ML270 Autobox fault

[psmart]

My ML270 has developed an autobox fault, following is the scenario:-

1. Car serviced 1 months ago, all fine, driven ~1000km no problems.
2. Car inspected for rust etc in Harrogate and they noticed a slight, but not of concern leak on the auto gearbox.
3. Car battery went flat, charged.
4. During the 800Km drive to Stuttgart, friend noticed that the engine speed was possibly higher than normal when initially setting off.
5. When arrived in Stuttgart, I noticed the problem only after about a 50km drive.
6. Disconnected battery, reconnected, all was fine. Car driven 400km down to Salzburg, no problems.
7. Car parked up for a week, then when driven, car would lock into 2nd gear. After engine stop/start would be fine until pushed a little, then locked into 2nd gear.
8. ADAC called, plugged in diagnostics, no fault found! Didnt know how to dip the auto box (I have the long Mercedes dipper in the car) and claimed the box to be over full, but after questioning, sounds like he forced the dipstick further than it should have gone, so information unreliable.
9. After ADAC gone, car re-tested and same problem.

So, not being with the car (its 400km away and have to make suggestions via phone) and not wanting it to go into a Mercedes dealership to pay top whack prices if it needs a new gearbox, any suggestions on what the fault may be?

Could it be low oil? or would it be a more sinister box break up?

 

[BlackC55]

Get the fault codes read first.

The sump pan needs to be removed and checked for debris. (metal flakes)

When was the ATF last changed?

 

[psmart]

Many thanks for the input BlackC55.

I believe the ADAC man (German AA) must have just had a generic reader, hence not getting a valid code. I have carsoft, but trying to tell someone who is not computer literate how to use it is a waste of time, so will ask them to nip into a dealership and get the codes read.

The ATF was changed by myself 20kmiles ago, but at the time, I did notice the oil was molasses in colour and there were a few filings in the sump pan (nothing big). Mercedes recommended putting a magnet into the sump, which my box didnt have, to prevent them circulating.

The Electric connector was leaking so I replaced the seal at the same time. I drained the box a 2nd time after about 1kmiles as I couldnt drain it down completely the first time because the Torque converter didnt have a drain plug (ie. Drained box, refilled, 1kmiles later, drained and refilled. On the 2nd refill, there was no filings or anything unusual about the ATF.

One other item to add, my friend said he noticed 2-3 times, a thump as the gearbox changed gears, a bit like a manual when the clutch is dumped to quickly.

 

[psmart]

Further update...

...just been phoned, code read and the faulty part is:-

Y3/6N3 - DreizahiSensor3 - Ie. Torque Sensor 3, which requires a complete module replacement apparently, costing around circa 600pounds for the part.

Does this sound correct, or is it a red herring?

 

[psmart]

Read quite a few threads about the subject and in essence, the code is not very helpful, a bit like P1470 Turbo Boost Pressure Control Valve fault, where it could be anything from a blocked exhaust to a fault in the inlet manifold flap!

Apparently, the problem started when my friend had to make a very sharp turn to avoid an obstacle, so my initial bet is on fluid level.

Further research shows that you can get a complete rebuilt 'box for EUR1800 with warranty (plus fitting if you cant do it yourself), so paying ~EUR1400 to get the DREIZAHLSENSOR3 module replaced in the old box makes no sense.

Will update this post if/when a solution is found or I bung in a new box.

 

[psmart]

So, I got to test the car myself this weekend and do some analysis. Basically the error indicates that the RPM Sensor n3 is faulty and would occasionally cause the 2nd to 3rd gear change to jolt and the box would go into emergency mode. If the car was going slow, it would stick in 2nd gear, if it was going fast, it would stick in 4th gear.

I looked at the realtime data for the gearbox, and all looked ok, although gear
changes werent so smooth and occasionally it would go into emergency mode and indicate that the turbine RPM was 8000rpm!

I looked at the MAF data and the values I was getting looked reasonable, but
I noticed the engine was sometimes dithering. I disconnected the MAF and
the gearbox would go more easily into emergency mode with the MAF disconnected. As I occasionally kept on getting 'Unspecified value' reading from the MAF and with the engine dithering, I replaced the MAF.

I measured the box oil level and it was high, and I extracted 300ml of oil from it (goodness knows how it got high, other than last service or when it went for its rust inspection in Leeds when they commented that there was a slight oil leak on the box).

After resetting the fault codes and adaptation, with the new MAF and reduced oil the gearbox was super smooth changing gears and ran perfectly over a 600km journey, except for 2 times and both times had a commonality, ie. a wrong turning saw a rapid reverse, forward, reverse manouver and a minute or so later the box would go into this emergency mode. Driving fast, accelerating fast or slowly, the box behaved perfectly!

Changing the MAF did make a big difference in smoothness of engine power and economy, so this has helped, but the box error still comes up. Does this
sound familiar to anyone, ie. Can the control module go faulty (the one which
lays inside the box, controlling the relays etc), or is it more likely to be a
bad connection, either into the gearbox, or into the EGS module?

The oil I drained out from the box was a light yellow in colour and didnt smell
burnt!

Any suggestions or pointers?

 

[Uncle Benz]

Trans fluid travelling up loom into transmission ecu poss??

 

[MB TECH WARRINGTON]

So, I got to test the car myself this weekend and do some analysis. Basically the error indicates that the RPM Sensor n3 is faulty and would occasionally cause the 2nd to 3rd gear change to jolt and the box would go into emergency mode. If the car was going slow, it would stick in 2nd gear, if it was going fast, it would stick in 4th gear.

I looked at the realtime data for the gearbox, and all looked ok, although gear
changes werent so smooth and occasionally it would go into emergency mode and indicate that the turbine RPM was 8000rpm!

I looked at the MAF data and the values I was getting looked reasonable, but
I noticed the engine was sometimes dithering. I disconnected the MAF and
the gearbox would go more easily into emergency mode with the MAF disconnected. As I occasionally kept on getting 'Unspecified value' reading from the MAF and with the engine dithering, I replaced the MAF.

I measured the box oil level and it was high, and I extracted 300ml of oil from it (goodness knows how it got high, other than last service or when it went for its rust inspection in Leeds when they commented that there was a slight oil leak on the box).

After resetting the fault codes and adaptation, with the new MAF and reduced oil the gearbox was super smooth changing gears and ran perfectly over a 600km journey, except for 2 times and both times had a commonality, ie. a wrong turning saw a rapid reverse, forward, reverse manouver and a minute or so later the box would go into this emergency mode. Driving fast, accelerating fast or slowly, the box behaved perfectly!

Changing the MAF did make a big difference in smoothness of engine power and economy, so this has helped, but the box error still comes up. Does this
sound familiar to anyone, ie. Can the control module go faulty (the one which
lays inside the box, controlling the relays etc), or is it more likely to be a
bad connection, either into the gearbox, or into the EGS module?

The oil I drained out from the box was a light yellow in colour and didnt smell
burnt!

Any suggestions or pointers?

THE ELECTRIC PACK IS THE NEXT STEP I WOULD TAKE AFTER OIL CHANGE, CHEAPEST OPTION, MOST GEARBOX SPECIALISTS WILL ADVISE THE SAME, TRY THE ELECTRICS PACK IS MY ADVICE, NOT TOO EXPENSIVE

 

[psmart]

Trans fluid travelling up loom into transmission ecu poss??

Thank you for the good tip, v.much appreciate. I wouldnt have thought that the ECU up in the engine compartment could get contaminated, but the more I think about it, the wireloom is just like a pipe, so it could well be possible. I replaced the seal 20k miles ago, but if the box has had excessive oil in, then increased pressure could have forced oil up the loom. Will take the EGS ECU out this weekend and investigate.

MB TECH WARRINGTON - Thankyou for the info, much appreciated. Do you mean the control module inside the box which you remove by taking the gearbox bottom cover off? This part is approx 600 quid plus new oils, so want to make changing this part the last on the list, especially as you can pick a re-con box here in Germany for around 1300 quid with a 2 year warranty and would be easier for me to just change out the box than spend around 800 and find that the module is not the problem. Do you know any sources which sell re-conned control modules?

 

[Blobcat]

Turn the AC on...

 

[psmart]

Turn the AC on...

Sssshhhh! I'll lose my AC cred ..... I must admit, the ac hasnt been off, in the ML or the A in the last few weeks!

 

[BlackC55]

Electrical plate is probably the cause.

 

[psmart]

Raining all weekend, so couldnt look at the car, albeit it drove 400 miles flawlessly, at high speed and in slow crawling jams! Last night, after driving about 20 miles at 50mph, I kicked down and it jumped out of gear, ie, it revved freely as there was no gear engaged, looks like when it kicked down to 2nd, it didnt engage 2nd (is this possible)? I cruised along for a while going up a slip road without power, and once the car got to about 30mph, it engaged gear and off it went! Once I arrived at a parking slot, put it into reverse, but no reverse gear, just the locked 2nd gear! Turned off the engine, restarted and all was fine again! Does this still sound like the Electrical/hydro control unit? I researched this unit and you can buy re-conditioned units from Merc for around 300 quid, which is reasonable if it is this unit thats gone faulty!

Sounds like BlackC55 and MB Tech Warrington suggest the same part, so does anyone else know of these symptoms (adding in yesterdays update) before I get the new part?

 

[Cosworth]

A friend of mine had the same problem as yours.

Answer was to replace the gearbox. No problems afterwards.

He was told that these ML's are too heavy for the type of gearbox fitted in them and they do not last very long.

Also he was told that there is a limit to how many times the gearbox locks up and re-sets after you re- start the engine.

Eventually the gearbox will lock permanently in 2 gear until put on a star diagnostic machine and clear all fault codes.

 

[psmart]

A friend of mine had the same problem as yours.

Answer was to replace the gearbox. No problems afterwards.

He was told that these ML's are too heavy for the type of gearbox fitted in them and they do not last very long.

Also he was told that there is a limit to how many times the gearbox locks up and re-sets after you re- start the engine.

Eventually the gearbox will lock permanently in 2 gear until put on a star diagnostic machine and clear all fault codes.

The colour of the oil doesnt dictate a damaged box and there were very few 'bits' in the fluid extracted. The gearbox runs very smoothly, changing without noticing except for the few occasions mentioned above. I have my own CarSoft diagnostics, so Im always reading and resetting the fault codes in the EGS and resetting the adaptation.

I spent a while on the american forum and apparently the valve springs can break, and also the control plate can break, just a matter of dropping the hydro relay unit to see if the valve springs are ok or if the control plate is ok. If both are and there is no damage to the EGS due to fluid escaping with metal filings shorting out the EGS module, then would think about box changing! Interesting reading up on these things!

With regards to the ML, the S-Class is just about as heavy and in the 500 guise pumps an awful lot more power and torque through the same box (not the 7 speeder, the 5 speeder). The manual box wasnt upto the task so they had to de-rate the engine for this purpose. I would think a lot of Merces circa 1800-2000kg would be failing if the box wasnt upto the weight and power of a 270cdi engine!

 

[kebo57]

Hi in you earliest post you said
"I measured the box oil level and it was high, and I extracted 300ml of oil from it (goodness knows how it got high,
Regarding this
I did a thrust plate mod on a diff for a guy whom mainly deal in auto boxes I got talking to him a he had done two ML auto boxes recently, he said that the problem was engine coolant contamination from the unit that sits behind & under the oil filter (I cant just remember what it is called) but I traced the price & it was around £60.00 he recons that it is difficult but can be changed without removing the inlet manifold The above tied in with a box rebuild & new torque converter £1700.00 + vat
He could do a glycol test that would show this up
I have had issues with jumping out of gear which I thought might be incorrect low range / high range selection
I am also running with three magnets in my auto box & have change the oil 3 times in the last 42,000 miles
Kevin

 

[kebo57]

Hi in you earliest post you said
"I measured the box oil level and it was high, and I extracted 300ml of oil from it (goodness knows how it got high,
Regarding this
I did a thrust plate mod on a diff for a guy whom mainly deal in auto boxes I got talking to him a he had done two ML auto boxes recently, he said that the problem was engine coolant contamination from the unit that sits behind & under the oil filter (I cant just remember what it is called) but I traced the price & it was around £60.00 he recons that it is difficult but can be changed without removing the inlet manifold The above tied in with a box rebuild & new torque converter £1700.00 + vat
He could do a glycol test that would show this up
I have had issues with jumping out of gear which I thought might be incorrect low range / high range selection
I am also running with three magnets in my auto box & have change the oil 3 times in the last 42,000 miles
Kevin

Hi I might have got this all wrong but the item that I was referring to above was the OIL/WATER HEAT EXCHANGER link http://www.detali.ru/cat/oem_mb2.as...GM=716.644&CT=M&cat=21T&SID=18&SGR=060&SGN=02 item No 35 but it doesn't show the pip connection neither does it show the OIL/WATER HEAT EXCHANGER in the auto box section so I have took some pictures,
hope this might help Kevin

 

[psmart]

Hi in you earliest post you said
"I measured the box oil level and it was high, and I extracted 300ml of oil from it (goodness knows how it got high,
Regarding this
I did a thrust plate mod on a diff for a guy whom mainly deal in auto boxes I got talking to him a he had done two ML auto boxes recently, he said that the problem was engine coolant contamination from the unit that sits behind & under the oil filter (I cant just remember what it is called) but I traced the price & it was around £60.00 he recons that it is difficult but can be changed without removing the inlet manifold The above tied in with a box rebuild & new torque converter £1700.00 + vat
He could do a glycol test that would show this up
I have had issues with jumping out of gear which I thought might be incorrect low range / high range selection
I am also running with three magnets in my auto box & have change the oil 3 times in the last 42,000 miles
Kevin

Hi Kevin, Thank-you very much for this information. I had thought only the E-Class suffered from the contamination issue due to a poorly designed joint radiator, and had not realised the M-Class had an oil to water heat exchanger for the gearbox! Mind boggles as to why they did this (other than saving oil, or limitation of pump)!

It could explain why there was excess oil in the gearbox. I'll keep resetting the 'box and keep an eye on the fluid level as I dont know of any company here (yet) that can do a glycol test. Can you buy Glycol test kits?

 

[psmart]

he recons that it is difficult but can be changed without removing the inlet manifold

Just to note, if you remove the left wheel arch cover and the wheel, and jack the front of the car up, you can get to most things. When I replaced the engine mounts, I did this and although tricky, I realised that most items could be got at this way.

 

[kebo57]

Can you buy Glycol test kits?

I don't know were our if you can buy a kit
I thought about getting my ATF checked but I don't trust anyone
Odds on that when you get the results low and behold there would be glycol

I don't know were our if you can buy a kit
I thought about getting my ATF checked but I don't trust anyone
Odds on that when you get the results low and behold there would be glycol

I'm going to change the ATF well 5.5 lts of it anyway and replace the OIL/WATER HEAT EXCHANGER, oil filter, and check the magnets

I could then pressure test the OIL/WATER HEAT EXCHANGER so then there would be no need for the glycol test
I’ve just priced the OIL/WATER HEAT EXCHANGER and is now showing £133.00 see link http://www.mercedes-benz-parts.co.uk...com_virtuemart obviously I've got something wrong

Kevin