Do we have hydraulic or mechanical serpentine polyribbed drive belt tensioners?

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?

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

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)

Originally Posted by doru

The hydraulic tensioner superseeds the mechanical ones

So do I assume mine are hydraulic from that?

Originally Posted by bluebee

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.

So if you have a car with a mechanical, could you install the hydraulic if no one carried the mechanicals anymore?

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

Pics here: http://www.bimmerfest.com/forums/sho...038&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.

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.

try inputting your vin to realoem. see if only hydraulic comes up for your car.

A mirror and flashlight with the hood open at noon on a sunny day will answer all these questions.

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.

Originally Posted by Jason5driver

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.

Originally Posted by bluebee

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:
http://www.eactuning.com/parts/produ...ails/090434001

Here for the tensioner:
http://www.eactuning.com/parts/produ...ls/11287838797

Originally Posted by Jason5driver

You need the conversion kit to install the hydraulic tensioner

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.

Originally Posted by bluebee

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

Hmm. I've had a few cars with this series of engine. They all had the mechanical tensioner. Guess I buy outside the curve.

I used this post for the conversion. Different car but same I6. It has links to realoem of the two. Should give a good idea what look for when under the hood.
http://forum.e46fanatics.com/showthread.php?t=410372

Ohh - you already found it.

Originally Posted by jayee_2003

I used this post for the conversion

Wow, that E46 post for Changing from Mechanical tensioner to Hydraulic tensioner is a great example of a wonderfully photographically detailed DIY. I'll add it to the VERY best of E39 Links so others benefit also.

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.

The only way to know what you have for sure is to look on the e39s. I have 2 1998 528i cars in the family, built a month apart from each other. One has mechanical AC tensioner, the other hydraulic. Both have a mechanical tensioner for the main belt. One has over 170k miles and is smooth and quiet, the other was changed at 120k when it got squeaky.

I've had excellent luck with both types of tensioners. I actually am fond of the simplicity of the mechanical tensioner myself.

Originally Posted by Mark@EACTuning

One has mechanical AC tensioner, the other hydraulic. Both have a mechanical tensioner for the main belt.

OMG!

Not only do we have the prospect of mechanical or hydraulic ... but we can have both on the same E39!

Thanks for that information (I wish I didn't know it ... but now I realize I need to look at BOTH to figure out what I have).

I am really not so sure what all this fuss is about.
They are both interchangeable. It really does not matter which one you have. If you want to switch from mechanical to hydraulic or vice-versa, you can do it with no ill effects.
One is more expensive than the other one. Also, a few people experienced better service with the hydraulic type. Other experienced better service with the mechanical one. BMW "recommends" the hydraulic one. Pick one and be done with it.

Originally Posted by doru

I am really not so sure what all this fuss is about.
They are both interchangeable. It really does not matter which one you have. If you want to switch from mechanical to hydraulic or vice-versa, you can do it with no ill effects.
One is more expensive than the other one. Also, a few people experienced better service with the hydraulic type. Other experienced better service with the mechanical one. BMW "recommends" the hydraulic one. Pick one and be done with it.

the 'fuss' is over ordering the parts. you have to figure which you have before you order, or do like Rjim and buy both and return the unused one, but thats $10 or so in return shipping...

what I find silly is the BMW dealer can't tell you what was put on via your VIN, thats like a hospital (that you visit often) not having your blood type on file, especially here and now in the computer age.

Right, but again, if you had an hydraulic tensioner and you ordered a mechanical, you can replace it no problems. And vice-versa. You might be baffled when you take off the tensioner and it does not look like the original one you had, but it fits and works.
Probably that;s why BMW did not payed such attention to this detail, and maybe that's why you have same model/year cars with different setups, and not recognizable by VIN.
It's not such a dramatic part that will fubar your system if switch them (like for instance you pick a 90A instead of a 120A or 140A alternator). It's almost like changing tires - Michelin vs Dunlop or similar.

For those of you who have curious mind, you may want to read the following article discussing the pros and cons of mechanical vs hydraulic tensioners.

Those of you with engineering background will like this article. Also, for those who want to read about Hydraulic Tensioner: it is basically like a car suspension with a Spring + Strut (to absorb sudden shock).

In the Hydraulic Tensioner, the Spring maintains the proper tension. The hydraulic oil works like a Strut to absorb sudden changes in TB tension.

Here is a very good link to read on how Hydraulic Tensioner works.
I also uploaded this pdf file to this forum in case they delete the pdf from their website in the future!
See attachment below for pdf.

http://www.gates.com/europe/file_sav...Tensioners.pdf

I am attaching a picture for a quick read:

For the cross linking record, dcotti wrote up his hindsight recommendations over here for what he'd do differently the next time he replaces his 2003 tensioners and belts.
- Belts / Tensioner s/ Idler Pulley Replacement

Notice that he had two mechanical tensioners, one of which was the TORX and the other the HEX pry point.

It seems that only the 2003 is so afflicted with the torx pry point.

Also dcotti described what he'd remove next time he contemplates the same job.