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MG TD TF 1500 - Low/Slow Oil Pressure

I just finished a light restoration on TD3042. However, after priming the oil system, I find the oil pressure to be painfully slow to come up and low when it gets there (20 pounds at idle) and not going higher. It's the 1 or 2 minute delay to rise that worries me. The following things were changed or checked.
1) Brand new oil pump gears.
2) Oil pump clearances checked and found good.
3) Oil pan pickup cleaned.
4) Main and rod bearing clearances checked and found to be well within tolerance.
5) Oil pump relief spring checked for size and strength.
6) Relief valve ball checked for wear. (.498" and perfectly spherical)
7) Oil gauge line bled and double checked against a known good gauge.
8) Fresh 20W50 Valvoline VR oil. Pressure filled system.

Oil pressure was 10 at idle and 40 at speed before rebuild. This is an early engine with the oil pressure takeoff still at the head.

What am I missing?
Lew Palmer


Lew, I know you sad your car is early TD, and I know they ran the oil pressure gauge off of the head fitting. I've got a really early one myself------


Recommend you swap the banjo fittings around and check the oil pressure and operation with the gauge hooked to the bottom fitting going in to the main gallery. This procedure will at least answer some of the possible causes for your slow/low pressure.
Richard Cameron


Also, check the flexible oil pressure hose to make sure it isn't coming apart inside and partially blocked internally.
Richard Cameron

Thanks, Richard, but it's not the 20 lbs pressure that bothers me. It's the time it takes to get up pressure. I can mentally add 15 lbs to the indicated pressure.

The hose was bypassed when checking with the other gauge, so I know the hose is not contributing to the problem.
Lew Palmer


Not to suggest counter to your desire to stay with original configuration, but using the bottom banjo might tell you something about the slow oil indication. Such as possible rocker arm bushing leakage rate.
Richard Cameron

Make sure pickup to sump, and sump to block bolts in the pickup area are snug. What kind of gasket sealer did you use in those areas? Definitely switch gauge banjo to the bottom and check pressure there. Check for blockage in the adaptor banjo bolt as well. George
George Butz III

Put a piece of duct tape along the block/sump joint area by where the pickup goes through. There should be enough oil sloshing around inside to cover there. If things improve then you have a suction leak.
Ray TF 2884
Ray Lee

Good idea, George and Ray. It will take me a bit to get the car up to check.

Most everything on the engine was sealed with Hylomar.
Lew Palmer

Hi Lew,

The oil pressure in the TF improved by about 5 psi after I renewed the rocker shaft and bearings.

Cheers

Jan T
J Targosz

Jan,

Although the rocker shaft and bushings were renewed a number of years ago, they seemed to still be OK. I'm thinking a suction leak is the most likely issue, but haven't had time to get back at the TD. I need to get the PB Airline Coupe and the PA running first.
Lew Palmer

Changing the banjo position does nothing to improve oil pressure, only a state of mind for those who think a higher number is important to them. 20psi is not a bad number. Not what some of us report but not a bad number nonetheless My oil gauge banjos are at the top of all my engines and I have 45 psi at idle. I am also using 20-50w

Check to make sure the oil line supplying the head is not kinked/crimped. For the benefit of others; likewise for the line to the gauge as it is quite small and easily bent. If the gauge line has been tightened heavy hand repeatedly one can crush the line at the ferrules restricting flow further. Is the gauge also slow to go to zero when the engine is shut off hot? Are you using a late pump on an early engine? What filter arrangement are you using ?

Make sure the plug is installed in the end of the rocker shaft. Also that no oil is in the cooling system which may indicate the plug in the head behind the rear plate is loose or missing.

You don’t say exactly what your clearances were so can’t comment on that.

I would also be inclined to say that slow oil pressure indicating a possible suction issue. Possibly gasket sealant entering the passageway at the oil pan rail. Failed gasket seal at the pick up tube to oil pan.

You also don’t state the clearances on the pump except that they are found good. Subjective descriptions don’t help. Numbers do and how you arrived at those numbers as well.

When you rebuilt the pump did you face the cover plate to remove wear patterns.

Bill Chasser
TD-4834

Did you also rework your rocker bushings and shafts as well?
W A Chasser

Bill,
Lots of questions. Let's see if I can provide answers:
1) I've not tested the flex line to the head. I will when I get a chance. Yes, the pressure is also slow to drop. but I don't recall how slow.
2) Early pump on a early engine.
3) Some twenty years ago, the end plug on the rocker shaft fell out with disastrous consequences, so I do keep an eye on that.
And no oil in the coolant and no coolant in the oil. Clean as a whistle.
4) Filter is a screw on modern type. I use a NAPA Gold 1315 filter.
5) The pump clearances were about .002" gears to case. I don't remember what the gear to top clearance was, but it was very minimal. Maybe .002" or so. No perceptible scoring in the lid.
6) Main bearings were changed about 10 - 12 years ago. Clearances were Plastigauged recently and found to be right around .0015"
I didn't measure the rockers to shaft clearance, but all were found to be snug.

Lew
Lew Palmer

I have an oil pressure gauge taken out of a car at the scrap yard many years ago. I have used it a number of times to verify that the gauge in the car I was working on is reading accurately. I even have a short flexi pipe so I can connect it directly to the engine.


Jan T
J Targosz

A few years ago, on the advise of this forum, I moved my oil gauge line to the bottom banjo and immediately gained an indicated 15-20 lbs pressure reading.
John Quilter (TD8986)

John, as Bill said, moving the banjo take-off does nothing to increase pressure - only the indicated reading at the gauge.

BTW, the flex line to the head and gauge is clear, not kinked, and wasn't involved while testing and verifying the pressure with a known good gauge.
Lew Palmer

I MAY have found the problem. The oil pickup where attached to the inside of the sump had its holes stripped, so the fastening bolts weren't able to be fully tightened. The gasket was fine and well coated with Hylomar. Still not sure, but I'm off to find some 6mm helicoils.
Lew Palmer

This thread was discussed between 02/05/2019 and 04/05/2019

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