843 Bobcat Oil Foams in Reservoir

[EdTrefger]

I have a 1986 Bobcat 843 and I'm having a problem with the oil foaming over into the reservoir and overfilling out of the tractor. This problem started all of a sudden. I've changed both filters and on the service port of the long filter it tests at 200 psi and I cannot find any leaks. I have 2200 psi at the main pressure pump. Could the radiator be stopped up? Any help or suggestions would be appreciated. Everything else on the tractor runs fine I use a Melrose 2500 series hydraulic breaker with this Bobcat. Thank you, Ed.

 

[OldMachinist]

More than likely you have a small leak on the suction side of the hydraulic pump. Sometimes the leak will be so small that it will suck air but won't drip with the machine off. Start by tracing the lines from the suction side of the pump and check all the connection to see if any are loose or leaking.

 

[jmatt20]

More than likely you have a small leak on the suction side of the hydraulic pump. Sometimes the leak will be so small that it will suck air but won't drip with the machine off. Start by tracing the lines from the suction side of the pump and check all the connection to see if any are loose or leaking.

i had a similar problem with a 843 i owned ..near the tank is a line with a tee in it ,one hose or tube going the tank . the tee is a check valve ..cold weather bypass valve .. on my machine the valve got a little bit of something stuck in it and allowed the oil to run under pressure back into the tank ...something about the way it was squirting caused the oil to foam into the tank overfilling it with foamy oil. ..could be your problem ....

 

[Fishfiles]

i had a similar problem with a 843 i owned ..near the tank is a line with a tee in it ,one hose or tube going the tank . the tee is a check valve ..cold weather bypass valve .. on my machine the valve got a little bit of something stuck in it and allowed the oil to run under pressure back into the tank ...something about the way it was squirting caused the oil to foam into the tank overfilling it with foamy oil. ..could be your problem ....

the diagnosis you don't want to hear is the pump is cavatating and thats were the bubbles are coming from ------------ I remember a really weird foaming problem , somebody let a 2 ft long piece of clear tubing , probally from a fill tube on a five gallon bucket , fall into the tank , the tube went into the hose off the bottom of the tank and extended up above the oil level , as it tried to suck oil it sucked air , I doubt thats your problem

 

[EdTrefger]

the diagnosis you don't want to hear is the pump is cavatating and thats were the bubbles are coming from ------------ I remember a really weird foaming problem , somebody let a 2 ft long piece of clear tubing , probally from a fill tube on a five gallon bucket , fall into the tank , the tube went into the hose off the bottom of the tank and extended up above the oil level , as it tried to suck oil it sucked air , I doubt thats your problem

Thanks everyone, I have already checked the port block valve and nothing was in it. I will check out the lower hose and clamps and will report back in a few days. If anyone else has more ideas please let me know.

 

[EdTrefger]

Update: If you have this oil foaming problem in your crank case. Problem solved! An old mechanic told me to change the main hydrostatic pump even though it was holding good pressure, he said it was internally leaking causing the foam in the oil tank. At first I didn't believe him but I changed the pump anyway as a last option and it was the problem. All problems now solved and have had no more problems in 3 years. Just saw this original post and realized I had not updated it for others who might have this problems.