Which alternator belt should i use? 240D - PeachParts Mercedes-Benz Forum

sun tortise · #1 07-25-2022, 02:18 PM

Replaced my alternator due to extreme ovalization of the pivot holes, and when i installed the old belt on the new alternator, it would not tighten within the range of the adjuster. It is Contitech 13 x 1030. I see that Pelican also has a 10 x 970 listed for my 1981 240D. How could that be?

My old belt is quite worn from running crooked for maybe 20,000 miles. Could that make it stretch or sit lower in the groove enough that it is too loose to tighten sufficiently?? Or do i need a smaller belt?

Thanks

t walgamuth · #2 07-25-2022, 02:47 PM

I'd say yes on the new belt.

sun tortise · #3 07-25-2022, 03:36 PM

Definitely need a new belt, but wondering if i should go to a smaller belt, or stick with the 13 x 1030

t walgamuth · #4 07-25-2022, 03:50 PM

I'd go with stock.

Frank Reiner · #5 07-25-2022, 06:05 PM

Quote:

Originally Posted by sun tortise

Replaced my alternator due to extreme ovalization of the pivot holes, and when i installed the old belt on the new alternator, it would not tighten within the range of the adjuster. It is Contitech 13 x 1030. I see that Pelican also has a 10 x 970 listed for my 1981 240D. How could that be?

My old belt is quite worn from running crooked for maybe 20,000 miles. Could that make it stretch or sit lower in the groove enough that it is too loose to tighten sufficiently?? Or do i need a smaller belt?

Thanks

The 10mm wide belt (OEM 9.5mm) will be the correct one for the alternator.
A 13mm wide belt is used for the A/C compressor, and for the steering pump.

vstech · #6 07-25-2022, 10:45 PM

Quote:

Originally Posted by Frank Reiner

The 10mm wide belt (OEM 9.5mm) will be the correct one for the alternator.
A 13mm wide belt is used for the A/C compressor, and for the steering pump.

10mm is for a dual belt alternator.
The single belt design is 13mm

sun tortise · #7 07-30-2022, 01:47 PM

I went with the 13 x 1030, and it seems to fit fine. My 1985 300D with the dual pulleys uses the narrower 10 x 970 belt.

Got a crappy alternator from Heartland Starter (on Flea Bay), and one of the pivot holes (pulley side) is too large, so it sat crooked. Shoulda sent it back, but it was such a PITA to install, so i shimmed it with some flattened folded over TV antenna elements. Hope it holds.

BillGrissom · #8 08-05-2022, 11:14 PM

For all V-belts in all cars, download a catalog like Gates. They generally come in 3 widths, with lengths in 50 mm increments, as I recall. Newer belts usually have a label like AV1130, meaning 1130 mm long OD. Some list the length at the mid-section. Once you get the length code, search ebay and Amazon. I had to try up to 3 belts to get a perfect fit for custom AC brackets on my 1960's Mopars, due to estimating length w/ rope, varying length definitions, and limited swing on the compressor. But most cost <$10 and oops go in my V-belt box. For the M'-B alternator, always but a matched pair.

vstech · #9 08-07-2022, 01:56 AM

Quote:

Originally Posted by BillGrissom

For all V-belts in all cars, download a catalog like Gates. They generally come in 3 widths, with lengths in 50 mm increments, as I recall. Newer belts usually have a label like AV1130, meaning 1130 mm long OD. Some list the length at the mid-section. Once you get the length code, search ebay and Amazon. I had to try up to 3 belts to get a perfect fit for custom AC brackets on my 1960's Mopars, due to estimating length w/ rope, varying length definitions, and limited swing on the compressor. But most cost <$10 and oops go in my V-belt box. For the M'-B alternator, always but a matched pair.

Again… only on the turbo v-belt alternators… the N/A uses a single belt…