Grease on M20 oil pump gears

[marquis-marc]

Hi there!

recently had my engine rebuilt by someone I’ve lost all faith in. Been going back and double checking his work.
Pulled off the oil pan and saw how dirty the oil pump still was, so I took it apart and found the gears caked in grease.
I couldn’t find any posts/documentation recommending this as part of an M20 oil pump rebuild procedure.

just wanted to verify: grease or no grease on the oil pump gears?

thanks!

[zaq123]

no need for any grease as it pumps oil.. some assembly lube won't hurt. But one should always manually prime the engine with like a drill or something before starting fresh rebuild.

[82eye]

never seen anyone do that before.

[hasa]

Looks like some marine grease. This is first time I see anything like this. Engine oil should to the lubrication.

[marquis-marc]

Thanks all!
glad I wasn’t crazy thinking this grease was totally unnecessary. Will clean out, apply a bit of assembly lube and manually prime the engine before any start attempts.

[TobyB]

That's actually legitimate.

It helps the pump seal and prime itself. The tolerances are such that if it's installed
dry, it can't pull a vacuum sufficient to draw oil up into itself. The grease acts as an air seal,
and allows it to pump air.
Assembly lube usually works, too, but if the pump's worn, the
grease is better.

It certainly won't hurt anything, and it'll break down in your assembly oil and get flushed out.

Me, I use assembly lube, and also run the pump with a drill before installing the
drive gear and plug, but I'm just a bit paranoid that way.

t

[E30SPDFRK]

That's actually legitimate.

It helps the pump seal and prime itself. The tolerances are such that if it's installed
dry, it can't pull a vacuum sufficient to draw oil up into itself. The grease acts as an air seal,
and allows it to pump air.
Assembly lube usually works, too, but if the pump's worn, the
grease is better.

It certainly won't hurt anything, and it'll break down in your assembly oil and get flushed out.

Me, I use assembly lube, and also run the pump with a drill before installing the
drive gear and plug, but I'm just a bit paranoid that way.

t

Seconded, it's common practice to prime the pumps with grease on a dry engine.

[uturn]

Same here,
I use trans-jel to pack the pump so it'll breakdown and flush easier.

[zaq123]

That looks like a lithium grease which does not breaks down with oil well. Now one can use a lithium grease mixed with ATF as an assembly lube in a pitch. However good and sticky assembly grease is the way to do it. In any event, good manual priming of the engine is all that's needed to lubricate the pump as well get the oil gallery and everything full of oil for that first start.

[TobyB]

If the pump's used and it's been cleaned out really well- and left dry- manual priming won't work.

I did that once by mistake, figured out what I'd done, managed to squirt a bit of oil back down into the pump to wet it,
and then it primed in about a second. Oil pumps make poor air pumps...

t

[82eye]

i just used a small amount of assembly lube and some regular oil. it's all i have ever used used on any build. had no issues, but am filing this for future reference.

[zaq123]

That's actually legitimate.

It helps the pump seal and prime itself. The tolerances are such that if it's installed
dry, it can't pull a vacuum sufficient to draw oil up into itself. The grease acts as an air seal,
and allows it to pump air.
Assembly lube usually works, too, but if the pump's worn, the
grease is better.

It certainly won't hurt anything, and it'll break down in your assembly oil and get flushed out.

Me, I use assembly lube, and also run the pump with a drill before installing the
drive gear and plug, but I'm just a bit paranoid that way.

t

Here is a picture of the pump with oil at 1/2 dipstick. As you can see, pump gears are well submerged in oil. was priming new motor so figured I'd snap a pic with my borescope cam for you all.

[digger]

how can you install a pump dry? it is submerged or atleast should be once you put oil in the engine. it may make assist to build pressure slightly quicker or to help bed things in by using a breakin lube on new parts but i cant see not being able to build pressure at all

[TobyB]

how can you install a pump dry? it is submerged or atleast should be once you put oil in the engine. it may make assist to build pressure slightly quicker or to help bed things in by using a breakin lube on new parts but i cant see not being able to build pressure at all

I was working on an M42...

it's also working against at least one, if not more, check valves.

t