Alternator Bracket:: Too Tight?

[113gray]

Hello group. Thinking about my 230SL in anticipation of spring, I recalled having to replace my alternator bracket last summer. The MB replacement bracket was thicker than the original & getting the fan belt back on was a struggle, even with loosening the alternator adjustment bolt to the max. reinstalled, the belt seemed very tight, although I was able to depress it the recommended 1/2" with my thumb, but with some force required.Now I am wondering if the belt is too tight, & if so, would this subject the crank, water pump bearings to XS wear &/or failure. Should I cut the old belt off & replace it with one 1-2 cm longer? The car has been driven perhaps 500 miles since with no ill effect I can detect. Appreciate your responses.       -JP-

[mdsalemi]

Hey JP,

You are wise to take this into consideration.  I once had consistent problems with a too-loose v-belt on my VW Golf some years ago, when I finally got it tight enough it was apparently too tight and trashed the alternator bearings!  

I don't know if MB publishes a spec on belt tension other then the old 1/2 deflection deal, but in some realms, v-belt tension is important, and to that end, Goodyear makes an inexpensive tool called an "Industrial V-Belt Tensioner" (Product code 522908003) which is used to measure the tension (tightness) on a v-belt.  If you have concern about what you have done, you might want to try and pick one of these up and add it to your tool kit.  I'm sure many other manufacturers make something similar; it isn't expensive or complex.

I have one in my bag of tricks for carwash pumps and motors, but it certainly can be used in other applications.

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[Jonny B]

From the BBB

"The Vee-belt must be tensioned to such an extent that it can be pressed out of the straight by 5 mm to a maximum of 10 mm when moderate thumb pressure is applied"

So you are correct, a range of 1/4 to 1/2 inch.

Jonny B
1967 250SL Auto

[gugel]

quote:"The Vee-belt must be tensioned to such an extent that it can be pressed out of the straight by 5 mm to a maximum of 10 mm when moderate thumb pressure is applied"   So you are correct, a range of 1/4 to 1/2 inch.

5mm ~ 3/16"; 10mm ~ 3/8".  
1/4" ~ 6mm; 1/2" ~ 13mm