Aircon pulley bypass

Diego06

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Hi folks I have a 2007 facelift E320 cdi OM642 3ltr V6.
I've had a rattle from the front of the engine for the last week or so which had been diagnosed as the tensioner, only really because it was wobbling whilst running.......it was very difficult to pinpoint where the sound was actually coming from. It was booked in to be replaced next Tuesday. Anyway, driving home from work yesterday & the aircon compressor pulley literally exploded!!!! I guess that pinpointed where the noise was coming from then :rolleyes:
With things being a bit tight at the moment (I know, owning a Mercedes & things being tight do not belong in the same sentence, I have only owned the car for a few weeks & I can't believe the cost of parts compared to my old Mondeo :() I was hoping to temporarily bypass the a/c compressor with a shorter belt, but after hours of searching I cannot find any info on the size of belt I need. The correct belt is a 7PK2035 but as a/c was fitted as standard there is no option for a 'non a/c' car.
Has anyone on here done this & can you remember what length of belt was used please?
 

Petrol Pete

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Hello and welcome . You could run a piece of string around the pulleys and measure it , most belts are printed with figures such as 6-25- 1370 etc these figures normally - in this case - would translate to 6 ribs 25 mm wide and 1370 mm length.

it is obviously a bit more complicated than that but the specs on to original belt will normally tell you at least the width and V or 'rib' set up as a starting point. Best of luck. 👍
 
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Diego06

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Hi Pete, thanks for the welcome & reply. I have done what you suggested & run a piece of string round the pulleys. It measured 1940mm but obviously the tensioner was fully open/'untensioned' (is that a word?) so I took an extra 20mm off to allow for that. I have ordered a 7PK1920 from ECP as it wasn't in stock. I'll fit it tomorrow with crossed fingers & report back..............
 
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Diego06

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Reporting back because I came across a few posts on various forums where people had the same problem as me but never came back to report their solution......soooo frustrating :wallbash:
OK so I guess my string measurement was a bit wayward. Maybe it slipped behind a pulley or something because the 1920 was not even close...far too small. Tried a 1933, still too small. Ended up using a 7PK1953 & could probably have even gone another size up from that. But no matter, the aircon compressor is bypassed for now & it all seems to be working fine :)
 

Bellow

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Reporting back because I came across a few posts on various forums where people had the same problem as me but never came back to report their solution......soooo frustrating :wallbash:
OK so I guess my string measurement was a bit wayward. Maybe it slipped behind a pulley or something because the 1920 was not even close...far too small. Tried a 1933, still too small. Ended up using a 7PK1953 & could probably have even gone another size up from that. But no matter, the aircon compressor is bypassed for now & it all seems to be working fine :)
Could the difference be accounted for by you measuring in the grooves and the belt measurement possibly relating to the length at mean thickness or on the outer? (If so, my quick calculation suggests the difference is 5.25mm. Belt thickness?)
I have an interest in doing similar and without having to import the substitute pulley which utilises the original belt.
 

DSM10000

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Unless you have returned the incorrect belts for a refund you could probably have bought the tensioner for the cost and certainly the hassle factor.
 
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Diego06

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Could the difference be accounted for by you measuring in the grooves and the belt measurement possibly relating to the length at mean thickness or on the outer? (If so, my quick calculation suggests the difference is 5.25mm. Belt thickness?)
I have an interest in doing similar and without having to import the substitute pulley which utilises the original belt.

To be honest I have no idea, anything could have happened because my arms filled the gap between the rad & the pulleys so I couldn't see what I was doing. Plus it was raining so I was rushing. Sorry that's no help :( The 1953mm belt is running fine if that helps. There is no rattling & the engine is running smooth. Damn this engine runs quiet for a diesel 😍

Unless you have returned the incorrect belts for a refund you could probably have bought the tensioner for the cost and certainly the hassle factor.

I was able to return the incorrect belts for refund with no problems but, as Trickythemerc said, there was no issue with the tensioner so it did not need replacing anyway. I suspect the wobble that I mentioned in my original post was likely caused by the aircon compressor seizing or the pulley breaking up & causing the belt to bounce.
 

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