That's a hydraulic tensioner. See below pic.

 

Are the idler pulleys also or sometimes called a deflection pulley?
this is what i found.
1st item under drive belt tensioners
11-28-7-516-847-M40 (Deflection Pulley for Water Pump/Alternator Belt (Center Mounting), 525i (2004-05), 530i (2004-05) )

BMW E60 - Main Engine Components - Page 3

and also i'm pretty sure this is the tensioner i want?
1st item under deflection pulleys
11-28-1-427-252-M40 (Drive Belt Tensioner with Pulley for Water Pump/Alternator Belt (Mechanical), 525i (2004-05), 530i (2004-05)

would i be better off going to the dealer and telling them to defeat shipping cost? i cant imagine pelican and the dealers prices would be different?

*2005 525 with m54*

 

Yea, idler pulley is also called as deflection pulley.
Dealer prices are usually marked up and will definitely be more than the on-line prices. I'd say the dealer would charge around $40 for that pulley. Dealer definitely can't and won't match on-line prices...It doesn't hurt to ask for discount;

 

I'm pretty sure the dealer will no longer sell you a mechanical tensioner for the main serpentine belt. BMW superceded the mechanical tensioner for the hydraulic tensioner. Why, I have no idea as the mechanical tensioner works just fine. When I replaced my pulleys, I took a mechanical tensioner out and put a new mechanical tensioner right back in.

What ever pulley you need, either order them from a reputable online parts distributor or get them from a local parts store (autozone, o'reilly, etc). The OEM manufacturer for these pulleys is INA, so as long as you are getting an INA pulley it doesn't really matter where it comes from.

Do yourself a favor and replace all tensioners, idler, and belts while you're in there. If you've never put a water pump and/or thermostat in your car, now would be a good time to do it.

I got all of my parts from Pelican Parts, except for water pump and water pump pulley which I bought from ECS tuning.

Good luck with your car.

 

i'd really like to do a water pump as well, however i don't know how to go about re filling the coolant (purging the air out of the system) at the same time id like to upgrade the wp pulley.

anyone have the bentley service manual? is it any good? or perhaps theres a really good diy to do a wp?

does the radiator need to be dropped, or just the fan?
thank you guys so far for all the help

 

The E60 cooling system 'bleeds' itself after a refill.

Only the fan needs to come out. Radiator can stay right where it is. I don't have the Bentley manual, but I will tell you there are more than enough DIY threads floating around the internet to help you with this. Just google "M54 water pump replacement" and you'll have all the information you need.

 

okay, so i went ahead and ordered the mech. tensioner, the idler, new oem waterpump with the composite fins/propeller along with an aluminum WP pulley from ECS.

I looked through DIY's and the actual replacement process of the tensioner and the idler seem simple.
I cannot seem to find info on bleeding the coolant system after loosing coolant from replacing water pump..
also finding a good an clear diy on removing the radiator fan is difficult to find.
is it just bolts/ and plastic clips and then sliding it out after disconnecting the two wire harnesses?
Thanks!
-bill

 

After removing the plastic cowling (on top of the radiator), disconnect the fan connector on the passenger side, slip the hoses attached to the fan on the bottom (facing engine), lift the fan up few inches and then you will see a plastic clip comes in the way of one of the hoses, fold that clip and continue to lift up the fan as you watch on both sides.

 

1. drain radiator. radiator drain screw is on the passenger side of the radiator. it's plastic and can break easily. be careful, b-e-careful. not a bad idea to swing by the dealer and have one on hand just in case.

2. there is no need to 'bleed' the cooling system after you refill. unlike older BMWs that had a bleed screw (either by the coolant reservoir or on the thermostat housing), the M54 E60 cooling system will bleed itself. fill the reservoir up to normal operating level. turn fan controls to full hot. turn on engine, let engine come up to full operating temperature (electric fan turns on). turn off engine, let sit overnight. check coolant level in morning, top off if needed. use BMW coolant; to quote wilford brimley, "there's just no reason not to"

if you run into trouble, feel free to PM me. budget yourself a solid 3 to 4 hours if you're a comfortable DIYer, longer if you're not.

 

Pcy, you are an awesome individual!!! If you were my neighbor, I'd invite you over for beers, lobsters and steak any time! Thanks for sharing your very valuable experiences on this forum!!!

OP,

As for removing the fan, don't forget to disconnect the three plastic hose clips on the passenger side and two plastic ones on the bottom; otherwise, you will have a hard time removing the fan!

The clip on the right side of the fan needs to be pushed TOWARD the car to unlock.

Good luck!