[Akki_5]

I wasn't there when this happened. Sunday, 8th Nov 2009. As heard from my father:

Driving at 100 kmph towards Thane at 7pm on the Eastern Express Highway, my dad heard a 'tung' sound from the rear left wheel of the E280 CDI Elegance. That started it all. Vibration came into existence. A noise (similar to one caused by friction between wheel and brake) could be heard from the R/L wheel in D mode of the tranny. He immediately pulled to the side of the road. However, when shifted into R, a loud 'tung' could be heard but, surprisingly, the car ran very smoothly in reverse. The wheel was as good as new. Shifting into D again, a relatively softer 'thug' could be heard and the vibration and noise came back. Sitting in the car you could only guess that the brakes on the R/L wheel had jammed causing the friction during the running of the wheel. Since the disc seemed ok, my dad guessed that the 'liners' used for the parking brake (commonly called handbrake but for the Mercs, it's the left foot brake) were causing the problem. He feared he may driven the car with the handbrake engaged without realizing and hence the problem arose. He called me immediately. I conferenced the call to the Mercedes Benz 24 hr helpline.

Having described the situation to the technician, he said he could not figure out what the problem could be. He was willing to send the van to where my dad was but that would mean waiting for one hour. My dad seemed unwilling and so he brought the car back home to Chembur/Ghatkopar at speeds below 20 kmph.
We put the car back in my house and called up the Helpline again asking him to send help the next day. I stayed in touch with AutoHangar on phone through Monday and 'help' arrived in the form of a Bolero (Mercedes Benz 24 hr Helpline vehicle) on Tuesday (10th Nov 2009 at 8.30 pm). First, i explained everything to the technician and then did a little TD for him but he just shrugged and said that there was nothing wrong. The driver who accompanied him then drove the car forward and reverse in my stilt which is about 40 ft long. This time i asked the technician to lay on the floor next to the car and look for any abnormal sign near the R/L wheel or underneath the car while the driver did the D and R in the stilt. The technician gasped at what he saw, quickly got up, went and whispered to the driver "Aila! Iska to differential khulke latak raha hai!"

He then explained to me what the problem was, went to the Bolero and got a hydraulic jack. By this time my dad had come home. Shockingly X (the technician) did not know how to use the hydraulic jack so my dad helped him understand the working of the jack. He then lifted the car and went underneath to check the differential. As soon as he touched the differential, a bolt fell to the floor. He then got a tool to fix it back. After trying for 15 mins, he still couldn't fix the bolt back. Then my dad asked if he could see the bolt. My dad was shocked at what he saw. The bolt had broken off!

I have attached some pictures to help give an idea of the broken bolt.

I went underneath the car and looked at the differential. I told the technician that the other part of the bolt was still in the differential.

I have attached a little layman's drawing to help understand the cause of the shearing of the bolt.
The technician then said that he'll have to take the car away. Since there is unexpected torrential rainfall in Mumbai currently, AutoHangar will be sending a flat bed tow truck tomorrow (Thursday 12th Nov 09) to take the car away.

Details-
Car: Mercedes Benz E280 CDI Elegance
Purchase: Feb 2007
Warranty: out of warranty
Mileage: approx. 18000 kms

I have a few questions:
1) This is definitely not a driver's fault but a manufacturing defect which could have led to a fatal accident. This was agreed by the technician. Can i claim warranty from the company citing manufacturing defect?
2) Will Mercedes Benz do this for me out of something called 'goodwill warranty' since they don't have extended warranty on the E.
3) I fail to understand how this can happen to a car like the E! It's supposed to be a VERY safe car. I guess it's sheer bad luck and some bad workmanship on my car (as explained in the drawing).
4) What steps do BHPians suggest i should take?
5) What is the kind of amount i can expect to be charged for this?

TIA!

Order of pictures:
1-4 : the technician getting ready to work
5-6 : the differential cup underneath the vehicle (you can see the broken bolt still stuck inside)
7-9 : the part of bolt that fell off
10 : explanation of a probable reason

[GTO]

Originally Posted by Akki_5

3) I fail to understand how this can happen to a car like the E! It's supposed to be a VERY safe car. I guess it's sheer bad luck and some bad workmanship on my car (as explained in the drawing).

Unfitting of a luxury car, no less a 50 lakh rupee Mercedes E280 CDI. This is exactly what I mean when I talk about their lack of reliability. Thankfully, for all the issues that my C220 has had, not a single one of them threatened to leave me stranded on the road.

Can i claim warranty from the company citing manufacturing defect?

Will Mercedes Benz do this for me out of something called 'goodwill warranty' since they don't have extended warranty on the E.

Talk to Auto Hangar + Mercedes. 99.99% the repairs will be done free of cost. You car is only 2.xx years old. My air-con evaporator was replaced FOC toward the end of the 3rd year. Merc's generous with replacements even after the standard warranty has expired.

[Akki_5]

Thank you for the info. I'll try pushing MBIL and AHIPL for warranty.

[Jaggu]

Really a horrific experience, thank god that nothing serious happened to occupants. Any signs of scarring on the bolt head or the surrounding area and where does it reside? Does it sit on the bottom or the sides?

One more thing, hope the bolt was broken already and was not broken by technician while trying to put it back?

[Akki_5]

Well, there were two hollow cylinders at the bottom of the vehicle and both are used to mount and hold the differential (as per the technician). This bolt fits into the left (standing behind the car facing towards the hood) cylinder. The assembly was somewhat like what i have tried to show in the drawing.
The bolt was definitely broken before the technician touched it because a part of it was stuck inside and hence the technician could not re-fix the bolt.
This is a manufacturing defect and is evident from the bolt. If you see the last picture, you can clearly see two different shades of color of steel at the point where the bolt is broken (the surface visible in the pic). The band of different tone of color indicates undesired crystallization of the bolt during the hardening process. During hardening of the bolt, this part had become brittle due to crystallization and hence, it eventually broke off at this point.

Plus, if you observe the bolt in the second-to-last image, it can be seen that the last two threads towards the washer and head of the bolt are still silver in shade whereas all the other threads have turned dark. This clearly supports my drawing indicating that the rubber bush could not touch these last two threads as the bolt had already been fixed tightly, before it could cover the entire rubber bush.

[Jaggu]

From the picture it looks like a wrong bolt also, since the threading is only at the end of the part. So a different bolt with thread only at the end is required. Check the other bolt also while getting the job done and from the looks of it they will have to down the differential and do a lathe job to get the broken/stuck bit out OR replace the whole base.

[Akki_5]

I had similar concerns regarding the type of bolt used. Will confirm with AutoHangar.
Yes, they will have to do a lathe job or weld a iron rod to the broken bit (pretty difficult) and then unscrew it.
Ok, i did not mention this earlier but only one of the two cylinders had a bolt for mounting and holding the differential. The other one was empty (i did say then that both cylinders should essentially have bolts but the technician said that the bolt is in only one by default! )

Just a small concern. The technician took the broken bolt with him. I hope this doesn't lead to any issue while settling this situation with AutoHangar.

[Jaggu]

The other bolt might have fallen off earlier. Anyways you have documented the events and photographs so you have some evidence, if it comes to that.

All the best and keep us updated.

[GTO]

Originally Posted by Akki_5

Just a small concern. The technician took the broken bolt with him. I hope this doesn't lead to any issue while settling this situation with AutoHangar.

Shouldn't be. Auto Hangar is an A+ grade organisation. They did a lot of arguing on my behalf (and for my benefit) with Mercedes . Do update this thread with developments.

[drpullockaran]

My humble opinion is that the bolt should be stepped with the diameter of the threaded portion being less by about 4-6 mm so that the thicker portion fits snuggly in the orifice and in contact with the innards of the metal clad rubber bush.

Rear Differential Bushings - Completed - Benzworld.org - Mercedes-Benz Discussion Forum

The bolt should look something like the bolts used to hold the dampers to the vertical link of front suspension of Macpherson strut design arms.

There would have been immense torque on some part which should not have this much of twisting force and that is the only problem I envisage. The question is why did the car behave normally when in reverse gear.

[Akki_5]

@drpullockaran - Thanks a lot for the link.

I'll definitely keep you'll updated on the proceedings of this event. The car will most probably be picked up tomorrow.

[Akki_5]

The car was supposed to be picked up today at 1400 hrs. However, I got a call from AutoHangar at 1300 hrs and was told that the replacement bolt is not available with them in stock. It is not available with Mercedes Pune either and will need to be sourced from Germany. They have placed the order and the part is expected in 8 days. Hence, it did not make sense for the car to be sent to AutoHangar. Now the car will be picked up after the part has arrived.
Meanwhile, I have sent an email to AutoHangar voicing my concerns over the poor quality of the part. I have asked them to forward it to Mercedes India on my behalf. I am expecting a reply soon. Will keep you all updated.

[drpullockaran]

Originally Posted by Akki_5

The car was supposed to be picked up today at 1400 hrs. However, I got a call from AutoHangar at 1300 hrs and was told that the replacement bolt is not available with them in stock.

Please ask them to give you back your old bolt along with the piece thats left in the differential seat at the moment. I have strong feeling that the part used originally in your car is not the recommended bolt. Compare the old bot with the new one thats going into your car 9 days from now.

[Akki_5]

Yes, i will do that. Will let you know the result. If possible, will upload pictures of both the bolts. In the mean time, reply awaited for the email sent to MBIL.

[Akki_5]

UPDATE:

Got a text from AutoHangar today. Part is expected on 25th of this month.
However, MBIL is yet to reply even after two emails! :(