Mercedes A-Class Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
22 Posts
Discussion Starter #1
Hi all
Looking for some help with an issue. I've noticed a strange squeal sound when lifting off throttle. It happens is all cases and speeds, for example at low speeds when I come out of a parking space as well as lifting off after heavy throttle. I've had the car for 3 years and never noticed this before.


is this normal? Car is out of warranty so dont want to pay MB for a diagnostic if this is normal.



Cheers, Jay
 

·
Registered
Joined
·
63 Posts
planet_amg said:
If it's pre-FL, it could be turbo compressor stall. There's no BOV on pre-FL. Fit a BOV. I used TurboMaster.
I'm pretty sure there's no BOV on any model, pre or FL. Anyway I doubt the sound compressor stall as you call it. That usually sounds like a flutter due to the way the compressor blades sort of chop the air or get in the way of the air as its reversing back through the compressor. Also, the stock air box does a good job of concealing that. I've even tried removing my air box lid and although hear the induction heavily as well as the back surge of air on shift, it still doesn't make any squeel sound. So I really think adding a blow off valve for the OP would be a waste of money as that ain't it.

Sometimes squeel sounds can be associated with auxiliary drive belts on their pulleys. They can chirp if over tensioned or slipping sometimes, and the squeel doesn't have to be consistent, it may just occur at the point in which the change in inertia is enough to case the belts to rub in a certain way. I'm not saying this is the issue, rather just for consideration.

Also, I know that mine more sounds like I've got a supercharger than a turbocharger particularly when giving it stick. It sounds like a whizzing sound on both run up and down. That's also apparently considered normal as I've read many report it. Again it sounds closer to a supercharger.Edited by: JA45AMG
 

·
Registered
Joined
·
211 Posts
FL has a BOV, although a "cheap" one.
I've a Renntech BOV - does it's job ok.


A squeal could be a worn off turbo where the bearingshell is off limits (thru friction). That would be a major issue and should be observed.
What you can do yourself to see if that's the problem is to try to move the turbo shaft (that means to disassamble the airbox). If there's movement possible you should bring the car in to let them control this. The tubro shaft must sit very tight.


It's just a guess... A driver from the German forum had this problem a few months ago and got his turbo swapped. ;)
 

·
Registered
Joined
·
181 Posts
Thanks frankster. Yep, FL has a factory fitted electronic bov. If the squeal occurred during tickover, then the problem could be elsewhere, but when you close the throttle, the turbo is generating up to 26psi downstream with nowhere to go because the throttle is closed. This causes stress on the turbo, so it makes sense to start looking there. Not necessarily good news, but hope this helps.
 

·
Registered
Joined
·
63 Posts
Ok I agree a general problem with the turbo such as a bearing issue could be a cause for the sound. It's not compressor surge or stall as such though as that would've been there from day one. The pre - FL turbos had a factory recall I believe. Many failed over a certain period of time.

And I was not aware the FL's got BOVs fitted. Thanks for that. Obviously merc thought there was a reason to do that. I'm surprised that didn't trigger a recall. Maybe sparked a few nerves about further turbo problems (longevity) of left without a BOV.
 

·
Registered
Joined
·
181 Posts
Exactly. The pre-FL has a blanking plate on the turbo where a BOV can be easily fitted. I want my turbo to last longer, hence the TurboMaster BOV.

Pre-FL's up to about July 2014 should have been subject to a recall and turbo change if necessary. As a minimum, there should be paperwork showing a dealer check has been made. Many failed the checks and were replaced because of excessive end float, including mine.
 

·
Super Moderator
Joined
·
1,893 Posts
Just to be pedantic for a moment, the FL has a recirc valve, not a BOV to atmosphere.

If you fit a BOV to a FL it will mess up the calculations done by the MAF.
 

·
Registered
Joined
·
22 Posts
Discussion Starter #10
Thanks all for your comments!Seems like the squeal is not normal so will get it booked in with MB.
 

·
Registered
Joined
·
48 Posts
Apologies for reviving an old thread, but have been searching the forum for anyone whose A45 has similar symptoms to mine, and the original post of this thread describes exactly what my car is doing. I've owned mine 3 and a half years and pretty sure this noise has only started happening in the last couple of months.

@JayT - Bit of a long shot as you may not visit this forum any longer but did your problem get resolved by MB in the end? If so, please can you share any details about the cause and what was done to resolve it?

Thanks in advance...
 
1 - 11 of 11 Posts
Top