mercedes 612d vario- air handbrake issues

[stevevoid]

Hello all
I have a mercedes 612d vario that im doing up ready for an expedition, there is an annoying problem that i havent got to the bottom of yet. For 6 months now the truck has been taking lots of time to build air pressure (air over hydraulic), this has got worse and will now not build enough air pressure to release handbrake, the air cylinder light on dashboard will not go off and the brakes are on (not completely but i can feel them on). There are no audible air leaks in the system. The air compressor is turning over and the first tank has pressure, the second tank does not seem to have any pressure, i realised this by pulling the cords to bleed system, first tank releases as it should, second tank there is no air at all, i guess the second tank is fed by the first. Does anybody have any experience of this? or any suggestions as to what I could try next? thanks

 

[Iain_U1250]

Here is a link to the official trouble shooting chart for a Vario 814d, not sure if it is the same.

http://ww2.justanswer.com/uploads/Chezario/2011-01-31_091344_w670_checking_compressed-air_syste...ring-loaded_parking_brake.pdf

Hope this helps a bit. It sounds like you don't have enough air pressure to get the second tank to even start filling. I would look at the compressor, as if there are no leaks, then it is possibly worn out.

 

[stevevoid]

ooo is that a mercedes manual section you sent me? i was looking for hours for something similar today, thanks! The compressor is definately ticking over and pressure is getting to the first tank, there are no pressure gauges on the tanks tho, i presume i need to attach a pressure gauge to them to check the relevant pressures...maybe time to invest in one, I know if I take it to a garage it will cost a fortune. So your guess is a malfunctioning compressor, if there was a leak I would hear it no? appreciate the help

 

[Iain_U1250]

If you get a spray bottle with some soap, and spray all the joints and fitting, you will soon find a leak,as it foams up quickly. If you have a really big air leak, you will hardly hear it. The first tank getting some pressure is good, but it should be filling up both tanks, pretty quickly, hence why I suspect the compressor is not up to the job anymore.

The only problem with getting a pressure gauge, is finding the proper fittings to connect to the test point. The alternative is permanently fit a gauge from each tank, and run them to the dash, that way you will always know what is going on with your air system.

 

[flint]

If needed, it looks like you can get repair kits for the compressor: http://www.ebay.co.uk/itm/Mercedes-...CommercialVehicleParts_SM&hash=item3a88f44739

Worth reading this listing too: http://www.ebay.co.uk/itm/Knorr-Bre...CommercialVehicleParts_SM&hash=item3f2f06d66f

 

[LukeH]

Somewhere in the system you should have a schrader valve with which you can pressurise the system from an external compressor. All HGVs have one so a recovery vehicle can connect up to tow you. Usually the emergency line is near the front under ot behind a bumper.
That would enable you to listen better, without the engine deafening you.
Good luck hunting for the leak...