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MG TD TF 1500 - Oil pressure issue

Oil pressure advice
I hoping for some help here as I am a bit stumped myself on the topic of reduced oil pressure. I have a 52 TD with the original style oil filter (the 2 piece verticle cast aluminum remote of the pump style). My car was has had the same oil pressure since forever (I've owned the car for 35 years)....always ran a 35 psi when warm and at idle and on the road 40+.

The car needed a valve adjustment due to lack of power (as a 1st step) and while it was in the shop I had brakes and bushing checked as well as an oil change. I can't remember the last time I did an oil change so it must be some time ago (I rarly drive the car 2400 miles in the past 25 years... Very few recently). The oil filter looked like it had tar on it and the oil was very dirty. Both replaced with new (20w50 and a new filter from Moss at a cost of $60+ just for the old style/size filter).

When I picked up the car I noticed the oil pressure was at 20 and didn't get much higher (maybe 25) while at speed. 25 minutes later when I got it home (all warmed up) oil pressure was at 6 at idle and I couldn't get it up over 20 with increased revs.

I checked the pressure relief ball -all good. So I decided to remove the filter to see where oil pressure was as that seemed to be the only change made that I could figure would result in lower pressure. Without the filter 40psi cold idle... Put the filter back and 20 psi at idle cold. Seems like the filter is the cause but it is supposedly the correct one according to Moss.....any ideas?
JS Sabah

Has your old filter clogged so much all the oil was going bypass perhaps?

I'm sorta with you too. I usually get 40+ idle, 50-70ish on the move.

Last Friday dropped the oil, flushed it several times with part sump fills and renewed filter element using Ryco R2058. Fresh 20W50 exactly like last fill (didn't do filter last oil change). Off filter didn't look too bad.

Now getting 35ish idle and about 50ish at 3000rpm.
W Chang

If you filter is too restrictive or your oil is too thick/cold, there's the filter bypass that should allow full delivery AND full pressure. Sounds like it is stuck closed. The workshop manual references it in case the filter gets plugged from neglected & skunky oil.

http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=118737

parts 118 thru 121 are just a simple relief/check valve to allow oil into the block. You have to pull the pump to access them.

The strainer in the sump might be gunked up, too (which might be part 125 if they gave it a number) which doesn't help.
JRN JIM

haha so that big knobbly assembly I kept skinning my knuckles against on Easter Friday was actually the oil pump! :)

Access thru the little side letterbox whilst hugging the left tyre.
W Chang

The filter I removed last weekend to see if the pressure went up was a brand new filter from Moss for the cast Al 2 part canister (with a cost of $65). So I don't think it was a clogged filter, nor the screen in the sump as (1) the filter is new and (2) when removed, the pressure went back up indicating the screen is not the issue. Still looking for advice ;-)
JS Sabah

Moss doesn't say what micron filter they supply. It probably isn't plugged, but even brand new, it offers resistance. I deal with all sorts of hydraulic fi;ters down as low as 3 micron. The original felt would probably be rated as 30,000 micron. The Moss filter is probably 10 micron or so.
I take it you didn't explore the filter bypass.
JRN JIM

Filter bi-pass? Please explain. Also, it stands to reason that the smaller micron filters would cause a difference in pressure ... But would that be a higher pressure on the inflow side or a lower pressure on the exit side... And where does the guage read from and what is in the actual engine. I would think that the high pressure would only be between the pump and the filter and the engine would be lacking
JS Sabah

Wouldn't have a clue what is exact path of oil thru these pushrod wonders, anybody know definitive oil route? :)

Does it go from sump into pickup, sucked into the filter (outside in?) then into the pump... where it's pressured upwards into the head & cylinder walls?
W Chang

https://www.youtube.com/watch?v=ShHAaDKL3gM
mog

http://www.mgccyregister.co.uk/technical-information/the-xpag-files/engine/the-xpag-oil-system/
mog

Gents,

The WSM shows the path(s) of oil flow through the pump/filter/block/cylinder head, etc. Filter is on the output side of the pump. The pressure relief is an over-pressure relief device. The gauge reading is affected by the valve train, rockers condition.

Regards,

Jim Haskins 1953 TD
J. M. Haskins

Repeat of what I originally posted above on the filter bypass circuit. You can see the parts in the Moss catalog.
The strainer in the sump isn't part of your situation, but I just thought I'd mention it. It can collect crud- I'm going to pressure wash one soon to remove trapped crap.


The gauge reads the block's oil gallery pressure after the filter. The inlet side of your filter is at a higher pressure and is probably running past the relief valve dumping back into the pump suction side, rather than running into the oil gallery through the filter bypass. That's why I suspect your filter bypass circuit is stuck or maybe has been plugged by a previous mechanic.

"If you filter is too restrictive or your oil is too thick/cold, there's the filter bypass that should allow full delivery AND full pressure. Sounds like it is stuck closed. The workshop manual references it in case the filter gets plugged from neglected & skunky oil.

http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=118737

parts 118 thru 121 are just a simple relief/check valve to allow oil into the block. You have to pull the pump to access them.

The strainer in the sump might be gunked up, too (which might be part 125 if they gave it a number) which doesn't help."
JRN JIM

Jim, The oil pressure line wasn't moved to a fitting on top near the head was it, after work was done on the engine. Putting the banjo fitting with the take off on top usually gives lower pressure readings on the gage. PJ
Paul S Jennings

The ‘Pump By-pass Valve’ ( The Emergency Feed.)

A great explanation thanks to:

mog, cattery, United Kingdom

http://www.mgccyregister.co.uk/technical-information/the-xpag-files/engine/the-xpag-oil-system/


Paul,
I wondered about the banjo fittings, too, but if removing the filter restored the preszure, then that issue wouldn't be the culprit (unless the banjos were mistakenly swapped back and forth with the filter).
JRN JIM

Excellent read on the link posted by Jim.

Thank you.
Frank Cronin

Frank,
Thank "mog, cattery, United Kingdom" not me.

I send my thanks, too, for an excellant post.

And thanks to Keith Cairns for writing it in the first place!
JRN JIM

Isnt it Neil Cairns?

some great resources out there, hats off to people who spend the time, I wish I had the gumption to do the same.
mog

My apologies to Neil. I do wish we could go back and edit our posts to correct misteaks (<-- and mzzpellingz).
JRN JIM

This thread was discussed between 07/04/2015 and 12/04/2015

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