Need advice

[BobT]

1997 Pontiac Bonneville, GM 3800 engine, 110,000 miles.

The mechanic tells me the upper manifold is leaking coolant but the lower manifold is okay. The question is whether I should have him replace both or just the one that is leaking.

If I fix just the top I save $350 now but if the lower one begins to leak later, I'll have to replace the upper one again in order to fix the lower one.

I am aware that the coolant in these engines is hard on the gaskets and the replacement gaskets have been improved for this but I'm wondering if they typically had trouble with both gaskets or if most of the problem has been with the upper one.

What do you think would be best?

Thanks,

[Big Buck Buster]

Have them do both. If the lower is the original, they are plastic. The new updated ones will have a steel core to them. It will cost you a little more now, but it is worth it. IMHO.

[Jeremy airjer W]

If you replace the upper plenum than you shouldn't have to worry about in in the future. There are gasket kits for the upper and thats all you should have to replace. On the bright side it is really unusual, although it does happen, for the lower intakes to leak coolant. More often the lower intake gaskets are done to take care of the oil leaks in the valley.

I have replaced many uppers for coolant leaks, a handfull of lowers for oil leaks and even less for coolant leaks.

[BobT]

Airjer, you've pretty much repeated what I thought I've read and heard that it is the upper plenum where most of the trouble comes from.

Thanks,