Northstar Engines and System Technical Discussion Discussion, headgasket repairs in Cadillac Engine Technical Discussion; 97 deville with 105k miles. runs perfectly. i am losing coolant. one caddy dealership had the car running all day ...
97 deville with 105k miles. runs perfectly. i am losing coolant. one caddy dealership had the car running all day and could not find any leaks or coolant loss. so it seems to only lose it going down the road. yes i do suspect headgasket letting combustion pressures into the cooling system and forcing coolant out through over-pressurising the coolant system. am about to put it into another dealership for the big tests (co, hydrocarbon in expansion tank, compression tests) we know that the headgasket replacement is very expensive. but my question is this. i am torn to put so much money into a simgle factor fix, ie: not a rebuild, with the chances of the other head going at anytime. what are the prices of a single headgasket repair as compared of doing both gaskets while the engine is out of the car? also, what kind of warrenty can i expect from the repairs?
btw: thanks to this forum for so much excellent information.
Automobile(s): White Diamond '03 DHS (with DTS floor shift)
Re: headgasket repairs
I am not sure about the prices but once the engine is out I think it would be a big gamble (and mistake) not to do both of them. Remember, the other side was under the same conditions as the one that failed. What ever you do, insist that all the head bolt holes be timeserted or you'll be doing this again in 10k-20K. There is someone on this or another board that had his done and it failed again in 16K. I suspect the dealer did not timesert. It obviously will cost more, but not as much as doing it again.
To expand a little more, they should use TIMESERTS, not helicoils. No matter what they say about helicoils, insist on timeserts.
You may not have anything to worry about with head gaskets, though. The cooling system won't be "overpressurized" by combustion gases. That's what the spring-loaded cap is for on the pressure tank. They're rated for specific pressures, which I think is 15 PSI on Northstars. If it exceeds 15, the excess blows out the overflow tube. They should be checking for combustion gases in the coolant and pressure-testing the cylinders. It's very possible you have one of the infamous water pump seal leaks. I don't know when the leaking occurs, but there was always a puddle in my garage after it had been sitting a while. Once the pressure dropped, it probably stopped leaking. I could never catch it leaking while it was running. So check the area under the water pump cover and pulley. If it's a water pump seal, replace it with an OEM pump. I've heard multiple stories about aftermarket pumps not fitting right and leaking after only a few thousand miles.
big myistery with the engine. waiting on my bronco's transmission before i get in the dealership. i'll still have pressure in the morning at the surge tank??? didn't leak a drop all day at the dealership (they didn't charge me). my theory is that up to running highway rpm's, the gasket (head) is letting combustion pressure into the coolant passages and overcoming the 15 psi, causing fluid to blow. been the barsleak route, no noticable difference, know that if i run it hard, the coolant loss is faster. i can do about 150 miles before the coolant loss affects my cooling capacity.
I suspected head gasket for about a year until the pin hole I had in the top hose finally became a big hole. Since I changed the top hose I have not lost a drop. I was losing about a gallon every five hundred miles.