: Is my head gasket blown 94 cadillac sedan deville????

08-24-12, 09:30 PM
Im not sure if the head gasket is blown. It overheats at freeway speeds and I can drive it in city traffic for about 25 min before over heating. Then coolant bubbles out of the radiator. And today i saw a small pubble of oil on the top of the engine towards the back of the engine. No pressure test yet.

08-25-12, 12:14 AM
The 4.9L does not have head gasket problems like the 4.6 N*. Here is what you need to do. Check the tube from your radiator neck to the OVERFLOW tank, make sure it isn't plugged. Check the radiator cap, the seals should look clean and have no cracks. If the coolant bubbles out of the radiator, that tells me the hose to the reservoir is either plugged or disconnected. When you check the cooling system COLD, where is the coolant level in the radiator? What condition is the coolant in your radiator? When was the last time it was flushed or the coolant was changed? Was does the outside of the core look like? Have you cleaned or blown off the bugs and debris from the outside of the radiator core? Have you ever changed the thermostat? Check all of these things and post back what you find.

08-25-12, 10:44 AM
Also a combustion gass check of the coolant will tell alot....but do all dennis reccomends first. He has it covered very well.

08-25-12, 09:29 PM
thanks for replying... the tube to the overflowtank is clear and coolant flows. I flushed it maybe 1.5 yrs ago. Have to look at core and thermas changed when it was flushed.

08-25-12, 10:14 PM
coolant is at the cold fill line when it is cold but it was using alot a coolant for a while but then it stopped. Coolant is green no mixing. core was clear of debris.

08-26-12, 02:13 PM
You might want to rent a block test kit from the parts store. Rent the tool, buy the test fluid. At least if you think there is a chance you have a blown gasket, you can rule one way or the other. If it is just overheating, there is a chance the impellor on the water pump is bad. Any thing is possible. If you think the impellor is bad, take the thermostat out and put the neck back on, fill with coolant and run engine. You should be able to see flow in the radiator with engine running and cap off.