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MG TD TF 1500 - oil pressure issue

My '54 TF has not kept a consistent 40-50 pounds of pressure and yesterday going to and from the Bellevue ABFM the oil pressure dropped to its lowest level.

When I first start up the TF the oil pressure reads 50, but then as the TF warms up it starts to drop with the needle resting between that first tick mark (after the "0" tick mark) and the 50 tick mark. Sometimes as "low" as about a third of the way down (towards 50) to resting in the middle between those two marks. I assume that first tick mark represents 25 pounds of pressure. So, after running for a while I estimate the oil pressure is riding between 30 and 35 pounds. Whenever the rpms reach 35 to 40 thousand the oil pressure kicks up a bit, but never up to 50 pounds.

Yesterday, when out on the Interstate and traveling between 60 - 68mph, the pressure dropped to that first tick mark which represents 25 pounds. It never dropped below that, but stayed there for the next hour on the ride home. When I finally pulled off the Interstate and was driving through town to home, the oil pressure went up to what I would estimate to be between 28 and 30 pounds. Oh, and the temp never went above 85c.

Facts: the engine was completely rebuilt by a very reputable shop; the gauges were refurbished by Vintage Restoration in England; I did an oil change recently and used Mobil 1 20-50 (couldn't find any Vavoline VR1).

I thought about adjusting the oil relief valve, but have read that it is non adjustable, except to "shorten" the spring when the oil pressure is consistently too high, which is not my problem.

Questions: This one may be too obvious, but need I be concerned; and two, what can I do to increase the oil pressure?

As always, thanks for your assistance -- John

John Brickell

One more thing: the TF ran just fine, with no lack of power, no unusual clacking or banging from the engine. If I hadn't been looking at the oil pressure gauge, I would not have know something was amiss.

John
John Brickell

john, many modern cars have idiot lights that don't illuminate until the oil pressure drops to 2-5 psi..so the pressures you are seeing will not harm you engine.
if you want to raise the pressure you could do what the factory did..use a stronger spring or add washers between the cap and the spring. unless this change in oil pressure is something new to your car..it sounds normal to me.
regards , tom
tom peterson

make that "youR engine"..sorry
tom peterson

The hotter the weather the hotter the oil which causes some viscosity loss and lower pressures. This is compounded by lengthy high speed running. Can't state what my pressure would be at 60-68 MPH with ambient temperatures of 85F or greater, as I never run my car at more than 55 MPH but at that speed it usually runs about 50 PSI at 3200 RPM with ambients of 80F plus using conventional 20-50 oil.
Not sure if shimming the oil pressure relief valve would have any effect once the pump and engine can no longer maintain the pressure achieved when first starting up cold.
John Quilter (TD8986)

John
Your oil pressure is NOT within factory specs - 50-80 psi. That fact alone would make me investigate the situation and rectify it. What pressure was the engine producing immediately following the rebuild? If it was showing the figures that you are currently seeing then I'd check the accuracy of your guage following it's refurb. I'm assuming that the relief valve spring is the correct length, the valve is in good condition, no filter issues, no oil pick up problems etc.
Peter Malkin

John,
You mentioned that the engine was rebuilt, but you neglected to say how many miles it has on it since the rebuild...
Is 60-68 a regular speed that the car is driven??

SPW
STEVE WINCZE

My 55 1500 runs at 60/62 lbs cold and a constant 55/58 lbs hot. The engine was rebuilt and has about 15 hours on it. Another thing is, it doesn't drip oil on the floor after running. Has the original setup on the back main. PJ
Paul sr

Try a different gauge first to verify that is the actual pressure. 25psi at highway speeds will hammer the rod bearings eventually. George
George Butz

John
You mentioned that the engine was completely rebuilt.Did that include replacing the rocker bushes and the rocker shaft?
Worn rocker gear can be the cause of failing oil pressure in XP series engines
Regards Wayne TD 1864, Y6668
W Routley

Also, make sure the gauge is being fed from the bottom banjo bolt, not the top. George
George Butz

Thanks all for your input. The engine has about 1,700 to 1, 900 miles on it since rebuild. Estimated milage due to tranny (Skyhook) and differential (4.3) changes. Since I have only recently been out on the Interstate traveling at 60-65mph, and that's the only time I have experienced this drop in oil pressure, I can't say if this change has been happening gradually over time.

I will post, later today, what was done in the engine rebuild, but will say now that it was a very complete rebuild.

Off to a hike on the coast, but will add more later this afternoon. Again, your input is greatly appreciated.

John
John Brickell

Hello John. I have had a simular problem. Was running 50-55, am now running 40-45. Only difference oil change. I also changed to VR-1 same weight oil, I guess it isn't really. I'm going to change it out soon.

Butch Taras
R Taras

The oil pressure on my 53TD is also very strange. Hot running around 3,000 rpm's the pressure reads 45psi and when the rpm's increase to around 3,500 the pressure drops to around 35psi. When the rpm's increase to around 4,000 rpm's the pressure pops back up to 45-50 psi. This engine has always had this nature before and after rebuilds. Rocker arm clearance is good, not excessive. I'm not sure what this is about.

Bill
TD24570
Bill Brown

This might be a bit obvious - but did you bleed the oil pipe that goes up to the gauge from the lower banjo union on the block?

Air will compress but oil won't - that might give you strange readings.

Just a thought.

Rod
R D Jones

rod..air might compress, but 50 psi is still 50 psi., yes? all aircraft hydraulic reservoirs use gas in the header tank...the air in the line will dampen pulses, but the pressure should read the same, yes? i have never heard of anyone bleeding the oil pressure line. regards, tom
tom peterson

Bill my guess is the oil pressure relief valve is popping open at around 3500 rpm and the pump doesn't get enough output to overcome it until 4000
Chris at Octarine Services

Again, thanks all for your input. Just returned from a delightful day hiking along the northern part of the Washington coast. Nice day, but kept thinking about this oil pressure issue I'm having. Taking all of your input together, it appears that the most consistent suggestion is that the problem resides in the pressure relief valve. If that's the case, what should be my next move. Remove and inspect? Check spring? Question: If I remove the nut holding all of the pressure relief valve mechanism in place, how much oil will be coming out that I should be prepared to deal with.

John

John Brickell

John asks: "If I remove the nut holding all of the pressure relief valve mechanism in place, how much oil will be coming out that I should be prepared to deal with."

Very little...it's not pressurized and if you let the car sit for an hour or so after you've run it, most oil will have drained back into the sump.

Gene Gillam

I mentioned earlier that I would post a list of the things that were done during the engine's rebuild. The following is a summary of the engine rebuild specs. I assume that#12 & #24 would not have any impact on oil pressure, but they're the only items that refer to oil specifically.

1. The engine & cylinder head were thermally cleaned & shot blasted then magnafluxed
2. Connecting rods & crankshaft were cleaned & magnafluxed as well.
3. Cylinder bores were resized to 2.658 (+ .040"), diamond honed
4. Cylinder block deck was notched to allow clearance for the valves & resurfaced (-.008")
5. Custom brass core plugs in block
6. The rear main seal carrier was align bored to match the main housing bore (.005" clearance)
7. The crankshaft was reground, radiused &; micropolished (-.020 rod &; main journals both)

8. Connecting rods were modified to accept ARP MGB rod bolts (11/32")
9. Connecting rods resized & aligned
10. High strength socket head cap screw gudgeon pin bolts were installed
11. The rod beams were polished & shot peened
12. The block interior & rocker galley surfaces were treated with Glyptal for sealing & to promote oil drain back

13. The flywheel was resurfaced and a new ring gear installed
14. The rotating assembly was balanced to within 1 gram
15. The cylinder head has been ported & polished - intake ports "knife edged"
16. Oversized stainless steel valves
17. Cylinder head has hardened seats conversion for unleaded fuel
18. 3 angle competition valve work
19. Cylinder head cut to 2.908" to achieve 9.2:1 C.R. approximately
20. Cylinder head is machined to accept positive viton valve seals

21. Bronze valve guides installed
22. R&L performance valve springs
23. Crane Camshaft street performance grind
24. The lifters were refaced, polished and have had the oil holes elongated for improved oiling

25. Crankshaft & lifters were treated with TX-1 a proprietary anti wear/friction treatment (  http://www.rlengines.com/tech/TX1.pdf )
26. Custom ARP cylinder head studs were installed
27. Rocker arms were refaced & the rocker assembly completely rebuilt
28. Custom JE Pistons with rings approx. 9.2:1
29. Carburetors rebuilt
30. Distributor has been blueprinted with an electronic conversion on an Allen Syncrograph

John
John Brickell

Sounds like a great rebuild. The main and rod bearing clearances are a big key to oil pressure. Similar but worse pressure issues after my rebuild years ago- the machine shop set everything up to the looser end of factory specs, which was the problem. Also, was the oil pump rebuilt? Whatever you do, verify that it is not the gauge first. Also, make sure the gauge flex line comes off of the lower banjo and not the head. And check for a restricted lower banjo bolt- a local guy here had a problem with that (hole had been soldered shut and re-drilled smaller to make up for worn rocker gear.)George
George Butz

Thanks George -- I'm not sure if the oil pump was rebuilt, but will check with the folks at R&L Engine to see. It appears that the gauge flex line is coming off the lower banjo, but since it doesn't seem that on what I'm viewing there is a "lower", but more side-to-side. See attached photos to see what I mean.

John


John Brickell

next photo


John Brickell

photo #3, connection at the other end


John Brickell

John. It's the upper banjo bolt which are
the restricted one.
Thoralf. Norway TD 4490
Thoralf Sorensen (TD4490)

Okay, maybe I have these banjo bolts mixed up. What should I be looking for? Thanks Thoralf

John
John Brickell

i respectfully disagree with george's statement about 25 psi resulting in "hammered" rod bearings...higher oil pressure is not what keeps the rod bearings lubricated..it is hydrodynamic pressure and the film strength of the oil. the pressure the rod exerts is FAR greater than whatever pressure the oil pump puts out.
my other car is a '35 terraplane straight six..a long stroke engine very similar to our XPAG engines..this engine was produced for almost 40 years..in these engines the rod bearing have ZERO oil pressure..as in none. for rod bearing lubrication the oil pump just moves the oil into trays and scoops on the big end caps just "scoop" oil out of the troughs for rod lubrication. the pump puts out about 4 psi to run oil to the crank bearings.
i stand by my statement that 25 psi is adequate for proper lubrication of these engines. regards, tom
tom peterson

John.
The oil goes from the pump through the channel
along the block to the lower banjo. from there
in a flexible hose and a tube to the gauge.
A steel tube goes from the lower banjo to the
banjo on the head The banjo on the head has a smaler hole which restrict the amount of oil to the
valv train. this upset will give you the
presure from the pump on your gauge.
Hope this is readable and understandable.

The oil to the crancshaft and rod bearings is taken from the channel.

Thoralf. Norway. TD 4490
Thoralf Sorensen (TD4490)

Good point Tom, I often wondered how older engines with a dip oil system survived.

Bill
Bill Brown

John, Connections are correct. Banjo bolts: Moss/Abingdon have sold the same hex bolt for upper and lower for years, neither with restriction. I think maybe some bolts were restricted years ago ( a running change during TD production?). But since the bolts look identical externally, they could have been switched top to bottom. Have to remove and measure/eyeball the central hole diameter to know for sure. Tom,I certainly agree some engines can run with no pressure and just splash lubrication. However, I think an XPAG run at 25psi at highway speeds would be very short lived. And if that is the actual pressure, something is very wrong with something in the rebuild and the rebuilder should fix it. George
George Butz

Thoralf, thanks for the detailed explanation, and yes it was understandable. Tom and George, thanks for your input and you've both made this issue more interesting to me being a novice in such matters.

To all who have so helpfully responded...this is such a great bunch of folks who assist on this BB....I have decided to change oil and filter as a first step. If that's doesn't resolve the problem of low oil pressure, then I will move on to step #2, which will be to remove the oil relief valve mechanism and check and/or adjust the spring. I will report back the results for each step.

Always appreciative -- John

John Brickell

john, i again respectfully disagree with george's post. the hudson engine's operating range is the same as our XPAG engines.
in addition, as i stated in a previous post..many (i would write most, but i cannot post links to that broad of a statement..so "MANY") modern, high reving engine's idiot light does not even come on until 5 psi. with 35+ years as a licensed mechanic, i stand by my post, 25psi is adequate oil pressure for normal street driving. there is no operationally significant difference in the stress on the XPAG vs. the hudson motors and they run the same operating range as the XPAG on ZERO oil pressure to the rod bearings and 4 psi to the crankshaft. the hudson engines have been doing so for 70 years now.
regards, tom
tom peterson

Tom your input is definitely welcomed and taken seriously as I work through the issues concerning the appropriate oil pressure levels in the operation of the XPAG engine in my TF. All such input is definitely appreciated, as I am on a steep learning curve and need all of the input I can get. The folks who participate on this BB have, and continue to, provide valuable information without which I could not be as far along with my TF as I am.

Thanks -- John
'54 mgtf 0781
"Meeker"

John Brickell

I don't seem to understand why taking the oil pressure at the upper or lower banjo would make any difference. Shouldn't the whole oil pressure system have the equal pressure? Isn't this a principal of hydraulics?

And second question: can good quality replacement gears be obtained for the oil pumps?
John Quilter (TD8986)

tom Peterson
I feel that I must chime in here and ask why you would question the specifications determined by the people who designed and built the XPAG engine and it's derivatives. If they say that the engine should operate within the 50-70psi range when hot then I would think that only a fool would not investigate consistently lower readings. I have owned 1 TD and 3 TCs since 1964 (my last TC still with for the past 25 years)and never had readings lower than 60psi.
I think that you are offering bad advice - who cares what a Hudson engine does?
Peter Malkin

John, You are right if everything is perfect- no wear on rocker bushings or shaft and no restriction in a banjo bolt or the copper pipe to the head, there will be no difference. In reality, if there is any bushing wear and/or restriction due to sludge or whatever, the "downstream" pressure at the top will be lower. The pressure in the main galley is what matters. George
George Butz

John, you've got the right idea. But that only applies to a static system. In this case there is flow of the fluid through a number of orifices. Think of your garden hose. The pressure of the water hitting the grass is much less than at the faucet. Bud
Bud Krueger

John, the line that feeds the head has a small internal diameter...mg refers to the oil supplied by this line as "metered" oil supply. You are correct if that line were dead headed pressure would be pressure, but because, as George points out, the rocker assembly is almost a free flow area there is a pressure drop in the area where the small line feeds oil into the relatively larger banjo bolt which has less back pressure from the rocker assembly.
In regards to Peter's comments you are certainly entitled to your opinion about the quality of the advice offered in this posting. I do feel the information about another engine with similar operating characteristics and design is relevant in this case. Ad is the information about modern, higher stressed, higher revving engines not even warning the operator about their oil pressure until it reaches 5 psi. Having said that, if you follow this board you know that i also advocate that the important information the oil pressure gauge gives you is not a peak oil pressure reading but the CHANGE in pressure either sudden...indicating a potentially catastrophic event or gradual reduction over time indicating normal wear. You are entitled to your opinion. I stand by my post based on 35+ years as a licensed mechanic. I would not advise a customer to overhaul an engine whose oil pressure has either gradually reduced to 25psi or a new owner of a car whose oil pressure tan at a steady 25psi. If there was adequate flow to the valve train and no other indication of a problem. 25psi is enough to safely continue to rn the engine..in my opinion. Regards, tom
tom peterson

I agree with Tom on a street engine! Many of the engines in the past had the "splash" system. The old Chevy "Cast Iron 6" is a good example. Those engines ran on 15 lbs of oil pressure,if you were lucky, zero on the crank shaft! What oil pressure was present, was for the cam bearings and rocker arms, no hydraulic lifters! You might get 30 lbs on a cold winter day with 30 weight oil before the engine warms up, if you could get it to warm up! They also had Babbitt bearings that were so soft, you could almost scrape a mark in them with your finger nail. Most of these engines owners used cheap non detergent 30 weight oil at the time, all they could afford, some never changed the oil, just added more when needed. The quality of the oil used plays an important factor on the longevity of the bearings and we have today oils far superior to those of yesteryear! Motor oil and oil pressure have always been a top article in the automotive field and there are a lot of wives tales out there on the subject, where personal use rises above technical proof! Also, forget the oil you used 20 years ago, not saying it was bad, but the new stuff protects your engine much better. JMHO. PJ
Paul sr

peter, i forgot to ask, where did you get your information regarding running oil pressure? you stated "If they say that the engine should operate within the 50-70psi range when hot.." the TD service manual does not give a minimum number and states normal running pressure is 40-45psi. i am not familiar with the TC service manual.
john, you maybe familiar, but if not, what Bud and others are referring to is bernoulli's principle. here is a pic.

regards, tom




tom peterson

tom
Let me start by saying that I don't intend any disrespect to you and I enjoy your input.
My factory "Instruction Manual for the MG midget (Series TC 1954)" states on Page 13, Section B, Lubrication that "as the engine warms up a normal pressure of 50-70psi will be indicated".
My BMC Service Manual(1957)for TC, TD, TF, TF1500 and MGA quotes "Normal Pressure 50 to 70 psi" for the TC.
However for the TD and TF it states that "the relief valve spring is set to allow the valve to bypass at 50-70psi. This provides a normal working pressure of from 40-45psi but so long as a reasonable pressure is indicated it may be taken that the circulating system is working satisfactorily".
Whilst I accept that the story is a little different with the TD/TF I don't resile from my comment that the men who designed and made the engines know best - after all, the Poms were the leaders in motor vehicle technology at the time!!!
Peter Malkin

This thread was discussed between 29/07/2013 and 31/07/2013

MG TD TF 1500 index

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