Last post on Aug 09, 2011 at 3:57 PM
You are in the Pontiac Bonneville
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Pontiac Bonneville, Sedan
#1 of 2 99 Bonneville engine noise
Aug 09, 2011 (11:45 am)
Hi,i,m trying to buy a 99 Bonneville 69,000 miles,it,s has a tapping noise from motor,the seller was told it needs an oil pump,the gage reads about 1/4.I,ve had a few cars that had that noise and never caused problem.Is this the same on the GM 3.8 motor?Or is it a major repair.what does it take to replace oil pump,this is the non-supercharged motor vin=K
#2 of 2 Re: 99 Bonneville engine noise [vicgoo]
Aug 09, 2011 (3:57 pm)
>Or is it a major repair
Depends on the noise and source. I certainly wouldn't trust the seller to give you correct information. You need to take it to your own mechanic who KNOWS 3800s from that early period of Series II motors.
That era has a high failure rate of upper intake manifold seals that carry water into the throttle body and the EGR passage through the plastic upper also deteriorates and allows coolant to flow into the manifold and the intake. The metal lower intake seals deteriorate where it's bolted against the heads, some claim due to the DexCool which had a problem with its early antioxidant chemical used.
If there are leaks of coolant into the oil, the bearings in the lower engine are at great risk from coolant damage.
The parts for repairing the upper intake and putting metal covered gaskets onto the lower are about $150 from ineedparts.com. Labor would be about 6 hours for a good mechanic, or less.
But if damage is already done due to leaks, the damaged bearing can take time to show up.
At 65,000 this would be a good engine to do the repair on before the leaks occur, if they haven't already. A good check for coolant leak is to have an oil sample suctioned out of the oil sump and pay $25 to send it off to blackstone labs for an analysis for coolant in the oil.
Depends on the selling situation what your choices and trust levels would be.
I cannot recall reading someone having a bad oil pump on a Bonneville or leSabre of that period at low mileage. That's why I'm suspicious.