Been having intermittent problems with a lack of power that I can’t quite fathom. Trucks been in the shop several times but to be honest, I have little faith in their diagnostic skills.
For no apparent reason the truck loses a lot of its power for acceleration, I’ve tried everything, every combination that could possibly affect it, yet I cannot induce it or replicate it on demand.
Occasionally, usually when I need it most, the bugger won’t rev through the range as normal.
IT IS NOT ENGINE MANAGEMENT & IT IS NOT DODGY DIESEL. The laptop diagnostics bring up 0 errors & the whole fuelling system has had manufacturer level mechanics look into it.
Some days it happens several times & some days it doesn’t happen at all !
Today was a bad day, & it’s doing my effin head in.
How does an exhuast brake work? Is it possible that this one has developed a mind of its own ?
Not sure with your merc but it is possible I had a 03 man with the pedal for the exhaust break on the floor (we called it a healie) any how when I used it the exhaust break would stick on not the pedal on the floor the actual diaghram in the exhaust break system so it can happen try disconnecting the exhaust break I had to on mine which was behind the cab on a few occasions I forgot I couldn’t use it
I drive a CF with AS-tronic and it happened to me afew weeks ago. Apparently the ECU activates exhaust brake during gearchanges but sometimes seizes up and so sticks on.
JIMBO47:
has the engine been worked on recently!!,
It’s funny you should say that. Yes, it’s been worked on at least every 6wks, + every time the mileage matches the service intervals & every time I’ve felt the need to report a fault that might, or might not, be engine related.
Do you think that the almost constant attention the truck gets is related to the problem?
what can happen is the ball joint on the ex brake can part company so then the butterfly valve does what it likes as you drive around
you could also make sure the butterfly valve in the exhaust pipe is in the open position , remove the air pipe to the cylinder and see if that improves anything
damoq:
You would hear the exhaust brake if it was stuck on plus there would be lots of black smoke coming from the exhaust too.
not necessarily, the exhaust brake on my MAN has been playing up for a couple of months, no black smoke just a loss of power and the turbo needle wont go past a 3rd, its the little piston that moves to activate the brake thats not fully retracting and opening the butterfly hence the restriction in power, i,ve turned the switch off on the dashboard on mine until i get a new block (cant replace the knackered bit i have to buy the full lot)
so the OP yes you are probably right in your diagnosis, get the fitter to disconnect the exhaust brake and see how you get on
Generally nowdays with all the sensors fitted t the engine you won’t get the black smoke …Yes you can have an imtermittant exhaust brake fault and it can stick …Not sure how merc work but generally you will have a mag valve with air at one side ,you press your switch etc and it energises the valve and air passes to the exhaust brake putting it on …when switched of fair exhaust via the mag valve …if mag valve is choked then it may be slow to release.or a wiring fault ie chaffed wire may short it causing it to energise ,or the butterfly in the exhaust may be seizing up,the cylinder that operates the butterfly may be seizing on it’s pivot.merc should be able to check the operation on their laptop …f you know where the mag valve is you can power it up yourself and see if it return ok
Don’t know wether your engine has EGR [exhaust gas recirculation] but if it has see if it can be blanked off so it is incapable of putting any gas back into the intake even if its valve is stuck open. Then carry out a long enough trial to determine if it has stopped the symptoms.
chester1:
sounds like the intercooler or an intercooler pipe drawing in air
I’m a half baked mechanic myself. I understand what an intercooler is & what it does. How could “drawing in air” on this circuit cause my symptoms?
Would it be totally intermittent & unrepeatable on demand?
I rescued a Swiss driver in a car one sunny afternoon, he pulled in behind me and was in a blind panic, his Saab kept losing power and black smoking. I opened the bonnet and asked him to start it up, when he revved it up the flexi pipe from the air cleaner to the turbo was perished and collapsing. I put him a piece of chopped up Evian bottle inside to keep it in shape. I got drunk on the 50CHF he gave me and told him to get it replaced ASAP.
Is it an automatic type that works when you apply the brake like on the Scanias?
If so, when it loses power, check to see if the brake lights are sticking on…I had it on my P380 tipper a few years back, intermittently the brake light switch would stick, causing the exhaust brake to stick and everytime it went to Scania…No fault logged…
