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MG TD TF 1500 - Oil Pressure Questions

Got a question 0r 3 on the oil pressure in my 1951 TD. To start, the p.o. broke the crank in the original engine. He took it to a Import repair shop to have it repaired. That was in 2009. They had it till 2010. The po furnished a different 51 block. they rebuilt it with a new steel crank, to the tune of $10,000. It had about 500 miles on the new engine when I bought it. When I got it, it was only running about 20 psi pressure. I found that the oil filter element was plugged, (he charged the po 11.50 for a element, but it was still the old sock type) I pulled the element out and the pressure came up to about 35 psi. I pulled the bypass valve, and shimmed it up with a .060 shim. That brought the pressure up to about 50, 40 at idle. This seemed ok, but then I found that after driving for about 15 miles, the pressure would drop to 35, but when I slowed down it would go back up. I tried dropping the valve again, and went to a .070 shim. This raised the pressure about another 5 lb. Today I took it for a longer drive. The pressure was about 55 till it got really warmed up, then would drop to 40 than come back up, than drop again. I tried running about 50 mph, and it would drop, a couple times to 35 than back up if I slowed down. I took it up to about 55+ and it ran about 40. When slowed to 50 it would drop a little, but if I went to 45 it would come up to 50-55. When I got home and it was well warmed up, the idle held about 38. After it sat for 5 minuets I started it again, and it idled at 45. Sorry to have rambled on so long, but I am confused. Any thoughts? Other wise it just runs like a clock.

Gary
G Parker

Do you have another "master" gauge to check the in-car gauge? Regards, Tom
tm peterson

Gary,
Doesn't sound like any catastrophic damage has occurred,
and the worst case scenario could ultimately mean... just changing bearing inserts.

QUESTION!
Your banjo bolts (block up to head)/pressure gauge hose- there is one banjo bolt with a small hole. Is that one in the block or the head?

Here's the thing- that small hole needs to be up into the head. If it is down in the block, the gauge is registering a fraction of the real the oil pressure up to the head alone, not the pressure of the block and bearings.

Yank out the two banjo bolts and identify whichi is where, then report back.
JRN JIM

Also, make sure the gauge feed is off of the lower banjo bolt, not off of the head. What weight oil are you using? Should be 20-50. George
George Butz

Tom, I don't have a master gauge, to check the original against. Possible I will have to find one.

Jim, I pulled the banjo bolts, and the hole in the top one is slightly larger than the bottom one Do you think I should reverse them? I an enclosing a couple picture of them. I looked in Moss's catalog, and they show the same part number for both of them.

George, The oil pressure line is coming off of the lower banjo. I am running Castrol 20 - 50 now, but I intend to order a screw on oil filter adapter from Butch Taras, but want to get this issue sorted out first. Then I will switch to Valvoline 20 - 50.

Right now I am running without any oil filter element. I wouldn't think that would make any difference, but thought I would throw that in.

Gary

G Parker

image 2

G Parker

Gary apart from the good advice from the other guy's .
Check the following,

Take the pressure regulator out ( bottom of the pump, sorry you have to get on your back under the car ) inspect the ball for scratches or other imperfections. I had similar problems some time a go after replacing the old sock type filter and mounted a spin - on filter with adapter.

Please keep us posted with your findings,

Gerard
Gerard Hengeveld

Gary I have tried to upload various pictures "how the banjo bolt should look" but they disappear in the cloud
(as usual I guess ) Send me your email address and I send them to you .

Gerard
Gerard Hengeveld

Here are Gerard Hengeveld's images, he sent them to me and I'll try to upload them here.

Geoffrey M Baker

And this one

Geoffrey M Baker

And this

Geoffrey M Baker

Many Thanks Geoffrey I hope this helps Gary and maybe others also.

Cheers,

Gerard
Gerard Hengeveld

My guess would be that there is an air leak between the oil pick-up in the sump and the pump. At higher rpm there would be more suction and a small leak could then allow enough air to get to the pump to drop the pressure. See if the connection between the oil pick-up tube and the sump is tight and not leaking air. The leak, if that is the cause, could also be the at the sump gasket where the oil passage in the sump and the one in the block meet.
Hugh Pite
H.D. Pite

Gary, the relevant hole diameter is the longitudinal bore, not the side hole. That is what is often smaller. The new bolts are the same, but many were soldered or brazed up and restricted over the years to reduce oil flow to the head with worn rockers, etc. If different, the big internal diameter goes on the bottom. All suggestions above may be the answer. George
George Butz

Thanks for all the replies guys.

Gerald, I have had the regulator ball out a couple of times, and could see no marks on it. On the other hand, I can not see the seat. I see by your pictures that Geoffrey posted for us, that it appears that they are reducing the hole size with a drilled plug. Do you have any idea what size hole for the upper bolt? I have not had a chance to put mine back in with the smaller hole on the top, but I did measure them. The larger hole is .195, and the smaller one is.19. Not much different, but visually it looks like more. I will report back after I put them in correctly.

Hugh, I am a little confused as to where you are referring to. I have never had a T engine apart, but I assume you are talking about the pickup in the sump, and where it attaches to the block. I presume that I need to drop the pan to check? Could you clarify it abit for me?

Thanks Again
Gary
G Parker

gary, the pan has to come down to check the pickup-to-sump gasket and the integrity of the pickup tube assembly. regards, tom
tm peterson

Gary, I drilled the hole for the upper banjo 2mm.
Hope this helps,

Gerard
Gerard Hengeveld

Before you drop the pan, try snugging the pickup to pan bolts- two or four (depending on early/late oil pan) bolts on the pan next to the clutch pivot, and also the two pan to block bolts beside the pickup passageway. If loose, that could cause air leak, etc.
George Butz

Here's a photo of the oil pickup in the sump

Willem van der Veer

and just for fun a photo of a worn and a new regulator ball

Willem van der Veer

and a new and old spring.

BTW I think the restrictor is the way to go for you.

Willem van der Veer

Jim Northrup's answer indicated that there were two different banjo bolts originally, one with a smaller oil hole than the other. These days, all our suppliers indicate one bolt for both upper and lower locations. If there were differences originally, would it be a wise thing to do to braze one hole closed and drill it out to a smaller diameter? If so, what size drill for the smaller hole? Maybe the idea that it would not be possible to flood the top of the cylinder head and create an oil leak is the reason that only one bolt is used for both upper and lower locations these days. What say all?
Jim Merz

Great photos of the ball and spring wear. I replaced my spring recently, but not the ball. Makes me wonder if I should go back and put a new ball in.

Alex
Alex Waugh

I was just thinking: in my (Y-type) XPAG there is a metal rod that goes in the cylinderhead and fits (loosly) in the top banjobolt.

I always wondered why it was in there, but I now realise that this acts as a restrictor. Do any of you also have that rod fitted?
Willem van der Veer

Today I put the banjo bolts back in with the smaller one on the head. As I was looking at this, I noticed the size of the line coming up to the banjo. It measured .19 on the out side, and the hole in the bolt is .19. I can't see as the smaller bolt could make much difference when it is larger than the line feeding it. I did check the bolts on the pan pickup, and the bolts where the pan bolts to the block. The pickup bolts where wired, but I could get a wrench on enough to tell that they were tight. The pan bolts did snug up a little, but not much. After I got down and looked at how the pickup Works, I understand what Hugh was saying. I did take the car for a ride, and nothing seems to have changed. After several miles of warming up the pressure would drop to 30 at about 45 or 50 mph, and fluctuate back up to 40-45. If I speed up or slow down, it comes back up to around 50. I guess that the next step is to make a restrictor for the top bolt. I will try at around 2mm like George said he did. That may be just a bit smaller than the i.d. of the feeder line. Still open to suggestions, or comments. I hate the thought of dropping the pan, but it may come to that.
Thanks Again
Gary
G Parker

Unless the rocker shaft/bushings are really worn, a restrictor won't do much good. That really wouldn't explain the fluctuation anyway, the pressure would just stay a bit higher overall. Are you sure the level in the pan is correct- not too high or low? Too high and the oil can foam, low obviously would suck air. Do you have the flat bottom or finned sump? George
George Butz

Flat bottom.
G Parker

This thread was discussed between 18/05/2014 and 22/05/2014

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