Cat 235 Final Drive Issue. Help please? :-)

[Bob Rolen]

We recently picked up a CAT 235 sn:32K855 to help us build a regenerative village in Vermont on 430 acres where you could come recharge, but I just discovered that it is leaking periodically out of a relief valve on top of the right final drive (8K2635) and that is DEFINITELY not very ecofriendly. In fact, it seems to even leak sometimes when the machine is off. Also, that side is missing one of the upper track carrier rollers, but it doesn't seem to really be binding, but could that be causing it? I just got another top roller but I have to figure out some way to drill out the sheared off stanchion bolts. Also, one of the tracks seemed weak and it didn't quite track straight... I think it was the same side but will confirm next trip up. When I pulled up the relief valve on the other final drive, there was actually a vacuum inside, probably from being transported up from RI.

I'm brand new to excavator maintenance but have the service and parts manuals and caps and gauges and was able to shim up the pressures today fairly well and don't think I went too high (3300 to 3600-3700,... and 4000-4100 for the tracks).

I found this thread which seems applicable... https://www.heavyequipmentforums.com/threads/cat-235b-final-drive-issue.93236/
and this one: https://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=crawlers&th=75618

and was wondering if it might be the brake assembly leaking and I just happen to have a set of Cat 235B brakes that were fully serviced,... but they have an extra plate in them and I'm not sure if they're compatible. Think they'd work?

Should I do this... "It can be one of 2 things,either the track motor is leaking more than the case drain line can carry away,or the brake is leaking.When you operate the travel pedal,it releases the brake then engages the drive. Maybe just unbolt the motor with the lines still attached and slide it away from the final,and have someone try the travel on that side while you watch. If it is the motor,it will leak around the shaft seal,if the oil is coming out of the final housing the brake needs to be resealed.You also may want to check the oil in the final and make sure it hasn't been overfilled by the leak."

...and how exactly do I do that?

So what are my odds? Brake problem? Drive Problem? Both? Something else?

P.S. (those aren't pics of the actual final drive but it looks similar... I'm missing one of the bolts on the relief valve cover (on both drives) and it seems like it was sheared off), I was half wondering if I could just plug that relief valve for now or press something down on it).

 

[Simon C]

Is there an o-ring under the oval cover with 2 bolts holding it on. Maybe o-ring is hard and brittle. just wondering. Don't have a parts book on it.
Simon C

 

[Bob Rolen]

No, it seems to just be a dust cover. The relief valve below it has a pretty weak spring and I doubt there is anything wrong with it.

 

[Vetech63]

Try a new cover oring. That area inside there is supposed to have oil there. Don't manufacture a problem that may not exist yet. Keep it simple starting off is all Im saying.

 

[Bob Rolen]

Try a new cover oring. That area inside there is supposed to have oil there. Don't manufacture a problem that may not exist yet. Keep it simple starting off is all Im saying.

I don't think there is a cover O-ring. It's just a relief valve and I doubt it's due to a weak spring. The other drive relief spring felt about the same and didn't have any oil in it. Any other ideas?

 

[Bob Rolen]

Yes, the track with the leak is the weak one.

 

[Bob Rolen]

And I plugged off the line to that brake and ran it in forward and reverse at various rpms and left and right for a good 5 minutes or more in small motions and it didn't seem to leak much more if at all. Does that mean I have a bad final drive? Are there anymore tests I should do before spending big bucks? Looking at the service manual, it seemed like a very daunting project to disassemble. Not sure what sending it for servicing to Cat would cost. Any thoughts my friends? Much thanks to you all.

 

[Bob Rolen]

Did I get that right or did less leaking mean that it is the brake that's likely the problem if it's plugged off. New troubleshooting plan is to check the magnetic plug on the final drive by the sprocket for big shavings; to reattach the brake lines and disconnect the final drive hydraulic motor and see if the track is locked up at all or if it free wheels which would mean it's likely not the problem... my guess is the final drive hydraulic motor is probably the source of the leak. I guess I could also probably remove the case drains and compare their leak rates. Any other thoughts?

 

[Nige]

see if the track is locked up at all or if it free wheels which would mean it's likely not the problem

You can "unlock" the track and most of the final drive from the track motor by following the procedure below. It may require some jiggling of the machine back & forth to get the assembly to separate. Both sides would be disconnected for towing the machine, obviously you only need to disconnect one side.


"To move the machine when the engine is stopped and not cause damage to the parking brake and motors, there must be a separation between the final drive gears and track motors. The cover (2) on the outside of both final drive cases should be removed. When nut (3) is loosened and turned counterclockwise, springs within pinion assembly (5) separate the final drive from the track brake and motor at point (A)."

 

[Bob Rolen]

Thanks Nige and everyone! I took the hydraulic travel motor off and the brakes and inspected everything and put a new used motor back on and I think it fixed all the track problems! Just need to give it a hard run for awhile to see if there is any leaking still. Next up is to get some more acetylene and oxy gas so I can get some stubborn sheared bolts out and to figure some way to dry out the hydraulic fluid using this sodium polyacrylate I bought on ebay. https://www.ebay.com/itm/153695664527 Maybe I will make some sort of sock for it and drop it down in the tank on a line.

 

[Acoals]

Dry out the hydraulic fluid? Why?

What is going to happen when the sock blows up and you can't get it back out of the tank?

 

[Tugger2]

Heres a sugestion on how to deal with your broken carrier roller bolts,i cant remember what the 235 mount looks like but this will give you an idea. You will need a welder , some 3/32 7018 rod a few heavy flat washers some nuts and maybe a bottoming tap to restore the threads.Sometimes it takes a few tries welding bolts out but you will get them. I would not consider putting stuff in your hyd tank ,drain it, flush it vaccum or pump it clean inside and get some new oil if the old stuff is milky.

 

[Simon C]

Have used the same rod and was successful. Have also used some special rod that doesn't stick to the sides and gotten some out even 1 inch down inside. Weld a little, Chip out with narrow screw driver with tiny hammer and blow slag out . Weld another bead and repeat. Time and patience are a virtue. Electronic helmut works very well also.
Simon C

 

[Tugger2]

My first try on broken bolts if they are broke off deep ,especially hard to access ones like overhead is a small piece of pipe .wrap the od of the pipe with electrical tape then weld inside that .It will protect the bolt hole sides or threads . If the broken bolt isnt seized this trick gets it usually. The bolts in the picture above were in a Vulcan pile hammer, broke long ago seized and some broke deep ,but all came out. Its amazing how the slag protects the threads and hole. Worked for Finning Tractor for a bit in the 70s and did a ton of broken roller bolts on track frames .

 

[Bob Rolen]

Well I got those bolt remnants out and the track carrier replaced... but even after replacing the hydraulic track motor (and replacing the brakes which fixed that leak at least), that right track was still acting weak... and it gets weaker the hotter the hydraulic fluid gets. Then I noticed the three outer bolts on the final drive were loose and leaking a bit, so I tightened them down. Then awhile later the left track started to get really weak and maybe quit altogether. Thinking this might be my last opportunity to make it to an extraction point, I began to laboriously inch my way up a hill, but then a hundred feet shy of my goal, the bucket cylinder end bolts shot off and a giant shower of fluid went everywhere. Later inspection revealed that a few of the bolts must have been broken quite some time ago. Now I have to decide wtf to do with this old Cat 235... Do I have two bad final drives? Is that going to cost over $10k to fix? Should I buy another Cat 235 for under $20k and keep this one for parts? Should I buy something newer and under 16 tons so I can move it myself?

 

[Bob Rolen]

Well I got those bolt remnants out and the track carrier replaced... but even after replacing the hydraulic track motor (and replacing the brakes which fixed that leak at least), that right track was still acting weak... and it gets weaker the hotter the hydraulic fluid gets. Then I noticed the three outer bolts on the final drive were loose and leaking a bit, so I tightened them down. Then awhile later the left track started to get really weak and maybe quit altogether. Thinking this might be my last opportunity to make it to an extraction point, I began to laboriously inch my way up a hill, but then a hundred feet shy of my goal, the bucket cylinder end bolts shot off and a giant shower of fluid went everywhere. Later inspection revealed that a few of the bolts must have been broken quite some time ago. Now I have to decide wtf to do with this old Cat 235... Do I have two bad final drives? Is that going to cost over $10k to fix? Should I buy another Cat 235 for under $20k and keep this one for parts? Should I buy something newer and under 16 tons so I can move it myself?

And when that left track got weak it started spilling out fluid from the final drive and those three outer bolts were loose. Tightening them down eventually reduced the oil pouring out of there but some was still some oil coming from elsewhere in the final drive. I need to look at a schematic to see what those three bolts connect to and what that might all mean. My guess is a bearing blew?

 

[Coaldust]

I remember Mr. Rolen when he first posted and introduced himself, his 235 and his Village. Good to get an update. Sorry to hear about the carnage. These old heavy machines seem like a good deal until they are not.

Homeowners buying old giant excavators?

Is this only viable for YouTubers looki ng to generate content? I have thirty acres on mountain side. My fantasy is to have giant excavator that works but is cheap.

www.heavyequipmentforums.com

 

[Bob Rolen]

I remember Mr. Rolen when he first posted and introduced himself, his 235 and his Village. Good to get an update. Sorry to hear about the carnage. These old heavy machines seem like a good deal until they are not.

Homeowners buying old giant excavators?

Is this only viable for YouTubers looki ng to generate content? I have thirty acres on mountain side. My fantasy is to have giant excavator that works but is cheap.

www.heavyequipmentforums.com

So true, but I did find two used final drives for 4k. However, I want to make sure that both hydraulic track motors are getting the right pressure at the motors but I dont know if there is a port where i can test that or how to make one. Anyone know? One of the tracks still has a little power, so i am worried that it isnt the final drives on that side and the problem is either in the motors, the swivel group, the main valve, or the pilot valve system. I already replaced the hydraulic motors on that side and it didnt given it that much more power. Can these final drives fail and still have a little power left?

 

[Coaldust]

It’s the same test ports as you use for checking pump 1 or pump 2. You have to jam a pin between the track frame and sprocket to stall the travel motor.

Probably gather more accurate data by checking the case drain of each motor.

 

[skyking1]

Here is my few cents. If you plan on working all over the 430 ares, you need a machine that either travels nicely, or goes on a trailer nicely.
Traveling was never a strong suit on the 200 series Cats. They are a Pain in the Ass when they were working OK, and this one is nearing 50 years old now.
My advice would be to not spend another nickel on that machine, and start looking for another big machine that is newer and functioning reasonably well. They can be had.
I searched Machinery trader for 1990 to 2005 machines near Burlington, just for kicks. There was a 50K 1992 Hitachi 400 that would walk little circles around the old 235, for example.
That is assuming you need a 400 class machine. You have not described the tasks at hand.
https://www.machinerytrader.com/listings/search?Category=1031&Year=1990*2005&sort=6

That's just my two cents but I have spent a few hours in 225,235,245 30 years ago, and not that big a fan of them. The track control system made me angry most of the time.