Valve and piston question

[jan_mast]

I have an 08 Cobalt LS that is having engine problems. I have had a cylinder #1 misfires code popping for awhile. I replaced the spark plugs and the coil pack for #1 cylinder, no joy. My local mechanic (Guam) insisted that we replace all the other 3 coil packs. Surprise...surprise... the fault remained. I eventually got sick of the local guy and took it to the GM dealer. The performed a compression test and determinded that #1 cylinder is losing compression. They want me to pay more to tear down the engine and inspect that cylinder.

After doing a ton of reading it seems to me that the valves could be bent or fouled, the piston ring broken, or the head gasket failed. I dont believe it is too difficult to tear down the engine to inspect the pistons and valves.

My question is how difficult is it to replace a valve or the piston ring? Is there a book that someone could reccomend to guide me through this? I dont have the $3,000 that the dealer is saying it would cost me for that type of repair. Thanks all in advance!

 

[YelloEye]

If you can handle basic hand tools and a torque wrench, you can tear down the motor.

Did they do a leak down test as well? Same as a compression test but they add oil into the cylinders to see if it's the rings or one of the other things you listed.

Is there coolant in your oil or oil in your coolant? If not your head gasket is probably fine.

Valves might be bent, hard to do though unless you over reved the motor bad.

In so far as a book to follow, you should check out the GM Service books. It's a set of 3 that cover everything on your car. Little pricey but worth it if you're going to dig this far into the motor. CED has all the parts you need, alternatively you can use RockAuto, they're a sponsor here.

In any case, I hope you have another vehicle in the mean time while this one is down. I'd say it's a weekend or two of work.

 

[jan_mast]

I dont think they did a leak test, but others have told me that if i do tear the engine down myself, i should probably replace the head gasket and head bolts anyways.

I have been looking at the set of GM service manuals, but hesitated because they are pretty pricey. Also i didnt know if they would guide me through this type of more advanced repair. Do you know if any special tools would be required for valve/piston work? I am going to go ahead and order the manuals,, it sucks that it takes about two weeks to get anything in the mail to Guam.

Thanks for the reply, much appreciated!

 

[YelloEye]

Those service books allow you to take the whole car apart and put it together again in another country if you wanted to

 

[jan_mast]

Do you have any experience with this type of repair?

 

[YelloEye]

Not with this motor.

 

[jan_mast]

So i pulled of teh head today and inspected the cylinders and valves. It looks like the intake valves are burnt. I wish i could post a picture on here.

So my plan is to replace the intake and exhaust valves in the #1 cylinder. My question is this: is there no website that sells a valve kit? Meaning the valve and all teh associated hardware? Thanks man!

 

[YelloEye]

Crate Engine Depot for sure has the parts and in sure they'd be willing to bundle it together. Valves appearing burnt is pretty normal, it isn't called the combustion chamber for nothing.

You should clean everything up before deciding if they need replaced. As long as they seal correctly there shouldn't be a problem.

 

[jan_mast]

I had an experienced guy with me. The valve isnt seating right because its charred around the edge. I wish i could put up a picture. Only teh valves in #1 cylinder looked like that.