R129 500 SL engine whine help

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Minimalist

New Member
Joined
Aug 30, 2020
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8
Location
London
Car
MERCEDES SL 500 R129
Hello All.

Can anyone help identify what this noise is... I'm thinking either idler or tensioner pulley, you can hear a slight grumble too and I think the bearing has gone in one of them.

Please see video link, you can hear the noise, much louder once engine is started and quietens down after idling, at which point you can hear the grinding/grumbling.

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Any help appreciated.

Thanks.
M.
 
It could be the auxiliary air pump which sounds like a hair dryer when going off or a pulley bearing that's going. Remove the drive belt and spin the pulleys to see if they're stiff.
 
Remove the belt and try it again. I’d be slightly concerned about plastic chain guides. They are getting brittle on m119’s now, and often end up in the sump
 
Thanks alabbasi for the reply. Agreed, I think that would be the next step in getting an accurate assessment. Is the air pump an easy thing to replace?
 
Remove the belt and try it again. I’d be slightly concerned about plastic chain guides. They are getting brittle on m119’s now, and often end up in the sump

Hi jobsworth. Thanks for the reply. As in you mean to run it with the belt removed with the hope there will be no noise which would suggest its the tensioner?

What to do about the chain guards?

Thanks,
M.
 
Hi jobsworth. Thanks for the reply. As in you mean to run it with the belt removed with the hope there will be no noise which would suggest its the tensioner?

What to do about the chain guards?

Thanks,
M.
Yes, hopefully with the belt off the noise will be gone, and you’ll know it’s something simple on the belt drive making the noise. Don’t run it too long, as the water pump will not be running. From cold, a few minutes is fine. If the noise is still evident with the belt off it’s more serious
 
Fi
Yes, hopefully with the belt off the noise will be gone, and you’ll know it’s something simple on the belt drive making the noise. Don’t run it too long, as the water pump will not be running. From cold, a few minutes is fine. If the noise is still evident with the belt off it’s more serious

Fingers crossed! How common is it for the air pump to go? I've replaced idlers and tensioner before as these are typical in my limited experience... But don't know anything about the air pump...
 
Fi


Fingers crossed! How common is it for the air pump to go? I've replaced idlers and tensioner before as these are typical in my limited experience... But don't know anything about the air pump...
If memory serves, when these were fitted with a smog pump it was a belt driven affair
 
If memory serves, when these were fitted with a smog pump it was a belt driven affair
Oh right, gotcha. So that would mean not all SL have the air pump. I haven't bought the car yet, I was sent a video and immediately I noticed the noise...so now I don't know what to do....go and see it and make a better assumption in person or skip it altogether. Service history wise its all there, looks to me the engine has been cleaned because in an earlier photo it was dirty. I'm thinking the cleaning (with water?) has caused this issue.
 
What mileage has been covered by the car? I ask because I had a '94 version which had been neglected, and at 144K miles the camchain tensioner let go and totalled the engine...
 
That's a proper horror story! Sorry to hear that E55BOF.

Mileage is 124k, its a '96 model.
 
Fingers crossed! How common is it for the air pump to go? I've replaced idlers and tensioner before as these are typical in my limited experience... But don't know anything about the air pump...

Not common, but not rare either. It's the pulley bearing that goes bad rather than the pump itself, but they're not easily rebuildable (or weren't 15 years ago when I did mine).
 
Not common, but not rare either. It's the pulley bearing that goes bad rather than the pump itself, but they're not easily rebuildable (or weren't 15 years ago when I did mine).
Thanks Doodle. I suppose it could be any one of these things with a car that's 25 years old and it can't be a surprise if something needs to be replaced.....I'm just hoping it's a simple fix like the tensioner...I am led to believe the car is well maintained and has had a bunch of work done.
 
Whine is also typical of an alternator under load- [ e.g. charging the battery after starting]-- yet another belt driven engine ancilliary to be checked. Is the car a private sale or from a dealer. Personally I would not buy a merc of that age on video evidence alone. Most classic benz owners entrust their pride and joy to regular servicing with a MB specialist who knows these cars- and their faults inside out- who is the service history with? the local garage round the corner - good tho it might be for routine stuff---ain't going to cut it I'm afraid. :(
 
Whine is also typical of an alternator under load- [ e.g. charging the battery after starting]-- yet another belt driven engine ancilliary to be checked. Is the car a private sale or from a dealer. Personally I would not buy a merc of that age on video evidence alone. Most classic benz owners entrust their pride and joy to regular servicing with a MB specialist who knows these cars- and their faults inside out- who is the service history with? the local garage round the corner - good tho it might be for routine stuff---ain't going to cut it I'm afraid. :(
I'm off to go and see the car today, it's a private sale. The chap has some other classic cars and has a regular mechanic that looks after all his cars. He mentioned the mechanic will be there working on another car when I come....
 
I am not much of a mechanic but I had a very bad startup whine on my E280(a totally different car I get it), but despite numerous members and mechanics all commenting similar to the above with airpump etc etc.. , it ended up being the oil pump. I can't quite hear properly in your video but it's worth an investigation in that area. What you can do is start it when cold and put your finger /hand on the sump(if you can get at it in the SL), roughly where the oil pickup is and if it's that you can feel the vibration in the sump. When the noise quietens down so does the vibration. Theres a M104 engine video here
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. How I solved it was to lift the engine, take off the sump and remove the pump. I replaced mine with a newer but still second hand oil pump and noise totally gone. It's interesting to note that there was nothing wrong with the noisy oil pump that i took out, it just so happened to vibrate. Could have been the pressure valve, could have just been an anomaly in the way the gears moved but it was not going to fail anyhowi actually still have it in the drawer. However mine is now whispery quiet and it's great :). Happy hunting.
 

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