Help diagnose weird cooking issue

Don Evans

New Member
Dec 23, 2019
9
Hey big daddy, throwing this out there. Way back in the late 70's I built my first small block and had a over heating issue, shut it down immediately, didn't want to damage it, plus money was tight. Reached out to one of the old timer mechanics and was told about an air pocket under the T-Stat, and was told to drill a 1/8" hole at the T-Stat plate and reinstall, that it would allow the trapped air to get past. Have built numerous engines for myself, friends air boats and family trucks in 40 years and have always drilled a hole on the T-Stat plate and have never had another issue with air pocket. Now I'm the old timer? Lol.
Hope that helps you or someone else and get your issues worked out.
Just saw the post were you had drilled a hole for air to get by.
My phone didn't let me see that post, so I got into it in the middle. Lol.
 

Cardinal

Veteran Member
Lifetime Gold Member
Jun 22, 2003
8,342
Endicott, NY
Pressure check the coolant system and test the radiator cap. Auto Zone and Advance Auto can loan you the coolant system tester.

Assuming the coolant system has no leaks and the cap tests good, buy a new Robert Shaw 180 degree thermostat and test it by putting it in a pan of cool water with a thermometer and slowly bring it to a boil. DO NOT DRILL HOLES IN IN THE THERMOSTAT! It already has a bypass built into it!

Install the new tested thermostat.

IMHO, fill the system with water because if there is still a problem, youre not going to lose expensive antifreeze. And antifreeze is TOXIC to the environment.
 

Misfire

Member
Jan 27, 2007
51
Doraville
If a 170 degF is all it got to, that wont hurt a thing, coolant does expand when gets hot, why they make expansion tanks for cars, put new thermostat in, you can top off the coolant thru intake before installing thermostat, then you know block is full.
 

turbobuick

Veteran Member
Nov 24, 2018
206
Just put everything back together. Going to let the rtv sealant cute and will start it up tomorrow. Will keep you guys updated thanks for the advice!!!’
 

turbobuick

Veteran Member
Nov 24, 2018
206
Update:
Filled up intake to right below T-stat with coolant. Installed 160 T stat. Started and let it warm up. Stat opened up right at 160 by feeling upper rad hose. Around 180 a tiny spit came out of overflow and stopped. Engine got up to 190 and electric fans kicked on and brought it back down to 160 real quick. Everything seems fine. I’m thinking it was a combination of overfilled system and an air bubble. Thanks for the info guys!!!!
 

Big Block Z

New Member
Jan 20, 2013
17
Phoenix,AZ
Hey big daddy, throwing this out there. Way back in the late 70's I built my first small block and had a over heating issue, shut it down immediately, didn't want to damage it, plus money was tight. Reached out to one of the old timer mechanics and was told about an air pocket under the T-Stat, and was told to drill a 1/8" hole at the T-Stat plate and reinstall, that it would allow the trapped air to get past. Have built numerous engines for myself, friends air boats and family trucks in 40 years and have always drilled a hole on the T-Stat plate and have never had another issue with air pocket. Now I'm the old timer? Lol.
Hope that helps you or someone else and get your issues worked out.
I learned that trick from an " old timer " when I was young also . I too , still do it to this very day . I also " pinch " the Radiator Hose while filling with Coolant to encourage the air to escape .
I too , am the Old Timer now !
LOL
 




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