Engine Cooling System problems of the 1998 Oldsmobile Regency

My 1998 Oldsmobile Regency was losing coolant. I could not see a visible leak. The check engine indicator light came on, so I took the vehicle to be serviced. The mechanic found the upper intake (plenum) to be leaking the coolant into the engine (cylinder #3. ) the leak was caused due to the fact that the intake plenum is made of plastic. I intend to send Oldsmobile a copy of my bill which was $533. 32. Why would a company make a part such as this out of plastic? by the way, my indicator light is still on, so I will need to have a dealer check it out, as the original mechanic can find no reason for it remaining lit.

I own a 1998 olds Regency with 62000 miles on it. This car has the standard 3. 8 liter v-6 which has been in production for probably 30 years. I noticed recently the coolant reservoir level was slightly down and added coolant to bring it up to level. Two weeks later my engine temperature was slightly high so I checked the reservoir level again. The reservoir was dry and I couldn't see any coolant in the radiator. I called the local dealership, added distilled water and got it there. When I arrived there was coolant leaking out of the intake manifold. The dealer informed me the next day they had to replace the upper and lower intake manifolds and gaskets at a cost of $1050. I questioned myself and the service manager how an intake manifold could go bad. He informed that the upper manifold was made of plastic. I talked to the mechanic after the fix. He informed me that the egr nipple that flow exhaust gases into the plastic upper manifold had thermally broke down the plastic and caused the leak. Gm's fix was to decrease the size of the nipple in the lower manifold so there was an air gap between the nipple and the plastic upper manifold. This fix would stop heat from being transferred directly to the plastic upper manifold. Gm has an engineering problem and they have addressed it by changing the replacement manifolds. No recall has been issued so the total cost is the burden of the owner. I have maintained my car properly and I believe this problem is not my fault. The problem is gm doesn't think it's their fault either.