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CAT 305 hydraulic oil heating problems

Discussion in 'Excavators' started by Stevensev, Sep 22, 2020.

  1. Stevensev

    Stevensev New Member

    Sep 22, 2020
    Surrey, BC
    I have a 2004, CAT 305 CR and I am having a problem. The machine runs smoothly for approximately 1.5 to 2 hours and then gradually looses power to the point that the engine stalls when performing lightly loaded hydraulic movements. I can prevent it from stalling by eliminating the load. It does not seem to matter which functions I am performing, aka moving the tracks, boom, blade etc. The hydraulic oil seems to be hot, but I have not taken a measurement and am not sure what "normal" is.

    There is sufficient hydraulic oil, I have not changed any of the hydraulic filters, air filter or oil filters yet. There is sufficient coolant and the radiator becomes quite hot to the touch, but there is no sign of overheating from the guages aka the water temperature is always in the middle of the green bar dial. The thumb hydraulic control is sticky, as in I need to make sure the left foot pedal is in neutral or else the valve is continuously on. I think the valve needs to be replaced or repaired.

    I am a novice. My hypothesis is that the hydraulic oil is not being sufficiently cooled by the radiator and becomes too hot causing power issues. I only think this due to the fact there are two low pressure lines from the coolant pump, which seem to go towards the hydraulic system ( I assume there is a radiator for the hydraulic oil??), which are not hot at all. Thus maybe there is a blockage or the fluid is not circulating through that circuit. Any help would be much appreciated. IMG_20200920_183738.jpg

    Attached Files:

  2. Nige

    Nige Senior Member

    Jun 22, 2011
    At some point a Serial Number will assist in the location of the appropriate technical information.
    First thing I would suggest is to get hold of a good non-contact infra-red thermometer and take some temperatures. Radiator inlet and outlet hose temperatures would be interesting.
    mg2361 likes this.
  3. Jgm

    Jgm Well-Known Member

    Jan 30, 2019
    There are numerous things that could cause overheating, main thing to take in consideration, is your oil cooler free, check your control levers when both sticks are in the middle, do you have any play, at least 1mm play, hope this helps
  4. Per Eriksson

    Per Eriksson Senior Member

    Oct 24, 2007
    I have never had a mini stall or overload the engine with the hydraulics, it has always been engine related like fuel starvation so start with a fresh set of fuel filters and blowing some air through the suction lines from the tank.
  5. 4bz

    4bz Member

    Mar 22, 2020
    Something similar happened to my hitachi zx55. The machine would run fine for quite a while, then start missing and even stalling under load. I found that there was water in the fuel tank, and the fuel tank drain was higher than the bottom of the tank, (on the hitachi it drains from the side, not the bottom) so it could not all be removed. Lots of wheelhouse motion (mostly left and right swings) would cause a blob of water trapped in the tank to move, and spill over into the fuel pickup. The water would get churned up into tiny bubbles as it went through the fuel pump and cause the engine to miss and stall. Parking the machine for about 20 minutes would allow the water to come out of solution again, and the cycle would start all over. Draining and replacing the old fuel helped a lot, but there was still water in the tank that could not be drained. I believe the long term fix will be the installation of an actual water separator on the fuel line - the hitachi only has a simple gravity bowl fuel filter, and it will not stop the circulation of water when the droplets are really small.