ML 2.7 CDI auto - intermittent loss of power/drive

ML blues

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Help please, I have a 52 reg 2.7 CDI ML tiptronic auto with 90k miles, and recently the car keeps losing power intermitently every 5-10 mins approx i.e no drive as if the car's gone into neutral & just coasts to a stop, after switching off & on the ignition the car drives fine until another 10 mins, the problem doesnt appear to be related to speed/gear at the time, more random from what I can tell.

MB dealer has checked & say they have found a small amount of swarf in the gearbox oil so they advise that the problem appears to be with the gearbox, no other indication or possibilities have been put forward.

Could a damage gearbox work in such a way where the problem happens intermittently regardless of the speed/current gear at the time?. Any advice, thoughts on this would be most appreciated.
 
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ML blues

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Bit of a guess, but touching the brake pedal gives a similar result. Wonder if there is a fault with the brake pedal switch?

Cheers for the comment, the loss of drive can happen whilst cruising/accelerating, I haven't find a way of reproducing the problem yet, its just happening as mentioned earlier. If it was a gearbox issue then surely I would be seeing at some point a problem whilst starting/accelerating/gear changes etc or am I being naive. It seems that I can drive the same speed/route etc multiple times with no problems then suddenly suffer the loss of drive, hence I'm thinking (& hoping) its not a gearbox issue. any ideas or suggestions most welcomed
 

kebo57

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Hi have you been messing with high & low ratio could be that its not properly engaged the instructions are under the cubby box lid (center consul) you should feel a clunk and hear a clonk when it engages and dis-engages

I have had this but only twice before I had the box fixed when I was accelerating from the lights fast, I got going about 40 mph then wham no drive had to coast in behind the guy that I had just waisted
(a bit embarrassing to say the least)
then switched of and restarted everything was OK for months
others have had the same

I wouldn't be thinking of taking it to the main dealers if I was you
Psmart might now more, might be some transfer gear box issues, wires, connections, sensors,

Kevin
 
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oigle

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Cheers for the comment, the loss of drive can happen whilst cruising/accelerating, I haven't find a way of reproducing the problem yet, its just happening as mentioned earlier. If it was a gearbox issue then surely I would be seeing at some point a problem whilst starting/accelerating/gear changes etc or am I being naive. It seems that I can drive the same speed/route etc multiple times with no problems then suddenly suffer the loss of drive, hence I'm thinking (& hoping) its not a gearbox issue. any ideas or suggestions most welcomed

You say "loss of drive" and "loss of power". Which do you mean? My thinking re the brake light switch was along the lines of the switch intermittently "connecting" - maybe faulty/maybe out of adjustment. If this happened, the engine cuts power and the car coasts until the switch connection opens again. Does make some sort of sense, given the strange intermittent nature of the fault. I would be very loathe to blame the gearbox, given your description of the fault. You need to differentiate between "power loss" and "drive loss" to go any further.
 

panason1c

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Help please, I have a 52 reg 2.7 CDI ML tiptronic auto with 90k miles, and recently the car keeps losing power intermitently every 5-10 mins approx i.e no drive as if the car's gone into neutral & just coasts to a stop, after switching off & on the ignition the car drives fine until another 10 mins, the problem doesnt appear to be related to speed/gear at the time, more random from what I can tell.

MB dealer has checked & say they have found a small amount of swarf in the gearbox oil so they advise that the problem appears to be with the gearbox, no other indication or possibilities have been put forward.

Could a damage gearbox work in such a way where the problem happens intermittently regardless of the speed/current gear at the time?. Any advice, thoughts on this would be most appreciated.

Sounds to me like a faulty electro hydraulic plate causing the neutrals, this can be changed in situ.
 
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ML blues

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You say "loss of drive" and "loss of power". Which do you mean? My thinking re the brake light switch was along the lines of the switch intermittently "connecting" - maybe faulty/maybe out of adjustment. If this happened, the engine cuts power and the car coasts until the switch connection opens again. Does make some sort of sense, given the strange intermittent nature of the fault. I would be very loathe to blame the gearbox, given your description of the fault. You need to differentiate between "power loss" and "drive loss" to go any further.

Loss of drive, as if the car has gone into neutral even thou its still in 'D' mode & has occurred during cruising around 30mph or gentle acceleration, hope that clarifies the problem better.
 
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ML blues

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Hi have you been messing with high & low ratio could be that its not properly engaged the instructions are under the cubby box lid (center consul) you should feel a clunk and hear a clonk when it engages and dis-engages

I have had this but only twice before I had the box fixed when I was accelerating from the lights fast, I got going about 40 mph then wham no drive had to coast in behind the guy that I had just waisted
(a bit embarrassing to say the least)
then switched of and restarted everything was OK for months
others have had the same

I wouldn't be thinking of taking it to the main dealers if I was you
Psmart might now more, might be some transfer gear box issues, wires, connections, sensors,

Kevin


Thanks, the problem originated half way up a mountain road in Austria last month when my ML was fully loaded with family and luggage, it was struggling going up & wouldn't accelerate & then it lost all drive, had to switch off/on the ignition to drive off again, had to repeat this exercise every few minutes (about 4 or 5 times) before we got to the top thereafter, on even road, it loses drive, only less frequently.

Maybe the surge/demand required to get up the steep hill is similar to a quick acceleration & associated effects ?
 

panason1c

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ML blues,

Do a search here on a well known problem regarding the 'gearbox electrical plug' and ensure you dont have the tranny 'oil travelling up the loom and into the control unit' problem first, and if that appears ok consider the following....

It has been known where small metalic (conducting) particles/swarf can settle on top of the electro hydraulic plate which is located inside the gearbox and cause intemittent electrical interference which could be a reason for random false neutrals, you could try dropping the sump and removing the plate and washing it off with an appropriate cleaner, refit plate with new oil filter and oil.

Otherwise, the plate assembly could be faulty and requiring renewal.

I would go for the 'cleaning' option first.

Good luck
 

Alex Crow

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Loss of drive, as if the car has gone into neutral even thou its still in 'D' mode & has occurred during cruising around 30mph or gentle acceleration, hope that clarifies the problem better.

so logically you would have seen the engine rpm rise to the maximum at the same instant that drive was lost? or did the rpm actually drop? if the latter then you did not loose drive, but engine power, there is an important difference from the point of view of diagnosis.
 
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ML blues

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so logically you would have seen the engine rpm rise to the maximum at the same instant that drive was lost? or did the rpm actually drop? if the latter then you did not loose drive, but engine power, there is an important difference from the point of view of diagnosis.

RPM just shoots up when it happens, theres no advance warning or indication when it goes.
 
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ML blues

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ML blues,

Do a search here on a well known problem regarding the 'gearbox electrical plug' and ensure you dont have the tranny 'oil travelling up the loom and into the control unit' problem first, and if that appears ok consider the following....

It has been known where small metalic (conducting) particles/swarf can settle on top of the electro hydraulic plate which is located inside the gearbox and cause intemittent electrical interference which could be a reason for random false neutrals, you could try dropping the sump and removing the plate and washing it off with an appropriate cleaner, refit plate with new oil filter and oil.

Otherwise, the plate assembly could be faulty and requiring renewal.

I would go for the 'cleaning' option first.

Thanks for the advice, I'm waiting for the car to be repatriateed back from Austria to the UK, maybe after MB's tampering with the sump that

Good luck

Thanks for the advice, I'm waiting for the car to be repatriated back from Austria to the UK, maybe after MB's tampering with the sump & plate may have removed any swarf & cure the fault in the process (if only). So I'll give it a good test drive on its return & post back, big thanks to everyone todate for all your help and suggestions especially as I had only originally had the one option of a new gearbox to pursue, many thanks to all & I'll let you know how it goes..fingers crossed..
 

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