I recently aquired an '81 wagon that was overheating. It would get hot and stay hot, not matter what- idling, highway, etc. I started by testing the t-stat, which was bad. I hooked the cooling system back up without a tstat, and ran it for a little while to see if it would still overheat. I got lots and lots of small bubbles in the coolant- enough for it to get foamy. Head gaskets were my first thought with all of thoes bubbles, so I ran a block test on it for combustion gases, which turned out negative. However, I'm not sure how good the block tester is- it's the $40 Napa variety with blue test fluid. As the coolant was foaming, the car started getting hot again, so I shut her down (total running time was 5-10 minutes).

 

All in all, the bubbles displaced about 1 quart of coolant. The gar doesn't have any other signs of HG failure- no crap in the oil, no white smoke, not losing coolant, etc, and it wasn't making foam until I messed with the tstat. Could it just be air stuck in the coolant system? As of now my plan is to put the new tstat in, flush the coolant system really well to make sure nothing is plugged, and to run a compression test, is there anything else I can do to track down the problem?

 

Thanks in advance!

I would probably flush the ENTIRE system out thourghly, including the block (special bolts for that). That is my best recommendation, after that, HG time

I'd say it will be the headgasket, often the only symptoms are bubbling coolant and overheating...

yeh just because you dont have coolent in your oil doesnot mean its not head gasket becuase all the oil passages may still be holding but just a coolent passage has blew its gasket between it and the cyclinder allowing air into the coolent system, explainin the bubles. Yeh a compression test would tell you which head has let go. Also if its the orriginal radiator it probaly 1/3 full of mud and all crusted up. But what ever you do dont use any stop leak or similar treatment as this will probaly not even work and will make your problem worse in the long run.

Pretty much what I was thinking, thanks. Hmmm....I have visions of what my weekend is going to look like...