oil pump questions

Specific conversations and info for the BMW E28 M5 and M535i.
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ronin
Posts: 71
Joined: Oct 27, 2008 3:02 PM
Location: Spartanburg, SC

oil pump questions

Post by ronin »

I have the oil pan off of my M88 (~80k miles). I plan to install a new sprocket and chain, and shim the oil pump down to achieve proper tension on the chain. So I have a few questions:

1) When pushing on the oil pump chain, what is considered an acceptable amount of movement before the chain becomes tight?

2) I actually have 2 different sprockets (and 2 different chains) with a different number of teeth on them. Is there a benefit to trying to run a larger or smaller sprocket? I would assume a smaller sprocket will turn the oil pump faster, pumping more oil, but can the pump be spun too fast?

3) "While I'm in there", is there anything else I should look to do? I haven't seen any overt reliability issues with the oil pump in our cars so not sure if there is anything else I should do, but wanted to see what everyone thought.

Thanks,

Eric

Here's a couple of pics of my engine:

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Randomg
Posts: 480
Joined: Jul 12, 2007 3:12 PM
Location: Seattle

Re: oil pump questions

Post by Randomg »

No answers...

The benefit of the a smaller sprocket with less teeth is that oil pressure is higher at idle (a sprocket with less teeth was recommended to me by my engine builder, Paul Burke), which is a good thing I'm told. There's a check valve at the back of the pump so you don't need to worry about it getting too high at high rpm.

I believe the newest s38 blocks have a hole for an oil pump chain tensioner to be mounted on the driver side of the block. If that's not an option for you, do an online search for the e24 m6 shop manual, it should have the procedure for determining how much slack is acceptable and how to shim the oil pump.

What else to do while you're in there... The long plastic claiming chain guide is what the community thinks is one of the reasons for the few s38 chain failures.
ronin
Posts: 71
Joined: Oct 27, 2008 3:02 PM
Location: Spartanburg, SC

Re: oil pump questions

Post by ronin »

Randomg,

Thank you for the reply. That is exactly the type of feedback I was hoping for. I'll go with the smaller sprocket and refer to the manual for shimming procedures. I am also replacing timing chain components and so will take care of the guide you mentioned.

Thanks again,

Eric
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