Bobcat 632 drive issue, I’m running out of ideas 🤔

[Needamow632]

Hello, I'm new here to the forum. Recently my dad and I bought an old 1977 bobcat 632. It runs great and everything worked but the hydraulics were weak.

I went ahead and replaced the hydraulic oil filter and copper filter. Now the arms and bucket work great with plenty of power, but the machine won't move. After lifting the machine off the ground I've figured out that the wheels move forward and backward but if I grab a tire they'll stop. They're very weak.

Our guess is there's air trapped somewhere, but I can't figure out how to get it out as it seems to be a closed system. I should also mention that the hydraulic oil is at the proper level. There were no metal shavings inside the filter so I doubt anything blew up inside. None of the hydraulic lines are leaking.

I'm new to the world of skid steers so any help is appreciated. I've got a landscaping business so I'd like to get this thing working and make some with it lol.

 

[Needamow632]

Bump

 

[Wayne440]

Have you done anything in the 2 days since your first post toward getting the machine to move?

 

[DakotaSkid]

My 632 is doing the same thing. No drive, bucket lifts and tilts fine.

Did you ever find out what was wrong with yours?

 

[needamow23]

My 632 is doing the same thing. No drive, bucket lifts and tilts fine.

Did you ever find out what was wrong with yours?

Hey recently had to make a new account. Took a break from working on the thing for a while. Got it started up today and there's still no power to the wheels. Only this time the bucket doesn't work either. I'm gonna read up on the manual some more, maybe there's a line going to the wrong place.

 

[cdmccul]

Did you rearrange the lines from the time it sorta worked?

I too am leading towards air on the system. I read in the forums of someone having similat issues after draining all hydraulic oil and refilling. They got air on it, and had to run it a little while, let the fluid foam, then let it sit to let the foam dissipate, then go at it again. After a while, it started working again.

I just don't remember how long that took our if that's exactly what they did.

 

[needamow23]

Did you rearrange the lines from the time it sorta worked?

I too am leading towards air on the system. I read in the forums of someone having similat issues after draining all hydraulic oil and refilling. They got air on it, and had to run it a little while, let the fluid foam, then let it sit to let the foam dissipate, then go at it again. After a while, it started working again.

I just don't remember how long that took our if that's exactly what they did.

Hey thanks for the reply. I took a picture of the lines before taking them off to ensure that they went back in their original place. Everything is good there. I just removed the port block, the block on top of the pump, and discovered that one of the valve poppets was in crooked. The other one was missing altogether. Definitely thinking this is part of the issue. I'm going to clean everything up and replace the missing parts. I'll come back here with an update when done.

 

[Ster1]

Did you really find a spool in the block had disappeared? And one got crooked? That's crazy That would certainly be part of the problem. Anyhow, I'm watching this thread, dying of curiosity. The manual is in my signature if you need it.

 

[needamow23]

I have the block sitting in a parts washer down stairs getting all the crud melted out of it. New parts have been ordered, when I get everything buttoned back up I'll return with an update.

 

[needamow23]

This is one of the valve springs from the port block. Noticed that one of the ends is broken off. I wonder if this was the initial cause of the machines lack of power? With a broken spring like this, wouldn't the pump have a hard time building good hydraulic pressure against the valve because it would compress too easily? Guess I'll find out when the new springs come in.

 

[Ster1]

WOW! That's nutty. Cool find there man. Yeah I'd say that's definitely a culprit Is that your charge pressure relief? I bet it is.

 

[needamow23]

WOW! That's nutty. Cool find there man. Yeah I'd say that's definitely a culprit Is that your charge pressure relief? I bet it is.

Looking at the diagram it was the spring for the neutral charge bypass valve. No idea what that means but it sounds important lol. But I'll check the charge pressure relief to make sure it's good. Thanks!

 

[needamow23]

So I got the new parts in. Assembled everything according to the schematics. Fired it up and still nothing.

At this point I'm wondering if this is a pump issue. I notice the main pump gets a little warm while the machine is running so I know it's working. I'm gonna get a pressure gauge to test for psi, if there is any. That way I can rule some things out.

 

[Ster1]

Just checking in, how did it go?

 

[foton]

did you ever find the rest of the spring?

 

[wwb]

Hi. I have an older Bobcat 843 and a few years ago I had a similar problem. It ran fine, and once in awhile it would just not drive ahead or reverse. The bucket worked ok, but it is on a different hydraulic circuit. Called a bobcat dealer and they advised of a screen style filter inline before the pumps. They cleaned that and it was better. I then used it and had an accesary connected and it started doing it again. I eventually took the pressure relief valve out and had it redone/rebuilt.(i was going to buy a new one but they were unavailable) Since I did that, it has worked great. So try the pressure relief valve in the drive circuit.