fluctuating oil press
 

HI I was wondering if someone could steer me in a right direction to start I just bought a 1995 supercharged bonne with 139,000 mi for my daughter. I checked the oil before driving it home the first time.... It was about 1/4" up on dipstick..( I live 20 mi away) when I stopped at a light when I was half way home, I heard a chime and noticed oil press gage was in the red I pulled out when light turned green, and as Rpm came up so did oil press. I stopped at store checked oil..(about the same as it was before) and I topped it off. Chime no longer goes off but oil press still drops to top of red zone on gage when stopped at idle with foot on brake....Put car in neutral ..sitting still... and press comes up to around 15 lbs with the higher idle (not under load). And pressure fluctuates between 15 and 50 lbs when driving depending on vehicle speed. The guy I bought the car from says he had a oil leak from the timing cover and replaced the pump for the heck of it while he had it apart and was replacing the covers gasket. The car had been sitting about 8 Months. Could my problem be caused by a faulty sender? Bad or worn pressure regulator / bypass valve ? I can smell and slightly see burning oil smoke. The block under the exhaust manifold is wet from leaking/seeping oil either from the valve cover or head gasket or something else in that area? although at this time it doesn't look too excessive..(only had the car 1 day) There is not any oil in the coolant or visa versa. I am a home repair mechanic, and always try to fix my own cars if possible. I have a (cheap) Hayes manual for this car..sometimes they are really vauge and generalized depending on what is wrong. I am just learning about this vehicle. Any help or suggestions would be greatly appreciated before I start pulling my hair and things apart in my garage. Also does anyone know if the rod bearings can be replaced with the vehicle in the car? Thanks Doc

Hmm...

You are going to have to drop your pan and see if any metallic sludge is hiding out there. The last time this happened to a fellow member, he had to leave his car at my house while he and his brother proceeded to Virginia. It was in the very early stages of rod bearing failure, and had just started to be more pronounced when I pulled his old engine. When we pulled his pan before he left, there was metallic sludge at the bottom, and bits of chewed up "stuff" clogging the oil pickup tube screen.

SSEi's will require you to loosen your oil cooler lines at the filter housing before you are able to drop your oil pan, and I think the inspection covers need to be removed from the bellhousing. Other than that, it's pretty straight-forward.

At the "gee, I hope THIS is the issue" end of scale, your oil pressure sending unit may be on the fritz.

EDIT - Don't try to replace the rod bearings. Don't ask how I know. ;)

I agree with Brad. That's not sounding too good. I'd be tempted to get a mechanical pressure gauge on that car and see if it agrees.

At hot idle, 20-25 psi should be the norm for these cars, and will shoot to 40 psi at just off-idle (around 1500 rpm), and upwards of 60 psi. That wet oil you see on the side of the block is most likely the valve cover gasket. Head gaskets rarely, if ever, go bad on these engines.

The previous owner didn't need to replace the oil pump. They are the gerotor-type, and seldom wear out. Timing cover gaskets rarely leak too, though the front crankshaft seal might. The oil pressure valve and spring are in the filter housing. Hmm.......OH SNAP.

Take that housing off, and look at the piston and spring. Tell us what you find there. I have a hunch that the previous owner may not have followed directions.

You may be onto something Brad.

And I just happen to have a spare timing cover, pump, and filter housing disassembled to that same extent right here to show him the difference if we find a problem.

139k sounds a bit too early for rod bearing failure, though if my suspicions are correct that may very well be the case now. Depends how long that engine idled after this repair.

Need to get a good strong magnet on the head of the pan drain bolt for the time being.

That'll tell one part of the story (the long-term important part).