Yanmar 186D shearing hydraulic woodruff key

[suburban99]

I recently replaced my Hydraulic pump on my 186D. (external one that pressurizes loader and 3 point) I cleaned out all the fluid and refilled. Changed spin on filter. New pump makes a slight noise. It operated the loader and 3 point ok, but an hour later it sheared the woodruff key on the pump shaft. I am thinking the relief valve is blocked/stuck or out of adjustment. Pump I removed was probably original to the tractor. Question is where is the relief valve? How to access it. And where to put a gauge on it to set the relief valve. I have the 186D parts and service manual but it has no service info for hydraulic pump. Thanks

 

[winston1]

I would guess you are deadheading somewhere. Your pump does not have a relief valve. Your loader valve will have one and your 3 point will have one. If you have any quick disconnects on your lines you might want to double check them assuring they are working properly. Don't know how your plumbed so don't know where you could put a pressure gauge.

 

[California]

I added a gauge just before the divider block, on the YM240 when I replaced the loader valve. I intended that as temporary but it's useful to prevent the loader from drifting upward at times, so I left it there. Now I wish I had put it under the loader valve where I could see it better.

Here's the post where I described that. There might be something in it relevant to this present issue.

In particular, I discovered the gauge occasionally gets pinned hard, 4,000+ psi, the sum of the 2k relief valve on the loader and on the 3-point. Apparently under a condition where both are unavailable.

 

[suburban99]

What does this screw valve do?

 

[California]

What does this screw valve do?

That valve can be closed to lock the 3-point up, when you need to work under a mower or something. For normal operation its left wide open. Looks like yours is missing the T-handle at the tip of the shaft. Maybe use Vise-Grip pliers to assure its wide open since that could be the cause of your overpressure problem. Then leave it wide open. (counterclockwise).

And this front valve is different from the drop-rate valve you can adjust for slow gentle descent of a heavy implement. That valve is on the side.

 

[oldnslo]

I added a gauge just before the divider block, on the YM240 when I replaced the loader valve. I intended that as temporary but it's useful to prevent the loader from drifting upward at times, so I left it there. Now I wish I had put it under the loader valve where I could see it better.

Here's the post where I described that. There might be something in it relevant to this present issue.

In particular, I discovered the gauge occasionally gets pinned hard, 4,000+ psi, the sum of the 2k relief valve on the loader and on the 3-point. Apparently under a condition where both are unavailable.

If you are pegging the gauge at over 4,000 your relief valve is plumbed incorrectly. The system relief must have the tank connection directly to tank. Sounds like yours is connected to down stream pressure.

 

[suburban99]

That valve can be closed to lock the 3-point up, when you need to work under a mower or something. For normal operation its left wide open. Looks like yours is missing the T-handle at the tip of the shaft. Maybe use Vise-Grip pliers to assure its wide open since that could be the cause of your overpressure problem. Then leave it wide open. (counterclockwise).

And this front valve is different from the drop-rate valve you can adjust for slow gentle descent of a heavy implement. That valve is on the side.

The original pump froze as I had water in the tranny/hydraulic oil. Changed the oil and filter and pump. Because this valve was stuck and the pump had more pressure (new) it sheared the first key. Replaced the key and cleared that little valve and all is good so far..

 

[California]

If you are pegging the gauge at over 4,000 your relief valve is plumbed incorrectly. The system relief must have the tank connection directly to tank. Sounds like yours is connected to down stream pressure.

I hear you but it's plumbed with the loader in series ahead of the 3- point as recommended in Yanmar-USA's original Operation Manual. The dealer-installed loader has worked that way for 40+ years now.

The only return to tank is a vent somewhere under the 3-point piston assembly, there are no openings available. Some aftermarket loaders have a T above the dipstick/fill and a longer dipstick but that's rare.

What's going on here is the 3-point backhoe is so heavy that the relief can squeal driving over a bump. There's no back pressure until the 3-point leaks down a little, then that weight/pressure is pushing back. That's when pressure starts to rise. Pulling the 3-point lever to Lift at that point is when the pressure soars. Not ideal but so far in the 20 years I've owned it, it hasn't sheared the pump key.