Hydraulic lift relief valve leaking

[garydee]

Having a problem with my 1641 hydraulic lift relief valve leaking. Fluid runs out from under the large bolt on top of the block where the hydraulic lines are connected over the hydro pump.

Is there a spring and a seal under the bolt head that relieves pressure? I haven't taken it apart yet as it is a little hard to get to. When I restored the tractor a few years ago, I never thought to remove the bolt to check on this little item.

If anyone knows about how this is supposed to work and how to fix it if it is not working, your help would be greatly appreciated!

Cub Cadet transmission fluid is nearly $20 a quart, so I need to get this little problem taken care of pretty soon!!

Thanks for your input!

[darkminion_17]

Which part is it in this picture?

https://www.cubcadet.com/en_US/conte...4905541e7140/y

[garydee]

Not the charge pump...the part I am referring to is a coupling block (about 2" x 2" x 5/8") with 2 hydraulic lines from the lift valve going in and 2 lines coming out going into the pump.

There is a hex head bolt about 5/8" diameter on top of the coupling block. It is leaking from under the hex head bolt where it goes into the block and running down, making a big mess!

Tried to take a screenshot of the diagram, but no luck attaching it for you to see what I an referring to. Hope the description helps.

[darkminion_17]

This diagram will help. Looks like #27

https://www.cubcadet.com/en_US/conte...f6e99b95f457/y

[garydee]

YUP!! #27!!! That be da part I'm havin' da problem with...

Does the part that looks like a hex head bolt on that coupling do anything to relieve pressure in the lines? Or, is it just something to bleed air out of the lines? If it does function as a relief valve, how does it work? Has anyone ever taken one apart to discover how it could bleed off hydraulic pressure in both the send and return lines?

Help is appreciated!!

[ironman]

Check this thread, post #8....
https://www.onlycubcadets.net/forum/...ad.php?t=44762

[Oak]

I've not had one apart but I would think that there is a spring and ball in there to dump the pressure to the return line when you hit the pressure limit. I would also assume that there is an O ring on the bolt to seal it. I don't see in the service manual where it shows a breakdown of the internal parts of it either.

Here is the link to the free service manual. Type in 1641 for the model and 1 for the serial number.
http://manuals.mtdproducts.com/mtd/D...r2=2&number3=3

[garydee]

Great information guys!

So, it's the hydro relief valve that relieves pressure in the pump internally, through the hydraulic lines. It's not supposed to leak out under the pin or hex head to relieve pressure and make a mess!

Knowing what I have learned from everyone, I'm going to take it apart, clean the valve and reinstall it with a new seal under the pin and hope it doesn't leak again!

I'm really glad my leak isn't with the hydro pump or transmission to pump seal. I have a little bit of a mess to clean up but nothing like that shown in some of the pictures. It's amazing how the hydraulic fluid gets blown around by the fan and the wind and gets all over everything in the tunnel.

My 1864 is out of service due a bad coil so I have been using a 1641 that I restored for grass duty. I sure miss the power steering on the 1864! The moderate drought up here in western NY will give me a little off time cutting the grass and a little more on time doing some fixing.

Thanks to everyone who shared their knowledge to get to the bottom of this problem. That's what makes the Only Cub Cadets website great! Great people willing to share what they know to help other Cub owners.

[garydee]

I did a little work on the relief valve at the top of the coupling block for the send and return hydraulic lift lines. I was able to retrieve the spring and ball (made of steel) with a magnet from the recess in the valve, however, I was not able to retrieve the copper piece which connects between the spring and the ball. I used a digital inspection camera to look into the recess prior to cleaning it out and found the copper piece. As I was unable to remove it, I decided to simply remove the block to clean and reassemble it on the bench.

Here are some pictures of what I was dealing with when I took the valve apart. I made sure to replace the o ring and clean and lube the parts before assembly into the housing. I had to assemble the valve parts upside down to keep the ball in just the right spot (not falling off) from its place on the removable valve pin.

If you could retrieve all the pieces from the housing while still mounted, it might be possible to assemble the valve if you used a strong magnet to keep things in place. I found it was easier just to remove the housing and clean things up before assembly. It was easier to replace the o ring as well.

I never thought to disassemble and clean/replace the o ring etc. on this valve coupling when restoring my Cub Cadets. I guess my thought at the time was, "if it ain't broke, don't fix it"!

Guess I learned my lesson!

Just to be sure the valve assembly is put together correctly...the spring goes inside the threaded hex head pin with the copper cap (concave side out) over the spring making a seat for the round steel ball. Assemble with the ball facing up and the hole for the housing down. My pictures don't show the correct sequence for the assembly. I have a picture showing the correct order, but somehow it didn't get attached...be sure to replace the o ring!!!

[ironman]

Great info and thanks for sharing.
You didn't say, but assume the leak is fixed??