94 Bonneville - Low oil pressure when warmed up

[94_Bonneville]

Hello Community.

I will skip formalities of the first post and go on to my problem, if thats ok.

94 Bonneville w/ 3800 engine.

• when cold, runs perfect, no problems
• when it starts to heat up after about 15 minutes, oil pressure drops very low when idling.
• putting the car in neutral and hitting the gas, or just driving will raise the pressure back up around normal.
• when its really heated up, idling will cause oil pressure to drop almost to zero, and the bell/alarm will ding.

I have replaced the oil pressure sensor, and that did not help at all.
also recently replaced the oil/filter.


also, once the oil pressure is dropping, there is a distinct "tick tick tick tick tick" in sync with the engine firing i suppose.

a friend says "it sounds like a lifter".

after letting it cool, its fine again.

------------------------------

What i am looking for is some information regarding this issue, so when i go to get it fixed, i wont be totally clueless as to what i may be dealing with.

my dad has run trans shops for over 30 years, and i know how shiesty some repair facilities can be.

Thanks a lot. i look forward to a reply!

time for some opcorn:

[94_Bonneville]

also, i just searched and came up with:

Replacing your t-stat to a 160deg and changing to a heaver weight oil may help keep your oil pressure up a little higher. It's not a fix but it may buy you some more time out of it.

does that sound like something worth trying?

[ChemMan]

To be honest with you, I wouldn't drive the car with low oil pressure. All you are doing is slowly destroying the engine, even if you don't notice anything right now. You are going to need to check the oil pump and the oil pressure regulating spring. Since you don't mention the mileage of the car I would start by checking the oil pressure regulating spring, piston, and gasket. These parts are located underneath the piece that you attach your oil filter to. A broken spring or leaky gasket could cause low oil pressure. If that checks out ok, then you will need to check the oil pump, which is located in the front engine cover, just behind the crank pulley. Getting to it is not an easy job and will take some time. I take it you are not going to fix it yourself, so ask your father if he knows any honest shops you could take the car to. Be prepared for a big bill if they need to pull the oil pump.

Now that I think of it, before you do any of the above:
1. Verify that you have the correct weight oil in the car, 10W30 or 10W40.
2. Verify that you don't have gasoline in the oil. If the oil on your dipstick smells like gas, then you have gas in the oil.

No I would not change the thermostat, you need to fix the problem.

[94_Bonneville]

1. just had an oil change, so im assuming they put the correct oil in.
2. ill check for a gas smell.

well, i guess it would have been worth mentioning that i have a pretty consistent yet small loss of oil under my car.

would finding out the location of this dripping help? maybe find out its a leaking gasket?

also, would what you posted be consistent with the fact that it will only do it once the car is warmed up?



edit: oh yeah... heh.. i bought the car with a bad engine... replaced it with a junkyard engine by my dads mechinics, so i dont know the milage. actually sold my 89 bonnevilly for $550, bought this one for $300, and got the engine for another $200.

[ChemMan]

Originally Posted by 94_Bonneville

1. just had an oil change, so im assuming they put the correct oil in.
2. ill check for a gas smell.

well, i guess it would have been worth mentioning that i have a pretty consistent yet small loss of oil under my car.

would finding out the location of this dripping help? maybe find out its a leaking gasket?

also, would what you posted be consistent with the fact that it will only do it once the car is warmed up?



edit: oh yeah... heh.. i bought the car with a bad engine... replaced it with a junkyard engine by my dads mechinics, so i dont know the milage. actually sold my 89 bonnevilly for $550, bought this one for $300, and got the engine for another $200.

I wouldn't just assume they put the right oil in. Although I can't really think of a way to be sure without changing the oil again and actually witnessing what oil is being used. Yes, finding the source of the oil leak may be helpful, but it probably is a leaky oil pan gasket which is common. The fact that you don't know the history of the engine, and the fact that is a junkyard engine, pretty much means to expect the worst. You have no idea what kind of care the engine got, how much abuse it took, etc. Have your mechanic take a look. Good Luck.

opcorn:

[94_Bonneville]

OK... before i go taking it in, id like to add that i have found that my oil is leaking a lot.

i put a clean square of cardboard under my engine, after it was warmed up and there were drops of oil from tire to tire after about 2 hours.

about 7 or 8 spots distruted in a straight line between the tires parallel to the oil filter; i watched an oil droplet fall from the oil filter itself.

i now have the back side of the cardboard laying under the engine, having flipped it after the engine was entirely cooled. I will see tomorrow if it only leaks warmed up.


SO... if it only leaks while its warm, could this be my pressure problem?
should i just replace the gaskets before anything else?

Thanks again.

[ChemMan]

No, those leaks are not the cause of your low oil pressure. For an oil leak to be affecting oil pressure, it would be spraying very forcefully. Further, as engine speed increases, the leak would spray harder, most likely quickly empty the crankcase of oil, and start a fire.

[94_Bonneville]

yep. thats what the guy at the repair shop i called said.

im dropping it off tuesday night, so he can put a guage on it cold, and warmed up.

he wouldnt even give me an esitimate to find out what the damages are going to be... looked like im in for a ride.

all he said that i could understand was "clearance problem in motor" , "pressure relief valve"..

in any light, thanks for the advice ChemMan.

hopefully i will luck out with damages under $500.00... i really like my car

[ChemMan]

"clearance problem in motor" = motor is too worn out for the oil pump to maintain pressure at idle = new engine = $$$$$

you never mentioned the mileage, did you?

Sounds like everything else he talked about I already mentioned. You might want to consider a newer Bonneville. The increased horsepower of the series 2 3800 is very nice.

[94_Bonneville]

Originally Posted by ChemMan

you never mentioned the mileage, did you?

bought the 94 bonneville with a bad engine for $300.
sold my 89 bonneville for $550.
bought a junkyard engine for $300 for the 94.
worked fine about 6 months.
replaced trans about 6 months ago after it completely went out.
replaced water pump 3 months ago.

thats all the background i have on the engine.



Come on man, dont tell me i need a new car!!! im almost done with school and have no money to afford one!

[ChemMan]

I take it that's your car in the picture? Looks to be in really good shape. If it turns out the engine is bad, it might be worth putting another engine in.

Good Luck!

[94_Bonneville]

yep, thats my Bonneville. she is real clean.

the family i bought it from had purchased it brand new for themselves.
they then bought a new car and gave it to the son who apparently tore up the engine within a year, so they wanted rid of it and i wanted to upgrade my 89.

I will be posting back wednesday or thursday after i get word of whats wrong and what the damages are.

[Blue Bowtie]

I'm with ChemMan. Disregard whatever the oil filler cap might have printed on it. Read the owner's manual instead. Forget about using 5W-Anything as a lubricant.

Your mechanic should be able to advise you once the oil pressure readings are taken. Bearing clearance problems are one possibility, oil pump wear is another, inadequate lubricant viscosity is another, and problems with the oil filter adapter/pressure relief valve are another possibility. Presuming this car used the Buick 231 V-6, the oil filter adapter is easily removed to inspect/replace the pressure relief valve and spring. The oil pump is serviceable at the front of the engine by removing the balancer and pump cover. Main and rod bearings may be able to be changed with the engine in the vehicle. The rod bearings can definitely be changed with the engine installed, and that will at least allow an inspection and measurement of the crank throws to gauge engine wear. All that is required is to remove the oil pan. Engine removal is not always necessary, and may not be required in your case.

[94_Bonneville]

I was not so lucky...

"bearing clearance problem... lower end knock... worn main bearing."

he told me its not worth fixing, just take it easy on her and drive it til' she dies..

so now i start engine shopping i guess... just dont know where to look, dont want another junkyard engine, thats for sure.


thanks for all the info/support.

[ChemMan]

Might help a little to put a heavy weight oil in it, maybe 20W50?