I have a 1998 Pontiac Bonneville which was brought into the dealer for repair due to not having any heat in the car. I expected a faulty thermostat or some other minor problem. It turned out that engine coolant leaked out from the plenum, water pump and gaskets requiring replacement of the water pump, water pump belt, and manifold (with the various gaskets) manifold was actually rotting from the inside due to coolant leak into it. This repair cost over $1,000. Upon talking to the dealer and my own internet research this is a common problem with the GM 3800 engine which is in Bonneville, Grand Prix and Buick Lesabre. I reference NHTSA consumer complaints listed under Bonneville and Grand Prix complaints of "engine cooling systems" and "engine." I also direct you to edmunds.com "town hall" section(Bonneville and Grand Prix) that is a chat room that shows numerous complaints about the exact same problem. I guess I was lucky in that at least my engine didn't completely seize as is also common when the antifreeze coolant leaks into the combustion chamber. GM will not reimburse me a dime on the cost. This car has just 36K miles on it but it is 4 1/2yrs old and thus out of warranty. The car has been properly maintained, including a dealer oil change just 2 months prior to this problem. My research has shown that the engine coolant leakage from the plastic gaskets and plenum into the manifold and combustion chamber is not an isolated incident and needs the NHTSA to investigate this issue further. GM customer service is of no service and they have basically told me to buy Japanese from now on.

- Wallingford, CT, USA

My complaint is: I was driving down Illinois interstate highway 55 at 70 mph when my engine died, because my manifold keeps cracking, this is the 4th time!! because my engine died, it kept blowing and forcing antifreeze down my intake and filling my cylinders with water and antifreeze, causing a vapor lock!!! I tried to restart the car in neutral going 70 mph, with 20-25 cars around me and 3-5 semi trucks, but the engine was locked up!!!! I lost control of my car!!! I had no power steering, no power brakes, no control to be able to avoid a 20-25 car pile up, with tens to hundreds being injured!!!!!!!!! this is a "safety issue that must be resolved!! GM needs to do a complete recall of all 3.1, 3.4 & 3.8 V6 engines made with plastic manifolds and plastic gaskets!!!! GM needs to replace them with the aluminum manifolds and rubber gaskets they used to place on "all engines manufactured since these changes", which I believe is 1995!!!!! also, do not allow GM to deny these charges of defective material, parts, workmanship, or manufacturing, because I was told yesterday there is a "new technical service bulletin" changing the manifold, gasket and installation!! please see the attached url - www.petitiononline.com/mod_perl/signed.cgi?gmcnsmrs to view the over 1,300 people so far that has been identified in just a few months by word of mouth. The dealerships stock these parts, where before their design change in 1996 from aluminum to plastic manifolds, the dealerships never stocked these manifolds!!! other support websites: www.geocities.com/gm_intake/index.htm#updates & www.GM-V6lemons.com

- Metamora, IL, USA

Car suddenly began missing and running very rough. Drove only a short distance & car stopped running. The dealer said the upper intake manifold plennuim needed replaced, as well as the plugs removed & cleaned. Also needed oil, filer & collant changed. Cost over $750 to repair & manifold was about the only engine component to not be included under the add'L service contract we had purchased.

- Cape Coral, FL, USA

Please see the attached complaint

- Metmora, IL, USA

While in motion, the engine died causing a pile up on the highway. The engine manifold and the gasket caused what is called a vapor lock up. This is a continuous problem with this vehicle. The manifold and gaskets have been replaced 4 times prior.

- Metmora, IL, USA