Thread: Overheated, Low Compression Cyl #3

Hi guys,

Recently my Gran Prix 3.8 Na overheated due to a radiator hole and loss of water. I replaced the radiator and restarted. Started fine but it was shaking more than usual and indicated a misfire on cyl #3 (ses flashed, scanned it). I did a dry compression test and got 180 psi in all except cyl 3 which got 65 psi and cyl 4 got 120. I was planning on removing the heads to inspect the pistons and replace the head gasket.

1. Any other things i should do while I am there?

2. I replaced the UIM/LIM in 2007 with the GM aluminum one, should I replace it again? Car was driven only 20k miles in those 4 years.

3. How hard is to take the rear exhaust manifold with the engine in the car?

4. Should I go change the rear head gasket or just change the front one?

5. Where do these metal shavings inside my cooling system come from? My thermostat and housing (pictured) were covered in what appears to be iron shavings. I know the were a result of the overheat because they were not there a month ago. They came off easily with water(they were not baked on).



Thanks.

Overheatign usually has little effect on these motors. Especially if it easn't an extended brutal beating overheat.

I'd try plug/plug wire/coil first and ensure that the compression test was accurate. I've seen some goofy compression readings without other issues ...typically because our valves like to carbon up.

IMHO…

1) Replace both coolant elbows, get rid of the Dexcool if you haven’t already.

2) no

4) I’d just do the front.