MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Oil Pressure Loss

I have a sudden loss of oil pressure- from 35 to 15 at idle and i don't get above 45 until 3000 revs when I used to have 60 at anything above idle. All this is after warmup. The engine has been running great and still does- no change. No rod knock or other noises have appeared. Again, this change happened suddenly from one day to the next. I know the pressure is still within spec but the sudden drop is worrisome.

Could I have a failure of the oil pressure relief valve? How do I tell? Could the oil pump be going out?
Like I said, the engine runs as well as ever with no smoke or noise. I want to pursue all avenues before I decide on a rebuild. Thanks
Mike

Does your car have an electric or mech. oil
pressure gauge? I would get a second gauge
and confirm the readings first. The electrical
senders especially are unreliable.

If the readings are also low when the engine is cold
and at high RPM, then the problem is definitely
bearing or oil pump related, since the relief
valve is open under these conditions.

Check the archives on tricks for replacing the
relief valve with the engine in the car -- its
worth a try before tearing down the engine.
Ronald

The relief valve is designed as a progressive valve that allows spill back of excess pressure, the valve will start opening when the pressure in the system overcomes the spring within the valve. If I were you I would check to see if dirt is causing the valve not to seat correctly, this is very easy to check just refer to the manual for a definitive description.
Bob

My car has suddenly developed a loss of oil pressure when starting from cold...

It used to run at 60psi from cold with full choke. When warm, idle was 20psi and driving when warm was a rock steady 60psi.

The last two startups from cold have resulted in 0psi with the pressure needle attempting to rise several times during idle but then falling again. This happens until nearing normal temp and then it picks up. pressures are then the same when warm.

Normally as the oil pressure is always fine i try to drive off asap after starting to let the fluids move around the engine thus warming it up quicker, however it shocked me so much to see the pressure falter on a normally fine engine ive let it idle to normal temp....

The car does not burn oil as a rule, howver it is due for an oil change this week, but as we're talking oil pumps above i thought i might ask the question and should i be looking for anything more serious.

The oil is rather black rather than nice and clear, it is exactly 3000miles since last change and my oil pressure gauge was replaced at this interval due to a snapped temp sender.

Is it a case of sediment in the pump causing probs or more serious?? Assistance apreciated chaps


~PHIL
Phil

This thread was discussed between 13/10/2002 and 14/10/2002

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.