Guys,

DIY stage 3 cammed C7 GS here.

I noticed my car spitting coolant out of the overflow tank after shutting it off hot several times lately.

Car does not seem to overheat...coolant around 195F when driving, oil around 215-220F. My last AutoX by 100F saw coolant temp at 230F oil 250F on the last run of the day, but AutoX is bad for that : low speeds and shutting down the car fast and no cooling time...

I noticed that after 185F coolant temp my radiator hoses are hard... They are soft before those coolant temps.

On my 17SS 1LE my coolant hose are soft at the same temperature...I did manage to make it go to 200F and hoses started to harden, but the fan kicked on and went soft again.

I never checked before if my hoses were hard. I bought a exhaust gas in coolant test kit and did several tests and it came negative...because I thought I could have a cracked head (tsp ported) or a head gasket issue.... I noticed the tank overflowing around 185F though.
I know water expand 4% before boiling but at 185F level should not raise this much no ? Though I know water is way hotter than 185F inside the block at certain spots...vapor pockets ?

My question : are your coolant hoses hard all the time when your car is above 185F coolant temp ?

My car take ages to heat, like if my thermostat is stuck open. I just ordered a new one... My camaro goes to 170F in less than 2 min. My C7 takes like 5-7 min driving at least.

Thanks for your help.

 

First thing I am thinking is the thermostat. If you change it, replace your hoses also while you have it apart. Too soft or too hard hoses is not good. Think Goldilocks. Firm is good. Even consider looking at silicone hose if the price doesn't raise your ire. They last forever.

 

When was the last time you changed and flushed engine coolant. Are you using Dexcool or other? Heat kills!

 

I flushed everything when I did my cam. Did not use GM Dexcool coolant though, bought Prestone Coolant at Walmart. I don't see coolant type having a hugue impact on temps...

 

Let me rephrase. When I said soft or hard it is related to the pressure in the coolant circuit.

 

So guys... Hard hose or soft hoses in the 195F-200F temps on yours ?

 

You need to bleed the coolant system properly, if that doesn't work or you think its bled correctly. Compare the inner and outlet temperatures, your thermo might be stuck.

 

There is no bleeding procedure for LT1 ...I have the tech manual and could not find anything about bleeding the system...

Replaced the thermostat tonight. Installing my DSX Flex fuel kit as well. Hopefully will restart the car this week end.

 

 

That kit works wonders, also make sure the bleeder on the thermostat was positioned at the 12 o'clock mark. You fill the reservoir reach the lower hose and squeeze to help push air out, refill, repeat a few times, repeat but squeeze upper.

The kit above is sold at autozone or advanced, they're cheap. After you do the above procedure, leave that filler installed and fire it up, let it reach temp. You should see it bubbling, if it starts to boil, insert the stop on the funnel remove, install the OEM fill cap and then shut the car off. You will see coolant pour out of the overflow slightly.

Since you did do the thermostat, it could've just been stuck and causing you those issues.

 

Still have the same issue after replacing the thermostat.

I'm wondering if my surge tank does not have an issue...may replace surge tank and cap to be sure...