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Buick Rescue - 1999 Park Avenue 3800 - Blown Head Gasket

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Another effort to try to rescue another Buick. I ran across a 1999 Park Avenue which has been diagnosed with a blown head gasket. The owner says he was driving it on the highway and heard a weird noise coming from the engine then it stopped running. He had it towed to a mechanic, who took a compression reading and said 3 of the 6 cylinders had very low compression, indicating a blown head gasket. He gave an estimate of $1,500 to fix. Obviously, the owner does not want to spend that much money on a 1999 Buick. So, the question is, how much effort is it to change a head gasket on a 3800 engine and is this something you would consider doing yourself? I am not a professional mechanic but I have changed head gaskets on older V-8 engines, so I could be up to the challenge, depending on your opinions. If I did it, I would only charge the owner a minimum amount, just to get the car back on the road again. He is a friend of mine, too. What do you think?

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There is a lot more wiring on top of a new 3800 compared to an older V8. The intake comes off in 2 pieces, an upper plenum, and the lower intake that bolts to the heads. That and the head near the firewall can be fun to get off. Otherwise, not too difficult of a job. There will be some extra plastic L connectors for the coolant lines that you'll want to replace. Also, be sure the head gasket kit you buy has the upgraded intake gaskets. The factory ones were less than par. Follow torque specs and I imagine you'll be fine. My suggestion if you feel this is a bit out of your wheelhouse is to take pictures and label wires.

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Are you just planning to change the gaskets without a machine shop checking the heads? That part right there is a few hundred. And obviously it's best to do both sides, not just the blown side.

Personally I would invest the time in a new compression test. In order for all three cylinders on one side to go at one time may mean a cracked head or some other damage. And for that type of damage I suspect something is damaged within the cooling system causing a major overheat. If a compression test comes up good, then I would just change the intake gasket and call it a day, or maybe two days, or maybe a week if, like me , you can't find where that one last wire goes.

Also if you try this, I recommend cutting the wire to the one sensor under the throttle body. That sensor did not want to budge on my 95 Riviera. I finally cut the wire back in the plastic harness shroud, so the repair would not be visible. Is this vehicle Supercharged?

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This can be a HUGE can of worms! A compression test only shows cylinder pressure in each cylinder. If it/they are low, there can be SEVERAL reasons other than a blown head gasket! The fact that all three low cylinders are on one side might be a coinkedink, too. Problem is that until the head(s) come off, there's not much to do except speculate.

IF the engine got "that hot", then just changing the head gaskets is not going to really fix it, I suspect. As mentioned, re-flattening the heads' gasket surface is just one thing. Doing a complete coolant system flush is another. NOT to forget putting a new timing chain set in, for good measure.

IF the engine got "that hot", then the oil rings and compression rings could have lost their tension, rendering them somewhat useless (with lowered compression test readings, too).

This whole deal could very easily be one where if you open it up, then everything you touch will need to be replaced/rebuilt. I'd vote for more "deeper" diagnosis before surgery.

Just some thoughts . . .

NTX5467

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From our Reatta experience, it is very unusual for a 3800 to have a head gasket problem. I agree with Willis..... more test need to be run.

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