'02 Buick Century Revisited

My wife swapped cars with my daughter last night. By the way, this was about poor shifting and bogging. Revs high before shifting.

I think the guys with the cat answer and brokenwrench were right. I put my code reader on this morning and got P0404 and P0420. Egr and Cat efficiency. I noticed what looks like glycol under the front drivers side on the starter mount. Looks like it's coming from the end of the front manifold. Couldn't realy see that well.

Opinions are welcome.

Hey CH,

If it"s a car you plan on keeping and driving, I would get the antifreeze issue resolved before replacing the cat.

Cats are expensive enough, you don"t want to kill another one.

02 should have the latest design head gaskets, so it may just be an intake leak. If it looks at all like a head gasket leak, I"d do the whole shebang at once. If you have the intake off, you"re half way there.

I can"t remember for sure how it goes, but I think you want to go aftermarket on the gaskets and get the better metal gaskets for the intake.

Good luck BW

If it has the 3800 series motor, it's more than likely the plastic plenum on top of the intake. The coolant passage thats in the intake to the plenum will rub a hole in the plenum and causing an external or internal leak. The head gaskets are usually not an issue on the 3100, 3400 or 3800 series engines unless it has been run hot. My opinion is to fix the coolant leak first before anything else. It's a good possibility the EGR could be plugged with debris. Secondly, I'd get a temp check done on the CAT before you replace it. A temp check will determine if the CAT is bad or not.

It's a 3100. I would like to run it a couple more years until my daughter's out of college and hopefully out of my pocket. That will probably never happen.

Do you have to remove the front engine mounts to get the valve cover, exhause manifold and head off if I just do the front? I do have the Hayse manual for it but didn't notice that part.

I plan on doing it myself. Money isn't so much the problem as time. I definately don't think it's worth paying someone 2-3K to do the work.

Thanks guys.

K. Daddy is right. I would have the cat checked out before doing anything. We"re kindof making alot of assumptions right now.

If you have a good shop in your area, I would have them diagnose it and give you an estimate for the repair. Even if you don"t have it fixed there, and they charge for the diagnosis, you will be money and time ahead.

Otherwise, you could be anywhere from intake gaskets to head gaskets to EGR problem to cat converter problem. Even doing it yourself, you"d spend a ton in parts if your not sure how far you have to go.

If it does lead into head gaskets, I"d do em both and have the heads checked and plained. At that point, yes you do have to pull the dog bones off the front and the manifolds have to come off. Not as bad as it looks though, once you have the dog bones off, with a come along and alittle inginuity you can rock the motor ahead and give yourself alot more room on the back side.

That said, I"m not saying that has to happen, just answering your question.

My swag would be that you have a lower intake gasket leaking both internally and externally. The antifreeze getting into the intake ruined the cat. The antifreeze leaking externally is running down the valley in the motor and making its way down by the starter. This is purely a guess.

More than likely it isn"t head gasket, or theres a good chance you"d see it in the oil.

I have an "02 Century and it is now pushing 270,000 miles on it.

I had a problem with the water going down and it over heating. I was advised that it was a manifold intake problem and cost about $800 to fix.

I finally got tired of messing with and took it to a new mechanic to fix. He said the problem was not with the gasket but rather the original water hoses and the anti freeze. He changed every hose on it, flushed it and I haven"t had a minutes trouble with it since. That was about a year ago.

My daily commute is a 130 miles so having a reliable and comfortable ride is important to me !!

Thanks BW. I'm going to pull the EGR tonight and see if it's stuck. I just stopped at NAPA for some oil. There was a mechanic there that told me they see alot of intake leaks and practally no head gasket problems on that motor. Something about a plastic gasket.

I'll tackle the EGR and coolant leak first, see where that gets me.

Thanks for the help. It's not like working on a 1970 350 Chevy motor.

Can I do a heat check with a precision infered thermomator?

The EGR if stuck partially open will cause the drivability issues you have.Can also cause the cat. low efficiency code to set.Pull the EGR valve off and inspect.

As far as the coolant leak,more than likely the lower intake gaskets leaking.Pressure test it when engine is cold and you'll see it.Fel-Pro makes a "problem solver" perma-dry gasket kit fro the 3100 and 3400's to eliminate future gasket replacement.

The front motor mount will have to come off to include removing the bolts holding the AC compressor to the front mount bracket in order to get it off. Once the mount is off, you'll be able to remove the valve cover and head. One thing you must pay particular attention too is the push rods. The push rods are different lengths pending on whether its an intake valve or exhaust valve.