As the title indicates, the problem in question is a D5C 3MK LGP with 3204 engine which is slowly making hydraulic oil. It has not been overfilled, has not been topped up with diesel by mistake, or anything normal like that. So I presume it is coming from the engine through the seal on the hydraulic pump? The engine oil use ranges between about 10 to 20 hours per litre of oil depending on how hard it is worked. I had been presuming it was burning the oil but now I am thinking some of it may be going into the hydraulic system. I guess the engine oil use had increased a little lately, but I hadn't really thought much of it until I noticed the hydraulic tank was over full. The hydraulic oil is going slightly darkish. So is it common for a pump seal to leak engine oil into the hydraulics? Will a putting a seal kit in the pump normally rectify it? Is it possible? Or is it something else causing the problem?
Gear pumps have a drilling from behind the shaft seal to the suction side of the gears to prevent oil pressure building up and leaking. A bad seal could allow engine oil access to the drilling. Later Bob
Thanks for the reply Bob. Has anybody else had the same thing happen? Is there anywhere else on a D5C that the hydraulics can gain oil? The transmission controls seem to be a self contained system so I can't see that it could pick up any oil from there, the main hydraulic pump is the only place that I can see would do it. The hydraulic system is pressurised but I guess it could suck in some engine oil through a bad seal when the system is cold and hasn't built up any pressurisation yet. I guess I will have to put a seal kit through the pump and see how it goes.
It was a worn lip seal on the shaft of the hydraulic pump. The new seal has solved the problem, but the shaft had a slight groove worn in it, so it may not last all that long. However it is fixed for now.
Any issues with the engine oil contaminating the hydraulic oil and causing too many impurities in the hydraulic oil? No hydraulic component failures? Andrew
No failures as yet, it is a one operator machine so it was caught early, I don't think much engine oil got into the hydraulics. The hydraulic system is very simple with just a single section gear pump.