vinny R

I had a problem this weekend when I got home my coolant was bubbling back into the res. tank. It was 3/4 filled. From what I can tell the temp was 220 when I shut the car off. After a few minutes of checking for leaks and such I started the car up and the bubbling stopped. The coolant in the res. started going down, back into the radiator. I also noticed that before I started the car the temp gauge was pegged. The temp immediately started to come back down to around 210. I let the car run for a few minutes and it did not bubble back and the coolant all went back into the radiator. Any Ideas?

tealman92

Replace your radiator cap

Pennieslogo

I had that problem you will have to put a pressure tester on the rad you probably have pressure leaking back into the violent jacket either a head gasket or cracked block I suggest to stop driving it thenwater pump will seize for sure and the head gasket will go completely
This engine is done

vinny R

I took off my cap and there was some crud (calcium deposit) under that rubber seal I cleaned it all up put it back and drove 5 miles and got it up to 220 shut it off and it was fine. I will get a new cap anyway. I hope this is it.

vinny R

I sure hope this is not the case! There are no signs of head gasket or block. Oil is clean, coolant is clean and green and no smoke from the tail pipe. I have a very slow drip from my heater core so if I pressure test it will leak down.

Pennieslogo

I had the same problem nothing indicated head gasket so we could only assume it was a crack in the block the engine still runs but it would still over heat at some time and do the same thing once an engine has got that hot your water pump is fried and the longer you run it sooner or later it will quit a compression test on your rad will show the amount of pressure blowing to your rad through the jacket
It's up to you what you do but I was just in the same situation this spring and as it was a
305 ho I shut her down and pulled her out replaced with an350 crate engine
Good luck my friend

tealman92

Gm made the thirdgen run hot. So the caps and plastic parts in the system tend to take all the abuse. Radiator caps and heater control valves and heater cores are the problem areas. Id your running hot put in a lower temp thermostat and make sure the front of your radiator is clean of debris. Also take a look at the air dam under the car and make sure its in good shape as well. Check your fan as well. Stock these cars run at 220. Im running at 180 all day with the air on and 90+ temps out

vinny R

Thanks. I already know I have a small leak in my heater core so that could be it right there. I was also wondering about that heater control valve and if that could have something to do with it. I am not real sure how this works but I know it somehow stops water flow to the core. My core drips even if the heater is off so that thing maybe is not working? I also found a coolant gas test strip kit at Napa. I think I am going to get one of those (along with the new cap) as it is under $20 so I can find out for sure if I have a HG or Block issue.

vinny R

Just wanted to give an update on this. I think I found the problem, the t-stat housing was leaking. When I removed the housing I decided to check the t-stat( it is about 1 yr old) and found it was not working. Something broke on the center shaft an it was barely opening. It was one from one of the discount places so not sure the brand. I purchased one of those high flow t-stats from a "better" parts house along with a new gasket and upper hose, my upper hose was swollen from the high temps. Put it back together, drove it for about 20 minutes and it was perfect! put a 180 t-stat in and it ran @ that temp with and without the a/c on and idling in drive. My temp gauge did not spike after shut off either. I did not get the test strips as I believe if it was a exhaust gas pushing into the coolant it would continue to bubble in the tank and the fact that the car runs at the temp it should now. Thanks for all the advice with this.

paulo57509

Thanks for closing the loop on this. Glad you found the problem.