feeshta

So I had my E55 on the lift the other day to look for an issue I was having with the steering (turned out to be a bad steering rack) and noticed a very odd sound coming from the very bottom of the engine. The noise was somewhat intermittent, waxing and waning in intensity with no real rhyme or reason that I could tell. I'll post a video below. It basically sounds like a loud buzzing sort of noise, and it seems to be coming from what I think is the oil pickup location in the front portion of the oil pan, which would lead me to believe the noise is coming from the oil pump as it is directly above this location.

So my question is, what could cause the oil pump to make such a noise, and how to repair it? I have seen the infamous video where the guy from XF Motorsports makes the claim that the seal on his oil pump cost him an engine, and part of me does think this noise sounds vaguely reminiscent of a straw with a hole in it, only amplified many times. It could be that air bubbles are getting into the system and causing cavitation, which tends to make similar noises in power steering pumps for example.

The car has been making a sort of "groaning" noise off and on for a while now, and I think this may be the source of that sound. It often shuts up if you give the engine some revs, either through spirited driving or shifting to neutral for a moment and blipping the throttle.

I should think that having the steering rack off is actually a somewhat opportune time to do any sort of work on the oil pump, as from my understanding you need to drop the front subframe in order to get the oil pan off the car anyway.

Here is the video of the noise for reference.

M113K Weird Noise

E55Greasemonkey

Year, mileage, service history?

feeshta

2006 Wagon, 148,000 km, MB maintained until last year as previous owner was a MB employee. All routine maintenance done by myself since then on a regular schedule. Only engine related issue during my ownership has been a slow coolant leak from a damaged line and a noisy water pump that was replaced along with the thermostat and the pulleys which were also noisy. No evidence of any other engine issues in the extensive service documentation.

mbmg

I have the same sound coming from my front oil pan. I was able to decrease the noise by switching to a heavier weight oil (I live in the desert) but it's still there. The problem is that the factory used flat cut gears in the scavenging state for the front sump. They are actually the same gears used in the main stage of the pump so it was more cost effective to do so. They fronts need to be a traditional scavenging lobe design to not make that sound but you'd have to get those custom made. The CL and S class have a different pump and only one sump.

feeshta

Good info, but that does not explain why the noise would be intermittent. Wouldn't the oil pump always be spinning at the same speed relative to the engine RPM? This noise comes and goes while the car is at idle at times.

mbmg

It could be amount of oil near the pickup vs other times, o-ring losing some suction, some debris partly covering the oil pick up, etc. Hard to know until you look. Mine is constant but changes pitch with rpm.

feeshta

Mine does change pitch with RPM, but also comes and goes when you are not touching the throttle at times, and is often loudest at idle. It generally goes away if you rev the engine over about 4k for a moment. Sometimes it will come back if the car is not yet fully up to temp, other times no. It could be read as the increased suction from higher revs helps seal things, as does heat which obviously causes expansion. Seems to be getting worse with the colder Temps.

MartinWake

CL55 ftw!

SICAMG

Normal operating noise from these engines and at some point comes to life for no reason or right after an oil change. Do a search.
You will have to live with it as I know of no fix....

feeshta

Nothing that appears out of nowhere is "normal". The fact that it will run with the noise does not mean you are not dealing with a long term wear issue. Especially in light of the potential grommet issue, I do not think it wise to ignore this problem, especially if you live in an area like I do (Germany) and drive at very high speeds and engine loads frequently, often for long periods of time.

SICAMG

Mine along with god knows how many others have this issue. Even if you You Tube these cars almost every one of them have a whine to it when started....not all but many. I have researched this to death trust me.
I have had it for 6 years now and only a particular oil will make it quieter. I have completely dissasembled my engine and rebuilt it for race season...new bearings , OIL PUMP, and every other wear item and still it has the same noise.
Most complaints always start off the same way... "As soon as I started the car after my oil change there was this noise". Trust me I would love to know what it is as this winter it will be out again for some work so now is the chance.

feeshta

This noise is not only on startup. Its there near constantly unless you really rev the engine up or drive the car for a long time. It will be there through my entire 15 minute drive to work for example, unless traffic happens to be clear enough to open it up which is rare.

Also, it has nothing to do with oil changes etc, and has been present for nearly a year now, and has been slowly gaining intensity.

SICAMG

Mine is there as well always which I did not mention. I said start up because it is the loudest then. It has to do with oil viscosity because a thin oil is much less and a thicker much louder. I have gone from 15-50 to 0-30 to prove this. I also believe it has to do with the scavenge gears for the front pan in the front of the pump. There are 3 sets of gears.
When i pull in the pits from a 1/2 mile run.....not a sound. Let the car sit for an hour....there it is !!
If you keep reving the engine in neutral you can make it fade away to an extent.

feeshta

Yeah, I do the rev it in neutral nearly every day. I guess for me though, the thing is I am willing to put in the time to replace the grommet because it is worth it to me for the peace of mine alone.

I've seen mentions of switching to Liquimoly Brand and/or different oil weights to help quite this noise down. Which oil weight and/or oil additive as I can only assume that would be what gives with Liquimoly brand in particular, helps to calm down the noise? I've been using Mobil 1 0-40 full synthetic on it since I bought it. Getting much else requires a lot of planning ahead, as I have to order it from the USA. Oil prices here in Germany are absolutely Bonkers. Not joking, it's like 20 Euro per liter for regular non-synthetic.

E55Greasemonkey

Keep in mind these cars were making the whine noise when they were brand new. I recently worked on a 9k mile SL55, yep, same noise.

feeshta

People don't seem to be getting that the noise has changed in my case. It's not the normal whine that it was making before, it is most definitely louder, by a factor of 2 or so, and has a different character. I've had this car on the lift with the engine running probably 5 times previous times, and It never sounded remotely like that under the car before.

THIS IS NOT NORMAL.

Clear enough?

coupesedan

what could it be other than the oil pump screaming “kill me now” ?

feeshta

Cavitation. Aka the oil pump sucking in air along with the oil.

E55Greasemonkey

Honestly, I've never listened to the noise on a lift. The internet isn't giving you the answer you're looking for, so I guess you'll have to figure it out yourself or pay someone who knows how to. You could try looking at the oil pickups with a borescope through the drain plug opening, and check for debris clogging the screen. This may not be possible with the oil pan baffles in the way. The rubber noise insulation from the timing gears is known to break loose and sometimes partially block the oil pickup.

feeshta

Why would I bother paying someone to see whether or not they can see a problem with their expensive tool when it literally costs less to open the oil pan up and check for myself?

E55Greasemonkey

Why would I bother responding to any more of your posts? Since you know so much, get off the internet and figure it out. Good luck with that oil pan!

feeshta

I think you read that with a different tone than was intended.

That said, I really don't see the point of taking the car in for an expensive evaluation procedure that can't actually correct any problems it may discover and cannot actually check the main potential trouble area I am worried about. It costs less to open the oil pan and replace the possibly faulty grommet, which the suggested procedure cannot evaluate the health of, as well as address any other issue that might be discovered.

I'm already planning on doing the job, just need to sort out some other potential concurrent work such as replacing the steering rack which is worn out. Having some trouble finding a shop that will confirm that the part they want to send me in exchange is actually a steering rack from a later model year E55 like my 06, rather than the slower rack from the earlier model years. Can buy one of the newer ones of course, but they want crazy money even for refurbished ones. Generally over $1200, even after core exchange. Can't imagine it would cost $3-400 worth of labor and parts to refresh this steering rack.

Pacer

I also have few variations of the oil pump noise depending of engine status. I would describe them "the normal" whine type noise that exist on idle and can be faded with revs or driving, and more like a grinding noise that to me could be cavitation if you compare to steering pump cavitation noise. The latter happens in cold start and is most existible during raised idle rpms and calms down when idle settles but can still come and go for some time. So, my in theory the normal whine could be the front pump gearing, I can buy that but the louder grinding noise could be cavitation caused either crap in pick up or the pick up O-ring.
So, if you execute opening the pan, please keep us posted what is it like there and if noises change or settle when you change the O-ring. I can't remember if XF Motorsport ever reported anything regarding the noise in his.
Even though there is cavitation, regardless of the the reason, it might not affect the oil pressure directly. If front pump cavitates, the secondary still might feed the engine well enough. If the secondary cavitates, it's not good, but lubrication might still be sufficient for the engine and thus we don't see damages.
Btw, my car has 90K kilometers. But these start to be oldish, so it's no suprise if some rubber gets hard and brittle even though being specified for chemicals. I'm running Liqui Moly 0w40 + Mos2. Pretty sama noise level as Mobil 0w40. LM 5w40 was louder or maybe not louder but it didn't fade away very easily even with revs.

feeshta

Mine started out as just a whine on startup that faded out shortly after. Then started to be more and more present at idle about a year ago, and eventually settled in to being there all the time unless you really revved up the engine. I replaced the water pump and pulleys due to failing bearings about 3 months ago and the noise almost completely disappeared. 2 months later it started to come back, and for the past week or two it has changed in character to something more pronounced and with a different tone.

I am planning to do the job is a couple weeks. Can't drive the car right now due to an airmatic leak, and decided to go with BC Racing coiloversas a replacement option, which should be here in about a week. Then I have 2 weeks of leave in late November, and plan to just do the whole list(oil pan, suspension, and steering rack) at once. Might take a few days to finish that whole list, but its not like I have anything better to do with my time off given that travel is a no-go now.

I'll try to see what the seal status of the grommet is if possible and report back, as well as the the status of the noise after completion.

SICAMG

Odd that the noise was gone after a water pump and pulley replacement.