AAaaarghh, possible gearbox failure (1 Viewer)

[DavidG58]

I do have a habit of panicking without cause on many occasions, but every now and again I am right

This time I fear the worst

For a while now we have had odd issues with the engine management on our Mercedes MH going into 'limp' mode, or so I thought at least, massively reduced power for no obvious reasons, even with Bev driving, so not just me

Pull over stop engine, key out and in again all OK, often for 100's of miles, today had to stop 6 times in 80 miles, the last time, close to home at least, 2 times coming up hill to our house it didn't reset, so limp mode up hill = 15mph, = Mr Unpopular by the top of the hill

My real concern is that immediately after one of the stop to reset incidents we had an awful metallic crunch from somewhere under my feet, but reassured by then driving 40 odd miles with no issues or noises

I am now home and booked into workshop tomorrow, but not sure if we will make the 10 mile journey, in some ways the worst case scenario is no obvious fault in morning, nothing on diagnostics (typical for me when taking a fault to a garage) then we set off for Bristol on Friday and partially block the M1 in rush hour

 

[kip]

You say you've had issues for a while now, just wondering why you didn't take it in sooner? Fingers crossed it's something that can be fixed easily & cheaply.

 

[DavidG58]

You say you've had issues for a while now, just wondering why you didn't take it in sooner? Fingers crossed it's something that can be fixed easily & cheaply.

it has been in for various checks, nothing shows up on diagnostics

had gearbox oil changed as a precaution 3 months ago, MH has only done 20K miles over 5 years

I hope something shows up tomorrow, but hope it is not too expensive

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[kip]

Oh I see, best of luck.

 

[Ethle the wondervan]

Sounds like serious lack of use.

 

[DavidG58]

Sounds like serious lack of use.

we have done 18K in the last 2 years though, since we bought it

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[Ethle the wondervan]

You've frightened it!

 

[RS_rob]

Limp Mode eh!
what engine you got ?
Possible overboost by the turbo engaging limp mode same a VW ? if so cured by winding back the nut on the wastegate due to these engines being very sensatively set.

 

[dave newell]

"My real concern is that immediately after one of the stop to reset incidents we had an awful metallic crunch from somewhere under my feet, but reassured by then driving 40 odd miles with no issues or noises"

So you heard "an awful metallic crunching noise" but instead of getting it checked you drove a further 40 miles? Personally I'd have pulled over and got out to see what made that "awful metallic crunching noise" just in case it was a mechanical failure in suspension or brakes.

D.

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[Chris]

Hope the workshop sorts it out for you

 

[funflair]

Hi David

As you say, hope they find something as it's been going on a long time now, I can't imagine there would be much problem with the gearbox that would put it into limp mode. Quite possibly turbo over boost as suggested as I believe hills have featured in the run up to the limp issue on several occasions.

Fingers crossed.

Martin

 

[DavidG58]

"My real concern is that immediately after one of the stop to reset incidents we had an awful metallic crunch from somewhere under my feet, but reassured by then driving 40 odd miles with no issues or noises"

So you heard "an awful metallic crunching noise" but instead of getting it checked you drove a further 40 miles? Personally I'd have pulled over and got out to see what made that "awful metallic crunching noise" just in case it was a mechanical failure in suspension or brakes.

D.

My knowledge of mechanics is limited to looking and trusting I notice anything changing, in the same way I normally know I have a puncture without actually looking at the wheel

I had noticed a massive lack of power, I am fairly sure I would have felt a change in suspension or felt a difference in braking, I did opt not to join the motorway and drove steadily along a straight road to a layby. Nothing obviously wrong, so yes I did continue, we all have different skills in life, thankfully in my case I can earn enough to pay to put right my mechanical failings and help keep workshops gainfully employed

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[busby]

Whats a limp mode,,,,mine doesn't even have a cat or so i am told...Hope its not serious,,,BUSBY

 

[Terry]

Hi David I dont think the gearbox will be at fault (you have automatic) it will be it's brain that's frazzled Are you into the Merc dealers ?---If so ask them to get a 16 year old to fix it Seriously hope they find something and hope it's not too expensive
terry
edit just been reading on faults on cars and mercs are prone to PCB probs with dry solder joints -this can be fixed a lot of the time by remelting the bits of solder with a very hot air gun thing.No idea if that's what is up with yours or if your garage would know/undertake such a thing but may be worth going to a specialist if they cannot diagnose any faults

 

[etap]

Davidg58,
Look up Mercedes Medic.com enter limp mode it might cheer you up.
Etap

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[DavidG58]

Whats a limp mode,,,,mine doesn't even have a cat or so i am told...Hope its not serious,,,BUSBY

Limp mode I think is some kind of too clever for its own good in most cases electronic restriction on the power output, so in theory if something has 'sort of' failed but it is still safe to continue but slowly, the engine management takes over

In most cases I think it is over cautious, but I am no expert

 

[DavidG58]

Davidg58,
Look up Mercedes Medic.com enter limp mode it might cheer you up.
Etap

http://sprinter-source.com/forum/showthread.php?t=7173

cheer me up?? now more confused and or more concerned

will leave it to those that know what they are doing

 

[StefAndDi]

@DavidG58

I think I'm right in saying that you have the same, or similar, engine and gearbox as me.
This reminds me of something which I experienced shortly after I purchased the vehicle, although I did not have the metallic crunching noise.
I noticed that on one trip I was struggling to pass some vehicles. When I pulled over and checked the settings on the steering wheel buttons I found that somehow I had managed to select 'winter tyres' mode and the computer was restricting me to, I think, 50 mph.
I'm not saying for one moment that it's the same issue. I just thought it might be useful to throw it into the mix because at the time it was a little concerning.
I hope you get things sorted out quickly and without too much expense.
Stef.

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[DanielFord]

I'm not sure gearbox failure would cause limp mode. Metallic crunch, quite possibly.
Either way, I feel your pain, ours is booked in to have the synchro rings replaced on 3rd, and possibly 2nd gear. On the plus side, I am in hospital so will be unable to drive for about a month, so ups and downs all around!
I don't think our gearbox issues were helped too much when a crazy Itallian swung in front of us yesterday and then pulled an emergency brake to make his exit. I accidently grabbed 3rd instead of 5th at 60mph! D'Oh!

 

[GWAYGWAY]

Depending on engine gearbox pairing, probable cause is the gearbox fluid level if it is an auto box. you need to get the right dipstick level and use the right auto fluid, merc's own, If there is a low level the gearbox will be clunky and probably suck in second gear, to stop you wrecking everything the ECU will restrict the engine output to limp mode and 30mph to stop the gearbox being damaged.
If there is no dipstick you will need to buy one,and dip the fluid yourself. DO NOT OVERFILL or underfill as either will cause the seal and pump to leak or not work. The box has a valve chamber of many sliding valves to direct the fluid to the correct brake in the box that allow the brakes to release one brake and then stop another as it changes up then. As they are seven gears it is a busy box and does depend on the fluid for lubrication, actuation and COOLING, Standing around can allow the oil to drop gunge in the valve chest.
It might be wisest to run it and then change the fluid altogether if there are suspicions about it's state.
The ECU will not necessarily record the fault as it is released on stop and start but it may be in a memory if you can have a good reader on it.
! Check the gearbox fluid.
2. Top up if low to the full mark
3. check the fluid again after topping up as it will have been spread about the gearbox.
hope that this might help.

 

[DavidG58]

@DavidG58

I think I'm right in saying that you have the same, or similar, engine and gearbox as me.
This reminds me of something which I experienced shortly after I purchased the vehicle, although I did not have the metallic crunching noise.
I noticed that on one trip I was struggling to pass some vehicles. When I pulled over and checked the settings on the steering wheel buttons I found that somehow I had managed to select 'winter tyres' mode and the computer was restricting me to, I think, 50 mph.
I'm not saying for one moment that it's the same issue. I just thought it might be useful to throw it into the mix because at the time it was a little concerning.
I hope you get things sorted out quickly and without too much expense.
Stef.

I wish, but thanks for your interest and concern, on my Mercedes car I am always catching the speed limiter stalk on roundabouts with similar effect

The metallic crunching noise I now think might be a red herring, will update thread below with engineers comments, goodish news though

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[DavidG58]

Depending on engine gearbox pairing, probable cause is the gearbox fluid level if it is an auto box. you need to get the right dipstick level and use the right auto fluid, merc's own, If there is a low level the gearbox will be clunky and probably suck in second gear, to stop you wrecking everything the ECU will restrict the engine output to limp mode and 30mph to stop the gearbox being damaged.
If there is no dipstick you will need to buy one,and dip the fluid yourself. DO NOT OVERFILL or underfill as either will cause the seal and pump to leak or not work. The box has a valve chamber of many sliding valves to direct the fluid to the correct brake in the box that allow the brakes to release one brake and then stop another as it changes up then. As they are seven gears it is a busy box and does depend on the fluid for lubrication, actuation and COOLING, Standing around can allow the oil to drop gunge in the valve chest.
It might be wisest to run it and then change the fluid altogether if there are suspicions about it's state.
The ECU will not necessarily record the fault as it is released on stop and start but it may be in a memory if you can have a good reader on it.
! Check the gearbox fluid.
2. Top up if low to the full mark
3. check the fluid again after topping up as it will have been spread about the gearbox.
hope that this might help.

Many thanks, my reasoning for suspecting gearbox is that we have recently suffered a fairly major oil leak on the gear box, so have gone through all your suggestions many times recently, the Merc system is not very customer friendly, sealed dip stick, so really an engineers job to even check the oil level (ours is the auto gear box)

Gearbox oil change is only scheduled for 60K miles, so way off, but the leak forced our hand, we are now confident we have the right level, not if the leak caused any issues while low

Just about to update thread with current position

 

[DavidG58]

Got MH to workshop this morning, all started off OK as so often does, after about 5 miles, dropped back to safe mode, but this time with the engine management light on, I am now not sure if this normally came on and I just missed it in my panic to stop safely

Stopped in a layby, turned off engine, limp mode and light would not reset, but more or less on the level all the way to workshop and all in 30mph zone from there so continued

Plugged in, 16 faults recorded, most cleared, problem seems to be a boost control unit, or something like that, I have to say I really don't know and was so elated to think the gearbox failure I had predicted and started to factor in financially was now looking less likely that I wasn't even really listening. I will confirm exactly what was changed when I have the bill in front of me

Fitting it could be a game, they are hoping that by removing the headlight they have a half chance of getting close to where it is

Back to the clunking noise, what I now think is, most auto gear boxes that I have driven don't really seem to like the move from Park to Drive, resulting in a clunk, that is what I think I heard and felt, but due to my massive negativity / concern I built the noise that we usually hear up into a gear box explosion

Still have a half chance of making Bristol, bit due for delivery any time now, have to hope they can get at it and that is the only thing causing the issue

and while its there they are swapping the cab battery, precautionary ref other thread of mine, so hopefully its going to be great. And all for well under £400 including the battery , beats the £6K + gearbox options

I'll be back to tell all

 

[TheCaller]

Fingers crossed for you that that's all it is.

Was going to add a 'thumbs up', but will save that until you report an incident-free trip to Brizzle & back.

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[andy63]

David @DavidG58 .I do hope that's you sorted... you don't seem to be having the best of times with that van and associated issues.... I'd have lost the plot by now...
Hope you make your next meet... with no engine ,battery or leak issues.
Ta Andy

 

[Sam and Viv]

Hi david
We were parked next to you at Falkirk wheel sorry to hear of your problems with m/home. Thats three things now so hopefully thats the lot. Good luck on the rest of your travels.
Sam@Viv.

 

[JeanLuc]

I think you have the same problem that I had until it was sorted out in 2012. I had experienced occasional lack of power as the ECU switched to limp mode. At first it would reset after a rest but eventually it gave up completely and would not go above about 30 mph. First time this happened was in Germany in 2010 and a MB commercial dealership chap took it out but by then, of course, the problem had reset.
Then in 2012 we were in Suffolk and it lost all sense of decent power. Into Orwell MB truck dealership at Ipswich and a technician diagnosed the problem very quickly. It was a pressure sensing transducer / control unit for the turbocharger. When this fails, it 'thinks' that the engine is getting all the power it needs even though it is not and the system just switches to limp / safety mode.
Ours is on an earlier chassis with the 2.7 litre 5-cylinder engine and 5-speed auto box. The turbo and control unit are down on the left of the engine (looking in from the front) below a heat shield. The chap bent the heat shield to access it (having assured me that this was more sensible than trying to un-bolt it as the bolts can be seized and shear off. A new transducer was fitted and half an hour later we were on our way.
MB man also showed me a quick way to test if the engine control has switched off power. Put the gear selector in N, apply the brakes (if not already on) and floor the throttle. It should rev to about 4,500 rpm (in my case - yours might be a little different) at which speed it will hold. If the tacho will not go above about 2,000 - 2,500 the system has shut down to protect the engine. Don't worry about over-reving the engine: there is a rev limiter built in to prevent it going over 4,500 rpm.

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[DavidG58]

I think you have the same problem that I had until it was sorted out in 2012. I had experienced occasional lack of power as the ECU switched to limp mode. At first it would reset after a rest but eventually it gave up completely and would not go above about 30 mph. First time this happened was in Germany in 2010 and a MB commercial dealership chap took it out but by then, of course, the problem had reset.
Then in 2012 we were in Suffolk and it lost all sense of decent power. Into Orwell MB truck dealership at Ipswich and a technician diagnosed the problem very quickly. It was a pressure sensing transducer / control unit for the turbocharger. When this fails, it 'thinks' that the engine is getting all the power it needs even though it is not and the system just switches to limp / safety mode.
Ours is on an earlier chassis with the 2.7 litre 5-cylinder engine and 5-speed auto box. The turbo and control unit are down on the left of the engine (looking in from the front) below a heat shield. The chap bent the heat shield to access it (having assured me that this was more sensible than trying to un-bolt it as the bolts can be seized and shear off. A new transducer was fitted and half an hour later we were on our way.
MB man also showed me a quick way to test if the engine control has switched off power. Put the gear selector in N, apply the brakes (if not already on) and floor the throttle. It should rev to about 4,500 rpm (in my case - yours might be a little different) at which speed it will hold. If the tacho will not go above about 2,000 - 2,500 the system has shut down to protect the engine. Don't worry about over-reving the engine: there is a rev limiter built in to prevent it going over 4,500 rpm.

You could be describing my problem exactly, the half hour turn would be nice, the access looks horrendous, but the position sounds very similar, albeit different engines as you say. The part is only £40, as ever the labour will do it, but mainly due to access issues.

 

[JeanLuc]

Well you have saved something on the part. The transducer for mine was £86 +VAT.

 

[dryad]

fingers crossed for you that they have now sorted the problem..

had a very similar problem with my renault trafic going into 'limp mode' but hooking up to the garage computer couldn't find the fault..
it was intermittent to start with, would limp for just a few miles, then clear, but over the weeks it happened more frequently and for longer periods..
in the end they hooked it up with a portable diagnostic computer and drove it around for a couple of hours, hoping the fault would happen and therefore show up....it didn't!! until i left the garage and was on my way home, sods law!

eventually discovered that it was the egr valve clogged up, very clogged actually, got that cleaned out, problem solved, phew..

(by the way, i know bugger all about modern engines, do all of them have egr valves?)

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