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MG TD TF 1500 - gear orientation oil pump

Again, hello. My stripped pump bolt is being addressed. My concern here now are the gears in the oil pump. They can be flipped end to end, but they have markings on one end only. Small notches. One end is flat while the other has a slight chamfer around the center hole. I have checked everything ever written, watched videos and even called a couple of suppliers. I still have no answer. Does it really even matter?
Thanks again, Sandy
smb brainsky

The driving shaft has a "snap ring" to prevent it being dragged into the interior of the engine. The "snap ring" is pulled up against the flat end of the driving gear which puts the "snap ring" in shear stress.
If the "snap ring" were to be placed adjacent to the chamfer, it would be subject to a bending stress which might displace the "snap ring" and result in the shaft being pulled into the engine block and no oil pressure.
E A Worpe

Spot on EA, I agree, IT matters
Chamfers inwards so that there is a nice square shoulder for the snap ring
Also there have been snap ring failures caused by this and incorrect fitting of the rings--Some replacement rings are machined flat on both sides so can be fitted as they come but some rings are flat on one side and semi curved on the other like they have been pressed from one side when they were made-IF you have one of these, you are better off getting a fully machined ring or be carefull fitting it--It has to go in with the curved side towards the gear, if it's fitted the other way round the pressure of the groove in the shaft on the circlip can open the circlip up and let the shaft go to do it's damage---

Sandy, on your thread issue, be aware that the longer bolts have slightly different lengths and if mixed up with the shorter bolts in the longer holes it can cause thread damage -there's 2 of each from memory
William Revit

Yes I have one of those snap rings that has a curved profile on one side. But I have ordered a replacement along with a new gasket. I believe it is a conventional ring with 2 holes at it's end to grab it with a snap ring pliers. The original one did not even feel like it was made from spring steel. I would have to compress it with the jaws of a pliers after installation because it was so loose. I was afraid it would break from metal fatigue.
I will insert the gears with the flattest and smoothest surface facing the pump cover. Seems to make sense since that is where the pressure is generated. It is so curious that they chose to use 3 different length bolts when 2 sizes would have worked just as well. I never caught that anomaly. Thank you both for educating me on the horrors of an errant shaft. There are so many ways to screw the pooch on this engine overhaul.
Thanks, Sandy
smb brainsky

Yep
Just make sure that snap ring is good quality and is a nice tight spring loaded fit in the groove of the shaft, and if it's a stamped/curved one, fit it with it's flat side out towards you as you fit it(towards the pump cover)

I know I said that before but there you go again

Cheers
willy
William Revit

Hello Sandy. Also the gear on the driving shaft has a groove on one end that groove goes against the bottom of the body, it provides lubrication to the shaft.

Butch
R Taras

Some things are worth repeating William.
And that groovy piece of info helps it all make sense now Butch.
Thanks, Sandy
smb brainsky

This thread was discussed between 15/07/2019 and 16/07/2019

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