m42 water pump replacement

[cerdman]

I'm having difficulty finding the procedure for replacing the water pump on my M42 engine. Actually, I just can't get the fan off. One procedure says to lock the nut with vise grips and wack "it" clockwise. I've tried that and everything moves. Ideas?

[AdamF 88iS]

It's reverse threaded. Whatever tool you can get on it (it's a 32mm) has to be turned clockwise. You may have to hold the pulley from turning with it.

[gstuning]

use wise grips on the pully , when it´s stuck against the engine clockwise, put on the 32mm wrench and tap it with a hammer, it should come loose and you can then rotate it with your hand to get it off

[asubimmer]

I got tired of dealing w/ it when I replaced the water pump on my m42 and I took the trusty milwaukee sawzall and cut off the fan clutch. After I finished changing the pump I put on an electric fan. I have taken them off before the "right" way by unscrewing them, but the sawzall is by far the most effective ;)

[sepehr]

Pulling the pump is easy. Once you got the fan clutch and the pulley off, take out the 4 bolts holding the pump in. Then thread 2 of them in the two extra threaded holes on the 12 and 6 o'clock positions. The holes are in the waterpump body only and are there to help you back the pump out by pushing against the timing case.

Be careful though. The O-ring that seals the pump gets really hard and brittle with age, and makes it holds on really tight. You can snap off pieces of the waterpump body as you try and back it out with the two holes. Go slow and and tighten the top and bottom bolts evenly. The pump will be a bitch to pull out, if you snap the two threaded holes off. This happened to me and it was a major PITA.

If the old pump has a plastic impeller thats missing pieces, flush the engine and try to get all the pieces out. Make sure the replacement has a metal impeller so that does not happen in the future.

Good luck

[asubimmer]

sepehr thats true all up the metal impeller part. The old factory ones are crap and fail. But BMW has redone the replacements and they won't fail like that anymore. So if you have a metal one then thats extra weight that you have to spin. Go w/ the new factory replacement and don't look back!

[AdamF 88iS]

If the old pump has a plastic impeller thats missing pieces, flush the engine and try to get all the pieces out. Make sure the replacement has a metal impeller so that does not happen in the future.

Just as an FYI- OEM BMW pumps no longer have metal impellers. They have some new high-tech plastic which is black in color. They do seem to be holding up as well as the metal ones do.

You only have to worry if you get the yellowish color plastic, thats what the old original ones were.

[sepehr]

I was not aware of that. I read something about the newer black coloured polymer/ceramic composite ones, but that was after I'd already changed the pump.

I doubt the cast-aluminum-impeller pump I put in is going to robbing any significant power though :).

The alcohol in the coolant and the heat do some funky stuff to the plastic in the cooling system though. The O-ring on my pump had changed colours to a nice light green, and had hardened into something like bakelite.