1973 Cat 815 No Hydraulics

S/N: 91P00572 Came to shop with no hydraulic functions. Runs fine, drives fine. No blade or turning. I took off the hydraulic pump from the rear structure and ran the engine. The gear that runs the pump was not moving. What is the next best course of action? What should I take apart to inspect gears?

Hunter013 said: What should I take apart to inspect gears? Click to expand... It looks to me as though the engine will have to come out to gain access to that rear gear train.

Is there anything else you would recommend doing while we have the motor out?

Hunter013 said: Is there anything else you would recommend doing while we have the motor out? Click to expand... I only said that it appears as though the engine would have to come out to gain access to the rear gear train, not 100% guaranteed but that’s the way it looks. Depending on how many hours are on the engine you could consider anything up to and including a complete overhaul if you do have to remove it.

Engine will have to come out and flywheel will have to come off of engine to gain access

Wondering if a gear stripped? Sucks if you have to pull the engine if it's running good otherwise.

Ended up pulling the engine. Idler gear bearing between crank gear and auxiliary drive gear was blown up. We flushed all the shavings out of the oil, put new parts back in and put the motor back in. Hydraulics work now, but it sounds like something is clacking around in those gears. My guy who did the work is confident everything is tight. When we took off the rear auxiliary drive inspection cover, there was only the assembly oil on the gear and bearings leading me to believe that oil is not getting pumped to those rear gears. Does anyone know how to figure out where oil is supposed to get pumped to those gears or if we’re supposed to put oil in the bottom of the flywheel housing?

Hunter013 said: Does anyone know how to figure out where oil is supposed to get pumped to those gears Click to expand... The oil feed under pressure to the timing gears is supplied through extensions of the same drilled passages that feed the crankshaft. If you are getting very little oil to those gears then maybe the engine is going to have to come out again and get completely stripped down to find the cause. Something blocking a passage somewhere.?

Where would be a good place to check the engine oil pressure on that motor?

Hunter013 said: Where would be a good place to check the engine oil pressure on that motor? Click to expand... Unscrew the engine oil pressure switch and plumb something in there.?

I’m not sure where it is on this motor. Is it the lower right side of the second picture? To the right of the trans cooler?

I see a line of plugs along the block at that height. Pull out the one closest to the timing gears. You should get oil out of it with the engine stopped. Then plumb in a gauge. However even if you measure pressure at that point that is no guarantee that it's getting to the gears.

Are there any particular common issues in these motors that would cause no oil going to those gears?

Hunter013 said: Are there any particular common issues in these motors that would cause no oil going to those gears? Click to expand... My first thought would be a blockage of some sort in the orifice at the end of the drilling that controls the oil feed oil into the gear train. The book says

• "The output of the oil pump goes to the oil manifold in the cylinder block. The oil manifold is the source of oil under pressure for the engine and its attachments. All the timing gear bearings get lubricant under pressure from the oil manifold through connecting drilled passages" .

Could a guy blow some compressed air through the passage?

Hunter013 said: Could a guy blow some compressed air through the passage? Click to expand... The problem with that is that the passage that feeds oil to the timing gears from the manifold is only one of many. All the feeds to the crankshaft, camshaft, rockers, etc, etc all originate from that same longitudinal passage in the block. Blow air into it and hear air come out somewhere. How do you know it’s coming out where it’s supposed to come out, and if the flow rate is correct.?

What would normal oil pressure be?

Around 65psi maybe.

I forgot to update this. We ended up taking the motor back out and checking that the flywheel housing was getting oil from the blocks oil rail. Turns out there was a plug on the end of the block, so lack of oil caused the initial gear to blow up and caused all the clacking noise after we had put it back together. After talking with Cat technical for a little but, a little adapter sleeve P/N: 1S-1768 was the fix. Our mechanics swapped motors in this machine maybe 6 years ago. I assume they must have swapped flywheel housings without looking at the blocks oil feed line before slapping everything together. Lesson learned, always do a deep inspection into why the part failed.

That’s a hard lesson to stomach.