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Compressor belt on an OM366

Frankhaddad

Well-Known Member
Joined
Aug 25, 2017
Messages
61
Location
Maine
Mercedes engine with an air compressor mounted to it, when compressor is activated, belt bounces around violently, not activated, looks okay. have a video on my phone. belts do not last long in this condition. Any ideas would be great. Compressor is true to the other pulleys.
 

MarshallPowerGen

Senior Member
Joined
Nov 26, 2017
Messages
442
Location
Northwestern USA
Occupation
Generator Technician & Equipment Mechanic
Tensioner been replaced? Is the compressor factory, or an add on? All the pulleys been checked for any bearing play or wobble?
 

Frankhaddad

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Joined
Aug 25, 2017
Messages
61
Location
Maine
Everything is factory, This model is mounted in a Unimog large vehicle. This compressor is the only component run on this belt from the crank shaft. Adjustments are made at the compressor. Yesterday was the test after extensive work making sure everything was spot on. I have a video on my phone that I could send you. He has had a lot of pros look at it, I have 25 years experience myself, just not on Mercedes. It looks great when the compressor is off but on the belt looks like its going into a death wobble. The belt is also from the manufacturer.
 

MarshallPowerGen

Senior Member
Joined
Nov 26, 2017
Messages
442
Location
Northwestern USA
Occupation
Generator Technician & Equipment Mechanic
Yeah, I was asking generally to knock out the basics. I'm not familiar with those Mercedes engines, and especially not in Unimogs, and especially when it's an issue with a belt drive compressor in the generator section of the forum.
 

Frankhaddad

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Aug 25, 2017
Messages
61
Location
Maine
I know right! I have a reputation of being the king of funky things up here in Maine. Everything that no one can figure out comes to me. Eventually I will prevail! But this is an odd one. Could I send a vid to your email just to get another set of eyes on it? it shows at the beginning at rest, then the compressor turns on.
 

Birken Vogt

Charter Member
Joined
Nov 30, 2003
Messages
5,305
Location
Grass Valley, Ca
Does it smooth out when the RPM is changed? Or happen at idle only? Tried changing the idle RPM either direction?

Old Ford diesel trucks used to have a v-belt that slapped around a good bit to the alternator. They usually ran fine like this, but occasionally would jump off, but not much you could do about it.
 

MarshallPowerGen

Senior Member
Joined
Nov 26, 2017
Messages
442
Location
Northwestern USA
Occupation
Generator Technician & Equipment Mechanic
Old Ford diesel trucks used to have a v-belt that slapped around a good bit to the alternator. They usually ran fine like this, but occasionally would jump off, but not much you could do about it.
I relate to that, having an '86 F350 6.9idi with the slappy alternator belt as a daily driver. You either let it do its thing, or wipe out the alternator bearings if you do ever get it tight enough to roll smooth, haha.
 

Volvomad

Senior Member
Joined
Jul 13, 2011
Messages
476
Location
Ireland
Just because everything is OEM including the belt doesnt make it right . I would try a gates automitive (not industrial ) belt
 

Frankhaddad

Well-Known Member
Joined
Aug 25, 2017
Messages
61
Location
Maine
Just because everything is OEM including the belt doesnt make it right . I would try a gates automitive (not industrial ) belt
I thought of an aftermarket belt, customer is very meticulous, wanted more input, thank you.
 

hosspuller

Senior Member
Joined
Aug 27, 2014
Messages
1,869
Location
North Carolina
A compressor has peaks & valleys of resistance. perhaps a less stiff belt would help to smooth the torque and the jumping. Another thought, lower the belt tension to let the rubber elements work.
 

funwithfuel

Senior Member
Joined
Mar 7, 2017
Messages
5,518
Location
Will county Illinois
Occupation
Mechanic
Late to the party here. Are we talking air compressor or A/C compressor.
I remember air compressor driving off camshaft on side of engine.
 

hosspuller

Senior Member
Joined
Aug 27, 2014
Messages
1,869
Location
North Carolina
Put a dial indicator on the compressor pulley. Bar the engine over. Looks like it's not running true by the photo blur. Do it at several places, edges, groove walls, etc.
 

Frankhaddad

Well-Known Member
Joined
Aug 25, 2017
Messages
61
Location
Maine
Put a dial indicator on the compressor pulley. Bar the engine over. Looks like it's not running true by the photo blur. Do it at several places, edges, groove walls, etc.
These photos are actually after I got it true. It was not before. Now it looks good until compressor starts and starts fluctuating and not sure but looks like it makes contact with the frame. I tried to load a video but wouldn't let me.
 

Volvomad

Senior Member
Joined
Jul 13, 2011
Messages
476
Location
Ireland
Other than looking terrible , is the belt flapping causing problems ?
Is it chewing up belts ?
If it was a pulley problem I would still expect flapping when the compressor is unloaded .
These compressors are hard to drive on 1 belt . From the pic ,the belt is loose under load due to belt stretch ,lack of tension or over loading .
If you start the vehicle with empty air tanks ,is it as bad from the start ?
Is it cutting out at the correct air pressure ?
 

Frankhaddad

Well-Known Member
Joined
Aug 25, 2017
Messages
61
Location
Maine
Other than looking terrible , is the belt flapping causing problems ?
Is it chewing up belts ?
If it was a pulley problem I would still expect flapping when the compressor is unloaded .
These compressors are hard to drive on 1 belt . From the pic ,the belt is loose under load due to belt stretch ,lack of tension or over loading .
If you start the vehicle with empty air tanks ,is it as bad from the start ?
Is it cutting out at the correct air pressure ?
Customer just came back inti the picture, he had bought a new compressor to try, I installed it, made sure it was true to the crank shaft, it does get chewed up when it hits the frame, starting out with empty tanks it jumps quite a bit, tanks full, it looks perfect.
 
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