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MG TD TF 1500 - Oil Pump Information needed

Early TD 4139

Ever since I purchased a rebuild motor for my TD, the oil pressure has been fair at best. The engine was built by an aircraft mechanic. I had it checked over by an MG shop and everything looked good. Bearings were checked with plastigage and were perfect for a rebuild.

The engine would not build oil pressure, so I had the pump rebuilt by John Twist's shop. Pressure has been around 15 at idle, and 40 at speed.

This was with the oil hose off the lower fitting on the block.

For this restoration, I moved it back to the head. Oil pressure is now 20 at startup, but drops to below 5 when warm. It will get to 40 on acceleration.

I pulled the relief valve (moss adjustable relief valve).

I am wondering if the ball seat is part of the issue. (See pictures)

Next question is I see two seats listed a brass seat and a steel seat. They are totally different looking. The one in my relieve valve looks like the steel one.

To me, the seat looks like it needs to be lapped. I can use the old ball and build a lapping tool but I don't know if that is needed.

If the seat looks bad, how is it removed. I assume it is pressed in.

I plan to loosen the oil pump cap to assure no gasket was put on it. I will also visualize the wear on the cap.







Bruce Cunha

Here are the two different seats.




Bruce Cunha

I had a similar problem, Bruce. Could never get good oil pressure. I tried everything. This is also an early engine. Finally, the only thing I had not replaced was the bypass valve in the oil pump. New ball, seat and spring and suddenly idle oil pressure went from 10 lbs to 40 lbs. I thing the bypass spring had simply lost much of its springiness after 74 years.
Lew Palmer

The lower seat in your photos goes in the block. The upper one in the oil pump. I have never removed one from the pump.




L E D LaVerne

Note the one is the block has an internal thread for removal.




L E D LaVerne

Thats all I have




L E D LaVerne

Thanks LaVerne. Thanks for the details on the valves.

What would happen if the brass ball valve was missing?

I can't say it is in the block. I did not do the rebuild, but I did replace the pump. I probably did not look to see that one is in place.

I plan to pull the pump (I see you can't take the lower bolts off the cap without raising the motor, so I may as well pull the pump and investigate the brass valve.
Bruce Cunha

Bruce, what are you reading at the lower fitting? Good chance this is the pressures that engine has been running since overhaul.
Regards, Tom
tm peterson

Bruce
Does your gauge fitting connect to the side of the banjo fitting or the end of the banjo bolt--either were available in TD's

There is probably a restrictor in the end of one of the banjo bolts

Might pay to check if one of the banjo bolts has a restrictor---If that restrictor is in the bottom hole the oil pressure will always read low on the gauge

willy
William Revit

No restrictor, checked that.

William. I agree. I am not terribly concerned as i do have good oil flow at the rockers, but I still want to check out the lower reading on my gauge.

Gauge was rebuilt about 3000 miles ago.
Bruce Cunha

The valve in the block is the oil filter bypass in case of filter blockage. If the ball was missing it would have little effect on oil pressure but the oil would not be filtered.
I made a plug to to clamp in the oil pressure relief hole to prove the pump condition in cases of oil pressure worries.
The later engines feed the oil through the block hole directly to the gallery and the filter bypass is integral to the pump/filter housing.
Ray TF 2884
Ray Lee

This thread was discussed between 23/10/2024 and 25/10/2024

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