Hydraulic Belt Tensioner Bolt

[Rovert]

So I think what I am looking for is #7 on this diagram:

http://www.realoem.com/bmw/showparts.do?model=EV53&mospid=47725&btnr=11_2190&hg=11&fg=18
http://www.realoem.com/bmw/diagrams/z/x/226.png

I used to use a T50 to loosen and take the belt off but today when I was going to change the pulley my T50 didn't fit right. I believe the mechanical tensioner is a T50 and the hydraulic tensioner is an 8mm hex. Here is my hydraulic tensioner picture I took with my phone:

https://lh3.googleusercontent.com/-QfbBEUIWeJA/UabjxcSGqlI/AAAAAAAAHHs/k4ZyT1qQW_0/w1051-h788-no/2013-05-29+20.09.47.jpg

Here is the bolt taken out with an 8mm hammered into it to take it out safely:
https://lh3.googleusercontent.com/-JAHXgChIETw/UabjvUBZolI/AAAAAAAAHHo/HiuKCHp5Qpo/w1011-h754-no/2013-05-29+20.40.46.jpg

Here is the bolt with the 8mm hex out of it:
https://lh6.googleusercontent.com/-xfriSac2IUw/Uabnev7Li5I/AAAAAAAAHHg/Yd4EjesPy88/w833-h818-no/2013-05-29+22.44.22.jpg

Do I have to get it at the dealership or do you think I can bring it to any place for a replacement?

[alexandre]

:hi

[webster]

when i put in my Rogue pulleys it was a bitch to get that off. definitely had to use an 8mm hex, where the instructions called for a t45/t50 (can't recall 100%).

i bet if you walked into the dealership and put on your prettiest face you could get it on the house.

[Rovert]

I'll make sure to do my makeup before I leave..... :thumbsup

Could I search for it at a car parts place? Or is this bolt a very special one? Real OEM says it's an "M10X25"....but I fit an 8mm into it...I'm confused.

[danewilson77]

I got mine from ecs. A dealer would have bit I doubt an indy would.

HTC DNA ON TT4 BETA, WILLIAMSBURG, VA

[BCS_ZHP]

M10 is the thread size/count not the size of the hex opening. The 25 is length of bolt in mm, so about a inch long. A good hardware store should have this, the kind of hardware store with drawers & drawers of fasteners. You could also change this to a normal hex head bolt of same size, if you wanted to.

[danewilson77]

http://www.zhpmafia.com/forums/showthread.php?36-AC-and-Serpentine-Belt-Diy

http://farm8.staticflickr.com/7149/6545690671_061f918f77_b.jpg (http://www.flickr.com/photos/dw77zhpmafia/6545690671/)
E46 Serp Tensioner Bolt (http://www.flickr.com/photos/dw77zhpmafia/6545690671/) by Dane Wilson77 (http://www.flickr.com/people/dw77zhpmafia/), on Flickr

[Rovert]

I think I want to change it to a hex head bolt. Anyone know sizes off hand to search at Home Depot? I read this from a posting at E46fanatics:

There is no reason I can think of for why you can't use a normal, high grade hex bolt. A socket head cap screw (what you have in the pics) is basically just a bolt with a different tool used to fasten it. There is no other difference in the function of the fastener. If it was inset into a counterbored hole, then it would be a different story (which is the primary reason why these types of fasteners are used).
Considering all of the problems I have read about dealing with these things, I may just replace all of mine with normal Grade 8.8 hex head bolts.

Also, the M10 x 25 description has nothing to do with the size of the hex bit used to remove it. The M10 means it is a Metric 10mm diameter fastener. The 25 means it is 25mm long.

[ryankokesh]

I hate that stupid bolt... Definitely going to replace it with whatever you do :)

[danewilson77]

Bruce listed size above? ;/

HTC DNA ON TT4 BETA, WILLIAMSBURG, VA

[Rovert]

So I went with wise people's advice and bought a HEX bolt from Home Depot.

https://lh3.googleusercontent.com/-9w5uIJ1KkZ0/UadwJ7SmFiI/AAAAAAAAHIk/Xx9gcmtEw6I/w420-h818-no/2013-05-30+07.37.52.jpg

Equal sizes:
https://lh3.googleusercontent.com/-FlyAJEPHWfg/Uadw5axNQsI/AAAAAAAAHIs/ku69oxQqlzg/w1051-h807-no/2013-05-30+07.56.43.jpg

https://lh5.googleusercontent.com/-JdawStGrAmU/UadwaK2hKbI/AAAAAAAAHI0/QwyN8vaSAJU/w1051-h802-no/2013-05-30+08.00.05.jpg

Equal thread:
https://lh5.googleusercontent.com/-6hWwzukI86M/Uadw2TgfYcI/AAAAAAAAHI4/8gPnJO58-Do/w572-h817-no/2013-05-30+08.01.58.jpg

Installation with this was WAY easier without any chance of slippage:
https://lh5.googleusercontent.com/-4GcLSWuC3kI/Uadw9XFZjGI/AAAAAAAAHI8/8WHNrGm37fY/w801-h818-no/2013-05-30+08.05.58.jpg

[alexandre]

:thumbsup

[webster]

nice job.

[danewilson77]

If you'd have bought the box and shipped them to us, you could have driven your cost down to $0.64 :)

Thanks for providing an alternative here Trevor.

[ryankokesh]

If you'd have bought the box and shipped them to us, you could have driven your cost down to $0.64 :)


Don't forget that's Canadian

[danewilson77]

Don't forget that's Canadian

:rofl

[Dave_B]

Only thing I would have done different would be an SS bolt, not a plated one.

Other than that, I can't wait to hear feedback in a few hundo miles. Mine currently is installed, but stripped. :P

[wsmeyer]

Only thing I would have done different would be an SS bolt, not a plated one.

+1

He's also replaced a Grade 5 bolt with a Grade 2 bolt.

[MrMaico]

+1

He's also replaced a Grade 5 bolt with a Grade 2 bolt.

Those are SAE grades though. Metric is different. It looks like the original was an 8.8 and the new one I can't read but it definitely isn't as strong, maybe a 5.8. If it were me I'd probably find at least an 8.8 somewhere and replace it when you get a chance. I'd guess there is probably quite a bit of pressure on that bolt from the tensioner.

http://www.engineeringtoolbox.com/steel-bolts-metric-grades-d_1428.html

[wsmeyer]

Those are SAE grades though. Metric is different. It looks like the original was an 8.8 and the new one I can't read but it definitely isn't as strong, maybe a 5.8. If it were me I'd probably find at least an 8.8 somewhere and replace it when you get a chance. I'd guess there is probably quite a bit of pressure on that bolt from the tensioner.

http://www.engineeringtoolbox.com/steel-bolts-metric-grades-d_1428.html

This is what happens when you buy bolts at the hardware store.

All metric bolts are supposed to be graded, so what is a metric bolt with no standardized mark? :dunno

In SAE no mark is Grade 1 or Grade 2 so anything without a mark I just refer to as a crappy hardware store bolt.

Plus Grade 5 SAE = Metric 8.8

Either way, I'd use a properly marked bolt for the pulley.

[Rovert]

The bolt I bought was under the Stainless Steel section and there was a clear 8.8 indent on the head.

[MrMaico]

The bolt I bought was under the Stainless Steel section and there was a clear 8.8 indent on the head.

Cool......in that case you should be alright then. I would be surprised if it is truly stainless though. Usually they have more of a silver grey finish.

One of these days I should tackle my pulleys/idlers. I have the parts, just haven't gotten around to doing them yet.

[Rovert]

I would be surprised if it is truly stainless though. Usually they have more of a silver grey finish.

One of these days I should tackle my pulleys/idlers. I have the parts, just haven't gotten around to doing them yet.

I hope it is SS too. LOL. If it isn't...what's the worse to happen even if it's covered by a nice little plastic cap in the engine bay? I assume the moisture in the air could play a role in degrading this bolt in the future? It's easy to do all the pulleys/idlers/belts. Just get start taking off the intake collector and radiator fan and you'll get into the mood! LOL

[ryankokesh]

Got a bolt... Not SS but it does say 8.8 on the head :dunno

http://i.imgur.com/NSx44GF.jpg


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[Rovert]

Does that mean if it doesn't strip...now it'll rust on? LOL

[ryankokesh]

Prolly... Will have to do for now though as I'm gonna put pulleys on and I don't think the bolt on there has two more removals left in it.


Sent from my iPhone using Tapatalk

[Rovert]

Maybe what you can do it protect it with some kind of grease or coating that'll make it more water resistant. That with the plastic cover on it should work ok for a decently long time.

[Rovert]

BUMP!!

I changed the OEM bolt (allen key type) on my ///M today. I only torqued the tensioner bolt twice in my lifetime of owning the car and it was showing metal fatigue. I'd give it maybe 3 more times of torquing the belt tensioner until it got really sketchy. Now the same 17mm bolt that holds the lower alternator and + terminal to it is used for the belt tensioner. I won't have to worry about that stripping out on me.