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CAT 988B works but won't move

Icarox3

New Member
Joined
Apr 25, 2023
Messages
1
Location
Jacksonville
Hi, I have a American CAT 988B which doesn't move.
The engine is working, the bucket is working, the steering is working, hydraulic oil filled, but it won't move.
It was moving 3 months ago, but suddenly its not moving anymore.

I pushed the lever to drive and reverse by many different ways, pressing the brake and/or the clutch pedal.
I also noticed that the wheels are NOT LOCKED.

Could it be any solenoid fault or electric sensor?
Please, I need take this machine off the port.

Thank you
 

Bluox

Senior Member
Joined
Jun 19, 2010
Messages
1,960
Location
WA state
My suggestion would be call Cat and have them send someone out you has worked on these loaders.
Does the parking brake release?
Have you checked the transmission oil?
No it don't have electric controls on the transmission, and the sensors are for the warning lites.
Bad Bob
 

Elmeche

Active Member
Joined
Sep 7, 2021
Messages
44
Location
Bulgaria
Occupation
service engineer and owner
Hi, do you hear noise of the hydraulic is changing when move the lever F or R. If not check the fuses of the transmission.
 

Nige

Senior Member
Joined
Jun 22, 2011
Messages
30,117
Location
G..G..G..Granville.........!! Fetch your cloth.
The engine is working, the bucket is working, the steering is working, hydraulic oil filled,
I hope that you are aware that there are two separate systems. The hydraulics for the bucket and steering are fed from a tank on the side of the machine. I would guess this is probably the tank you checked and found it full in the sight glass..

The transmission oil is contained inside the transmission transfer gear case. The level is checked using a long dipstick located next to the transmission oil filler cap up on top. Check the oil level with the engine idling and the transmission in neutral. It should be between the LOW and FULL marks. With the engine stopped it will probably be slightly higher.

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Elmeche

Active Member
Joined
Sep 7, 2021
Messages
44
Location
Bulgaria
Occupation
service engineer and owner
I don't know this loader and didn't find a manual, but if it is a pure hydraulic control - first step after
It was moving 3 months ago,
someone has to check the transmission oil filter for clogging.
If there has solenoids,
Could it be any solenoid fault or electric sensor?

or some blocking relay' schematics for prevent unintentionally moving like neutral, brake, seat.... control
I will check the fuses in first - it's easy comparing other / following actions.
 

kshansen

Senior Member
Joined
Mar 11, 2012
Messages
11,269
Location
Central New York, USA
Occupation
Retired Mechanic in Stone Quarry
Been many moons since I played with a 988B but did work on many back in the day. Don't recall any solenoids that would stop it from moving. Trying to think about what if any part of a 988B I have not removed, rebuilt or installed over the years!

Just off the top of my head thinking here, when it's running with shift in neutral is the drive shaft between the converter and transmission turning? If so does it stop pretty fast if shifted into a gear with foot brakes released, no pressure on the foot peddle?

Do you know where the parking brake is on the transmission? If so and you know where to watch is it releasing when you work the parking brake valve with engine running.

With a serial number as I asked for above I might have more ideas if I can find info on SIS, not sure what is available there these days.
 

Simon C

Senior Member
Joined
Jul 1, 2015
Messages
692
Location
Rocky Mountain House , AB., Canada
Occupation
Heavy Equipment Mechanic
If the transmission charge pump is not picking up, Does it have correct oil in transmission? Could the transmission pump be air locked.? Could the transmission Neutralizer be stuck on and nothing is moving. Did anyone try putting 2Psi into the transmission filler with a rag over hole with blow gun while trying to put it in gear. If it goes ino gear like that Pump is finished or strainer is plugged . Few questions to ponder.
Simon C
 
Joined
Sep 9, 2023
Messages
8
Location
Newcastle, Australia
Seeing as he hasn't been back since his first post you are probably correct.
Hi Nige,

I have been reading all your comments as i have similar issues on mine, We Checked fluid levels, checked brake pressures and assumed a leak internally on Wheel cylinders as it is dropping a lot of pressure in the braking circuit- 600psi down too 200. Accumulator is reading correct pressure at 2000psi when charged after engine running.

So from what i can understand - Park brake, steering damper and foot brakes are using same accumulator and share some plumbing, If one wheel cylinder/slave is bypassing oil into hub internally
then the loader remains in park brake Locked mode and some of these functions will be affected

Hopefully we can fix seals if not block the brake line to that problem Hub/brake to get it mobile again?
it is just a yard machine working on sand and a doer upper!

thanks for your help mate,
 

kshansen

Senior Member
Joined
Mar 11, 2012
Messages
11,269
Location
Central New York, USA
Occupation
Retired Mechanic in Stone Quarry
Might be just me but I would suggest starting a new thread for your machine so as not to get lost in this old thread. Also might help if you include a S/N on the chance there are changes over the years to deal with.

I'm a bit rusty on these although I worked on many back it the day as they say.

Just one question to start with have you checked the oil levels in the axles? This would help narrow down if and where a leak might be located.

Second, are you aware these brakes have what they call slack adjusters? Nothing like you would see on an air brake system. It is a hydraulic device that will let as much oil as needed to get the the wheel brakes but only let a set amount back out when brake is released. These have been know to fail internally letting too much oil back out when brakes are release.

I'll leave it at that for now.
 
Joined
Sep 21, 2022
Messages
7
Location
Toronto
Hi, I have a American CAT 988B which doesn't move.
The engine is working, the bucket is working, the steering is working, hydraulic oil filled, but it won't move.
It was moving 3 months ago, but suddenly its not moving anymore.

I pushed the lever to drive and reverse by many different ways, pressing the brake and/or the clutch pedal.
I also noticed that the wheels are NOT LOCKED.

Could it be any solenoid fault or electric sensor?
Please, I need take this machine off the port.

Thank
Hi, I have a American CAT 988B which doesn't move.
The engine is working, the bucket is working, the steering is working, hydraulic oil filled, but it won't move.
It was moving 3 months ago, but suddenly its not moving anymore.

I pushed the lever to drive and reverse by many different ways, pressing the brake and/or the clutch pedal.
I also noticed that the wheels are NOT LOCKED.

Could it be any solenoid fault or electric sensor?
Please, I need take this machine off the port.

Thank you
we just had a similar problem,the transfilter was changed and got crushed due to inproper installation.the transmision pump sucked debri up into the modulation valve and would not let us shift into forward or rev
 
Joined
Sep 21, 2022
Messages
7
Location
Toronto
we just had this problem.the transmission filters were just changed and were installed incorrectly crushing one filter and when started the trans pump sucked debris up into the modulation valve and jammed forward and reverse shift spool.
 
Joined
Sep 9, 2023
Messages
8
Location
Newcastle, Australia
Have a look behind the cab where all the cables ends are,put another bloke in the seat and you can monitor for full movement on linkages at end of cables, mine were seized. The cables we’re moving back and forward for gear selection but barely for foot brake valve. I oiled it up bled the brakes and now it’s moving.
 
Joined
Sep 9, 2023
Messages
8
Location
Newcastle, Australia
Hey mate check the suction line from the transmission to the transmission gear pump on the back of the engine.

Mine had a small leak and sucked air into the whole system. Cavitated the oil and made no power or drive.

Hydraulic Hose rubbed onto steel suction line.
 
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