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2008 Cat 236B2 Drive Motor(s)

pbd05

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Sep 12, 2021
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I recently bought the machine at auction (sight unseen of course) which was described as having a brake issue, but ran ok otherwise. The machine looked relatively clean with a little over 6900 hours on it so I took a chance.

When the shipper picked the machine up he reported that it wasn't moving and had no brakes. The engine did run after a boost. Shortly after he reported a large oil spill on his deck and nothing on the sight glass. It got delivered late last night and during the initial inspection I found a tag indicating that the machine needed me drive motors.

This afternoon I started looking the machine over. Sure enough no oil left in the tank. I lifted the cab up and found a whole bunch of absorption pads in the belly pan under the motors. I also found a disconnected electrical connector on a solenoid ob what seems to be the parking brake manifold. I reconnected that, put 5 gallons of oil in the machine and fired it up to see. The drive motors moved a little and the lift cylinders worked, but I shut it down quickly.

I relifted the cab and found hydraulic oil flowing out the side of the right side motor housing. It almost seems as though this is the brake end of the motor.

My question, how much of a pain is it to pull the motor? And what's the best recourse for repair? Rebuildable myself? Cat rebuild is about $4800 plus taxes.

SN HEN08192
20220928_192641.jpg
 

Nige

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Hard to see from your photo but it might be a leaking park brake cover.

From what I can see your machine was built as a 2-speed. All the info that follows is based on that.
In the case of it being single speed the motor parts info will not be correct.
Parts and R&I info attached.
 

Attachments

  • Motor Gp.pdf
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pbd05

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You are correct, it is a 2 speed machine. And yes, its leaking out of the park brake cover from what I could see. I tried attaching a video, but it was too big. Does a leak from this area indicate a complete failure?
 

pbd05

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After taking a second glance at it, it's not coming from the cover itself, but between the housing the cover bolts to and the main motor housing.
 

Nige

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I tried attaching a video, but it was too big.
You have to host videos on YouTube first then link them to a post.
After taking a second glance at it, it's not coming from the cover itself, but between the housing the cover bolts to and the main motor housing.
Could still be a seal, unless you can see that the housing is cracked somewhere.
 

Nige

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I'm sorry I've never been inside the guts of one of these motors. It might be the park brake piston seal leaking, or possibly a seal further into the motor because there does not seem to be a seal/gasket between the park brake housing and the motor housing, at least not one that is listed separately.

However in Step 13 on Page 19 of the attachment above it states "install O-Ring seal (12)" and that looks like it fits between the motor and park brake housings. This is the step right before the installation of the park brake housing.

upload_2022-9-29_18-44-33.png
 
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pbd05

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I'd suspect that's what's leaking, #12 in the picture. It doesn't seem to come up with a part number though. I'm waiting on a call back from our Cat Rep at work to see what my options are. I think either way it's coming out though, so I'll start prepping for that. It just seems odd that a seal would just suddenly let go on a part that is stationary, unless it was subjected to greater pressures than it would typically see.
 

pbd05

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I talked to our Cat Rep, from how I've described it he thinks it's just an o-ring seal failing from age. He also thought that the brake solenoid being disconnected could be an indication that it was acting up, causing extra heat which could have cooked it. I'm going to try and take things apart in the machine, instead of pulling the motor completely. I'll definitely keep you guys updated.
 

Nige

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I'm going to try and take things apart in the machine, instead of pulling the motor completely.
I dunno about anyone else but that might be a bad idea. Disassembling the motor when it’s standing on its end (as per the service manual procedure) is one thing. Trying to hold everything in place while all the time fighting gravity in an extremely restricted space has disaster written all over it IMO. But don’t let fear stop you.....
 

pbd05

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I dunno about anyone else but that might be a bad idea. Disassembling the motor when it’s standing on its end (as per the service manual procedure) is one thing. Trying to hold everything in place while all the time fighting gravity in an extremely restricted space has disaster written all over it IMO. But don’t let fear stop you.....

I'm just going to go as deep as o-ring #12, if nothing is obvious up to that point, I'll stop and pull the motor completely.
 

92U 3406

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Pulling the motor is really not a huge task. About an hour or 2. Have to jack the machine up and slide the axle assemblies slightly to de-tension the drive chains. Re-tensioning them is a bit of a pain without the tool but it is doable. Easier with some help.
 

Vetech63

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pbd05

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Got things apart, the brake is fried as suspected. From the manual it should have 10 steels and 9 clutches, I counted 12 discs of some sort. I'm thinking I'm going to drag the machine over to a better spot and pull both motors and go through both brakes. If the first one is shot, the second is likely not far behind.

20220929_202444.jpg 20220929_202449.jpg 20220929_202439.jpg 20220929_202431.jpg
 

pbd05

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The oring that was leaking was pretty hard, and one area had an ever so slight deformation to it.
 

Attachments

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pbd05

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Pulling the motor is really not a huge task. About an hour or 2. Have to jack the machine up and slide the axle assemblies slightly to de-tension the drive chains. Re-tensioning them is a bit of a pain without the tool but it is doable. Easier with some help.

The machine isn't in a good spot right now so I couldn't get it up on stands. As mentioned above, I think I'll be moving it over so that it can go up on jack stands then pulling the motors out completely.
 

pbd05

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Taking another look at the parts diagram, it appears as though the spring (3) mentioned in step 2 of the disassembly process is missing. When I removed the cover there was nothing there, just the piston. It doesn't look like this part is available on its own either, so I might be in for a whole new motor after all...
 

pbd05

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Not sure but I think those motors were manufactured for Cat by Rexroth. I think the model was an A6.
I have no idea if a Rexroth dealer might have parts available.
You're correct, the Cat ID tag actually has a Rexroth number on it. I'm in discussions with a hydraulic motor shop now for parts and/or a rebuild. He's looking for a detailed parts breakdown to see if the spring is available or not.
 
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