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MG TD TF 1500 - Oil Pressure shows 100 psi

Bala - Germany,

Starting another thread to not hi-jack the other.

Did you bleed the oil pressure pipe up to the gauge?
To remove any air.
With the dash pulled forward a little and a rag under the oil gauge - Loosen the nut at the gauge and wait till a little oil is seen. Should be enough.
Just a thought.

Alternative, have you had the gauge tested for correct reading?
100psi just seem really high to me. Certainly never seen it on the two TD's I have owned. Even after a full engine rebuild.

Have you changed any of the springs in the oil pump?

Lower readings I have seen - Sad to say :)

Rod
R D Jones

Bleeding the oil pressure line is totally unnecessary.
Hugh Pite
H.D. Pite

Seems to me like something is definitely wrong. I'm wondering if a blockage in another oil feed might cause higher pressure readings on the oil gauge feed?
Don't want to cause undue alarm, but I've never heard of 100 lbs on an oil gauge in a TD before.
Geoffrey M Baker

Check the relief valve assembly. Air in the line to the gauge will not affect anything. The first time you shut off the car, the oil will drain out and it fills with air again anyway.
Steve Simmons

I have not tested the gauge for correct reading in absence of an other instrument.

I'd bought the car from a mechanic. After engine rebuild he had been dissatisfied with oil pressure. Overhauling the oil pump gave not a significant result. After that he had modified the rocker arm shaft by replacing the bearing and shaft. The oil pressure then was high. He also was bored waiting for the oil pressure after parking the car a longer time. So he decided to integrate a valve at a place I don't know. This valve keep the oil in the upper rooms of the engine after stopping. He drove the car many years but couldn't tell the milage because speedometer was changed two times. I'm still wondering if such a high pressure is a real advantage.

Bela

Rocker shaft may have been installed upside down and backwards. This could acct for some of the increase. I would consider a pressure relief valve that may be stuck closed. Running a very heavy oil. Is this sudden for the engine or has it always been that way since you acquired it. Pressure is not near as important as volume as pressure increases ->. Volume decreases
W. A. Chasser Jr

It always appears since I acquired the car and since the preowner had made the changes some years ago (he said so and I believe him).

Oil is 20-W50 Castrol Classic.
Bela

Heavy oil or an upside down rocker shaft will not make the oil pressure increase past the setting of the oil pressure release mechanism. Therefore it follows that the oil pressure release is not working properly. Perhaps the PO put a heavier spring or a bunch of spacers under the original spring to increase the pressure. Take the big brass plug off the oil pump and check that all is well with the spring tension and ball.
Hugh Pite
H.D. Pite

I guess you are right. The PO could not remember if he had also modified the oil pressure release mechanism. The release should start at aproximate 50PSI.
Bela

I learned that my oil pressure readings that are up in the 95 psi range are caused by a non-linearity in the gauge. It's fine up to about 65 psi, and then starts getting optimistic. I'd suggest checking the gauge. My actual high reading is about 80-85 psi. Hot running is (and has been for years) about 70 psi. Bud
Bud Krueger

Does the gauge always return to zero when the engine is turned off? The gauge in my TF often hangs up. Current pressure plus the "hung up" pressure equals high pressure reading. Even worse, I can't trust it at idle. It will return to zero if I tap on the back of the gauge with a metal object, or sometimes it returns to zero all by itself.

Lonnie
TF7211
LM Cook

Yes the gauge always returns to zero.
Bela

I once got a 100 lb reading momentarily after I had played around with shimming the oil pressure relief valve. Immediately redid my work.
John Quilter

Bela, put a test gauge in place and see what you get for readings. Bud
Bud Krueger

Thanks to all!

Next stop in the workshop I will let them compare the gauge against a test equipment. Before I will have a look at the release valve.
Bela

Hi Rod,

If it is actually high pressure, and not a faulty gauge, I would suggest you do not run the engine for long. You risk chewing out the camshaft/oil pump drive cogs. I have had that experience in my race TC! I regard about 60 psi, or a bit less, as optimum.

Bob Schapel
R L Schapel

This thread was discussed between 08/10/2015 and 09/10/2015

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