Oliver 770 hydraulic issues

We have a Oliver 770 that we replaced the hydraulic pump and base plate.
The base plate was cracked. Reassembled and we have constant pressure
On the hydraulic outlets on both sides when the levers are in the neutral position. PSI is around 1400 right at the start up and doesn't go down.
It doesn't take long for the system to get hot. Any help is appreciated.

This post was edited by 195 on 08/29/2023 at 08:35 pm.

Did someone tap into the power beyond port and then mistakenly
block it off?

The power beyond plug is on the left side towards the front I believe.
That has the plug in it yet if that's what you mean. There is a
Plug under the reservoir towards the front and center of the base plate.
I'm not sure what that is for.

The power beyond plug on the left side is the front one. Two inches in is the plug that needs to be removed. The one in the base plate in the center needs to stay as is is there from machining.

Tramway is most likely correct.

This post was edited by Centerplate on 08/30/2023 at 04:25 am.

Ill answer your other question. Olivers have constant
pressure on the remotes , you need couplers that you can
release pressure to connect and disconnect hoses.
Shutting the tractor off and wiggling the levers doesnt
relieve the pressure.

I don't want to contradict super99 as he's probably a lot smarter than me on these - especially since I haven't been around this series of Oliver since I was almost a kid - but the remotes definitely shouldn't have constant pressure on them. At least, not constant pressure from the pump. With that open system constant pressure on the remotes would mean you're not flowing through to tank, and you'd be blowing by the relief constantly, creating the heat the OP noticed and wearing out the system in short order. Would also mean any cylinder you hook up would constantly be pressurized/moving.

It may be that if the valves/spools are new and well fitting and if and everything's sealed up well, when the valve's shifted to Neutral there may be a little residual pressure in the remote lines that's not bleeding back, making it hard to connect the remotes. I'm guessing that's what super99 is referring to. But from what the OP says it sounds like the OP has another issue.

A little clarity might be required: where are you seeing the 1400 psi? If at the remotes, the valve spool must not be returning to neutral and flowing through to tank. If the pressure is up-stream of the valve, however, and no pressure at the remotes, it's probably an issue with the PB as others have mentioned. I think these are nominally 1000 or 1100 psi systems, so if you're seeing 1400 psi it's certainly blowing over the relief and explains your heat.

There have been a few posts on the Oliver page about these spools not shifting, either due to a stuck spool or a linkage issue. There was one a couple of months ago that was really good, but I can't find it now.

Those are my thoughts at least, but I also don't pretend to be an expert. I'd post this on the Oliver forum below - there's some really good Oliver hydraulics folks who watch that page.

I wouldn't run it until you check the seat
on the pressure relief valve. We had a
Super 88 that happened to. We had cracked
the center plate and replaced it. Promptly
Cracked another one, took the hydraulic
unit back off and took it to the White
dealer. They looked it over and found the
Seat had backed out of the aluminum
housing. They tightened it up and staked
it in place. It is a hex plug on the right
rear base of unit. Those center plates
aren't cheap. Just something to check.

Hello 195 welcome to YT! I know nothing about the specifics of an Oliver hydraulic system but just a question or two and comment based on general hydraulic application knowledge. In order to eliminate some questions about what is going on, if you put your test gauge into one remote and start the tractor and touch nothing the gauge will go to 1400? Or do you have to move the remote lever to get it to show the pressure? If you move the lever to pressure the opposite coupler of the pair does that drop the psi of the gauge off to zero or nearly? If it does not will stopping the engine and cycling the remote lever drop off the pressure? If not you have some kind of a quick coupler mismatch that is holding the pressure to the gauge. Are the remote valves you are talking about the original equipment valves or added on valves. The only thing I can think of is that if hoses are involved between the pump valves then what has possibly happened is you have plumbed pressure to the return side of the remote valve. Then to allow this to happen the valves were not designed to hold pressure back from the return side and are being pushed off their seats allowing the work ports to be pressurized.

We removed the plug on the left side and sure enough there was another plug in there. We will try it tomorrow to see if that fixed the problem.
I sure it did.........I hope.