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MG TD TF 1500 - TF oil pressure

XPAG-TF35626 has been completely rebuilt and runs very well, with no overheating or other problems.However,maximum oil pressure is 35psi at any revs above idle where it maintains 27psi. The oil pump has been rebuilt and the relief valve spring is new.After adding one and then two copper coins ther is no improvement.I have about 200 miles on the car.
Am I risking damaging
the engine ? Any advice would be much appreciated. Thanks,
Bob




R.P.S. Stewart

Are you sure the gauge is working correctly? I would try to verify the pressure with a mechanical test gauge before going any further.
D. Sander

If the hose to the pressure gauge is connected to the top banjo bolt into the head, try switching your pickup down to the lower banjo bolt.

Make sure you're running diesel oil! You shouldn't have any problems with 35/27 psi with diesel oil.

Bumping up viscosity wouldn't hurt either if the pressures are in the medium range.
Jim Northrup

Make sure it is 20/50 wt oil. Check above two things with the gauge and take-off location. Also, make sure that the lower small banjo bolt has not been "restricted". Some years back I helped a friend chase similar pressure problem. A DPO had soldered one banjo bolt shut and drilled a tiny hole in it to make up for worn rocker bushings and shaft. When we put the motor back together, that banjo went in the lower fitting, and similar low oil pressure deal resulted. If it is really only 35,I think that is too low- the old-time standars was 10psi/1000 RPM. George
George Butz

Thank you all for the fast and informative responses.
The oil is 20/50wt.I will switch to diesel. Checked with another pressure gauge and same readings.
Neither banjo bolt is restricted.I realize I will get a higher reading from the lower bolt but really is no actual improvement (except visually).Also the lower hole has "bulges" surrounding it on the block making it very difficult to fit the flex line adapter.
Believe I will have to dissassemble the pump to see if there is anything obvious there.
Thanks again,
Bob
R.P.S. Stewart

Bob, IMHO you should nix the idea of going to diesel oil. Stick with a 20W-50 that has an adequate concentration of ZDDP. It sounds to me as if your problem is related to the oil pump bypass valve. I don't know what the 'two copper coins' is about. Pull the bypass components out and inspect them. The ball that does the actuating is known to develop grooves that prevent proper actuation. It you have 27 psi at idle you should have a good pressure (60-70) psi at higher speeds. Bud
Bud Krueger (TD10855)

Thanks Bud, appreciate your comments.The copper pennies are shims to increase the relief valve spring tension.I have examined the ball and it does not have any grooves and seats very well.I agree that with 27psi at idle there should be 60-70 at speed, which makes me wonder if the rebuild of the pump left some clearances that are too large.
Bob
R.P.S. Stewart

One other simple idea to rule out a problem with rocker arm/shaft leakage: remove the top of the line to the head and block it off (nut/bolt/washers). See what that does to the pressure. I went through the same thing and I hope you find something simple! George
George Butz

Bob,

If you are getting 27 lbs oil pressure on idle, I would suggest the problem is elsewhere, and not with the oil pump. George B's suggestion is a good starting point.

George Raham
George Raham [TD4224]

When I first started to drive my TD around 11 years ago, it idled at around 8 lbs and never got above 15-20 when hot at driving speed. I researched the po's paperwork (which was extensive-I wish I had what he spent through the years), and found that since the car was restored (poorly) in the late 70's, the po constantly complained about the lack of oil pressure. I was afraid to drive it as it was, so I started to try to sort it out. The first thing I did, after troubleshooting and verifying the accuracy of the guage, was to redo the rocker shaft and rocker bushes, as George mentioned. This made a small, but noticable difference. I next removed the engine and pulled the pan to check out the main and connecting rod bearings and found that the #1 main bearing cap had been installed backwards, which caused it not to seat properly, produceng a huge gap. I recut the crank .020 under and installed all new bearings. When I put everything back, I got 15-20psi at a hot idle and 40-50 psi at a hot highway speed. I guess what I'm trying to say is that if you are getting such high pressure (if it is indeed accurate) at idle, the only thing, to my thinking, that would not allow it to increase linearly with speed is if the pressure relief valve is venting at or slightly above 27 psi. It's very strange, because your idle pressure is on the high and healthy side, but your high speed pressure is a bit low, but not unacceptable! Perhaps your oil pick-up screen is a bit clogged, not allowing enough flow. It just seems that any loss of pressure due to any sort of excessive gaps, would murder your idle pressure!
Steven Tobias

Hello George, George, and Steven.Apologies for the slow response. Your comments and suggestions give me more ideas to try.
The engine is just completely rebuilt (rebore, new pistons, rings, bearings,cam, rocker arm, the works)and was reassembled by a profssional engine rebuilder while I watched.I do think the relief valve and seat need to be rechecked and also will recheck the pump clearances. When I do find the solution, will post the details here.
Thanks everyone,
Bob
R.P.S. Stewart

All above are good, but start with the gauge. If you can verify the pressure with another gauge and the shims under the spring are not increasing the pressure, you could have an air leak where the pickup tube hooks to the oil pan. Did you install a gasket on this when you put it together?


You have great idling pressure, so you can most likely rule out any issue with the pump working properly. You either have an air leak or a bearing clearance is off.
Bruce Cunha

Bruce,
Thank you for your comments.An air leak is something that had not occurred to me but I am almost positive that I did use a gasket on the pickup tube.It's been about two years so the memory fails but I always use a gasket in such a situation. As to a bearing clearance, it's possible but unlikely, knowing the reputation of the person who fitted it.
Just spoke to a person who restored an early TD several years ago and claims to have never had any more pressure than mine! Still, I am sure there is something not right.
Thanks again,
Bob
R.P.S. Stewart

... and don't forget a dose of dialkylzink diothiophosphate.

gc
Gordon A Clark

Bob, Not sure how the cam bearings get lubed in this engine, so take this information on a generic bases. I didn't see any mention of the cam or cam bearings. Was a new cam installed with new bearings or was the old cam left in there? If the old cam was used, were new bearings installed? Was the old cam, if used, miked at each bearing surface? I know I'm harping on the cam a lot, but I've seen it where one of the old cam bearing surfaces was worn a tad more than the others and when new bearings were installed, two bearings were tight and one was loose. That's why I always use a new cam with new bearings and line bore. Just a thought. I, like others, would certainly like to know what the solution to the problem is. PJ
P S Jennings

Hi all,
Many thanks again for all your interest and input.I have tried many of the suggestions to no avail, so have decided to keep driving the car, lightly and infrequently, until the summer is over. Then the oil pump will be removed and checked out for clearances etc.
Bob
R.P.S. Stewart

bob, i just read your post. if what you are saying is 35 psi at road speed with hot oil and 27 psi idling with hot oil, with the upper banjo used as the pick off for oil pressure...i think you are good to go. 27 psi at idle with hot oil at the upper pick off point is more than enough pressure.
i agree with you, whether you tap off upper or lower, you are still looking for a change in pressure to indicate trouble. (personally, i think the factory moved the pick up for psychological reasons and to quiet customer comments.)
the pressure up top is still the pressure up top whether the pick up is there or not. i say drive your car and watch for a change. enjoy the rest of the summer.
i also suggest you NOT switch to diesel oil. gas engine oils and diesel engine oils are formulated to run in COMPLETELY different operating conditions with COMPLETELY different combustion by-product contaminants. one reason guys switched to diesel oil was that diesel oils were later in reducing the zinc content. all my reading indicates the zinc is now reduced in those oils as well. regards tom
tom peterson

Do you have a spin-on filter adaptor, and if so, what filter are you using?
George Butz

Tom,
I agree with what you are saying. With 300 miles on the engine now,it is running well so will continue to drive it (carefully).
George,
I am using a spin on, a FRAM PH3600.Drove the car for a few miles with the original filter and had the same oil pressure then as now. Changed to the spin on because I could not get the original to stop leaking!
Thanks to you both.
Bob
R.P.S. Stewart

Bob,

You say the engine was totally overhauled.

Did you change the rocker shaft bushings and the shaft?

This is a sure source of low oil pressure.

Gord Clark TF4592
Rockburn, Qué.
Gordon A Clark

... incidentally, The FRAM PH3600 filter is an absolute piece of junk especially on a new, tight engine. Replace it immediatly with a K&N HP2009.

WalMart sell the PH3600 for $3.92 and the HP2009 for $12.25

Remember, you only get what you paid for.

Gord Clark TF4592
Rockburn, Qu.
Gordon A Clark

This thread was discussed between 13/07/2010 and 04/08/2010

MG TD TF 1500 index

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