New motor overheating!!!

[DRJDVM's '69]

Well I got the new 434 running but I'm having overheating issues.....

The car runs good, but it quickly gets uo to 180 and the steadily climbs from there. Idling in the garage it slowly goes up to 220+ and then if I take it out it goes up to 250 real quick...it started puking coolant out around the cap.

I'm using the same rad and dual spal fans I had before, same waterpump, same cap, new t-stat and new coolant..never had an issue before.

I left one of the top plugs out of the intake, filled the coolant until coolant came up to the hole in the intake. I figured that was the best way to get any air out. Then put the plug in and filled the rest of the way.

When the car is running, the upper hose gets warm but not very tight... I can collapse it with pretty easy pressure. The lower hose has a spring, so its not collapsing....

Once I stop the car and take the cap off, it doesnt seem like there is any pressure. If I take it off when the car is running the coolant flow out the neck.

Does that sound like a rad cap issue ??? The fact that the upper hose doesnt seem to be tight, leads me to believe I'm not getting any pressure in the system....

I cant find any leaks (anymore at least... I had one at the waterneck and then one at a sensor, but those are leak free now)

[69bird]

Sounds like it might be the t-stat what temp are you running? Do you have a high flow water pump? Is the t-stat a high flow? Try putting the t-stat in hot water and see if it opens and at what temp.

[DRJDVM's '69]

I borrows a friends cooling system tester..

Pump up the system to 14 PSI and it holds steady.... no leaks..

Pump up the cap to 15 PSI and it slowly starts to drop.....

It should hold, except about a pressure of 15 or so, right ??

The t-stat is new, but you know how that goes...... the fact that the top hose gets warm tells me the t-stat is opening...right??

[DHARROD]

Have you verified you have "flow"; that the water pump is in fact circulating the water (i.e. take cap off, fill radiator full, leave cap off, start - you should see water movement once your thermostat opens). If you don't trust your thermostat no harm it removing it for awhile - then you should see immediate flow and this time of year the car should stay at/below 165-175 for a long time. If your wife/you have a probe style thermometer (like one used to poke into a turkey) you can stick that in the actual radiator webbing to get a temp at the radiator (allows you not to have to run back and forth looking at your gauge)

[MarkM66]

I'd also suggest drilling a couple small holes in the outside ring of the thermostat.

[DRJDVM's '69]

I did drill a small hole in the thermostat....it actually had one, but I drilled it alittle bigger.

With the car running, if I take the cap off the coolant flows up and out the neck and runs everywhere. With the car off it just sits at the top of the neck.

I'm gonna put a new cap on and see what happens.

[DRJDVM's '69]

New cap....no change..

Yanked the brand new Mr Gasket thermostat....problem gone...... it doesnt overheat and the upper hose has some pressure in it now....

[Blown353]

New cap....no change..

Yanked the brand new Mr Gasket thermostat....problem gone...... it doesnt overheat and the upper hose has some pressure in it now....

Probably a stuck/defective thermostat. It happens sometimes.

Put some boiling water on the stove and lower the thermstat into it; if it doesn't open, you have found your culprit.

[andrew5]

i just put a 454 in my chevelle.ran at 185,190 for the first 5 or 6 test runs.then it overheated.it was the brand new mr gasket t-stat as well.took it out and it was stuck closed.put in a gm one and had no problems since.

[DRJDVM's '69]

Yeah I boiled the crap out of it...it didnt open....POS....

[Blown353]

So did a new thermostat fix the problem?

I know it sounds paranoid, but before I put a thermostat in anything I always dunk it in boiling water. I'd rather take the 5 minutes to test it than have to drain & refill the cooling system again after having to change a defective thermostat!

[DRJDVM's '69]

With no thermostst it runs 150-170 no problem.

I'm gonna get another thermostat (not a Mr Gasket) soon since I dont want it running that cool, but it will work for now....... I think I'm gonna pre-test this one first :)

[MtotheIKEo]

I had a MR.Gasket thermostat that would stick closed also. I don't think Ill buy another one from them again.