Mercedes GL320 2007 - Stuck in Neutral
Discussion
It's my sister's car - she lives in Dubai, uses it during the UK summer and the car has resided with me since Aug 2025.
It sat on my drive, with the battery removed, for 3 months September - December 2025. During this time, the front driver's footwell filled with water due to a split in the sunroof drain tubes. I fixed the leak, thoroughly dried the car (including the Signal Acquisition Module - SAM - which sits in a cavity under the front seat along with the battery), reinstalled the battery and the SAM, and started the vehicle.
To my surprise it started and drove absolutely fine - for about 10 minutes.
I put the vehicle in Park and left it on my driveway with the engine running while I weeded the drive
. To my dismay I found that instead of being in Park, it was stuck in Neutral - and it rolled gently downhill, knocking over my garden wall, before I was able to jump in and apply the handbrake, luckily only making it about a metre or so into the road. Not a scratch on the Mercedes though. PHEW!!! It took five fully grown men to push it back up the gentle slope onto my drive.
As per the title, it is stuck in Neutral. Attempting to engage Drive or Reverse does nothing at all. If I attempt to engage Park, a rhythmic "clack-clack-clack" noise emanates from somewhere under the car, and that's it. I can then select Neutral on the gear selector and the noise ceases.
I do not have access to any diagnostic tools. I have toured local garages and none of them are keen to take the job on. It is a particular unappealing job (I guess) because the vehicle cannot be driven.
I wonder if anyone could point me in the direction of a specialist in the Bristol area who is likely to be interested in investigating/fixing the issue. I am unsure whether the water ingress could be the root cause of the problem or not. It did drive OK for about 10 mins, so possibly not. Failing that, any help or clues you could give me would be appreciated. This does not seem to be a common problem.
It's a shame because the car is otherwise is in excellent condition with only 120,000 miles and is the ideal car for my sister to use over the summer with her family (hiring a car this size is extremely expensive!!)
Here's the aftermath. And thanks in advance.
It sat on my drive, with the battery removed, for 3 months September - December 2025. During this time, the front driver's footwell filled with water due to a split in the sunroof drain tubes. I fixed the leak, thoroughly dried the car (including the Signal Acquisition Module - SAM - which sits in a cavity under the front seat along with the battery), reinstalled the battery and the SAM, and started the vehicle.
To my surprise it started and drove absolutely fine - for about 10 minutes.
I put the vehicle in Park and left it on my driveway with the engine running while I weeded the drive
. To my dismay I found that instead of being in Park, it was stuck in Neutral - and it rolled gently downhill, knocking over my garden wall, before I was able to jump in and apply the handbrake, luckily only making it about a metre or so into the road. Not a scratch on the Mercedes though. PHEW!!! It took five fully grown men to push it back up the gentle slope onto my drive. As per the title, it is stuck in Neutral. Attempting to engage Drive or Reverse does nothing at all. If I attempt to engage Park, a rhythmic "clack-clack-clack" noise emanates from somewhere under the car, and that's it. I can then select Neutral on the gear selector and the noise ceases.
I do not have access to any diagnostic tools. I have toured local garages and none of them are keen to take the job on. It is a particular unappealing job (I guess) because the vehicle cannot be driven.
I wonder if anyone could point me in the direction of a specialist in the Bristol area who is likely to be interested in investigating/fixing the issue. I am unsure whether the water ingress could be the root cause of the problem or not. It did drive OK for about 10 mins, so possibly not. Failing that, any help or clues you could give me would be appreciated. This does not seem to be a common problem.
It's a shame because the car is otherwise is in excellent condition with only 120,000 miles and is the ideal car for my sister to use over the summer with her family (hiring a car this size is extremely expensive!!)
Here's the aftermath. And thanks in advance.
Edited by Wheatsheaf on Tuesday 6th January 13:51
Suggest you ask in the Mercedes subforum - Mercedes specialists are fortunately plentiful and you'll usually get a recommendation.
Hindsight is 20:20 etc, but I'd suggest you work out how to use the parking brake too! Being a 2007 would yours have a pedal or a switch?
Merc drivers are habitually likely to rely on the gearbox parking pawl instead of using the parking brake. The Indy who looked after mine (nowhere near you I'm afraid!) had seen a lot of seized parking brakes from lack of use, and even trained his staff not to put them on when cars were in for service after having them seize on at the garage and having unpleasant conversations with customers about who's fault it was.
Hindsight is 20:20 etc, but I'd suggest you work out how to use the parking brake too! Being a 2007 would yours have a pedal or a switch?
Merc drivers are habitually likely to rely on the gearbox parking pawl instead of using the parking brake. The Indy who looked after mine (nowhere near you I'm afraid!) had seen a lot of seized parking brakes from lack of use, and even trained his staff not to put them on when cars were in for service after having them seize on at the garage and having unpleasant conversations with customers about who's fault it was.
Thanks for the reply - I certainly do feel like a prat for not deploying the handbrake and I will never do that again in an automatic car!
Just to bring the tale to a conclusion, I eventually found a garage close to me that was prepared to take on the job. One of the mechanics was apparently a former Mercedes master tech, which sounded promising.
The problem was a gearbox control module, situated under the driver's footwell, which was swimming in water (!). As I said above, I was aware of a problem with water ingress, due to a detached sunroof drain tube, and had fixed the leak. What I did not know is that as well as under the driver's seat, where the battery and SAM module sit, there is an additional recess in the driver's footwell (covered with carpet and what looks like a fibreglass panel) in which the gearbox control module sits.
A visual inspection showed it immersed in water, so they got a second-hand module, coded it and fitted it, and the gearbox now works perfectly.
I'm considering this quite a good result - the garage were great, very knowledgeable and took considerable time to talk me through the issue and how they were going to fix it, acknowledging that there was no guarantee the second-hand module would fix the problem. Including the module, recovery fee, and labour, it set me back (or rather my sister back) £670.
I am now considering driving it down to the south of France where my sister is currently residing, a challenge I will love, and may journal on a separate thread
Just to bring the tale to a conclusion, I eventually found a garage close to me that was prepared to take on the job. One of the mechanics was apparently a former Mercedes master tech, which sounded promising.
The problem was a gearbox control module, situated under the driver's footwell, which was swimming in water (!). As I said above, I was aware of a problem with water ingress, due to a detached sunroof drain tube, and had fixed the leak. What I did not know is that as well as under the driver's seat, where the battery and SAM module sit, there is an additional recess in the driver's footwell (covered with carpet and what looks like a fibreglass panel) in which the gearbox control module sits.
A visual inspection showed it immersed in water, so they got a second-hand module, coded it and fitted it, and the gearbox now works perfectly.
I'm considering this quite a good result - the garage were great, very knowledgeable and took considerable time to talk me through the issue and how they were going to fix it, acknowledging that there was no guarantee the second-hand module would fix the problem. Including the module, recovery fee, and labour, it set me back (or rather my sister back) £670.
I am now considering driving it down to the south of France where my sister is currently residing, a challenge I will love, and may journal on a separate thread
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