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MG TD TF 1500 - Oil pump rebuild 51 TD

I've put the oil pump back together, and it spins nicely. However, the discovery of a short bolt being used to increase oil pressure leads me to believe I need to do a rebuild. I'm curious as to whether a rebuild just using new gears is generally sufficient, or should I go for the whole rebuild kit, including bushings, springs and drive shaft. What have others done here?
Geoffrey M Baker

Go to the Moss catalog page for the oil pump rebuild kit, and print out the INFO tab - it gives all the measurements to be checked. "Spinning nicely" doesn't measure any clearances.

You had the shaft out, I believe; what wear was there on it? That will be an indication of the need for a rebuild.

Tom Lange
MGT Repair
t lange

Geof,
Your comment "short bolt being used to increase oil pressure" has me scratching my head. No comprendo. The worst case scenario comes to mind- a previous owner stuck a bolt in that fit, but was shorter than the original.

Look, you reported excellant oil pressures before, RIGHT? Am I wrong? It doesn't make sense to mess with it. Maybe just procure the correct screw(s) lest threads get stripped tightening it back up.

I oncesurface ground one of our pump's components, cleaning up only a few thousandths of an inch (a bit of overkill on my part anyway), but didn't need to substitue shorter screws.

Please explain your concerns better; it doesn't make sense that a short bolt has anything to do with your oil pressure. I'm an engineer and run a hydraulics business, so, on the surface, I think you have nothing to be concerned over.

I'm there in your corner, like the others here,
JIM
JRN JIM

While I agree with Jim, that if you had good oil pressure there may not be a need to rebuild yours, I am also of the mind that While you have it apart, new parts can't hurt and will give you piece of mind on the condition.

I also did not understand your short bolt comment. Normal things I have seen with oil pumps to increase pressure is usually washers under the pressure relief spring.

The body does not normally wear, just the gears, the drive shaft and the cover cap. If there are wear marks on the cap, it can be resurfaced as Jim stated. Also as Jim stated, unless the cap was resurfaced in the past and they took off a lot of metal, normal length bolts would still work.

I don;t know what the maximum you can mill one of the oil caps. Perhaps someone on the site has that information.

I am not sure if the cap is the same on all TD's or if the ones with the oil filter attached are different, but I do have a cover for the early type oil pump if you find yours is scored and can't be resurfaced any more.
Bruce TD4139 Cunha

I also wrote in another thread that I had never seen a bolt used to increase oil pressure. Also, I suggest you look at the Moss page with all the specs.

I don't consider 10 pounds at idle anything more than marginal...

Tom Lange
MGT Repair
t lange

Jim, Bruce, I think you are misunderstanding the issue. The bolt was simply used to provide a spacer to increase pressure on the spring. it didnt' screw into anything; it was a spacer used to compress the pressure relief spring and therefore increase pressure in the system. There are no "shorter screws"... where others have reported putting a washer between the spring and the plug to increase pressure, this person used a bolt head and a washer to increase the pressure, that's all. I'll post pictures on Monday if that helps.
Geoffrey M Baker

Gentlemen,

I am reading this thread with great interest. In my world (plumbing & heating) cranking down on the pressure regulating valve increases pressure but often reduces volume (depending on the type of control valve used). Would that apply here? Is pressure more important than volume.
Daniel Nordstrom

Geof,
Let's try this one question at a time. What was your oil pressure warmed up, running and at idle?
The issue of oil pressure was originally addressed in "engine failure 51 TD" but it was never stated oil pressure was a problem.
Considering the bearings and pistons came out looking good is indicative of adequate lubrication, pressure, volume and viscosity wise!

Again, what was your oil pressure warmed up, running and at idle?

JIM
JRN JIM

I see now, this is a continuation of your previous thread "51TD oil pump weirdness."

At 10psi idle, I can see why someone tried to up the oil pressure shimming the relief valve which only bleeds excess pressure/flow. It doesn't compensate for low pressure.

Oil pumps are often the focus of attention when pressure runs low, but more often than not, it is worn components letting too much oil bleed by. If your pump is abnormally worn:
1) the end plates & gear ends can look scored;
2) one side of the housing may shinier from wear by the gears.
My hunch is, you won't observe either.
If you want to put it in perspective, a gear pump this size (or just a touch larger) might power a log splitter with a few thousand psi.

Recently, someone asked about opening the hole in the banjo bolt for the oil line to the head. That's one way to lose some oil pressure, particularly at idle. You might take a moment to pull the two banjo bolts for that line and inspect that one has a hole much smaller than the other.

What weight oil are you running? Since ours was running soooo hot (supercharged, 80+mph, 230F on hot days) I fed it diesel oil, like 15W-40. I had switched to diesel oil anyway after ZDDP was left out of automotive oils, but now I add Rislone with ZDDP to the diesel oil in some of our vehicles. If you're dead set on rebuilding the engine, heavier oil will let enjoy this driving season and become more familiar with your TD.
JRN JIM

A test provided by Sandy Sanders of FL years ago,
"Try this little experiment. Undo the oil line to the cylinder head and plug the fitting with a nut and bolt with two soft washers. This will eliminate the oil to the rockers. Do not be afraid to run them without oil for a few miles. It will not hurt anything. There is a good chance that your oil pressure will rise greatly.If so then you will need to replace the bushings and rockershaft. I bet that is your problem.
I have seen at least 15,lbs difference with new bushings properly reamed along with a replacement shaft.These rocker bushings impart a strange appearing wear pattern to the shaft."

A lot of guys have suggested over the years, double check you pressure with a new pressure gauge. It could be your old one is displaying a touch low.


JRN JIM

Remember Moss had an adjustable pressure regulator, which was a nut with a knob that screwed in to the pump in place of the lower cap. Somewhere in the archives is a quote about the factory using different springs or shims if the pressure was out of spec on some engines. This would really only help if a spring was too weak and bypassed causing low pressure, or with a tight clearance engine would raise the pressure before bypassing. Tom and Jim's advice spot on- read the Moss info and check clearances, an visually inspect.
George Butz

still delivering good oil pressure though worn.

mog

Years ago I had low oil and had the oil pump housing flat lapped and put it back together and viola good pressure. I have put on the Moss adapter as shown in Georges photo and it has now been on 8 years with no problems. .
T Maine

I've read the Moss tech info stuff on oil pumps and dug through the archives. I'll do what measuring I can for wear and make a decision at that point what I need to do with the oil pump. I definitely want to get the pressure back up, and it seems like I should at least lap the oil pump face and housing flat again as well as probably replace the gears. If that fails to increase the oil pressure sufficiently I'll look into a full oil pump rebuild.
As far as wear on the rest of the engine components, I hope to be able to get it all torn apart and into a shop for evaluation and measurement this week.
Geoffrey M Baker

Geoffrey - I recently rebuilt (last year) my oil pump with the MOSS rebuild kit. Lapped the face by hand (several hours) despite being told I couldn't get it smooth or level enough that way and now have 50 lbs at idle hot, 60 - 75 lbs running.

Gene
Gene Gillam

John Twist wrote a comment on the MGB thread relating to lapping a MGB cam thrust plate. He gives advise on how to do this. Having used his advice, I can say that it works and I can't see why it would not work on the oil pump cap.

I use a piece of glass with my sand paper on it. If

http://www2.mg-cars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=71&subjectar=71&thread=2003052820431924218
Bruce TD4139 Cunha

"I definitely want to get the pressure back up"- How do you know it is the pump? Could be worn rocker bushings, main/rod bearing clearances, etc.
George Butz

George, I don't know. But I will soon know how much wear there is throughout the engine. (I assume there is quite a bit, already, looking at it so far). But I have the pump out now and seems like just lapping the faces and the gears, at a minimum, is a good investment. After all, it's not really an issue of one thing wearing, they ALL wear together, bearings, engine, crankshaft, oil pump... doing one but not the other probably won't get me too far. My end goal here is to a) KNOW what is wrong with the engine, thoughout, and b) fix it!
The end result should be great oil pressure!
Geoffrey M Baker

This thread was discussed between 21/03/2015 and 24/03/2015

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