Replace timing belt/chain soon?

I'll be buying my mom's '99 Grand Prix SE (3.8 Non-SC) soon, it has about 113k miles on it. Right now we need to get the headgaskets replaced.

The timing belt/chain on it has never been replaced before. How soon should I get it done? How difficult is it to do?

And also, is the 3800 SII an interference design (no clearance for valve heads if piston head is at TDC)? Or, will I be able to run it untill something goes wrong with the timing set?

The 3800 non-sc is a non-interference engine since it is of overhead valve design and not overhead cam. The timing chain is difficult to get to due to the limited amount of space that you have to work with. I wouldn't change it at this point since you shouldn't have any issues with it. The head gasket problem isn't common but it does happen. If someone changes them for you make sure you go to someone with a good reputation for engine work. The head bolts need to be replaced at the same time as the gaskets so make sure they don't reuse them. Also make sure they use good quality gaskets and that they use a good set of intake manifold gaskets. They are prone to failure on these engines. You may want to flush the cooling system too and replace the dexcool with Prestone extended life antifreeze. Should cure some of the gasket issues.

Are you sure it's the head gaskets and not the intake gaskets? As far as the timing chain, mine has 335,000 miles on it and still runs like a top. Just drive it and don't fret. For normal use they're pretty much bullet proof.

Thanks for the info :). I have my thoughts about the mechanic we took it to (he tried to explain to me that "camshaft" was another term for "crankshaft" when I told him how I replaced a sensor on a Neon), but he claimed there was antifreeze in the oil, so our first assumption was the head gasket. We'll be taking it elsewhere for the work, and probably will buy the parts ourselves. Seeing as the timing chain won't need to be replaced (hallelujah), it'll just be the intake & head gaskets, and then the bolts, right? What brand would you recommend for the gaskets? AutoZone only seems to have the Fel Pro intake gasket set (http://www.partsamerica.com/ProductDetail.aspx?MfrCode=FEL&MfrPartNumber=MS958091). Is it worth the money?

It coukld be the upper intake and those a big problem with the 3800 series II engines.Check this too and if you see any water in the intake manifold,replace the upper intake also.The upper intake has come off too,covers up one of the intake bolts.

Do a compression test. If the car runs ok, and it passes the compression test, then all you need to replace is the upper and lower intake gaskets. They are the most common cause of coolant in the cylinders and oil on these engines (3800 VIN-K). Unless the car is running badly, or was overheated due to the coolant loss, I'd say you don't need to do the head gaskets.

When mine was leaking it was only the upper intake. It is most likely not the head gaskets but the intakes. They are not that hard to replace. I used the Fel-Pro and have not had any more trouble. Also check the upper plenum hole around the little pipe call the stovepipe. If it is melted, you'll need an upper plenum. You will also most likely need the L shaped pipe between the lower intake and the belt tensioner assembly which is only about $6.00 at the dealer. You will also need new fuel injector o-rings. It's also a good time to replace the plugs and wires and do the valve cover gaskets. I did all mine at the same time and haven't regretted it. You won't need new bolts for the job but follow the procedure for tightening the bolts to the proper torque.

The gasket you reference in post 4 is the lower set only. You will also need an Upper intake set (fel-pro #ms95812) if you decide to change only the gasket and not the plenum. I would strongly suggest you inspect the plenum and look for damage/warpage around the EGR stovepipe. If it looks even questionable, buy a new plenum as it comes with everything you'll need to do that half of the job (upper gaskets, inj o-rings, new pcv and MAP sensor mount, etc...). On the lower set, I would go to the dealer and buy the GM improved design metal framed gasket for this engine. It's cheaper than the Fel-Pro, and better made. GM part #89017816, dealer retail $63.29. Many dealers will sell to you below full retail, so you may be able to get a better deal.

Well we've got another mechanic taking on the job, everything was inspected and it was confirmed to be the intake gaskets like you guys said. Thanks again for the advice :).