OM642 Bypass AC Compressor
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2021 GLS580 | 2011 ML350 BlueTec | 2009 Pontiac G8 GXP
OM642 Bypass AC Compressor
Potentially looking at a failing AC compressor. Has anyone bypassed the compressor with a shorter belt? I see that the compressor pulley should breakaway in the event the compressor seizes but it would be preferable to prevent that until I get it replaced.
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2021 GLS580 | 2011 ML350 BlueTec | 2009 Pontiac G8 GXP
I don't think it's a gassing problem. More context, the compressor was replaced in 2022 when it began knocking. Last week I believe the replacement began knocking. Have an appointment to get it checked on the 13th but was going to see if I can prevent sending shrapnel through the system should it explode before we get it diagnosed/replaced.
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From: V E G A S
1922 Ford Model T / no OBD
With proper scanner it takes about 90 seconds to access AC pressure and start troubleshooting.
I believe that even in cold states, car without AC will loose lot of value.
I believe that even in cold states, car without AC will loose lot of value.
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From: Allentown, PA
'08 GL 320 CDI
I think there was a very recent thread about this... maybe it was in the X164 forum... and I THOUGHT I had responded in that thread, making it easy to find. But I can't seem to find it.
As long as there is clearance for the belt (I don't have my car right now to look) so it doesn't contact other pulleys, sure, I can't think of any problems in doing so. Just measure the distance with something that doesn't stretch like poly strapping. You need to take into account the tensioner - but you could probably don that with the strapping by pulling it tight. OR... measure the current round trip with the belt off and compare that to the current belt length. Then adjust the new belt's length vs the roundtrip without the AC to match the difference.
What about ribs vs smooth vs pulleys? Probably won't matter for a short time, though.
As long as there is clearance for the belt (I don't have my car right now to look) so it doesn't contact other pulleys, sure, I can't think of any problems in doing so. Just measure the distance with something that doesn't stretch like poly strapping. You need to take into account the tensioner - but you could probably don that with the strapping by pulling it tight. OR... measure the current round trip with the belt off and compare that to the current belt length. Then adjust the new belt's length vs the roundtrip without the AC to match the difference.
What about ribs vs smooth vs pulleys? Probably won't matter for a short time, though.
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Joined: Apr 2011
Posts: 541
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2021 GLS580 | 2011 ML350 BlueTec | 2009 Pontiac G8 GXP
I think there was a very recent thread about this... maybe it was in the X164 forum... and I THOUGHT I had responded in that thread, making it easy to find. But I can't seem to find it.
As long as there is clearance for the belt (I don't have my car right now to look) so it doesn't contact other pulleys, sure, I can't think of any problems in doing so. Just measure the distance with something that doesn't stretch like poly strapping. You need to take into account the tensioner - but you could probably don that with the strapping by pulling it tight. OR... measure the current round trip with the belt off and compare that to the current belt length. Then adjust the new belt's length vs the roundtrip without the AC to match the difference.
What about ribs vs smooth vs pulleys? Probably won't matter for a short time, though.
As long as there is clearance for the belt (I don't have my car right now to look) so it doesn't contact other pulleys, sure, I can't think of any problems in doing so. Just measure the distance with something that doesn't stretch like poly strapping. You need to take into account the tensioner - but you could probably don that with the strapping by pulling it tight. OR... measure the current round trip with the belt off and compare that to the current belt length. Then adjust the new belt's length vs the roundtrip without the AC to match the difference.
What about ribs vs smooth vs pulleys? Probably won't matter for a short time, though.
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From: Allentown, PA
'08 GL 320 CDI
As long as it's not a bearing, I think you should be fine. Typically a bearing wouldn't make a "knock" sound, but who knows.
How is the pulley attached? Can it be easily removed?
How is the pulley attached? Can it be easily removed?
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From: New Hampsha
'17 GLS450, '14 GLK250, Grandpa's Roadster
If you turn the AC off the compressor shouldn't spin, and if that stops the noise, all should be good. Just watch out for things that may turn the pump on regardless, like Defrost.
If it's not spinning there should be no further damage. If the problem is in the pulley/clutch, which is still spinning, then that can be (I assume) replaced separately.
If it's not spinning there should be no further damage. If the problem is in the pulley/clutch, which is still spinning, then that can be (I assume) replaced separately.
Last edited by John CC; Dec 3, 2024 at 04:16 PM.
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Joined: Oct 2015
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From: New York
2012 GL350
And here is an excerpt after my success...
Long story short, the OM642 diesel will need a 78.5 belt to bypass the A/C compressor.
Unfortunately, the belt rubs on the seized A/C clutch and I didn’t check until I had everything back together. It will be fine for the short term (2 short trips this weekend) but I need to see if I can remove the clutch from the A/C compressor. If memory serves, I don’t think the clutch is replaceable on the GL350 compressor.
Thanks again for the support and hopefully this can help the next person stuck in a pinch.
And I never addressed the slight rubbing on the AC compressor and all is still well about 500 miles later. Also, when my compressor seized, the pulley did not break away. There is burnt rubber on the bottom of the pulley from the belt melting.
Last edited by 91stealthes; Dec 13, 2024 at 10:43 AM.
