BlackZ28629

iTrader: (8)

So my car did it during the hot months of Summer and anytime I drive it for a few minutes. The coolant boils (you can hear it bubbling/boiling, etc. after driving it when parked and off) and steams a fine mist out of the overflow tube that contains the long dipstick or whatever. There are no leaks on the ground, no visible leaks on the heads, and the temp. gauge stays right below mid way like it always has. I pulled the fans and tested them, they work. I tested the relays and they work. The waterpump is semi-new, prob. only has a couple thousand miles on it if that. My guess is that it could be the thermostat sticking open and the water is not getting cool cuz it doesn't stay in the radiator to cool off. The Coolant-temp. sensor has never been replaced so it may need replacing, but it seems to work fine. Please enlighten me with suggestions. I need to know what to try first before I start spending $!

davidws6

iTrader: (36)

If it's not overheating, have the radiator cap checked as it may not be holding enough pressure.

If it was compression leaking through a head gasket, it would probably be overheating, + it would smell.

BlackZ28629

iTrader: (8)

Anybody else have something similar happen? Drives perfect no problems. The radiator cap is tight, I don't see it being the problem but I'll check again. I don't see anything around the head...The sound it makes is the main thing. I hear it when I pull it in the garage and turn it off. It sounds like I'm boiling a pot of tea under the hood. I just need to hook up HPtuners and see if the gauge is working properly and it is in fact running in normal operating temp. range. Then I'll prob. just go ahead and change the thermostat. Please chime in if you have any ideas. Thanks.

brian_rs/ss

when was the last time you flushed your radiator?

01ssreda4

iTrader: (96)

I'd flush the radiator and change the cap and thermostat if you haven't already. A blown head gasket or cracked head/block can cause similar conditions.

joecar

He's not saying the cap is loose/leaking, he's saying the spring on the cap's pressure relief valve is weak and it's not holding pressure upto its rated value.

LS1W66

This

BlackZ28629

iTrader: (8)

Thanks for the replies guys. I'll try a new cap and see what happens. I'll post back when I find out.

senicalj4579

iTrader: (41)

This right here

jrpimp00

iTrader: (17)

Had the same problem, couldnt figure it out. Tried 3 new caps, checked for leaks, thermostat, everything. Turned out when I flushed my system and the overflow tank., I hooked up the overflow tube and the head vents backwards. Problem solved.

BlackZ28629

iTrader: (8)

[QUOTE=jrpimp00;14225160]Had the same problem, couldnt figure it out. Tried 3 new caps, checked for leaks, thermostat, everything. Turned out when I flushed my system and the overflow tank., I hooked up the overflow tube and the head vents backwards. Problem solved.[/QUOTE

So you're saying that you hooked up a hose backwards?

I just inspected the cap again, and it does seem a little worn out and rickety, so I'm going to get one from GM. From what I read about the pressurization of the coolant, the cap increases the boiling point by using pressure, etc. etc.
So this may be the problem. Hopefully it is, cheap fix!

ISMELLRICE

iTrader: (22)

Flush the radiator, clean the grooves in between...my radiator was plastered with dirt and bugs :/

StreetLethal

I had that happen to my about a year ago. It turned out that the radiator fan was not coming on, and the coolant would slowly reach a boil until it overflowed. I replaced he thermostat initially, but eventually figured out that I just needed a fuse. I'd check and make sure that your fan is kicking in just to be safe; it could be that simple.

BlackZ28629

iTrader: (8)

Thanks to all for your suggestions. Prior to writing this, I already checked the fans and relays and they're all good. Looks like it WAS the radiator cap. The new one fit MUCH better and compared to the old one, it is a night and day difference as far as the spring tension and putting it on. I took her out for a nice spirited drive after a good warmup and temp. was good and she drove like a beast. I pulled her back into the garage to see if I heard the boiling sound; I didn't hear so much as a slosh of anything going on. Granted it is pretty cold here, but still I did not hear the sound nor hear or see steam of any kind so hopefully this was it. The hot months will be the telling sign, but for now I will enjoy the cold weather and let her rip!

davidws6

iTrader: (36)

Glad it was something simple !

BlackZ28629

iTrader: (8)

ME TOO!!!! Thanks for the tip!