Grand Prix 3800 motor toasted?

[Cat Fuzz]

Hey there,

One of my customers has a 97 Grand Prix 3800 with about 125,000 miles on it. He called me and said the new starter he put in just clicks. When I got there, the starter is actually trying to turn the engine over, but its not going. I put a socket on the lower crank pulley and it turned for awhile, then it stopped, then after messing with it, it will turn now. I randomly pulled the spark plug on #3 and it was covered in oil and the top of the piston is oily as well. I pulled #5 plug and it was gassy. The car ran fine before with no smoking. We finally got the car to where it will crank but it won't run and it backfired out the throttle body. I'm thinking I have a timing chain that slipped? It's not broken, because I can see the rocker arms moving on the front side through the oil filler. Is this an interference engine? If so, the thing is probably toasted, eh? I'm thinking there's a busted or bent valve that has finally moved out of the way.

Any help would be great.

Oh, yeah, the old starters nose cone was busted clean off. I found a post somewhere else about that but I figured someone hit the starter with the engine running.

[BNaylor]

You might consider running a compression test. You could have blown head gasket or lower intake gaskets. If the timing chain slipped you would not see the valvetrain move. On the starter when the car is running the starter is supposed to be inhibited from engaging. It sounds like you may need to do some disassembly like removing the timing chain cover and valve covers for further inspection. Doesn't sound good. Good luck.

[troy1]

If the chain just jumped the valve train would still work. If its broke it wouldn't

[BNaylor]

Are we referring to slipping or jumping?

If the chain jumps off either the cam sprocket or crank sprocket I seriously doubt the valvetrain would be working unless the camshaft is being driven. I've never seen one simply slip which means it would be off a tooth or more. When a timing chain goes on a SII 3800 or any car for that matter you will know it.

And if the timing is off it will be due to sprocket and chain wear, excessive slop/backlash.

[Mickey#1]

It sounds like another case of intake manifold/gasket failure. Engine coolant leaks into the combustion chamber & hydrolocks the engine. I'd drain the coolant, replace all the spark plugs then try starting. It would be great if you could check the engine compression while the plugs are out. Report back with what you find.

PS - Don't run for more than about 15 seconds without coolant!

[troy1]

I was thinking that he thougth it just jumped a tooth and has not broke or came off the sprocket

[Cat Fuzz]

Originally Posted by troy1

I was thinking that he thougth it just jumped a tooth and has not broke or came off the sprocket

That is what I was thinking.

[Cat Fuzz]

The back fire out the intake is what has me wondering about the timing chain. The somewhat large amount of oil in #3 cylinder has me wondering. And I couldn't hand turn the motor before and the starter wouldn't turn it, but I can and the starter turns the engine now.

[richtazz]

Pull the plugs and look for coolant in the cylinders. I think Mickey is on to something with the hydrolocked theory. If the coolant was low when you got it, it's VERY possible that the intake plenum leaked coolant in to a cylinder hydrolocking it, and that's what broke the starter nosecone. Coolant doesn't compress like air, so when the motor hits the compression stroke on a cylinder with coolant in it, it stops turning abruptly, and the starter breaks. It is very rare for a timing chain to jump a tooth and not come off or break, so it's unlikely jumped timing is the cause.

[BNaylor]

The solution as to diagnosis is simple. I repeat compression test and if that doesn't work or tell anything which I doubt in this case then a teardown is in order. Start dismantling. Remove the timing chain cover and check cam/crank timing. Remove valve covers. And in a worse case remove the intake manifolds and if necessary, cylinder heads.