phoenix_iii

2002 C230K Sport Coupe, A/T, 98k, fully serviced.


When doing moderate (60%+ braking, and in W (winter) mode, I get a single THUMP from (what feels like) the rear differential as the car downshifts before the final stop.

When in S (Sport) mode, I do not get that THUMP as consistently, though it still feels like something may not be right.

The diff has been serviced (92k by Mercedes Indie, and car was a CPO before me so hopefully before that, too), as has the trans and filter.

What should I be looking for when I put the car on jack stands? I also do not get the thump when braking (from 30mph to 0) when the car is in neutral. It seems to be either the transmission, or something in the differential. Need knowledge! Will test/pics/whatever is necessary, otherwise I may have to pay the dealer to diagnose.

Thank you MBworld!


[edit]
'Yes, ALL fluids and filters were done around 96k (and probably prior). The brake fluid (for example) looks brand new (reservoir clear, etc). I was happy with this part of the service they performed.'

mleskovar

First check your fluid level, this transmission is critical of fluid level. It's odd that you get the symptom in W (1st gear bypassed) and not S mode. Look for a leaking trans plug wicking fluid up to the electronics, check u joints and flex discs, and look at trans mount.

phoenix_iii

I do not have the service manual. Are there any threads where people have posted pics of the...
1) U-Joints
2) Flex Discs
3) Trans mount (if not obvious).

Low fluid/pre-purchase inspection tutorial said to do a 'really slow' 1st to 2nd shift (in D(rive), just let the car go, nice and slow), and the car shifts very smoothly.

I almost wonder if it's Suspension (or a mount), because it's only when done at 60%+ in terms of hardness, typically. I hate 'forcing it to happen' because I worry I will make something minor (worn trans mount, let's say) into something major (broken mount, etc)!

I will take pics this weekend.

ontmiss

http://www.mbusa.com/mercedes/data/p...0_c320_c32.pdf

phoenix_iii

ontmiss. Nice! That covers the C230 as well I take it? Downloading now!

Edit. Looks like it is the Owner's Manual. I have one of those, but the PDF is GREAT (easier to search), so still a GREAT link. thank you.

=)

ontmiss

http://www.mbusa.com/mercedes/data/p...nce_manual.pdf

johnand

When you say "fully serviced", does that mean the transmission has been serviced? If you have never had a transmission service, it is time.

Follow mleskovar's advise.

phoenix_iii

Yes, ALL fluids and filters were done around 96k (and probably prior). The brake fluid (for example) looks brand new (reservoir clear, etc). I was happy with this part of the service they performed.

I DID ask for a sample of ATF to send off, but they failed/forgot to do this... but the slow take off from 1st to 2nd is very smooth, and I do check this periodically (warning sign of contaminated ATF is jerk going from 1st to 2nd on slow acceleration). Updating original post.

mbdragon55

i have the same problem and with my 2001 C240 it hesitates to shift from 2nd to 3rd gear also. i went to dealer and they told me i need a new flex disc and trans mounts. how much do you think that repair would roughly cost?

johnand

Hmm, did this symptom start just after the transmission service, or did it occur before the service?

nlpamg

have you changed your transmission mount yet?

it's a cheap part/fix and it does wonders for the car.

kirax2

damn great info!!! thx on that too

phoenix_iii

I have not changed the Transmission Mount. I will search to see if I can find a DIY.

I do not know if the problem started before/after the service, I brought the car in immediately as I got it from a private sale and wanted to catch it up on service.

mbdragon55 - My problem is different, please start another thread/search/don't confuse my helpers!

Thank you everyone so far for questions/input!

phoenix_iii

Did not find. Anyone have a link/idea where to look.

phoenix_iii

Anyone have a link to the DIY (did not find), or the PDF on how to do it, and the part #? I bet the car needs it, and I would like to do this.


This issue still worries me... a lot. Car just turned 101k miles.

johnand

I'll post a PDF tomorrow when I get my laptop back.

phoenix_iii

Johnand, that would be MUCH appreciated. I am off this weekend and could even post a DIY if needed!

p3

carbonfiberwhor

Im just gonna put this out there, my Service advisor is resetting the cars TCU to adjust this problem as we speak. Maybe give it a shot?

phoenix_iii

cfw, Is there a fee for this? I would imagine it should be a courtesy service... =) I'd like to say that other dealers/SA's perform this for free.

mleskovar

You can reset the TCU yourself:

https://mbworld.org/forums/c-class-w...-question.html

If it needs to be reflashed/programmed it will cost you.

phoenix_iii

read the whole thread (very interesting). Only post #4 (I think) mentioned how to do the reset
'you mean the throttle adaptation reset trick? the one where you hold the throttle down with the engine off, key in on position. i've tried that'

But it was not very descript. Anyone know the step by step procedure? That thread sounds like my problem, explained by Glynn well as drivetrain lash, probably exacerbated by flex disk, ujoint, etc etc...

johnand

Here is the WIS document for replacing the transmission/rear engine mount. Let me know if you need anything else.

phoenix_iii

Thanks so much johnand. Is this the same for the M111 Engine? I have a 2002. =) Should be though, right?

johnand

Should be. I just selected W203 and no engine preference. It only came up with one procedure, so they are all the same. Should be a pretty straight forward job.

Still getting used to WIS, so I am bot quite sure about the notes on self locking nuts and bolts. It in not clear if none, some, or all, of the bolts are self locking and should be replaced when servicing. Maybe one of our gurus here can chime in about it.

carbonfiberwhor

Theres a 100$ fee that is basically reseting the control moule from the gear selector (egs) to the tcu and the esp(electronic shift plate). The car runs and drives 10x better now Shifts are much faster and smoother