Hi,
not sure if this is in the correct place or not, but would be interested to know if anyone has experienced clutch master cylinder problems with MAN’s. So far this year we have went through 15 and MAN doesn’t seem to think there is a problem. I do at £470.00 a go + labour and recovery. I have been told that there is a dedicated forum for this somewhere on the web and would be interested if someone knew where. Any help would be appreciated…thanks
thats almost £7000. if that was me i would have got rid of the truck by now 15 in a year thats one almost every 3 weeks surley you shouldnt let it go on that much. two maybe three at a push i would have started to creat a fuss at your dealer but 15 is ridiculas
john
busy fool:
thats almost £7000. if that was me i would have got rid of the truck by now 15 in a year thats one almost every 3 weeks surley you shouldnt let it go on that much. two maybe three at a push i would have started to creat a fuss at your dealer but 15 is ridiculasjohn
Maybe just maybe he has more than one MAN truck 
sorry guys, I should have said that this was 6 vehicles but still excessive
If they’re TGL’s they do seem to go through one or two, but 15 on 6 motors is excessive.
What is happening to the master cylinders then to fail so often. I have a TGS and the gearchange is awful [cables] so far they have replaced the gearbox,clutch and now they want to do the cables and they are talking about the slave cylinder too.
I know this is an old post but we have a 2006 tgl , had no issues until it went into garage for mot and they decided it needed a new master cylinder as the one which was working fine released air if you sat with your foot on clutch pedal , so they put new master on , and immediately i could feel a big difference in the pedal and over next few days realised you couldnt find the bite point for the clutch at junctions etc and the wagon would start to roll back until suddenly the clutch bit and wagon would leap forward . A week later started wagon and clutch just went to floor no resistance at all , garage too busy n over worked n didnt seem interested , we have bled the system umpteen times , had it all apart nothing looks out of place , when you drive the truck u have to pump clutch like crazy get 1st gear then while accelerating and going up the gears its ok , then soon as you take foot off accelerator you lose clutch and cannot go down gears etc . We now think its an air issue as we also noticed tank doesnt blow excess air no more and when air supply to pedal ok clutch works .
Any ideas what we need to look at thanks
Usually this is the master cylinder issue on a solely hydraulic system. I’m not familiar with the TGL and " master cylinder released air with foot on clutch pedal " sounds very odd unless you mean that the remote clutch air servo released air…which points to a servo issue. However AEC had this problem many years ago. It would usually occur after a long period of not using the clutch, ie at the end of a motorway exit slip. It was found that the slave cylinder piston was creeping along the bore thought to be due to the release bearing being thrown back towards the gearbox because everything was spinning. (can’t find the right words to express this) . The result was that the slave cylinder did not have a full stroke. Although this sounds odd, fitting a light spring attached to a small bracket bolted to the slave cyinder pushrod to bottom its piston, and ensuring that there was a small clearance between the release bearing and the clutch fingers seemed to cure the issue.
Cheers , im maybe not best at explaining myself .
As far as i know the clutch is hydraulic , only when you press the pedal it uses air to push the plunger inside the master cylinder on a man truck . How exactly it all works i dont know as information is very limited as cannot find anything anywhere on how it all works .
The old cylinder removed by garage would release air if you sat in traffic with foot on pedal or junction or just sat in neutral , but wagon worked perfectly .
We now tried 2 different masters niether release air and wagon has no clutch pedal , im no mechanic but to me i would say the pressure not being released is causing an issue now , but if you get into gear and are accelerating you get resistance in pedal and can go up the gears no problem , once you drop revs you lose pedal so in my none mechanical opinion , it seems to now need the extra power or drive to get the pressure up into the pedal .
We have also noticed not sure when it started but the wagon is no longer blowing excess air off as if its not quite getting to max pressure , the gauge in cab is not good as it uses fuel gauge as the air gauge if u press a button but it looks like it only gets to maybe 98% full the pointer is just off the max line .
Thanks
Having had a look at Bison parts picture of a TGL master cylinder there does not appear to be an air connection. I presume from the mention of an air leak when pressing he clutch pedal the vehicle has an air servo to assist the operation of the clutch slave cylinder. This leak has now been rectified you say, so I’d now be looking at a faulty servo, possibly a sticking piston which will produce some pretty odd symproms at the pedal… An internal hydraulic leak ought to show up as needing to top up the hydraulic reservoir often.
Hopefully that is a pic of master cylinder off bison parts , the 2 thin black pipes are air one is a feed into cylinder from an air saddle next to cylinder under front flap the 2nd one is just an exhaust for expelling air im assuming after use of clutch , the feed is connected to the air saddle via a kind of valve type bolt where the middle of bolt pushes in and out as you use pedal opening and closing the air off i presume .
The picture not very clear on the bison parts site really . So im assuming you press pedal , the air is released from saddle via nut moving which allows air into pipe then into cylinder , pushes plunger down then as plunger rises back up air is released via exhaust pipe .
The saddle is just a 3 way junction box i think has one feed in and 3 out which go to seat , steering wheel and clutch cylinder .
Thanks
