Cat 235 hydraulic issues

[Gman9700]

Thank you for letting me join, I have a cat 235 excavator I’m not sure of the exact year 64R00978 is the serial #, I recently acquired it from another mine who used it with slow hydraulics for years and they are SLOW unless the machine is ran at 100% throttle then it is still slow but it moves. At idle machine will hardly move I’ve pulled pressure from both pumps and had a reading of around 1600-2400 off of them and peaks at 3600-4000 when a ram was maxed out. I’ve opened what I thought was all pressure reliefs that could slow it down to a crawl but nothing is clearly wrong with any aswell verified they all had proper shims/springs according to the manual. I have no issue spending some money to keep the ole girl moving as it’s currently the backup for our small mining operation but would love to not need to run it at 100% for it to be able to work somewhat. If anyone’s had a similar issue with one I’d love to discuss it and what the remedy was as I am up against a wall with it. Thank you in advance for any help

 

[DustAndRay]

1600-2400 at normal operation is pretty low for a 235. My first thought is the pilot pressure circuit. If pilot pressure is weak, the main control valves won't open up all the way, no matter what the main pumps are doing. It's easy to overlook because most guys go straight to the main pumps first. Worth pulling the pilot pressure and checking it against spec before anything else.

 

[Gman9700]

1600-2400 at normal operation is pretty low for a 235. My first thought is the pilot pressure circuit. If pilot pressure is weak, the main control valves won't open up all the way, no matter what the main pumps are doing. It's easy to overlook because most guys go straight to the main pumps first. Worth pulling the pilot pressure and checking it against spec before anything else.

I’m sorry late night and forgot to add, pulled pressure from pilot system also and had around 480 psi peak while running 100% throttle

 

[Nige]

I’m sorry late night and forgot to add, pulled pressure from pilot system also and had around 480 psi peak while running 100% throttle

How does that compare to the specification in the manual.?

 

[Gman9700]

How does that compare to the specification in the manual.?

From what I’ve been able to find spec is 350-500 psi we’ve ran the pilot controls in a good bit to increase the pressure on them and we got a little more out of it with that but not anything significant

 

[Nige]

The "according to the manual" comment in your OP led me to believe you had one.
What exactly do you have.? A parts manual.?

If you don't have a Service Manual you really need one. The Cat Publication reference is REG01388. Here's a link to one (there may be others) on eBay

 

[Gman9700]

The "according to the manual" comment in your OP led me to believe you had one.
What exactly do you have.? A parts manual.?

If you don't have a Service Manual you really need one. The Cat Publication reference is REG01388. Here's a link to one (there may be others) on eBay

I’ve got it and I’ve found in some places it calls for 350 at partial throttle and 500 at maximum speed which checks with the pressure tests I’ve preformed. Another thought I had is the pump control valve possibly not giving the pump full stroke allowing it to make pressure but not giving me full movement speed due to reduced volume ? I’m currently in central Canada traveling home to visit family while the great north thaws out and looking for any ideas of what to double check once I’m back and running again

 

[Coaldust]

This comment stands out to me. “ and they are SLOW unless the machine is ran at 100% throttle”.

I’ve been called out to diagnose performance issues on excavators many times, just to discover the operator is running the machine at 1/2 speed. It’s like “Dude, spin her up and it will work fine”.

The hydraulics are designed for 100% high idle. It will act slow and weird if it’s not at high idle. You might want to check the engine speeds with a tach. It might be something simple as that.

What do you guys say in Canada? …… give'r. Yup. give'r. Spin her up. Don’t hold back.

 

[Gman9700]

This comment stands out to me. “ and they are SLOW unless the machine is ran at 100% throttle”.

I’ve been called out to diagnose performance issues on excavators many times, just to discover the operator is running the machine at 1/2 speed. It’s like “Dude, spin her up and it will work fine”.

The hydraulics are designed for 100% high idle. It will act slow and weird if it’s not at high idle. You might want to check the engine speeds with a tach. It might be something simple as that.

What do you guys say in Canada? …… give'r. Yup. give'r. Spin her up. Don’t hold back.

I wish that was the case but I’ve run a few of these old pigs and this one has to be run TIGHT for it to have any decent speed but I’ve also found an adjustment for the pump signal pressure that I’m wondering if it could be part of the issue and the pumps might not be reaching a full stroke ?

 

[Coaldust]

Ok, then. When was the last time you looked at the hydraulic filter? These beasts are far beyond getting long in the tooth. I’d probably check the pump case drain before going much deeper and see how healthy the pumps are.

 

[Gman9700]

Filters were done when I received the machine around September of last year when I started into diagnosing this issue, I didn’t do pump drains to check them but it had the fluid done within a few hundred hours of me getting it. I was told it was just a drain and fill when I pulled filters they had a little bit of material on them but from what I’m aware from the previous owner it should’ve had a few thousand hours on those filter

Ok, then. When was the last time you looked at the hydraulic filter? These beasts are far beyond getting long in the tooth. I’d probably check the pump case drain before going much deeper and see how healthy the pumps are.

Gonna try and adjust the pump signal pressure and see how it responds to that and keep gauges on it, if that doesn’t work I will pull drains and empty the system and start going through every relief replacing springs and seals

 

[Nige]

Try Coaldust’s suggestion of looking at the pump case drain flow before you go adjusting anything would be my suggestion. If it is outside specifications then you immediately know that you have a pump problem that no amount of adjustment will fix.

As soon as you get into adjustments the point will rapidly arrive where the adjustments will be so farked up that nobody will have the faintest idea where they should be. Don’t ask how I know this…..

 

[Coaldust]

Why did I think you were in Canada? I’m getting my broken 235 threads mixed up. It’s only 11:35am Alaska time and I haven’t made the noon time switch over from coffee to liquor, yet. I’m still mostly sober.

Welcome to the HEF. It’s great to have another Alaskan on-board. My office is located in the MatSu, but I travel the state fixing things.

 

[Gman9700]

Why did I think you were in Canada? I’m getting my broken 235 threads mixed up. It’s only 11:35am Alaska time and I haven’t made the noon time switch over from coffee to liquor, yet. I’m still mostly sober.

Welcome to the HEF. It’s great to have another Alaskan on-board. My office is located in the MatSu, but I travel the state fixing things.

Yessir thank you ! I’m currently just outside Edmonton headed south to visit family for a week waiting on the thaw to let loose of the valleys ! And yeah I did my best to search them but nothing seemed to quite fit what I’m chasing with this machine

 

[Nige]

If you’re not going to be back to the machine for a while then my best suggestion would be to read the Systems Operation and Testing/Adjusting sections of the service manual for the hydraulic system over and over until you can repeat them in your sleep. There’s no substitute for that. Once you understand exactly how the system is supposed to operate it’s far easier to get into diagnosing it.

 

[Coaldust]

Let us know how your season goes. Speaking of gold mines, I just did some work for the Volcano Creek reclamation project. I didn’t realize how large of an a gold operation that was. Fun stuff.

 

[bccat]

Balls to the walls, let her rip, pedal to the metal, that’s all I got