ML270 cdi Auto Gearbox (...again) :(

[psmart]

Any ideas, got a call to say the car has stopped, faults are:

1. Engine starts, engage D, put foot on accelerator, car moves, back off on accelerator, drive stops and car stops.
2. Engine wont rev above 1000rpm when in Drive and no forward or reverse motion.
3. No noises from the box.

...... I guess Mercedes are sent to us good people to try our patience

 

[Cole@MBS]

Sorry to ask but gearbox oil level been checked, no oil signs under the car???

You say car dont move, but you also say put foot down "car moves"???

 

[psmart]

Thanks for the info, Im just relaying what Ive been told. To recap:-

The car was driving fine this morning, then slowing down to a roundabout, the car lost total power, ie. no drive, but engine running and revs limited to 1000rpm.

When you turn off engine, start engine, engage drive and press accelerator, car begins to move forward, but as soon as you back off on the accelerator, all drive disappears and car comes to a standstill. If you press the accelerator again, engine revs limited to 1000rpm but no drive to the wheels, even if you shift to N-R-P. Same if you shift into R from D or from P.

On the initial loss of power this morning, car stopped, turned off and started and no drive at all. When shifted into low range, car drove ok but shortly stopped with no power. Now in both normal and low range, car behaves as in above paragraph.

Oil level hasnt been checked, albeit it has just come back from a service and MOT 1 week ago, so I would have thought that any gearbox oil leak would have been investigated or noted and that the level checked in the service.

After coming back from the service, the car had a hellova job to start, went back in and fuel pipes replaced, but didnt cure the fault. A friend got down to look for the problem and noted a cracked fuel pipe, which he fixed and the car started and ran perfectly for the last 2 days. Not sure if this is related, but thought worth noting just in case.

The gearbox and transfer case was replaced about 10,000 miles ago after a total failure. The new gearbox was a 26,000 mile unit (which has now gone out of warranty)! Im wondering though if it could be the brake switch being faulty, or I read on one thread sometime back that a switch in the gear selector pack goes faulty, could any of these cause the fault?

 

[Cole@MBS]

A speed sensor gone in the box would still give you drive, you would get a thump as you put it into gear, but it would move,

Sounds to me like something major has let go inside.

If it was on the electric side of the box i dont think it would be acting as it is! need to think about this one!

 

[psmart]

Thanks for your help, just wish I was with the car to plug the diagnostics in!

Apparently there was no noise and still is no noise. When the box went last time, there was an almighty bang and any attempt to change gear gave an awful winding down grating noise.

If the selector is in N or P then the engine revs freely and when in D or R the engine doesnt sound to be fighting a load, hence it could be a safety protocol to restrict revs by the engine ECU limiting torque and revs to 1000rpm.

There was no jerking or obvious gearbox fault prior to this, other than the 4x4 take up in 1st gear I reported longtime back.

 

[Wellington]

To help you with this, try this reasoning,
It is likely to be a problem with the engine or the transmission not both at the same time.
If the engine is OK it should free rev to whatever it is limited or governed to in neutral (or at least the torque converter stall speed which is usually around the 2,200 rev mark but varies slightly from model to model if the input shaft of the transmission is not allowed to turn as in the case of a severe breakup or other causes).
When someone mentions power to me it means the torque producing capacity of the engine, others might take the meaning to be loss of traction at the wheels so there fore either the engine is producing the torque and the transmission is not transmitting it to the wheels, in which case you will have the engine screaming away and the car getting nowhere, or if the torque produced by the engine is down then the good transmission will only send to the wheels what it is provided with.
I hope these thoughts will help you make a reasoned diagnosis, there is one further thought which I have left till now because I do not think it relevant in this instance but it is to help you with future diagnosis and not blame torque converters which on the whole are quite robust. As mentioned earlier a fully functioning engine will stall a fully functioning torque converter at around 2,200 rpm or whatever spec the particular model has, if the one way clutch on the stator inside fails by not locking up it will cut the stall speed exactly in half and the car will have difficulty setting off but then will drive nearly normally and have a high speed capability, if the one way clutch siezes and the stator will not turn it will still achieve the correct stall speed but the engine will not rev high, the car will pull away normally but will then not achieve a high speed, in this case put the transmission into neutral and the engine will free rev as it should, also in this case I would expect the transmission fluid to be severely burnt and evil smelling. In the case of the engine performance being down I would expect a stall test reading some where between 2,200 rpm and 1,100 rpm. So exactly half the stall speed condemn the torque converter, between the two have a look at the engine.
No intention to ramble on but this might save you a lot of time and expense in the future, there again they say that a little knowledge is a dangerous thing, Good Luck

 

[Wellington]

Sorry I miss typed earlier a torque converter with a siezed stator will pull down the peak revs on the engine

 

[psmart]

Thank-you for your input Wellington, much appreciated. Having had one box go and also on my SD1, I have a few ideas on what to look at, your info adding to this, but from what my brother describes, it doesnt sound like its mechanical within the box. At a guess, its part electronic part mechanical, such as a sensor, but one thing came to mind, and thus need input from Kebo57, is what happens if a diff fails or a prop coupling fails (shears)? I remember Kebo57 saying that when he removed a prop, he had no drive, but what he failed to mention was what was the engine revs?

Ive had my suspicion regarding the diffs/props for some time due to the 4x4 takeup (as described in my previous thread when the last gearbox failed on the same car)! The other suspicion is the ETC, which MERCEDES AG (or DAIMLER AG) were supposed to have tested when they replaced the box!

 

[Wellington]

If you lose drive downstream of the gearbox when you try to drive and the car does not move when you quickly put the lever into park with the car stationary I would expect to hear a clattering noise when the parking pawl attempts to engage the parking wheel spinning on the gearbox outputshaft.
On other cars where the speedo is taken from the gearbox output shaft I would expect to see a speedo reading when the car is stationary, not when the speedo is taken from abs or wheel sensor.

 

[kebo57]

but one thing came to mind, and thus need input from Kebo57, is what happens if a diff fails or a prop coupling fails (shears)? I remember Kebo57 saying that when he removed a prop, he had no drive, but what he failed to mention was what was the engine revs?

Ive had my suspicion regarding the diffs/props for some time due to the 4x4 takeup (as described in my previous thread when the last gearbox failed on the same car)! The other suspicion is the ETC, which MERCEDES AG (or DAIMLER AG) were supposed to have tested when they replaced the box!

Hi Phil I’ve been following this thread, I had removed the prop as it was knocking that badly I thought it was ready to shear of, having only one motor I thought that I would collect the new prop in the ML using the rear prop drive (like you could do with a Land rover) I was sat in the ml in the garage ready to go and collect my replacement prop selected drive and the engine revved up but there wasn't forwards out reverse motion high our low range
I don’t think it felt like it was driving the box but not the props. Sort of just revved up no gear changes no movement forwards our back I gave it a good revving but there wasn't drive
I would phone Sean see what he can offer


Kevin

 

[Philip12]

transmission

Hi Kevin

I would bet at this stage that it is the limp home mode problem. What happens is the gear sticks in one gear , generally 1st or 2nd and the revs go up but you go nowhere! Generally these problems are linked to an oil leakage and what happens that the oil leaks from the transmission and travels up hill along the cable and enters the ECU which then gets contaminated and then reacts as stated leading to your problem. It is sometimes referred to as the " wick principle" (Remember the old wicks in the oil lamps where the oil travelled up the wick, defying gravity , and allowing the flame to be fuelled with the rising oil. It sounds amazing but it is true, believe me. I have spent the last 4 years researching this problem and also have had a number of experts who have been of immense help to me.
Whats worse is the MB are awre of it and have allowed these vehicles to remain on the road. Fatalitys are around the corner.

Best wishes, Philip

 

[kebo57]

Hi Kevin

I would bet at this stage that it is the limp home mode problem. What happens is the gear sticks in one gear , generally 1st or 2nd and the revs go up but you go nowhere! Generally these problems are linked to an oil leakage and what happens that the oil leaks from the transmission and travels up hill along the cable and enters the ECU which then gets contaminated and then reacts as stated leading to your problem. It is sometimes referred to as the " wick principle" (Remember the old wicks in the oil lamps where the oil travelled up the wick, defying gravity , and allowing the flame to be fuelled with the rising oil. It sounds amazing but it is true, believe me. I have spent the last 4 years researching this problem and also have had a number of experts who have been of immense help to me.
Whats worse is the MB are awre of it and have allowed these vehicles to remain on the road. Fatalitys are around the corner.

Best wishes, Philip

Ok then if you think you know the problem that I had
"when I only had one prop shaft fitted to the vehicle"
then how would you go about fixing it

Kevin

 

[Cosworth]

Hi Kevin

I would bet at this stage that it is the limp home mode problem. What happens is the gear sticks in one gear , generally 1st or 2nd and the revs go up but you go nowhere! Generally these problems are linked to an oil leakage and what happens that the oil leaks from the transmission and travels up hill along the cable and enters the ECU which then gets contaminated and then reacts as stated leading to your problem. It is sometimes referred to as the " wick principle" (Remember the old wicks in the oil lamps where the oil travelled up the wick, defying gravity , and allowing the flame to be fuelled with the rising oil. It sounds amazing but it is true, believe me. I have spent the last 4 years researching this problem and also have had a number of experts who have been of immense help to me.
Whats worse is the MB are awre of it and have allowed these vehicles to remain on the road. Fatalitys are around the corner.

Best wishes, Philip

Just out of interest, where is the Gearbox ECU Located?