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660 piston pump leaking. A lot

B

Billybuck

Member
I rebuilt the pump on this tractor a few months ago after losing lift. Got my lift back and its fast, maybe too fast?
Had lots of planting work to do and got it done but maybe didnt notice there was leaking happening until I found low fluid level. Filled it up and started paying attention and found a steady drip per second or so from the bottom curve of the pump manifold. Thought maybe a problem with orings on installation so ordered new set. Installed and leak continued. Pulled, checked and reinstalled and still leaking. Two quad orings though not CNH.
Everything seems to bolt up true and properly but still pushing out from between front end of pump and manifold. No sign of crack in manifold or pump.
Can the system be over pressure causing this? I can test for that, and would that be an pressure relief or safety valve issue?
Other possibilities?
 
I'd keep looking at manifold seals. New
Holland seals are CONNB998A for the
pressure tube and CONNB997A, replaced by
47697560. They went to square seals as
opposed to O-rings as indicated in the
original diagrams. Expensive -$7.81 and
$6.47. There is a test for relief valve,
set at 2000 PSI, but the test in the
service manual is done with the lift cover
off. The safety valve is mainly to
protect against shock loads such as
hitting a bump with a heavy implement on
the 3PH. If you put those NH seal numbers
into a general search engine you will find
lots of YT discussions on manifold seals.
 
I thought of this too ... are you sure the pump itself is resealed after you worked on it? If you wipe it down then look carefully for where the fluid originates is it at the manifold interface, or from above (as in from the pump).
 
They have been usuing the square seals for 50 years. I would look at pump head gskt. These new gskts are something to be desired. For one thing are very thin compared to the ones from 20-30 years ago.
 
It is not uncommon to find cracked hydraulic manifolds resulting from incorrect or improperly positioned O-rings and/or overtightening of the nuts.

I always use the correct square cut CNH O rings, install grade 8 flat washers on the studs before installing the nuts, and DO NOT overtighten.

The hydraulic manifold is aluminum. If cracked, it may be very difficult to find the crack(s) by visual inspection. Thoroughly clean the manifold with gasoline or other suitable solvent and inspect for leaks
immediately after starting.

Dean
 
(quoted from post at 02:39:40 07/16/21) I thought of this too ... are you sure the pump itself is resealed after you worked on it? If you wipe it down then look carefully for where the fluid originates is it at the manifold interface, or from above (as in from the pump).
Click to expand...

This had occurred to me so I got it cleaned up quite well last time I pulled it off to look for cracks and watched it carefully on startup. The fluid appears to originate from the rear edge where the pump cover joins the manifold. It gets increasingly difficult to see as that edge disappears under the pump and to the invisible back side. Maybe Ill throw baby powder on it to help locate it.
You may be right on it originating from the pump as I recall questioning the gap between the pump cover and body (and posted about it here) on reassembly.
 
Thanks, I actually did the pressure test which led to the pump rebuild. Top cover can stay on and accessory plate gets flipped around over a self-made paper gasket to block pressure tubes.
 
I think you may be right. If the pump cover is leaking where it joins the body it would be very difficult to see until it got to where I can see it.
 
UD - could you offer a little more clarity in your reply re:pressure test? If it is too high and you send me to the pump, based upon other replies, Id just head there now.
Wont happen today though. Gotta go spew a couple more gallons of hydraulic fluid around the farm mowing buffers.
 
If you want to take a look at the pump
pressure why couldn't you remove the hex
plug from the pump and stick a gauge there
(I'm thinking quick and dirty, never
tried, but I don't see why it wouldn't
work).
 
Finally got around to this. Pulled pump, removed end cap and replaced gaskets. Had to remove the other end of housing to reassemble as piston springs protruding prevent reinstallation of the end cap. No big deal and immediately obvious the gap between end cap and pump housing was smaller. Reinstalled and leak is gone. Thanks for input
 
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