Would post what the oil pressures were reading with the mechanical gauge at operating temperature?

Thanks
Jim

Sorry 96 i was not there when he ran the test.. I will shoot him a call 2marro try and find some one that will show me.

So?!?!? Did replacing the sensor fix it?!?! I have a very similar issue with my car.

I've always run the recommended oil in the summer, something lighter in the winter. e.g. in my 6000 5w30 was recommended, I'd run that in the summer, 0w30 in the winter. On my Bonneville 10w30 is recommended, I'll run 5w30 in the winter. Then again I've lived in areas where it literally got to -50 on the mercury.

I just took care of a very similar problem for my brothers engine. Here is what I found to be wrong with his:

A year ago the car was driven for a significant period of time with a failed upper intake gasket, the car eventually hydro locked due to excessive coolant leaking into the intake. I tore it down re-sealed the entire upper end from head gaskets to the throttle body. All was well for about 3 months until the oil pressure started to fluctuate. Cold or above 2k rpm hot it would get to 40psi, hot at idle it would struggle to make 10-20psi.

We tried adding assorted liquid fixes and heavy weight oil with some success. 30 wt and zmax got him limping by until we found a low mileage replacement engine. Still ran fine with maybe a slight lifter tick the day I pulled it. The original had 145k.

After removing the engine I removed the oil pan and found excessive play on two maybe three of the rod bearings, I have no questions that the mixing of the coolant with the oil for however long that gasket had been leaking toasted the bearings. It is very possible that replacing the bearings would have corrected the problem but I found a great 50k used engine trans combo instead.

Best of luck with yours.

Thank you for your post. Very informative. Do you know if the rod bearings you found loose, whether they could be changed with the engine in the vehicle.

Some individuals I spoke with about my car indicated too much guessing as to where the problem is and would recommend overhaul or new engine. Cost and value of the vehicle becomes the issue. My car really has no ticking noise; once it gets to operating temperature it wants to stall out.

I've contemplated changing the IAC motor. No codes other than security light is on.


My Bonneville, it cranks fine and runs but is presently not reliable.

thanks again

My '98 just developed the same oil press. problem so I changed the oil level sensor and no change.
I plan on also installiing a mech. gauge and go from there.

The oil pan can be easily removed with the engine in the car, clean working conditions and working on your back may be an issue trying to replace the bearings though. I imagine with the right amount of determination and small fingers it would be possible.

An important note, the Oil level sensor on the front of the pan has clearance issues with the oil sump tube when dropping and installing the pan. Unscrew the sensor and let it set loose through the hole and it will make life much easier. I broke one the first time. through.

The problem with picking and replacing parts is that if one part has excessive wear, it is likely that other parts have excessive wear also. Main bearings, balance shaft bearings, rings, valve guides... it is a game of luck at best. The overall condition and mileage of the car should help decide what to do. If the car is very solid otherwise a rebuild or low mileage salvage may be a reasonable option. If there are other looming issues, Chassis rust, suspension issues, body corrosion, transmission problems, limping by on heavy weight oil and additives may be the way to go while saving for a new vehicle.

To my brother I recommended nursing the old one along and saving for a replacement car. He disagreed as he does not have much money and really likes this car. It has a considerable amount of under body rust but is in excellent shape on top. I've already replaced most of the suspension, portions of the brake and fuel lines, fuel pump, wheel bearings, and brake calipers.

We were fortunate to find a 51,000 mile car fax verified motor and transmission pair for $1000.00 less than an hour away. Finding this was very fortunate as a direct swap needed to be from an H body 96-99 vehicle. There are two possible final drive ratios also further complicating matters, a 2.84 and 3.06. Engines from W body and later model Bonneville'* will work but they require some electronics and parts swaps.

I installed a mech. gauge today drove it and the oil press only went down to 20 psi at idle when the car was in gear.
Tomorrow I'm going to buy & install a brass tee so I can hook up both gauges to see what the mech. gauge says when the elec. gauge nosedives.
My b-in-law thinks it may be either main bearings or the oil pump.

Okay I installed a brass nipple & brass Tee then installed both the Dash elec. gauge sending unit & the mech. gauge line and fired the car up upon startup the mech. gauge was reading about 20 p.*.i. more than the dash elec. gauge drove it and after it warmed up the dash gauge started dropping into the red almost near zero while the mech gauge never dropped much below 20 p.*.i.

I'm going to call the auto parts store tomorrow just to make sure they sold me the right sending unit for the dash gauge.
So for now it looks like the dash gauge is at fault.
Surely someone else has had the same problem and figured it out.