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MG TD TF 1500 - oil pump specs

I am still messing with this oil pump. I just was not confident using the circlip supplied by our usual merchants. It is on the top of the driving shaft and gear. I have obtained one from a local hardware store that at least wraps all the way around the shaft. That is good. But all these clips available are much thinner than the original. That introduces 17 thousands of freeplay in the up and down movement of my shaft and gear. My questions are: should I find a washer to use as a spacer to take up this free play and if yes, do I install it at the cam gear end or the pump gear end? Also, does anyone know what the specs are for the freeplay? I am concerned with the gear rising up and wearing badly against the pump cover.
Thanks to all, Sandy
smb brainsky

Hello Sandy. I was working on an oil pump today. The person sent new gears. When I went to assemble it the gear just slid on the shaft. The inside of the gear measured .5155. The shaft measured .5125 (13 mm). An old gear measured .5120. That gives a .0005 press fit. So I contacted the person an told him the the new gears were no good. This is after I spent about 30 minutes grind them to the proper end float. With the press fit a standard circlip will hold the gear fine.

Butch
R Taras

Butch do you know who supplied your customer with the new gears? Cheers
Peter TD 5801
P Hehir

Hello Butch, nice to hear from you. Very frustrating for sure when new parts don't fit. My gears are fine. I checked clearance with plasti-gauge and it is withing spec. I just would like to know how to get rid of all the up and down end play of the whole shaft and what it is supposed to be set at. Any cues on that?
Again thanks, Sandy
smb brainsky

Sandy -exactly how thick is your hardware store circlip
William Revit

Also ,which drive shaft do you have
The original had a 1mm deep groove about1.5mm wide and the robust sized circlip wasn't spring steel, it was stretched on then being softer it was able to be squashed inwards for a tight fit
The newer replacement shafts only have a 0.5mm deep groove so that a spring steel snap ring can be fitted without having to distort the spring steel
The problem arrises with the use of the later spring clip on the early deep groove shaft
When this happens the snapring isn't a snug fit in the deep groove and can move out sideways and get itself out
William Revit

Yes William, I appear to have the old shaft. The groove is 1.5mm wide and 1.7mm deep. I still have the old snap ring here. I thought it had lost it's spring steel properties. The new rings are only .9mm thickness where the original is 1.2mm. The problem with the old one is that it is so deformed that when installed in the pump, everything binds up. (The gear to pump body clearances are spot on.) Remove it and all is fine. It is acting as a wavy washer. It removes all freeplay and I can only assume it will become a problem when it gets hot. Maybe I can work on straightening it flat.
I also notice that the old ring fits very nicely into the round pocket hole in the pump cover. The new rings outer circumference is so much smaller that it could conceivably pop off in there.
Do I need to start over with a replacement shaft? Seems like there must be a better solution. Am I worrying too much here?
Thanks for the insight, Sandy



smb brainsky


William --- What Company sells the shaft with the 0.5mm deep groove?
Richard Cameron

Hello Sandy. My customer said that he thought it was Moss. I went back and started checking old shafts and gears. It appears that the gear ID is .002 larger than the shaft. What is curious to me is that on all the pumps I have worked on I had to use a press to remove the gear from the shaft. I guess it must be gummed and hardened oil between the gear and the shaft.

Sandy once the pump is assembled the end float of the gears should be the only end play .0015 - .003.

Butch
R Taras

Thank you Butch. That info may give me something to work with.
Sandy
smb brainsky

My personal choice would be the shaft with the deeper groove(original style)
If you can save that original circlip and fit it with the best/flattest side out towards you,then squeeze it in tight, that would be the best option and as you have picked up on, the pocket in the pump cover will hold this bigger o.d. clip into it's groove

Richard
Pretty sure the one I got was from Brown and Gammons, and the story was that the groove was shallower so they could use a larger base id circlip so that it didn't get over stretched / distorted when being fitted
They just don't look good to me and haven't been brave enough to risk using one
William Revit

My personal choice would be the shaft with the deeper groove(original style)
If you can save that original circlip and fit it with the best/flattest side out towards you,then squeeze it in tight, that would be the best option and as you have picked up on, the pocket in the pump cover will hold this bigger o.d. clip into it's groove


Richard
Pretty sure the one I got was from Brown and Gammons,it would have been 12 months ago, and the story was that the groove was shallower so they could use a larger base id circlip so that it didn't get over stretched / distorted when being fitted
They just don't look good to me and haven't been brave enough to risk using one
William Revit

You're right to worry about the circlip! I rebuilt my oil pump using the MOSS rebuild kit (Part No 435-088
https://mossmotors.com/mg-tc-td-tf/engine-performance/oil-system/oil-system-1).

It lasted about 2 years then one day as I was tuning the engine there was a bang, a crunch, and other weird noises coming from the engine...and no oil pressure). Thankfully I was in the garage. I pulled the top off the oil pump and the gear drive shaft wasn't visible but two pieces of the circlip were. The shaft had been pulled part way into the engine and hit/tore up one of my rods.

The circlip that came in the MOSS kit looks very similar to the one you have listed as being from the "hardware store"...in my opinion it's not up to the job being too thin.

I ended up sending my pump to From The Frame Up to have it rebuilt (the bottom of the pump that goes thru the block was cracked from the shaft hitting the rod). That little treat cost me over $500...the new rod (a Saenz balanced rod to match the other three) was another $250.

Get the heaviest duty circlip you can find to use...I'm not even certain that the FTFU circlip is as good as the original but I'm not taking it off to find out.

Gene
Gene Gillam

Wow, loosing an engine over a circlip. That is messed up. But exactly what I was fearing. So fortunate you weren't tooling down the high way. That would have been a total wright off.
Sure hope they don't use these in airplanes. Sandy
smb brainsky

Sandy
I'm glad Gene came in on this I can remember his damaged rod issue but couldn't remember where I saw the pic (sorry Gene)
Maybe if you can't restore your clip you could contact from the frame up and they 'might' have original style clips-----or not
William Revit

Here is a plug for magnetic sump plugs (which I know Tom Lange supplies). About forty years ago I changed the oil in my race TC. A couple of oil-pump teeth were stuck to the magnet. Removal of the oil pump revealed two "flattened" sides of the drive gear, and a look up the hole, revealed neat helical marks across the previously polished #2 con-rod. The exhaust noise and helmet had prevented me from hearing any associated noise, which could not have been happening for long. When I fitted another pump (and con-rod) I oxy-braised the circlip. However, I think that was overkill and have never done that since.

Yes, The circlip is VERY important, especially as the rotation of the camshaft and angle of the teeth tend to pull the shaft out. Incidentally, over the years, the magnet has also "revealed" a cracked timing chain link-clip and timing chain roller segments. It also collects half a thimble-full of metal powder/mud at every oil change.

Bob Schapel
R L Schapel

For sure, Gene had the worst possible outcome. Thanks to everyone. This appears to be a pretty important subject. Heaven knows how many potential engine failures are driving around out there. I may drop a note to Don Lawson about a short tech article in the Sacred Octagon. Sandy
smb brainsky

This thread was discussed between 29/07/2019 and 01/08/2019

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