Unimog - Driving Licence

[nick channer]

tried that. year or so ago. didnt make any difference.. i've spent over a grand in past few yrs and got no where. should of had the pump etc fitted on chipper when i bought it. i just thought it would be one less thing that could go wrong if it wasnt fitted and thought mog spool valves would be up to the job..

[skyhuck]

I took the pump and tank off my 400 and converted to run off the mog, made no difference to the running temp of mine.

[nick channer]

i didnt think it would or should.. even if the oil gets red hot it shouldn't make diff to the water temperature.. the chipper must be producing more dust than the old one cos by keepin rad blown out does seem to cure it..

[b101uk]

The hydraulic system on the mog only draws up to ~19HP under full load (assuming <55L/min @ 205bar), your chipper may well be working on the more normal ~180bar (<16.5HP) at the point the feed rollers are almost stalled when the no-stress is off with a high feed rate, so it is unlikely that hydraulic load is the cause because even if the chipper had its own pump delivering ~180bar @ 55L/min it would then draw that power from the PTO shaft, so regardless the power for the feed-rollers be if from the mogs own pump or a chipper mounted pump it would ALL come from the engine anyway, also when chipping the duty cycle is unlikely to be very high anyway.

 

The main fan belt the goes from the crank to the pulley mounted on the radiator for the fan can also become hard and glazed on its running surface which can cause moderate slip without associated belt squeal, also the tensioning arm with a pulley on the end (which is required for chassis/engine flex) can also lose its tensioning capacity because it relays on a rubber bush on the radiator to distort to hold tension then eventually the rubber will separate from the inner or outer metal part of the bush which can be masked by the damper on later mogs.

 

The crank/water pump/alternator belt can also glaze up &/or drop down so the bottom of the V-belt s running in the bottom of the V of the pulley causing slip without squealing so the water pump is not going full speed.

 

The water pump its self has a slip clutch affair within it so if the water in the engine freezes the impellor doesn’t get twisted off, over time the "clutch" can become weak leading to slippage of the impellor at high RPM especially when there is some play in the pulley.

 

Obviously the thermostat could be playing its part in not opening fully which it should do by 83degC (73degC if a tropical thermostat)

[nick channer]

the tensioning arms and bush's etc inc all belts were replaced a yr or so ago. and the water pump was also replaced couple yrs ago when it had a previous over heating problem. my fitter and couple others are pretty clued up on lorry/plant etc and it was them that advised these changes... its a mystery to them also... thinking about it it still raises the temp considerably when the chippers not been used and its towing a big trailer..

[b101uk]

There is the other possibility that the temperature sender is getting a little old or the wire connection to it is a little dirty so the resistance has changed so the gauge is showing ~95C at a true 85C.

[nick channer]

dont think its that cos it does actually boil over if left with dirty rad and as it runs hot lot of time it uses water... not to mention i'm on my 3rd compressor 1n 2 yrs which is obviously watercooled and exessive heat causes it to seize..

[b101uk]

Then you definitely have a problem! As the water should not boil until ~120C due to the pressure in the cooling system from the expansion tank cap.

 

Have you tried a combustion gas detector placed on the expansion tank in lieu of the cap, in case it’s a head gasket problem causing bubbles that gather in the head that then cause a localise hot-spot which in turn causes rapid boil