What does this pulley drive?

[Tangent]

I'm in the process of replacing the head on my 88 325iS that broke its timing belt and I noticed that this one pulley that the timing belt drives is a whole lot harder to turn than it is on the 89 I'm parting out. Does this pulley drive anything and if so what is it and how hard is it to replace?

[James Crivellone]

Thats the oil pump, I find that over time they will loosen up as the seal tends to wear out, mine is pretty tight to turn on my motor with a new seal.

[Tangent]

Tight enough that it's tough to move by hand?

[James Crivellone]

Tight enough that it's tough to move by hand?

Mine is pretty darn tight, nowhere as tight as the cam though.

If you think it is too tight then the only way to get to the oil pump is to drop the pan.

Its probably okay, the oil pump is a VERY simple design and I've never seen one fail.

[AdamF 88iS]

A bit of random info- it also drives the distributor on non-motronic cars, so you have not 2 but 3 TDC marks to line up on those. Fun fun fun.

If it leaks you can change the radial seal behind it without much trouble. The bearing for the shaft is NLA though, so you either have to find a generic one that works or deal with it. It's probably fine though.

[Sean]

Mine is pretty loose - what seals in there should be changed? I'm doing a complete rebuild, be dumb is skimp out on that!

[ryan_george]

Mine is pretty loose - what seals in there should be changed? I'm doing a complete rebuild, be dumb is skimp out on that!

There are 2 seals in that cover. One for the crank, and one for that oil pump shaft.

To get that cover off you'll need to loosen off that big mf'er crank nut (RIGHT beside the yellow arrow). That thing's a PITA. Hopefully your whole engine is coming out if you are doing a complete rebuild.

[Sean]

Oh, you're talking about the front engine cover. yea - those are gettin changed out. My engine is down to the bare block.

I was actually talking about that shaft that goes into the block - should I worry about changing the bearings holding that shaft in? (in the block inself)

[AdamF 88iS]

Oh, you're talking about the front engine cover. yea - those are gettin changed out. My engine is down to the bare block.

I was actually talking about that shaft that goes into the block - should I worry about changing the bearings holding that shaft in? (in the block inself)

Don't worry about that one. You can change the o-ring thats under the block off plug above it though.