fans sooner or should i have a shop do it?? how hard is this to do??

You can do it if you have a handheld programmer or a shop, either one.

**2001NBMZ28** · 05-07-2007, 02:50 PM

It's easy to reprogram the fans, but you need tuning software or a handheld to to it yourself. A shop will probably charge you one hour shop time minimum for easy PCM adjustments/codes turned off, etc.

**L3THAL_Z28** · 05-07-2007, 02:57 PM

alrite..thanx for da feedback on fixing my problem

**jigger1166** · 05-08-2007, 08:25 AM

Originally Posted by 67CamaroRSSS

IMHO, the factory water pumps and thermostats used for these cars is crap. Remember, they get parts from the LOWEST bidder. 39,xxx miles and I've already had to replace both. I vote for a thermostat that's stuck open in your case. Have you checked the weep hole on the water pump?

A thermostat that's stuck open lets the coolant flow before the engine has a chance to warm-up. A thermostat that's stuck closed keeps the coolant in the engine, preventing it from flowing through the radiator, and cooling, thus overheating.

**spawn_ta** · 05-15-2007, 03:35 PM

I am having the same problem

Fans coming on
New water pump
Radiator flow checked and fully cleaned
New thermostat
New 50/50 mix
Coolant checked for exhaust gases, nothing

I seems to run a little hotter and when I shut the engine off, it sits a second and then boils over. The car idles cool, and only gets hot at high rpm's. I don't know for sure if my cap is good, but I replaced it with one I had around the house. I am about to go crazy, anyone have any suggestions?