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Has anyone had a whiny power steering pump? Does it eventually explode? It's annoying but I can live with it for a while until I get sick of the noise. I can make a video if necessary. Changed pulleys and belt and it's the P/S pump.
Zero vibrations felt through wheel. No boost assist issues. Doesn't really even get louder when I steer it. I did try bleeding with the wheels off the ground (turn wheels back and forth with engine off and also tried while running), no change at all. Could try new fluid I guess...
you opened the door to some critical judgement on NVH and the Merc approach
I started life as RR motor vehicle tech, moved on as sales took off to Jags, so of course we were always critical of the noise vibration harshness and the mechanical refinement of the "premium" German cars. They never had any.
In the UK Mercedes have always had the nickname of being "taxis". The whole ethos of Merc was to be a stylish and long lasting vehicle. But the mechanical refinement was only ever that of a worn panzer tank. Now the sad news is that reliability has completely gone. Its now all about selling dressed up bling from a marketing department on fire. My V8 has always has noises from its water pump, air con pump, power steering pump and gearbox that you wouldn't ever find on a Jag or RR even high mileage, abused ones that have been scrapped
Turn off the AC and see if it stops? When low on gas you get these strange noises that sound like its PAS or the Gearbox
Yeah tried that, too. No change at all. FWIW, when I did the belt, I did play with the P/S pulley just to see if anything felt off. The bearing felt tight but when I rotated it back and forth it felt like there was some amount of play in the coupler or something. Maybe there is a damper or rubber coupler internally that fell apart. If so, then this is just a noise and nothing more.
I feel like if there was enough air in it to cause noise, I'd feel something abnormal in the steering or maybe a lot MORE whine when working the steering. But that doesn't seem to be the case. However, I know the reservoir is an issue on these (though mine doesn't seem to be leaking) so it may be worth just throwing one at it since it should be "cheap and easy."
Story time:
We bought a used car for my wife back in 2015 and went on a vacation trip with it that summer. The power steering pump failed up in NH and we had to complete the trip with no power steering at all. I replaced the pump after the trip and it was an awful job; I think this one will be easier. We are driving from New England to FL in Feb with the S550 which will do about 2,500 miles. You can see where I am going with this....
you opened the door to some critical judgement on NVH and the Merc approach
I started life as RR motor vehicle tech, moved on as sales took off to Jags, so of course we were always critical of the noise vibration harshness and the mechanical refinement of the "premium" German cars. They never had any.
In the UK Mercedes have always had the nickname of being "taxis". The whole ethos of Merc was to be a stylish and long lasting vehicle. But the mechanical refinement was only ever that of a worn panzer tank. Now the sad news is that reliability has completely gone. Its now all about selling dressed up bling from a marketing department on fire. My V8 has always has noises from its water pump, air con pump, power steering pump and gearbox that you wouldn't ever find on a Jag or RR even high mileage, abused ones that have been scrapped .
I have practically no experience with cars across the pond of any kind. But I will say my E55 (owned for a year and a half now, my first) makes untoward noises from the oil pump and supercharger. But on that car I don't mind. On this car, I can tell it is supposed to be uber-refined. And really, it is, except for this noise. You can barely hear it inside the car but where I work you have to roll the window down to enter and it's quite loud reflecting off surfaces. A little embarrassing really. I actually think it will be impressively quiet once I fix this issue. Funny noises are of course back on direct injected engines, but that's one of the things I like about the M273. I have assessed it as a larger displacement version of the two GM Northstar V8s I have in my fleet. The HP is actually exactly the same per liter. DOHC, variable cam phasing. Only extra is the variable intake geometry. The result is a flatter torque curve and more bottom end (relative to the peak) than the Northstars manage. The Northstars also make a specific and odd noise. The uninitiated would assume rod knock or something significant. It's not. I don't actually know what it is but it's nothing bad. Just the sound it makes idling. Very smooth and rev happy. Oh, I think the M273 gets better fuel economy, even with the larger engine and heavier car.
Now I feel like I need to make my official introduction post with a little more background on how I got here.....not like anyone cares, all of 15 people will read it.
Thanks!! Those are all good leads. I'll try to narrow it down. I hope it's not the A/C pulley. Unless that's easy to replace with the compressor in place....
The noise does not change by switching the A/C compressor on and off. Evacuating the refrigerant will not change the noise since the A/C compressor belt pulley runs continuously with the engine.
It certainly would suck to do the P/S pump and have it be something else. They want me to get a shorter belt and cut out the A/C. That's a bit of effort and cost but I guess worth it. And I can't really think of a good way to isolate any other way. I wish I spun the A/C though I thought I did. It was hard to reach from the top.
So the list of potential fixes is:
- A/C compressor pulley (holy crap I just noticed the embedded MP3s!! That does kind of sound like my issue......hmmmm)
- P/S reservoir/filter restriction. Replace reservoir/filter.
- Improperly bled system. This one is unlikely. The car sounded like this when I bought it and hasn't changed at all. I also tried manually bleeding with the steering wheel technique as listed. Zero change.
- Or if not any of this, maybe it does need a P/S pump
So I guess it's probably #1 or #2. Or....it does actually need a P/S pump. But I'm now thinking it's something else. This is great info, thanks again.
the ac pulley bearings are a pathetic width and do fail - I did mine its relatively easy - If you just try to buy the bearing you find its the same size audi use except there's is 15mm wide vs to narrow and fails on a Merc at 12mm
trouble is although the pulley seems to be metal its phenolic resin plastic crap like they use on brake pistons these days.
It has a large circlip you need to take off around the outer edge of the pulley (this will likely crack off part of the pulley, but don't worry it wouldn't have survived pressing out the bearing anyway) - then its as simple at "undoing" the 7 mm headed bolt.... if you pretend its LHD you can hold the pulley still whilst the belt is on and just undo it.
This is it if you have the new pulley with the bearing you just swap it out - getting the circlip in right is a little bugger
I guess Mercedes doesn't consider the compressor serviceable as I found no part number for the pulley. So I'll have to find a supplier on my side of the pond....or just get a bearing, though it sounds like the pulley isn't going to survive that job. If the stock is 12mm how does a 15mm one fit?
I have a 2013 S550 4Matic and I first noticed the whine in a drive thru about 15,000 miles ago. Dealer added fluid when I had the main belt replaced and said everything appeared normal. The noise generally emanates from the right hand side when turning the wheel. I park in an underground garage and can hear it whistle/whine when turning. I set my phone up to video the right front wheel and can here the noise only when turning. Also interesting is that I don't hear the whine until after the car has warmed up and it's been driven a few minutes. Initially when I leave the parking garage I don't hear the sound, but I hear it when I return from a drive. It hasn't seemed to impact the power steering which is still smooth and effortless.
If it can be fixed replacing the seal between pump and reservoir as Minh suggests, how difficult a job is that? Would love to be able to fix it and eliminate the whistle/whine.
I guess Mercedes doesn't consider the compressor serviceable as I found no part number for the pulley. So I'll have to find a supplier on my side of the pond....or just get a bearing, though it sounds like the pulley isn't going to survive that job. If the stock is 12mm how does a 15mm one fit?
I meant don't buy a bearing of any size the pulley will just crumble
of course merc don't list spares, a nice $3000 job because they use a bearing 3mm narrower than Audi think it needs
Thanks for all the tips/tricks/info. I threw on the A/C bypass test belt this afternoon and confirmed the noise was, in fact, my A/C pulley bearing.
So I tackled it this afternoon. Wasn't too bad. Had some difficulty loosening the hub from the compressor shaft without the 3 prong holding tool but I improvised with an Irwin clamp to hold the pulley still and whacked on the ratchet with a sledge. Loosened up and the hub came off. Then I had to modify my snap ring pliers to fit into the small holes in the snap ring. Eventually I got that sorted and the snap ring came off. Walked the pulley off the compressor snout.
The new pulley (eBay/China special) is about 10mm larger than the old one. Old one seemed to be ~104mm ish and the new one around 114mm. So the compressor will be turning slower.
The included snap ring was a bit too thick for the snout groove so I used the old snap ring. The directions also said to torque the hub to like 35 Nm which seems high to me. I just threaded the hub on until it started turning the compressor then tried tightening it more. It didn't really go any more. At that point I tried the circlip and it went right in so....it was on there enough.
Anyway the noise is fixed. Maybe I should update the thread title. Oh, the belt fit fine even with the bigger pulley. Tensioner had enough extra travel. It is on a Quickjack 6000ELX
Tons of room and enough to use a creeper
Star just touches ceiling. I know my garage ceiling is low...
It's funny you mention that. I was at Harbor Freight last week and forgot to buy one, to diagnose this issue further. But then I just said screw it and got the bypass belt. Fortunately that was the right track.
Anyway I was out with my brother in law today at HF again and said I am getting that damn stethoscope because we all know this won't be the last engine noise I need to diagnose. We get back to my house and my brother in law is like "help me troubleshoot this engine noise." He has a ~2001 Jeep Grand Cherokee with the 4.0L and it sounded kind of like rod knock. Took me less than 5 minutes with my new stethoscope and you'll never believe what the issue was.
It was the A/C pulley bearing. Can't make it up, folks.
We were both impressed and yeah I should have gotten one of these a LONG time ago.
Thanks for all the tips/tricks/info. I threw on the A/C bypass test belt this afternoon and confirmed the noise was, in fact, my A/C pulley bearing.
So I tackled it this afternoon. Wasn't too bad.
Had some difficulty loosening the hub from the compressor shaft without the 3 prong holding tool but I improvised with an Irwin clamp to hold the pulley still and whacked on the ratchet with a sledge. Loosened up and the hub came off. Then I had to modify my snap ring pliers to fit into the small holes in the snap ring. Eventually I got that sorted and the snap ring came off. Walked the pulley off the compressor snout.
Done!
see bold - I too thought that was the idea but its just a bit of tin cover and can't hold anything - as I mentioned and is in the Merc docs Konigstiger added as a second method - leave the belt on and "just do up the nut in the centre of the compressor". You are not doing anything "up" you are undoing it but as you are turning the shaft not the nut it works !!! and to do up is not an issue as it tightens under use (incase you don't do it enough)
see bold - I too thought that was the idea but its just a bit of tin cover and can't hold anything - as I mentioned and is in the Merc docs Konigstiger added as a second method - leave the belt on and "just do up the nut in the centre of the compressor". You are not doing anything "up" you are undoing it but as you are turning the shaft not the nut it works !!! and to do up is not an issue as it tightens under use (incase you don't do it enough)
I had the short A/C bypass belt on and felt too lazy to route the regular belt just to hold the pulley and have to remove it again. Probably would have been worth it considering the extra time I spent trying to hold the pulley still....
I disagree about the hub. Yes the outer skin is sheet but inside are 3 spokes that should hold the torque just fine.
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