2G GST boiling thermostat

[Velmin hu]

Greetings I have rebuilt gst, after I drive push 20psi on evo 16g big with all the mods, when I come to stop turn off the car I hear boiling gargueling sound coming from thermostat area under radiator cap and hoses feeling like moving still. I also never changed that hoses for like 7 years car has been siting. Feels like some are cracked when there cold when I press on them inside.

 

[Kryndon]

I am in almost the same situation but I get no more than 17 psi. I recently discovered I had a lot of air bubbles in my cooling system and just behind the thermostat which was f***ing with the temp sensor.

How is your coolant? Are you running straight water? Antifreeze actually raises the boiling point of the water so if you do 30-70 mix or even 40-60 since you're in the desert, it may raise the boiling temp a bit. The very, VERY worst case would be a blown headgasket but that will have other symptoms such as white-ish smoke from the exhaust with a sweet aroma, and the coolant will get mixed with some oil and become murky/milky. Is your coolant cap clean?

Also, try to get a logger or something and monitor the coolant temps from a cold start to fully warmed up and then do a few good pulls to see how high it will go.

 

[AWD-Tony]

Yup, sounds like you have air in the system, or you're getting air in the system. I'd try getting the air out first. If it returns, you have a leak somewhere. If you don't see any external leaks, time to check heater core or headgasket.

 

[Velmin hu]

I use 50/50 antifreeze the thermostat stays normal only once or twice when up a bit past normal then drop down.

 

[Kai Hefner]

Bubbling noises near thermostat housing is an improperly bled cooling system. I ran my car with the same problem for a few weeks. I had the exact same symptoms where the temp gauge when up a bit, then dropped down a lot. I also use 50/50.

1. Jack up the car.
2. Top it off with coolant. Leave the rad cap off.
3. Turn on the car, with the heat turned to max and the fans blasting.
4. Squeeze the lower rad hose a bit. You will see the bubbles coming up.
5. Let the car get up to temp while continually topping off the coolant.

Now you shouldn't have any bubbling sounds unless it's some other issue. If you think your hoses are cracked, replace them. These lines have some decent pressure going through them. I had a coolant line blow up on me a few days ago (I'm guessing because it was cracked), and it's no fun to deal with it on the side of the road or get a tow (if you're interested, that little story is on my Talon's build profile).

 

[AWD-Tony]

+1

Definitely air in the system. You'll want to let it idle with the cap off until the radiator fan turns on. This ensures that your thermostat has opened.

 

[Kai Hefner]

Not sure if you want to hear the explanation of the problem but I'm pretty sure what happens is that the air bubbles are messing with your thermostat and giving it a weird reading. That's why the temp goes a bit above normal, but then settles back down as it gets the correct temperature reading and opens.
This explanation is just guessing, but it's mainly because I used to not know how to bleed coolant properly, and had a much worse case of the temperature surging. Then I just added coolant (didn't do the proper bleed procedure) had the same moderate case as you do.

 

[motomattx]

You can pull your thermostat and leave the car sit overnight with the cap off, that generally does a good job of bleeding the air out.

 

[JeffwithaG]

I would bleed the system and possibly think about picking up a new radiator cap. I picked one up on Amazon for like $4.

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