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-   -   alternator belt tension (http://www.peachparts.com/shopforum/diesel-discussion/191918-alternator-belt-tension.html)

rjonnal 06-21-2007 12:39 PM

alternator belt tension
 
Dieselers,

I'm going to replace the alternator in my '83 240D this weekend, and I have a couple of specific questions:

1. Are there tools I should have other than my socket set and an adjustable wrench?

2. When installing the new alternator, how do I know if the tension is right? I mean, I'll feel the tension in the current configuration, but will it be okay if I ballpark the same tension when I reinstall? And, I assume if it squeals, I'll need to tighten the belt tension; but how do I know if it's too tight?

Thanks!

-Ravi

truckinik 06-21-2007 12:42 PM

Find a flat spot, between two pullys, and push on it firmly.

Three quarters, to one inch of play, is what you are aiming for. You do need to allow at least three quarters of an inch of play though, They tighten up, uppon acceleration.

If the belt is either too tight, or too loose, it wil squeel. It can snap (Not very likely though), or burn, or squeel, being overly tightened, so be careful.

vstech 06-21-2007 12:44 PM

first, if you have never worked on the alternator on this car, use PB BLASTER on the thin adjuster nut/bolt combo! let it sit all day, and be VERY CAREFULL loosening this bolt. it's 50.00 to replace it. next pop off the wire harness, (you may want to disconnect the battery for this, cause you can short out the wires with a screwdriver if you're not carefull) on the back of the alternator there are three 17mm bolt heads, loosen and remove all three, and take the alternator out with the bracket still attached. much easier! now, how long has the belt been in service? a new belt works MUCH better than a slightly hardened belt... now is the time to change it, but you have to remove the other belts to get it off, so changing them all is recommended.

tangofox007 06-21-2007 01:37 PM

Quote:

Originally Posted by rjonnal (Post 1542321)
Are there tools I should have other than my socket set and an adjustable wrench?

http://www.napaonline.com/MasterPages/NOLMaster.aspx?PageId=470&LineCode=NBH&PartNumber=KR1&Description=Belt+Tension+Gauge

Piratejason 06-21-2007 03:50 PM

yes -
 
On my 85 I had to use a short, 17 mm racheting wrench for the top inboard bolt.

Go ahead and remove the EGR junk and the turbo air inlet u tube. Much easier. Previous posters are correct - easier to leave it attached to the bracket and drop it through the bottom.

Oh and that nut on the front of the bracket is welded and will not budge. Don't ask me or my knuckles how I know.

PJ

rjonnal 06-23-2007 01:37 PM

Dieselers,

Thanks for your great advice. I replaced the alternator successfully yesterday, and now I've got 14 volts, idling. I think the car is roadworthy now.

I wound up taking just the alternator out, and not the bracket. The bolt holding the bracket to the engine was super-tight, and inaccessible to the pb blaster can. The other bolts gave in to the blaster, and were easy to remove.

I didn't know that there would be an aluminum bushing/sleeve around the body of the upper (adjustment) bolt, so when I pulled that bolt out and the sleeve fell on the ground, I was like, "Oh *****, where did that come from? I hope that I'm not dismantling the engine."

All told, though, it was an easy, straightforward, and fun job, and thank you all for your helpful advise and generally positive attitudes.

-Ravi

DeltaDave 07-19-2007 10:53 PM

When I bought my 81 240D the alternator mounting system was a little messed up. The micrometer adjustment screw was gone, there wasn't a sleeve on the top bolt as mentioned in the previous post. I replaced the alternator and bought a new top bracket. But now the bracket mounting holes on the rebuilt alt. are worn oval shaped, letting the alt.tip towards the centerline of the car, loosing the belt. Sound familar ? Do I need the sleeve ? My alternator on my 85 300TD has never done this.

toomany MBZ 07-20-2007 04:24 PM

Quote:

Originally Posted by DeltaDave (Post 1567903)
When I bought my 81 240D the alternator mounting system was a little messed up. The micrometer adjustment screw was gone, there wasn't a sleeve on the top bolt as mentioned in the previous post. I replaced the alternator and bought a new top bracket. But now the bracket mounting holes on the rebuilt alt. are worn oval shaped, letting the alt.tip towards the centerline of the car, loosing the belt. Sound familar ? Do I need the sleeve ? My alternator on my 85 300TD has never done this.

Start a thread.


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