fleanote

2003 E500 with 111K miles

Just replaced the idler belt pulley and accessory belt tensioner FYI. Now when I accelerate I hear whirring from the under the hood and when I come off the accelerator the whirring slowly diminishes - it also feels like teh car is being sucked of all its horsepower when I come off the gas and my deceleration is pretty rapid.

Any ideas? Belt not taut (although the tensioner should do that)? The noise can only be heard from the moment you pres the accelerator.

Thanks as always for a great forum.

ozusa

When you say "accelerate" do you mean this issue only occurs while driving, or does it happen also when you rev the engine and the car is in Park? Is it easily reproducible, like clockwork?

Any burning smells and does the new belt show wear signs already?

With the engine off, you can try putting a dab of liquid paper or white paint on each pulley that the belt goes over so you can clearly observe each pulley rotating. Then start up and watch the pulleys spin. Have a friend work the accelerator peddle. The pulleys should, of course, be spinning at a steady rate if engine speed is maintained constant.

If one pulley is seized, you'll probably hear a squeal and if a pulley "freezes" from time to time or slows down and speeds up unrelated to engine speed, that's pointing to your problem. Your water pump may be the culprit, but it would have to be severely seized for you to notice the deceleration you wrote of and I think you'd get more of a squeal than a whirring sound.

(I presume you know what your SBC brake pump is and what it sounds like. It is unrelated to the belt you changed, but it sure does whir a lot.)

If the pulleys spin freely and consistently, but make a noise you can't quite trace, use an automobile stethoscope or screwdriver to figure out which device is whirring.

All that said, a whirring does indicate more of a bearing issue in a device (any of the pumps (water, steering, aircon) or the alternator) than a belt / pulley issue.

jcat

I've also noticed that most benz cars make kind of a groan/moan sound when they run. If this is what you're referring to it may be normal.

I dont know what you mean by 'sucked of all it's horsepower when letting off the gas'...that's what letting off the gas does...

fleanote

I tried revving the gas in PARK to see if the noise was present and it was. I also noticed that the whirring was there (or more like a wind blowing louder and louder), when using cruise control at 65mph. When I released the cruise control the whirring died instantly, it also dies as you come off the accelerator.

I also notice that as the car is a bit warmer, the whirring at acceleration will randomly not happen. Then a few miles down the road later, I'll press the accelerator and there's the whirring.

I think its the belt, but I can't imagine what path it could be taking or what it could be 'blowing' against to cause that sound. It's very loud and very noticeable.

Will continue to troubleshoot, but all advice is welcome.

vettdvr

Every time I hear that I find a defective bearing on tensioner or idle pulley.

I use a piece of 3/4" pvc pipe about 2 ft long and listen to it while CAREFULLY pointing at each item. You will hear the bearing if it is one.

Never assume "New" = GOOD. this canl lead you away for the problem.

Mechedjun

Ditto Everytime I find the sound you've described, it's almost always a bearing.

-Dave

fleanote

Thanks for all the input. I am 100% sure it is one of them because they were both replaced (by me). The tricky part now is getting them out and replaced (paid dealer prices for parts because I needed them quick) in a timely manner since I need the car daily.

Thanks again for all you help here! - Fleanote

fleanote

The plot thickens....

Now the whirring is alternating. What does that mean? Initially the whirring will start and get louder as you press down on the accelerator then the whir will get lower as you come off the accelerator.

Now it's switching. Sometimes the whirring will happen when coming off the accelerator and not at all when pressing down on it.

My question is - does the speed of the belt spinning increase/decrease with acceleration or is the belt moving at the same speed no matter MPH you're at?

And to the comment of : New does not always equal good. I hear ya, and my instinct tells me its the bearings in the pulley not the tensioner. In the opinion of this forum, which is more likely to be the culprit of the whirring problem - the pulley or the tensioner? Both have bearings. Or should I just replace them both again?

Mechedjun

The speed of your belt is directly related to the engine rotational speed RPM and not the MPH (Vehicle speed). Simply put, your engine drives the belt which rides on a pulley (same as chain riding on gear) which rides on a bearing. Therefore, the faster your engine turns, the faster your belt moves, the faster your pulley moves, and faster your bearing moves. However, because your engine is able to run without the engagement of your transmision, the correlation between your vehicle speed (MPH) and your engine speed (RPM) would only exist if your transmission is engaged while your engine is running. Therefore, the sound you are hearing, if it is a bearing on your pulley on your engine somewhere, should increase with your RPM regardless of how fast your car is moving.

If your noise was intermediate (came on at only certain RPM or came on and off) before and now is constant and changes pitch with RPM, it most likely means that the bearing is slowly degrading and getting worse. Number one reason a bearing might start to make this type of noise is if lubrication is inadequate and the bearing have begun to have metal to metal contact. Such contact wears the bearing quickly and may lead to deformation, heat damage, and ultimately failure. Check for areas with possible leak(s). Hot spots in my experience have been flywheel bearing, alternator assembly and related components, and timing gear.

fleanote

That's a great and helpful reply. It's interesting where you mention the path and stress points because this all started with the wheel on my tensioner being 'torn' apart. I found the wheel at the bottom of the engine well and it had been chewed and ripped from the inside if you can picture that. The outside of the wheel the belt spins around was smooth and round, the inner core was chewed away down to the metal ring that connects the wheel to the tensioner. At the dealerships push, I also replaced the pulley but I can't say anything was wrong with it.

I still need to try the PVC sound test against the paths of the belt. It could be any of the pulleys whose bearings are wearing.

jcat

if the inside of the pulley was toast, i'm inclined to think it was a bearing failure and/or improper torque that caused it..

fleanote

Ok, after a few weeks I figured out that I can't verify the 'whir' unless the car is in drive, and since i don't have a lift system (and a buddy to press the accelerator while I listen) - I had to take it into a Benz garage (non dealer).

They grabbed me for a B service as well, and seemingly couldn't figure out where the noise was coming from either. They finally left it at it's a transmission service that's needed. Specifically a new pan gasket, fluid, filter etc. They want $380 which I already know is ludicrous.

The question is - is there diagnosis good? Could it not be the bearings/pulleys at all and be an issue in the tranny? It is a rebuilt tranny with over 80K miles on that has never been serviced. The sound can only be re-produced when the car is in drive and the sound only appears as I rev RPM's during acceleration and deceleration.

ozusa

I expect $300 + for a transmission flush and filter change. I don't think their price is ludicrous. It may be high, but it is not totally out of the ballpark. If the system is throwing no codes, then a flush and fluid replacement is a pretty good place to start with a transmission issue and, if competently done, can't gurt. Repairs and replacement of parts will add up fast, so let them do the fluid change and cross your fingers. Especially if this is just a nuisance issue.

jimbo1763

+1 if you have not had your fluid changed before or if it has been more than 40K miles since you did.

spinn

I've got a whirring noise in my 04 E500 that just developed...which seems to be coming from the power steering pump. Does the whirring get louder when at standstill, you turn the wheel left and right?

fleanote

Don't think so. This is definitely transmission. Whirring moves with RPM's and gear shifts. Disappears at 3K-RPM+ and driving 70mph+, but as soon as you drop a gear the whir resumes. It's a rebuilt tranny at 60K miles and now has 130K, its overdue for a flush and fill and I can only hope that's the extent of it. I'll post after the service is done.

fleanote

I took the car to a transmission service center and their concerned that 'glycol' may have dripped into the radiator and if so, the radiator would need to be replaced. They sent a sample of the fluid out for analysis and if it comes back positive, they recommend a new radiator. If it comes back negative, they recommend the drain and fill transmission service but they don't guarantee that to fix the problem.

They were very forthcoming about the difference and benefits to a 'flush and fill' tranny service and a 'drain and fill' Most garages don't have the equipment to flush and MB doesn't necessarily say tat is whats best to do, so most shops will just drain and fill.

They still have the car now and I'm waiting for the results of the test. Worst case scenario, I could need a new transmission.

fleanote

It appears 2x the amount of Glycol is in the radiator and they recommend replacing it. A Used aftermarket radiator is $925 installed and a new one is $1125 installed.

Add to that, it would still need a drain/fill and filter for the transmission (another $541 which includes an electrical sensor that is best replaced if the tranny is getting taken apart).

Following both jobs the car would need to be driven for a few days and then returned for another Glycol test in which another transmission drain/fill would need to be done (at a slightly discounted rate) if the levels are too high.

It's not the cost i'm immediately concerned with, its the justification that all of that is needed. Anyone have thoughts on this?

konigstiger

MB DTB (dealer technical bulletin) requires radiator replacement, clean and flush the transmission with torque converter and transmission oil cooler lines if the condition is still reproducible after the flush routine, replace the torque converter - PM your email address if you want a copy.

fleanote

I think there's a reason you can't find a DIY radiator replacement for the W211 Benz - it's not something you want to DIY

The issue is, there is no way to determine the extent of damage to the transmission beyond glycol contamination, so you have to decide (take your chances) on which service you get. A reputable independent said the best thing to do (if cost is the issue) is to start with a drain/fill of ATF, then replace the Valeo radiator when you can (the leak is slow but will eventually gum up your fluid again).

You wont know the extent of torque converter damage until you try these things first and if they don't work - consider skipping a new torque converter ($1500 + labor) and go right to a reman'd transmission.

Suddenly the $23K price for this car I paid in 2007 is making SOOO much more sense to me. I thought it odd that a 4 year old E class with a huge V8 would sell so cheaply. Turns out Benz has known about the Valeo radiators since it began they just never issued a recall and dealt with as it was reported.

Anyone out there with a W211/E500/E55 manufactured prior to 4/2003 and has a Valeo radiator would be wise to get it replaced asap, or get ATF flush/fills every 4K miles.

KAOTICAL

my E500 makes a howling air tunnel or blowing air over a pipe or hose noise when warming up or while driving if this is another way of describing it.. boggles me too

Mercedes has a deceleration (semi braking)feature that can be toggled on and off.. may want to look into it “SBC hold”