Hunting Thermostat

[DAVID GAGNARD]

Originally Posted by KirkV

Ok guy's,

So I too thought a 3/8" hole seemed a little large, what is the correct size hole, or holes that should be there? I do not have a thermostat bypass hose and need some help there.

I can get the engine up a slope and verify all of the air is out of the system though and will try to do it soon. I take it you think the pump may be cavitating?

The overflow sump is there and it has a 16 pound radiator cap I believe that would blow to it if it were to blow.

I will try to verify all the air is bled out before going too much further.

1/8th inch hole is the correct size and I like to drill 4 in the thermo flange, just make sure one of them is at 12:00 high when you re-install the thermostat, you'll need this more so since you do not have the bypass hose......I don't have the bypass hose on my race car (331 cu in) and have 4, 1/8th holes and have had no problems at all........
It's not unusual to have air pockets and I've had to run the engine up to temp and then let it cool down, doing this 3 or 4 times to get all the air out of the system....
Drill 4 holes in an X pattern,re-install the thermostat, fill radiator and crank it up and let it come up to temp with the radiator cap off and add water as needed to fill it as the thermostat opens and water is circulating,once full let it cool down, check your fluid level and put the cap on and take it for a drive, let it sit overnight and re-check the fluid level. by then the air should be purged and everything should be fine.......
If all is working as designed, your temp will come up and when your thermostat opens, you should see a drop in temp as the cooler water goes thru the engine and cools it down some, then after a few minutes of running, it should come up to operating temp and stay there, maybe you'll see a 5 to 10 degree swing bewteen highway driving and city driving, but that should be about the max..

David