1066 Hydraulic pressure bleeding off

[pembinapasture]

Good Evening All,
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(video of pressure test at back outlets)
I have a 1066 that the hydraulic pressure will start at 2000 psi then bleed off to 1500 psi even when the valve is open. Just wondering where to start with more testing. Is it a pressure relief valve issue, or a valve body, or the pump?

 

[caterpillar guy]

Now are these figures you present to us at rated speed and oil warmed up (operating temperature ) or just started to go hitch up. Does make a difference. Pressure dropping off sounds like a leaking line internally or a cracked casting to a valve or housing like the pump. Or blown o-ring. This could and I would suspect an o-ring or gasket in the MCV since a valve would tend to either leak all the time or not leak. Though an o-ring could leak off with pressure at the start then leak down immediately. I pump would either make volume with little pressure or pressure with little volume. So That is the reason I would doubt the pump unless it continued to drop or volume was reducing as well. Valve could be a culprit though they usually just sag or leak by so oil is showing some place. relief valve would leak off internally as it is in the main cover on top of the rearend. I supose a broken spring could make pressure then leak off once the pressure is called for. Though again I would suspect a relief valve to not reach pressure and stay low all the time. I believe you have a pump problem or an MCV leaking through a spring or gaske/o-ring.

 

[pembinapasture]

The numbers were at temperature and the rpm’s in the middle of the range 1500 rpm +\- . The tests are on the main hitch pump ( the 1066 has two pumps the mcv and hitch pump) and there is no 3pt on this tractor. I have pulled the pump before the test and I have put new orings and gaskets in as I thought that might be the problem. I like your thoughts on a leak in a casing or valve body. I’m going to check on the other outlets and see if there is a difference. Also try and get a pressure right at the pump.

Thanks

 

[caterpillar guy]

That plug on the pump casting the pump mounts to would get a direct pump pressure with fittings to get from it as an o-ring plug to a gauge. Yup they do have 2 pumps just like the 06and56 series and are the same tractor except for sheet iron and fancy dash. The pressures are a bit higher than the 06 series. There is only one more on it unless somebody added a third one it has the front cultivator couplers under the platform. If it has the third valve I would like to see pictures of how the lever is put on it since it only had provisons for 2 valves and a third would almost have to have a lever on the left side. I suppose the filter could also be sucking a bit of air causing it to drop when you call for oil . Might try the 5 gallon over full for a cracked internal line . IF it is sucking air I would think it would lose prime on the lift pump for the rear remotes and 3point. I would also think since that filter is for both systems it would affect the steering and brakes and such if it was sucking much air.

 

[Mrfred54]

Easiest thing to check,( change ) in your situation would be the relief valve. The relief valves for the 66 series are the same as for the 06,56, and 86 series. Pressures do differ for each series. A loaner valve from another tractor would be the way to go for testing, before you buy one. Some of the valves are stamped with their pressure. Some leak down is allowed because the auxiliary valves are machined fit for the spool and through normal wear over the years you will have some pressure drop. A cure for it is alternating check valves mounted in front of the outlets. Can you specify what lead you to check the pressure? This would help to diagnose

 

[pembinapasture]

I went looking for the problem when the tractor was struggling to lift the discbine and won’t turn the hay bale in the hay processor when it had the winter before.

The pressure relief valve is probably the easiest and cheapest option to start with. The salvage place has used one for a decent price but might just fork out for a new one.

 

[Mrfred54]

In the bore where the relief valve goes is a oring, make sure it is ok or just replace it. It is hard to get at

 

[pembinapasture]

So the valve rest up against it, or slide into it? I’ll go check my manual. Thanks

 

[Mrfred54]

The valve will slide thru the oring when you install it