Is this the relief valve? it's leaking

[irwin]

Was having a good day. The backhoe was working great!


Dug one 5 foot hole for sonotube and base..then saw the puddle under boom. Found the leak at the hydraulic cylinder lower banjo fitting. NAPA had the brass washers got six, just in case, removed fitting-scraped off paint covering washer seat on cylinder .. back to work on hole number two. Ten minutes later bottom of boom is dripping again.. this time it's the upper fitting, much harder to get at, but all done and back to work.

Ten minutes later under operators station is a growing pool of hydro fluid. With my wifes help we found the leak from here

in center of picture. is this a relief valve? or something else? it has a copper washer, under what appears to be a cap with a hole in the center, the hole is shaped for a 10mm allen wrench.. and under this I can see a torx bit screw head? It was late so only had time to drive 60 miles round trip to shop for T50 torx bit and 10mm allen wrench. Will take it apart in morning.. question will a spring pop out, a BB drop in the dirt? What am I in for?

This a picture of hydraulic control manifold, on bottom is the part in question

 

[john_bud]

Your pics are about 1" by 1.5". These eyes ain't gonna see nothin ....

Can you post larger (old folk friendly) sized pictures?

jb

 

[KJM]

Your pics are about 1" by 1.5". These eyes ain't gonna see nothin ....

Can you post larger (old folk friendly) sized pictures?

jb

PLEASE!

But I don't think it is a relief valve! All the relief's I've seen are at the end of the valve stack and have an allen key screw with a locknut and then a cap nut (acorn nut) on the top. They normally stick up.

All the things on my valve stack that have a 10mm allen key are caps that cover bits of the spool mechanism, and I haven't had the need or gumption to take them to bits Yet.

Not sure what you'll get when you remove the bits.. Pressure reliefs are simple - they have a spring which pushes on a poppet-like part. The spring pressure is relieved when you unscrew it, so there is no "spring surprise"[TM].

Cheers
/Kevin

 

[irwin]

sorry for the wee photo size, tried to do a thumbnail and have it enlarge like I've seen 3RRL do.

the round cap in center is leaking from area on side thats missing paint, it's at a copper washer under the cap.

Heres another slightly different view

and the back of the controller.. the leak is at bottom of picture. Thanks for taking a look....
tim

 

[KJM]

I'm not a hydraulics guru, but I'd pick the big sticky-out-bit on the bottom as the relief and that one as a plug. But I could be wrong! Is that the input end of the manifold? (If it is the opposite end, it might be the hole for a power beyond sleeve).

Hope this is helping?
/Kevin

 

[irwin]

I'm not a hydraulics guru, but I'd pick the big sticky-out-bit on the bottom as the relief and that one as a plug. But I could be wrong! Is that the input end of the manifold? (If it is the opposite end, it might be the hole for a power beyond sleeve).

Hope this is helping?
/Kevin

Thanks Kevin: Thats what I thought also..but I haven't yet studied backhoe hydraulics so am hoping to avoid losing some tiny, weeny, bitty piece that'll spriiiinggg off when I loosen this cap part.. I really hope it's another painted mating area leak. and not a micro crack.

I think it's the return side, but will have to check again when I walk back out there..(hope I carry ALL the tools I'll need - time consuming to keep walking back to workshop, and too much hassle to run tractor back)

Is the relief valve on return side of manifold?

Thanks ...tim

 

[KJM]

(Insert "I'm no hydraulic expert disclaimer here")

Reliefs are normally on the input side - they bypass into the return line - protect the controlled equipment from overpressure situations.

There are normally some extra ports on the output end (maybe that should read 'other end'?) of the manifold for power beyond, return lines etc. Your big plug looks 100% like the plugs my new loader valve has on the output side for power beyond. On my loader valve, the seal on this is the copper washer. So your fix might be as cheap as a 5c washer - here's hoping!

Cheers
/Kevin

 

[irwin]

Okay, it's on the input side. The other side has two caps like you said.

Just applied 90 psi and it didn't budge. seems a little wimpy so not feeling good about applying more press.. anybody know if heat will damage the manifolds insides? like MAP gas torch..I might just finish the other three holes with it leaking ya know before I break something

 

[john_bud]

Okay, it's on the input side. The other side has two caps like you said.

Just applied 90 psi and it didn't budge. seems a little wimpy so not feeling good about applying more press.. anybody know if heat will damage the manifolds insides? like MAP gas torch..I might just finish the other three holes with it leaking ya know before I break something

NO~! Don't use heat on the valve, unless you enjoy rebuilding expensive hardware. You will melt o-rings and possibly do other "bad" things. Certainly you could carbon up the passages if you over heat the hydraulic oil.


I wonder if your relief valve is set correctly or is stuck closed. It is abnormal to have so many leaks. Unless the unit is new and the assembler didn't tighten up stuff correctly.

Oh, it looks like a power beyond plug location. If so, it will have o-ring seals on the backside of it. Some low price suppliers (China) will epoxy threads to hide casting flaws. Hope you don't have a unit like that. A 6 spool valve is $100-150 per spool... Looking at the photo of the hex location, it appears like your tool was slipping. Is that a metric hex?

jb

 

[3RRL]

irwin,
I'm no hydraulics expert either but I think KJM has it nailed.
I'm attaching a couple photos of a 3 spool valve, a little different than yours.
Look at the valve on the right where the pressure gage goes to it. The pressure relief valve is just to the right of the lever. It looks just like the one KJM pointed out on your valve, and I think he is correct. That is also the INLET end of the valve.



This one shows the the outlet end of the valve. The power beyond is the large top one and the return to sump is below it. On my valve, both those are larger than the other inlets/outlets. that may help determine which is power beyond and return to sump on your valve. Again, they are both on the outlet side (usually). So I think the plug you took out may not be the power beyond, especially if you find it on the outlet end of your valve.



Here is another photo that clearly shows the power beyond. It is the top one, which has a bushing that goes into the valve and the hose goes into that. That bushing can either be a plug when power beyond is not used, or a bushing like in my case, which allows fluid to pass through under high pressure to power another valve down the line.



I hope those photos help a little?