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Is it mandatory to disassemble oil pump?

Hi everyone,

Rebuilding my 89 911 3.2 engine.

Looking at my remaining list of tasks before assembling case halves. Is it common practice and mandatory to open up oil pump and inspect / clean internals? I see postings in the forums of sending out for cleaning and/or opening up pump but it is generally people that had a failure of some sort that generated metallic debris, or people with used pumps of unknown origin.

My car and engine seems to have lived a generally happy life, with 212K miles and the only cause for rebuild was excessive oil consumption due to worn valve guides.

My oil pressure was around 1 bar at idle, and peaked out somewhere just under 4 bar on the gauge.

Every oil change I dated and photographed my drain plugs and never documented any metallic content. Only mild traces of sludge.

I'd rather not disassemble if not necessary. Wayne says "clean" it. Not sure exactly what that means.

Thanks,

Mark
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Old 04-09-2019, 05:15 PM
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Wayne probably means something like soaking it in some solvent and rotating the input shaft and flushing solvent thru the pump.

The solvent should be something with a low flash point maybe even diesel fuel.

oil pumps have steel gears and often steel bodies and they are the first thing that gets oil so they don't wear as much as other parts like valve guides and rings.
Old 04-09-2019, 06:41 PM
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No, it's not mandatory at all. In fact, if you don't know what you're doing, there is a chance that you won't put it together properly and cause the pump to not function right. The gears are meshed to each other after a long period of running and need to be replaced in the positions they were in. It's not hard, it just takes care and time.

Your average used pump just needs a good flush with carb cleaner. You can very easily do this with the pump assembled and by turning the pump shaft or chucking the shaft up into a cordless drill you can spin the pump and check if there is any debris coming out while pumping cleaner through it.

If you have a pump that has metal inside of it from a known failure, I just find it easier to toss it and get a new one rather than risk not flushing it right.
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Old 04-10-2019, 05:59 AM
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Quote:
Originally Posted by Catorce View Post

Your average used pump just needs a good flush with carb cleaner. You can very easily do this with the pump assembled and by turning the pump shaft or chucking the shaft up into a cordless drill you can spin the pump and check if there is any debris coming out while pumping cleaner through it.
I was going to attempt this... which direction should I be turning the shaft (if looking directly at end of shaft with pump body in the background)??
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Old 04-10-2019, 06:54 AM
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550.00 expert rebuild on my 3.2 pump.

I couldn't find a single 3.2 oil pump failure and only a handful of low oil pressure readings and no final word that pump was reason for low pressure.

That said when I went down the rabbit hole and decided to do the whole motor and not just the top end, we had the pump sent out and had it rebuilt. When you spend 18k on engine rebuild whats another 550.00 to do the pump was my flawed thinking at the time.
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Old 04-10-2019, 07:00 AM
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I was going to attempt this... which direction should I be turning the shaft (if looking directly at end of shaft with pump body in the background)??
Both ways!
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Old 04-10-2019, 07:08 AM
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Both ways!
hmm... I was told that you never want to turn the gears in the opposite direction they were designed to move, as it causes undue stress to the gear teeth.
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Old 04-10-2019, 11:15 AM
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I doubt you are going to put undue stress if you turn it at moderate rpm with low viscosity fluid for a short period of time.
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Old 04-10-2019, 02:04 PM
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hmm... I was told that you never want to turn the gears in the opposite direction they were designed to move, as it causes undue stress to the gear teeth.
Total BS. You are using your hand or a low speed cordless drill to rotate it. and you are only doing it for like 30 seconds you aren't running the car for 3 hours at 8000 rpm backwards.
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Old 04-10-2019, 02:19 PM
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You're not going to damage the pump rotors by rotating them in the opposite direction of their normal rotation. The pump rotors are hardened and even when they mash up bearing material, they don't look any worse for wear. Here's how I know



So if anybody sees any signs of metal debris on the screen of their pump? They can be assured that there is some significant scoring on the interior body of the pump. That scoring provides additional surface area and clearance for the oil to escape the rotors, reducing the pressure the pump can make.

The pump rotates counterclockwise if anybody really needs to know. The crankshaft turns in a clockwise direction and the crankshaft has a gear on it that meshes with the adjacent intermediate shaft gear. Since the crank gear turns clockwise, that means the intermediate shaft gear is turned counterclockwise. Therefore so do the camshafts turn counterclockwise due to the sprockets on the intermediate shaft turning in the same counterclockwise direction, which is transferred via the chains to the cam sprockets. The end of the intermediate shaft is splined directly to the oil pump via a splined coupling tube and therefore the oil pump also turns counterclockwise.
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Old 04-10-2019, 02:29 PM
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oil pump

That is a great picture of what not to reuse.
Old 04-10-2019, 02:55 PM
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Thanks for all of the feedback everyone!

Mark
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Old 04-10-2019, 06:44 PM
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When the rebuild is due to an engine blow up, you start thinking of a closer examination of the pump's innards and what that stuff may have done to it. Anything short of that isn't likely to damage the pump. Your pressures sound like maybe you found the bearings were really OK when you had it apart, but by then it doesn't make sense not to put in new ones.

Here is to another happy 200K miles.
Old 04-10-2019, 10:16 PM
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And that pump I pictured above seemed just fine by "feel" when you spun it by hand. Any pump with unknown history should be opened for inspection. It's not hard to do and it's worth the peace of mind. Plus nowadays it seems there's more and more asshattery infiltrating the Porsche community and jerks are trying to screw people.

FYI for comparison reference, here's what an unmolested pump body should look like. The above pump was a 964 magnesium pump. The picture below is an aluminum 3.0L SC pump.

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Old 04-11-2019, 07:09 AM
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