Belt tensioner help
 

I recently had a serpentine belt break on my 3.0L X5, and was able to put on a spare and drive home. I went to order new pulleys and belt and was informed that there are two types, mechanical and hydraulic (with different pulleys). Is there an easy way to tell the difference without removing all the housings and clutch fan again so i can order the the correct pulleys?

Additionally when i was snapping photos to see if i could get a view of the hydraulic piston, I noticed what appeared to be fairly clean bolt threads into the engine behind the deflector pulley. I attached photos below. Did some bolt back out causing serpentine to break, or is this just unused bolt threads?

Look like you have hydraulic tensioner from the picture. The mechanical tensioner will have a 15mm hex on the housing. You have hydraulic tensioner if you dont see that bolt.
BMW E53 X5 M54 3.0L > ES#2187565 Mechanical Belt Tensioner Assembly - 11281427252
I have mechanical ones on both my BMWs so I can't comment on your empty bolt thread. How many miles on your X5 when the belt snapped?

These photos should help you

Mechanical
http://c1552172.r72.cf0.rackcdn.com/151545_x600.jpg

Hydraulic
http://c1552172.r72.cf0.rackcdn.com/16033_x600.jpg


From your photos it looks like you have a mechanical set up. So you have two choices, one replace the current mechanical with a new one (I have them available HERE) or convert the system over to a hydraulic tensioner set up with something like the kit found HERE. Hydraulic tensioner are a lot less prone to failure than mechanical ones, hence the reason we created that kit.

My thought exactly, and i can see that little black bushing ring behind the pulley which looks to be on the ends of the hydraulic cylinder.

I have 70K miles on it, but I just replaced the serpentine 6 months ago (oem manufacturer but not oem) when i did the thermostat and water pump. I had a 2-3K miles on it which made me think it wasn't incorrect install or it would have failed much sooner. Just in case I was going to replace the pulleys this time.

I see what you are looking at, but i think that circular metal region behind the pulley is part of the engine block and not the mechanical tensioner. I can see what looks to be the black bushing at the end of the hydraulic piston in the photos behind the pulley. However your photo of the Mechanical one makes me think that empty bolt hole was to fasten the mechanical tensioner, but may not be used if you have hydraulic? Has anyone ever done a mechanical to hydraulic tensioner swap and seen this missing bolt hole?

Thanks.

-Nick

Correct, the spot your looking at is used on the Hydraulic but not on the mechanical. Sorry bout that I should have included that info in my other post.

Get OEM this time (Conti). I am about to replace all the pulleys and belts on my 95K mi 3.0i, with metal impeller water pump. Thermostat was taken care of 5K mi ago.

Im a bit confused with conflicting results. You believe i have mechanical from the pictures (and the missing bolt is used with hydraulic), however the other member said I have hydraulic.

From the picture it appears the rubber bushing looks like the bushing (red arrow) on the hydraulic tensioner, and the top part appears to match (double red arrow). If you agree that i do infact have hydraulic, what could those threads be used for?

Thanks.

-Nick

^My money is on the hydraulic tensioner. I think ECS agree too, in post #6.

I know this post is over 5 years old now but I am now in the same situation. I want to order the belts and tensioner kit from ECS or FCP and need to know which version I need. Is there an easy way to determine hydraulic or mechanical without disassembling the front of the motor so I can order the correct parts? :dunno: