24th Oct 2003, 17:48

Since I purchased my car (used with approx 50K miles on it) I have had very similar problems with it. I too had to have the EGR valve replaced right after I purchased it and then the transmission went - TWICE. First the transmission was slipping so they had to rebuild it ($$!) and then after that the torque converter went bad and they had to rebuild it AGAIN. All this and it was just nearing 60 K miles. Next thing was the serpentine belt and since its screwed up position in the car they had to drop the engine to replace it. Just last week the car wouldn't start on me because the fuel pump and sender went bad ($700 repair) and now, only yesterday the car quit dead on me again while driving it because the battery was dead, leaking from the + terminal and trying to kill my alternator in the process. Now my car is making a whining sound when I step on the gas!!! AHHHHH! What next? So it looks like I have had just about the same problems as the rest of you with my car. Don't get me wrong, I love the car and how it drives (when it works), and how it looks, but if one more thing goes wrong I am tempted to take it out back and shoot it!

14th Nov 2003, 18:50

Wow, this is unbelievable. I thought you were describing my car. I have a 1998 Bonneville SE. First alternator was replaced under warranty before 20K miles. Second alternator around 50K. At around 63K the car starts shuttering at firm take-offs. Needs a trans rebuild they say, $2200. Haven't done that repair yet. Just babying it when taking off. Now have 68K miles on it and when I started it up Monday morning it started to crank and then the cheap plastic intake manifold exploded! That's right exploded! The dealer/and GM says "it's out of warranty, sorry"! $1000 more to from the consumer to cover an obvious design flaw. I say that because when I looked at the 2004 Series III 3800 motor, what do you know, the intake manifold was aluminum. I'm seriously doubting GM commitment to their customers!!!

10th Feb 2004, 16:42

I have enjoyed my Bonneville very much, however I have to agree with the comments about the cheaply-built plastic intake manifold. This is a heat-sensitive component that should never have been made of plastic. Failure is almost inevitable, usually occuring around 75,000 to 90,000 miles. The same plastic manifold is used in other GM cars as well (not just Bonnevilles). There should at least be an aftermarket aluminum replacement to avoid a repair that is also destined to fail.

4th Mar 2004, 09:54

The GM Series II 3800 engine suffers from a fundamental design defect that is common to countless other engines that were designed and manufactured in the 90s. I have repaired many 3800's and find that unexplained coolant loss is usually a sign that the lower intake manifold to cylinder head gaskets (manufactured out of plastic) have failed. The aluminum lower intake manifold expands much more than the cast iron cylinder heads. When you put a plastic gasket, which expands at yet a different rate, between the two dissimilar metals, issues of durability arise. The plastic upper manifold was redesigned in late 1999 to be more heat resistant. There are GM technical service bulletins that address these concerns. Finally, when coolant is burned in the cylinders of an engine, the result will almost certainly lead to contamination of the Oxygen sensors. NAPA sells an aftermarket upper intake kit for the 3800 series II. It too is made from plastic and my cost was $129.00.

6th Apr 2004, 19:56

Well just checking in as I wrote the original review on this, the car now has 72,000 miles on it and am happy to report since we invested the $2900 we haven't had any issues in 12,000 miles. So we have our fingers crossed for a few more hopeful years.

One note to those experiencing the same issue, a quick recommended fix is to install a 180 degree thermostat. This will allow the L36 engine to run cooler with the plastic intake issues, as the original thermostat on a 97 non-supercharged Bonneville is a 200 degree model.

I'm not a mechanic, but have seen this note on 180 degree thermostat usage on other web sites; my mechanic also thought it was a good idea. There is a TSB out on later Bonnevilles mentioning the use of the 180 degree thermostat versus a 200 degree.

One positive note - with gas at almost $2.00 a gallon, it's nice to have a large vehicle that gets fairly decent mileage. Next car is gonna be a hybrid though if gas keeps going at these levels...

1st Sep 2004, 09:41

I own a 1997 Bonneville SE with 153,000 miles. The car has had no major problems or any major repair work done since bought new. Other than a few small problems such as a broken gas gauge and two broken accesory outlets, the car has run great. I have had many people tell me that the 3800 series II engine in unreliable. I have no complaints.

30th Oct 2004, 08:53

Nearly all of the Series 2 suffered from a defective intake manifold. GM Alternators have also been known to go out.

These cars are still a very good deal if you are in the market for a used car.

Cheap to Fix, Last 200,000 Miles, Low Insurance, Safe, Usually Reliable if not Abused.

8th Nov 2004, 18:11

I have a 1999 Pontiac Bonneville that I've spent over $3,000 on repairs. The fuel pressure regulator backfired, which cracked the intake manifold plenum, which leaked coolant into the engine, which corroded the main bearing and caused the engine to seize and damaged the lower half. The car had 74,000 miles on it and I owed $3,500, so I didn't want to pay for a new engine (over $4,500), so I had the lower half rebuilt (bearings, crank, etc.) and had the manifold and fuel pressure regulator replaced. Total bill so far is over $3,000 and counting.

GM only reimbursed me $125 for the fuel pressure regulator replacement due to the recall, and refused to pay for the damage caused by this part. Thanks GM.

There's class action against GM for the manifold problem at Sheller.com; I'm getting in on it.

27th Jul 2005, 07:45

I have a 97 Bonneville and have experienced several major problems. We bought the car used from my sister with about 80,000 miles on it. At 90K the transmission went. that was a $2,700 repair. Then the power steering pump went out. at 107K the plenum intake leaked and filled all cylinders with coolant, causing misfire on all 6 cylinders. Now the egr valve has gone. My God, what's next?