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MG MGB Technical - Zero oil pressure

All of a sudden I have zero, zip, nada oil pressure. The engine was completely rebuild a few years ago where everything including oil pump was replaced. The car only has a couple thousand miles on it since then and was running absolutely perfectly for the past few spring and summers. I drove it more this year than I have in quite some time and was impressed with how perfect everything seemed. Then this!

I disconected the oil pipe line and blew compressed air through the guage and confirmed it was not the culprit. I then started the engine (coil disconnected) to see if I could pump oil out of the line. Zero oil flow! I reconnected the coil and started the engine for a few seconds and heard an awful bang coming from somewhere down deep. Didn't sound good. I connected a tight rubber hose on the end of the oil line going to the block and tried to suck oil up that way. All I could suck was air!

I guess I need to remove the sump and do a visual inspection. Any ideas anyone? Can the oil pump be removed with the engine in the car?

Regards
BOB in Atlanta
RES Schultz

Bob-
Nope, the oil pump cannot be removed with the engine in the car. The oil sump can be removed with the engine in the car, but you'll have to lift it off of its mounts to get a wrench on the bolts on the front of the sump. That "bang" was the sound of destruction taking place, so the engine should be pulled out and everything inspected. Expect major repairs.
Steve S.

Steve

Are you sure? I consulted a couple of workshop manuals and they make it sound like removal and replacement of the oil pump can be done from under the car. Memory tells me I did this once about 20-25 years ago. seems to be that back then I did a rebuild and put the wrong oil pump gasket in. Replaced it with the right one and everything was fine. This current problem is just plain weird!

I'm really confused how an engine with perfect oil pressure could show zero after setting for about a month.

Didn't mention before this is a 73B with the 18V engine (not that that should matter).

Bob from Atlanta
RES Schultz

Bob, Did happen to change the oil filter between the time you had good oil pressure and the loss of oil pressure? Some oil filters that are labeled as fitting the MGB are too short and will block or restrict oil pressure. Bosch and Walmart Supertech are two that I have seen, there are some others.

With a bang type noise you are probably going to have to remove the engine. That said, after the sump is off you can remove and replace the oil pump with the engine in the car.

Clifton
Clifton Gordon

It's possible that the oil pump drive rotor has sheared off inside the oil pump. There were several postings not that long ago reporting defective oil pumps failing after being in service for very short periods. Also the oil pump/distributer drive shaft, that is driven off the camshaft, may have snapped in half resulting in no oil pressure. Ray
RAY

I solved the original mystery only to find another. Upon crawling unde my B to remove the sump I noticed that my the sump appeared to have imploded. I pulled the oil pan off the car and discovered that the vaccum was enough to suck the bottom of the sump cover in to the point where it actually snapped off the aluminum shaft going to the oil strainer!!! The bang I heard was when the broken part bounced off the bottom of the crank. Thank goodness it was made from soft aliminum and so there was no other apparent damage done.

Now the question is...what caused the vaccum?? Since the subject has now seemed to change I will ask this question under a new thread.
RES Schultz

This thread was discussed on 02/09/2007

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