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MG TD TF 1500 - Oil Pressure and Leaks

I just did an oil change on my 51 TD, using 20W50 as recommended in various posts. The new filter I purchased doesn’t fit, there seems to be a slight taper in the filter housing so it won’t seat to the bottom, so for the sake of firing it up I put the old filter back in which wasn’t in too bad shape, I’ll get another filter in the next few days.

My oil pressure did come up a bit, but after the engine is nice and not I’m still only getting about 10 at idle and tops out around 30ish driving 40-50mph. So first question is…is it safe to drive it around with 20-30 oil pressure?

Second question…I looked underneath with he engine running and there was a lot of oil leaking out. Prior to the oil change the car would leave a small hand sized oil spot after parked, but this was significant. It’s not leaking from the sump bolt or filter housing, rather from a small hole with what looks like a cotter pin inserted. I’m attaching a couple of pics, what is this and is it a correct part? I do think I added too much oil, is this for oil overflow? I can't find anything in the manual or online about it.

Thanks,



SD Denham

That is a weep hole behind the sump. It is dripping oil from the rear main. That cotter pin is there to help keep hole open and clear so oil does not fill up the clutch area..
With the new thin oil, it is leaking more than before, correct?

M Grogan

SD,
How about some history on your engine, how many miles on the engine? I'm thinking a possible bearing problem, or blow by, ,, Do you have oil getting up into the distributor ?
Steve Wincze

The oil is not thinner, the oil that was in it before was 10W20 so 20W50 should be thicker which is what various threads said to use in general and also some thoughts that it would up the oil pressure. I did find out this is the cotter key and I think the extra dripping is because I put in two extra quarts by mistake. I don't have the desire to open the sump again so will just let the oil leak while driving and keep an eye on it and see how she's running when the oil level is normal. Still looking for feedback as to if its safe to drive with the oil pressure in that 25-30 range.

Steve
SD Denham

Steve,

I believe the recommendation is 10psi per every 1000 rpms. Around town you should be fine and it may go up when you change out the old filter.

Not sure why you're against draining the excess oil...
Gene Gillam

Steve
If you really put two quarts too much in the engine, drain some out.

Tom
'54 TF
T Norby

I agree get you oil level corrected. The excess volume is likely being churned up by the crankshaft windage causing foaming and aeration of the oil in the pan. The resulting aerated oil will be pushed out of every orifice due to positive crankcase pressure. Re low oil pressure When the aerated oil enters the pump, the volume then compresses, the gas and pressure is lost. A liquid does not compress thus the volume and the pressure are maintained minus friction loss and elevation.
W. A. Chasser

Thanks, I will drain the excees oil tomorrow morning, I had no idea it could cause these issues!
SD Denham


Since your car is an early TD, I wonder if your oil pressure gauge pipe is connected to the fitting at the head or on the lower one at the main oil gallery?
Some owners have seen significantly lower oil pressure readings from those cars where it goes to the fitting on the head.
Richard Cameron

A year or so ago, I learned of the correct location for the oil gauge line and changed mine to the correct lower location. Immediately gained 15-20 lbs indicated pressure on the gauge. A worthwhile change I would never have learned about except for the forum.
John Quilter

You seem to have two problems.
Low oil pressure could simply be a symptom of a worn engine. What is the history of the car? it could also be the wrong sized spring in the oil pump pressure relief system. I found when I rebuilt my engine that I could manipulate the pressure by altering the spring size.

You obviously have a leaking rear main oil seal. Most of these cars leak oil out of the rear seal. To do a proper fix means taking the engine out. There are two other options:
Collect the oil in a drip tray or try fitting positive crankcase ventilation. You can look up either of these in the site archives.

A
A R Jones

Regarding the overfilling, I have done some measuring on an early TD sump, which I assume is correct as the finned sump was not introduced until April 1952 - also, all dimensions metric to avoid the US/UK imperial confusion.
The bottom oil recess below the metal plate is 28.5cm long X 19.5cm wide X 9.3cm deep. This is a capacity of 5.2 litres. Above this recess the sump expands into an area 37cm long X 19.5cm wide, which are the same dimensions for the later finned sump. The crankshaft rotates in this area and clears the plate by 9.5mm.
The TD manual states that the sump needs 9 UK pints of oil, which is 5.11 litres. This is close to the 5.2 litre capacity of the oil recess, but once the engine is started, the oil filter will fill, assuming it was also changed. As best I can measure, the original oil cannister filter is 0.86 litres - the later replaceable element housing may be slightly larger, but does not seriously affect the calculations. There are other places that hold oil, such as the oil pump, but during an oil change they will retain what oil they had before.
Thus of the 5.11 litres added, after the first engine start and stop, only 4.25 litres will drain back into the sump. This allows 0.95 litres of spare capacity below the metal plate.
2 US quarts extra have been added, which is 1.892 litres. Deducting 0.95 litres to fill up to the metal plate leaves 0.942 litres over the plate. This will go into the 37cm X 19.4cm area, and will go to a height of 13mm. As the counterweight clearance is only 9.5mm, they, and possibly the big ends, will dip into the oil.
(PS, SD Denham only changed the oil; he didn't make any other changes).
R A WILSON

WA Chasser correct- grossly overfilled, crank hits oil and foams and causes low oil pressure and leaks everywhere. George
George Butz

Additional information.
The finned sump has a capacity of 6.7 litres below the metal plate. When it was introduced, the required amount of oil, according to my manual, was increased to 10 UK pints, 5.68 litres. Deducting the 0.86 litres to fill the filter means 4.82 litres will drain back to the sump. This will leave 6.7 - 4.82 = 1.88 litres 'spare' capacity below the metal plate.
Oddly, my manual indicates that when the TF1500, with the XPEG engine, was introduced, the required amount of oil was increased further to 10.5 UK pints, 5.97 litres, with no change to the sump capacity. Again, deducting the 0.86 litres for the filter leaves 5.11 litres draining back to the sump. This leaves 6.7 - 5.11 = 1.59 litres 'spare' capacity below the plate.
(I apologise for the previous use of three decimal places - just trying not to introduce errors).
R A WILSON

Drained excess oil, pressure came up to 35ish driving which is a new high, still drops after warm down to 10 at idle and about 25ish driving, I'll keep at it.

I'm not expecting miracles but has anyone had any success reducing oil leaking using Lucas Oil Stop Treatment?

Steve
SD Denham

Suggest plumbing in another pressure gauge to verify that is the actual pressure as originals can fail to read accurately. As asked above, where is the gauge takeoff- at the block or head? George
George Butz

Steve, consider having your rocker arm assembly rebuilt.
Doing so gained an additional 10 psi of oil pressure for me. There's an outfit on the west coast that does it for a very reasonable price. Bud
Bud Krueger

Hey Bud, do you remember the name of the place out west? I'm in CA so if it's local that would be convenient, also have been looking for a shop that has good working knowledge of MGs that I can partner with for repairs and upkeep, I'm near Huntington Beach so there's plenty of hot rod shops which I don't need :-)

Steve
SD Denham

Steve,

This is the place Bud is referring to...I had a rocker arm rebuilt by them also.

http://www.rockerarms.com/pages/contact.html

Gene
Gene Gillam

Before you strip out your rocker gear. Disconnect and cap off your oil supply to the rockers. If there is no big change in oil pressure then look elsewhere (pressure relief valve and spring),
Ray TF 2884
Ray Lee raybar2(at) tiscalidotcodotuk

Steve,
Unless I missed it, We still dont know any history of your motor. Does it have a lot of miles on it ?

Steve
Steve Wincze

That's the place, Steve. If I were starting the rebuild of an engine one of my first steps would be to send the rocker assembly to them. Just be sure to check the assembly sequence when you get it back. Bud
Bud Krueger

Thanks Bud, I don't have the experience or tools to pull the engine and remove the rocker, when I win the lottery I will find a place that will do a full engine rebuild for me! I drove it about 50 miles yesterday with a lunch break and it drove decent, oil leak is minimal drip and after checking oil when home it looks like I lost maybe a half quart, so not horrible. As long as I can get to the beach and back without worrying about a call to AAA I'm happy :-)

Steve
SD Denham

This thread was discussed between 09/07/2016 and 17/07/2016

MG TD TF 1500 index

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