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MG TD TF 1500 - Low oil pressure

A friend has a MG TD with new rebuild on engine and oil pump. Engine and oil pump work done by a very reputable MG restorer. Oil pressure Max 40 lb. at idle 10 to 15 lb. engine cold straight off bottom oil line direct to gauge (no line going to head) for test purpose. 3 different gauges 1 American made. Large quantities of oil going to rocker assembly. No restriction at bottom banjo fitting new oil line to gauge. Any Ideas?
ECS Stanfield

Why do you think it is too low?

See manual

Bela

That is pretty low for a new engine. What weight oil is in it? 20/50wt best. Suggest searching archives, volumes about this in there over the years. George
George Butz

Definitely something going on, with a new engine. I look for 70 cold, 55 hot, and 35 at idle on a newly-rebuilt oil pump.

I'd pull the pump and have it checked out.

Tom Lange
MGT Repair
t lange

Did you have a new rocker shaft and bushes fitted? If worn they will lower oil pressure. You say there is a lot of oil going to the rockers. This could be caused by loose rockers.

Jan T
J Targosz

40-50 is normal for an XPAG. Some people boost it by shimming the relief spring. But flow is what really matters.
Steve Simmons

I also had low oil pressure at idle and beyond (20psi) I increased this to 40 psi at idle by machining a small top hat type extension to the spring compressing it further into the ball valve guide. Washers were no good under the spring as they bounded on the bottom of the ball valve guide.This modification was needed after installing a new spring and ball. I don't believe replacement spring materials are of the same hardness as the originals were, hence the problem.
I have included an image of what I machined up to rectify the situation.

John Walton...Sydney

John Walton

The XPAG oil pump pumps enough oil to fill up a bath tub in a few minutes running unrestricted, given a large enough supply reservoir. The pressure relief valve controls what pressure is going to the engine by way of the PRV spring. I felt the oil pressure was a bit high after getting the XPAG in my TC going again after 60 years of storage. Upon removing the pressure relief valve here is what I found. One spring is the normal spring and the other is BMC part # 706/226 "oil pressure booster spring." Upon removal of the booster spring, the pressure now is much more normal, and no more 75 psi readings on the gauge. Shimming, or use of a stiffer spring will boost up the pressure.

D mckellar

My engine runs 50 lbs almost across the board. Idle when hot is about 45 lbs. You can see a slight flicker in the gage when it reaches 50 lbs when starting up, I'm assuming that's when the ball releases. At 50 lbs, I see no need to touch it. PJ
Paul161

That's my point it is the spring rate that controls the pressure. The new spring which I installed was obviously made from inferior material hence the need to add the 100 thou washer to the bottom of the spring.
Flow was not a problem but should not be confused with pressure.
John
John Walton

This thread was discussed between 19/08/2016 and 21/08/2016

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