Engine oil goes into hydraulic system and tank...

Salem7 · Post by **Salem7** » Sun May 24, 2015 8:55 pm

420C. The hydraulic pump os located on the right side driven off the cam gear. After about an hour running about 1/2 quart of engine oil ends up in the hyd. tank. Eventually it over fills and comes out the breather-fill tube. For a long time I thought I was burning oil. Finally a light bulb came on and i put 2 +2 together.

I have searched for information on this with no luck. Anybody out there dealt with a similar problem? Any suggestions? I thought I would ask before taking anything apart.

Thanks.

wizner85 · Post by **wizner85** » Sun May 24, 2015 9:30 pm

Didn't even know that was possible, but I'd say a seal in your pump is bad since it bolts to the engine with 3 allen head screws?? and probably is lubed by engine oil....

Salem7 · Post by **Salem7** » Sun May 24, 2015 9:54 pm

Definitely possible. According to the service manual all that seals the drive shaft is a leather washer and an o-ring.

Does anyone know the parts availability for the pump, or a good rebuild shop?

Post by **Lavoy** » Mon May 25, 2015 10:05 am

When hyd pump seals fail, it dumps hyd oil into the engine, not the other way around. The hyd pump is running at 1000PSI, it is not drawing oil from the crankcase, virtually impossible.
I can rebuild your pump, or have parts available but I would guess it is not going to solve your problem.
Lavoy

wizner85 · Post by **wizner85** » Mon May 25, 2015 11:10 am

Something is definitely faningled on your machine.
Pics pics pics

Stan Disbrow · Post by **Stan Disbrow** » Mon May 25, 2015 11:15 am

Hi,

Yeah. I was going to say. But, Lavoy beat me to it.

Lots more pressure in the hyd pump than in the engine oil pump, so any leakage has to go from hyd to engine.

My M has this happen if I use Hygard, which is really rather thin compared to the 30 weight ND oil the M specifies. Does not happen with heavier oil, so no need to fix it just yet.

My 420 keeps the Hygard in, but I still use a hesvier oil as it gets pretty noisy with the thin stuff.

I really can't think of a passage for engine oil to get into the suction side of the hyd pump...Unless...

...the hyd suction line is plugged and it draws a partial vacuum and so literally sucks the engine oil past the hyd pump driveshaft seal.

That would push engine oil thru the pressure side of the hyd and so into the hyd sump tank....

There would have to be a suction pressure to get the engine oil out, I really do think...

Stan

Salem7 · Post by **Salem7** » Mon May 25, 2015 11:44 am

The plugged suction line seems like a likely culprit. I will check it out and report back.

boler76 · Post by **boler76** » Mon May 25, 2015 1:22 pm

My 40c will do the same thing in very cold weather as it seems it is easier for the pump to suck through the seal than from the cold hydraulic oil, I just let it sit and idle for a period of time before I use it and seems to help, Doesnt do it in summer time, maybe your screen is plugged on suction from hyd tank?????

Salem7 · Post by **Salem7** » Fri Jun 26, 2015 8:26 pm

A quick report back. I drained the hydraulic tank and removed the suction tube to inspect it. The tube was clear, no obstructions. I refilled the tank with non detergent 30 wt oil, just bring it to the low level on the stick. I have run the machine < 1 hour, but there seems to be no problem and the level is staying the same. I will see what happens when I run the machine hard with some driveway work in the next month or so. Thanks for the input.

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Engine oil goes into hydraulic system and tank...

Engine oil goes into hydraulic system and tank...

Thanks for the replies.

engine oil in hydraulics

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