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Seek to understand,^Value
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Discussion Starter · #1 · (Edited)
How do I know if I have a 2002 6-cylinder engine with hydraulic belt tensioners or a 6-cylinder engine with spring-loaded belt tensioners?

On page 020-17, the Bentley manual shows an incomprehensibly grainy picture of both polyribbed serpentine drive belt systems - which is bad enough; but it's worse because you can't easily "see" the various pulleys and tensioners inside the actual engine compartment.

Since the Bentley does not say WHICH cars have hydraulic vs spring-loaded belt tensioners - and since I don't know what to look for (or even if it's possibly to "see" them from above - I ask ...

How do we know whether we have hydraulic or mechanical drive belt tensioners on our BMW E39 engines?

 

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- -The first pic are hydro, the last pic are mechanical.- -
 

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The hydraulic tensioner superseeds the mechanical ones. I don't think you can find a mechanical one for sale anymore.
The new hydraulic tensioner p/n you will have to order is 11287838797 (this is for a 2002 525). I am not sure if car ever had a mechanical tensioner, but if it had one, the new design will not ressemble with the old one (mechanical vs hydraulic)
 

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So do I assume mine are hydraulic from that?
No, you will have to look at your part closely. Also, I checked Autohausaz, and they re-stocked the mechanical one. Link. Check the last item - you will see that actually the mechanical was dropped. There were a few months, you could not buy the mechanical anymore.
 

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I think you can (or could a few months ago) still get the mechanical ones from NAPA.

Pics here: http://www.bimmerfest.com/forums/showthread.php?t=443038&highlight=

I have around 3000 miles on my replacement so far with no complaints. I believe you can convert from mechanical to hydraulic, but IIRC the cost for the kit was much more.
 

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Discussion Starter · #8 ·
All I wanna know is what I have so I can see if I need to order them ahead of time because I don't want to take the whole thing apart twice.
 

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Doru is correct.
The hydraulic tensioner supercedes the mechanical tensioner.
There were too many failures with the mechanical tensioners, so BMW went back to the hydraulic tensioners.
And, yes, if you have a mechanical tensioner, you can install the hydraulic tensioner.
I had my mechanical tensioner replaced with another mechanical one.
Two months later, I had to replace it again, but this time with a hydraulic tensioner.
 

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Discussion Starter · #12 · (Edited)
if you have a mechanical tensioner, you can install the hydraulic tensioner
Well, if they're interchangeable, they must look similar, at least in outline where bolts attach. That would make visual identification problematic.

Looking at realoem, it's still very confusing because BOTH mechanical and hydraulic belt tensioners are shown for the same serial number!

How confusing is that! Here's a screenshot of realoem's $70 (nominal) hydraulic tensioners and the mechanical tensioner. If they're interchangeable, they certainly look different! I guess that's why folks say to just look.

At least now I know a bit more of what to look for, but, as stated, it's pretty packed in there; but with these diagrams, I have yet another nugget of information to look for.

 

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Seek to understand,^Value
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Discussion Starter · #14 ·

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Discussion Starter · #15 ·
Realoem didn't provide any clear idea whether I have hydraulic or mechanical serpentine drive belt tensioners; but the consensus is much closer to hydraulic than mechanical.

Now that I have a much clearer picture of the different look of the hydraulic versus the mechanical, I might now be able to look inside the engine to see if I can tuck my camera down there amongst the belts to confirm which is what I have.

 

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Well, if they're interchangeable, they must look similar, at least in outline where bolts attach. That would make visual identification problematic.

Looking at realoem, it's still very confusing because BOTH mechanical and hydraulic belt tensioners are shown for the same serial number!

How confusing is that! Here's a screenshot of realoem's $70 (nominal) hydraulic tensioners and the mechanical tensioner. If they're interchangeable, they certainly look different! I guess that's why folks say to just look.

At least now I know a bit more of what to look for, but, as stated, it's pretty packed in there; but with these diagrams, I have yet another nugget of information to look for.
You need the conversion kit to install the hydraulic tensioner.
Look here:
www.eactuning.com/parts/product_details/090434001

Here for the tensioner:
www.eactuning.com/parts/product_details/11287838797
 

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Discussion Starter · #17 ·
You need the conversion kit to install the hydraulic tensionerhttp://www.eactuning.com/parts/product_details/11287838797
Thanks, but I don't actually wanna convert anything. All I wanna know is what I have. :)

I suspect most of us have hydraulic tensioners; so, from a statistical standpoint, that's likely what I have.

But that's a lousy way to determine what I have so now that I know what each looks like (no thanks to my $100 Bentleys! :) ) ... I can peek to identify by shape which ones I have.

Thanks.
 

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Just replaced entire cooling system on my '03 530 and found I had the mechanical tensioners. Once the shroud, fan/clutch and radiator are removed it's possible to see what you have. I ordered both types from Pelican with the understanding I could return the unused new part, which I did without problem. The fact that Pelican could not tell me which type I had leads me to believe both types were used on M54 engines in '03 and maybe other years too.
 

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Discussion Starter · #20 ·
The consensus seems to be that it's a crap shoot whether we have hydraulic or mechanical tensioners, which makes it harder to order parts ahead of time.

We just have to look and see. Here's what the two parts look like side by side.

Based on information in this thread, it might be that one system has one fewer idler pulley than the other system (needs to be confirmed) so a good test would be the number of "round things" (not all of which are pulleys).

 

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