Which parts fail
Components named in complaints (engine, cooling system, oil leaks, timing chain, exhaust).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 1998 Pontiac Bonneville owners, lightly cleaned up (personal details are redacted by NHTSA).
Tl* the contact owns a 1998 Pontiac Bonneville. The contact stated that while driving 20 MPH, the vehicle overheated. The contact then attempted to park the vehicle however, the vehicle then stalled without warning. The vehicle was taken to a dealer for diagnosis and the contact was informed that the intake manifold was melted and the head gasket was blown. The vehicle was not repaired. The failure and current mileage was 62,000.
The back two cradle mounts on both sides rusted out and mounts pulled through the cradle causing the steering to become loose filling and causing steering to be out of alignment and when hit brakes front would dart one way or the other and lots of noise coming from under vehicle from cradle bouncing when hitting bumps tried the find one in junk yards and all are that way.
Tried to start car 1998 Pontiac Bonneville with 54,000 miles, it backfired and cought fire. It is totalled. I read on the internet that there was a problem with the plastic intake manifold, but I have never been advised. My car which was like new is gone.
Vehicle was parked, consumer proceeded to start it, and it caught fire. The fire was extinguished by the fire department. Consumer later found a recall for the intake manifold, however, his vehicle was not included.
Purchased used 1998 Pontiac Bonneville in January, 2002 with 56, 000 miles from GM dealership. Car was GM certified. About 6 months later with 65,000 miles during routine oil change I notice the coolant was a little low. Going back to dealer I purchased GM long life antifreeze and bottle of GM sealant. There were no visible signs of antifreeze leak anywhere. Coolant level maintained from that time. On April 30th, 2004 while driving down the expressway, the car suddenly begain to miss fire severley and quit running within seconds. There was no power steering and no power breaks. The engine had hydrolocked. All cylinders were full of antifreeze. The car now had 115,000 miles. I removed the upper intake manifold to find it full of antifreeze. …
Sudden catastrophic failure of the intake manifold causing anti-freeze to enter the engine, oil resulting in complete engine failure at 75 MPH. Ase certified mechanic replaced engine, intake manifold and peripherals for over $5000. Have possession of original factory intake manifold showing hole in EGR area that failed. Ruined engine had to be returned for core fee. Car recently off extended warranty. GM customer service uncooperative and claims that TSB 010601007a (NHTSA item #620835) not published by GM. GM customer service claims car has not been properly maintained, did not care to have details of oil changes (every 3000 miles) or other service performed as recommended in owner's manual. This is an obvious product failure and is a serious safety issue at higway speeds! When engine locked up, lost all power and had difficulty getting off the highway and onto the shoulder. …
Noticed slow loss of engine coolant (no obvious leaks) over the month prior to incident date. On incident date, engine popped, banged, and ran extremely rough on start-up. I had read about a problem with the 3.8 liter v-6 GM engine, and brought vehicle to dealer. Dealer found warped/cracked plastic intake manifold, which was replaced at a cost of over $700. Pontiac/GM would not consider any cost sharing on the repair. Failure was in area of manifold/plenum where throttle body/EGR valve mount, and is due to excessive heat build-up over time. This problem is a design defect (use of plastic manifold vs. Metal in high temperature application) on this and several other GM v6 engine types from 1995 to at least 2002. GM installs these engines in various models of pontiacs, buicks, oldsmobiles, and I believe some chevrolets. …
Vehicle was operating under normal conditions, vehicle was purchased used. Two blocks from my destination, the car was running rough, almost like it was sputtering. I parked the car in the hopes it would start,the backfire that I never heard, not only broke the nose off the starter, blew a hole in the intake manifold and filled the engine with antifreeze. Luckily for me I had shut the car off before any major damage had been done to the engine. I had the car towed back to the dealer I had purchased the vehicle from. Monday came and I then went to the dealer to have them fix this vehicle I had just purchased only 3 months prior, they looked at it and gave me a $700 estimate, knowing full well that this is a defect with the vehicle, but would not provide me with temporary transportation while waiting for the repars to be done. …
The fuel pressure regulator leaked gasoline; allowing fuel to enter the intake manifold through a vacuum line. A spark ignited the excess fuel causing an explosion and rupturing the manifold. The blast hit the car in front of me so hard they thought they had been rear-ended. Smoke bellowed out from under the hood, but luckily it didn't burn. It happened as I was entering an intersection and we nearly missed being broadsided. The car lost both power steering and brakes when it exploded and was very difficult to control. About 2 weeks before this it had been taken in for repairs because it was stalling out, difficult to start and the power steering and brakes had been failing. A new vacuum hose was installed. It had been repaired the year before because it leaked antifreeze into the engine, damaging it extensively. It is the second Bonneville I own that has done this. …
For the second time in about 2 years my 98 Bonneville had the plenum crack while simply driving at normal speeds. This allows water to enter top of motor which requires vehicle to be shut off immediately or motor will overheat until it is ruined. The car had about 50,000 miles at first occurrence and has 72,108 miles on it when it occurred again last Friday. Car is undrivable until parts can be bought and installed, making this a very dangerous situation if you are on highway when that occurs. It has cost more than $ 800.00 each time to get vehicle fixed and I now have no trust in this part of motor what so ever as there is no real reason why it occurs other than plenum being plastic so it can't stand up to normal pressures or temperature changes. …
NHTSA investigations
Engine compartment fires
Engine complaints in other Bonneville years
Frequently asked questions
How common are engine problems on the 1998 Pontiac Bonneville?
NHTSA has 200 complaints about the engine & cooling of the 1998 Pontiac Bonneville, 72% of the model year's 277 complaints. The component named most often is engine › gasoline (52 mentions).
Is there a recall for 1998 Pontiac Bonneville engine problems?
No. NHTSA lists no engine & cooling recall for the 1998 Pontiac Bonneville, though it has 1 recall for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 1998 Pontiac Bonneville engine problems start?
Half of the complaints with a recorded mileage happened before about 70,000 miles, and 1% before 25,000 miles.
Is it dangerous?
Owners linked 1 crash, 18 fires and 2 injuries to engine & cooling problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.