95 base model LT-1 - How can you tell if a head gasket is bad or if an over heating problem is cracked head?

 

leak down test or pressure test your radiator. auto stores will loan you some of the tools. hope for a gasket most likely but no way to tell that I know of till you get them off.

 

Usually the head gasket will go before cracking a head. You really have to heat things up to crack a head. The aluminum head on the LT's can be welded if it is cracked in a good spot. If things are VERY BAD....you will find coolant in the oil and/or oil in the coolant.

Most gaskets will give out on the rear cylinders #7 or #8. My 85 and 95 have both blown in this area. I think it is because the passageway for the waterjacket is so very close to the cylinder wall on these two cylinders. Quickest way is to pull the plugs. If one plug looks very clean....ceramic .....then you are spraying coolant into the cylinder. You will also be experiencing a coolant loss with no visible leaks. You might also notice more white smoke out the exhausts or smell the sweet coolant smell at the exhaust.

Here is the gasket from my 95 about 2 months ago now.....#7 cylinder....



It took me awhile to pull the heads on the 95 working a couple of hours each day when I got home from work. The biggest issue was trying to get to the bottom row of bolts at the rear of the head. Once I pulled off the pipe screwed into the passenger side exhaust manifold, that gave me the clearance needed. My suggestion if your going to do this yourself is to mix up a very small about of 50% acetone and 50% automatic transmission fluid and use a small brush to put this on the threads of the pipe that screws into the exhaust manifold (in the center of the manifold top side). Do this a couple of times over a couple of days. This combination is the best out there to looses stuck and rusted threads. It is sure needed on this!

 

Thank you Sir. I found at least part of the problem, but, won't know how extensive till I get the head off. The #4 cylinder exhaust rocker bolt was broken off at the base when I opened the valve cover. The pushrod is not at all bent or marred. The engine overheated to >270 on probably 5 occasions and each reattempt to correct, did not. Plugs look fine, stat working, I put in a new DeWitt Radiator, added Wetter Water, found heater core leaking/I bypassed, vented repeatedly. Must have been other than the broken rocker that's caused overheating as it only ran rough the last time it dumped antifreeze on roadway. If it got hot enough to weaken case-hardened bolt, it's got to be a warped or cracked head. Thanks again, BJ

 

Leak down/pressure test will only pick it up if the gasket's totally blown out. Do a combustion leak test (see my signature or get a Block Tester from NAPA auto parts) for a definitive test of head gasket failure. Fix the rocker, run a block test, and maybe you'll get lucky and not have to pull the head.