How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Curtis B. Your Own Question
Curtis B.
Curtis B., Technician
Category: Construction and Road Equipment
Satisfied Customers: 1166
Experience:  Technican turned service manager with multiple lines of equipment and rental units.
Type Your Construction and Road Equipment Question Here...
Curtis B. is online now
A new question is answered every 9 seconds

I have a D5 M LGP which has a braking problem where the

Customer Question

Hey I have a D5 M LGP which has a braking problem where the brake does not release. I have changed everything on there such as alternator,brake valve,all solenoids,brake seals etc. I get steering pressure but not brake pressure, nothing above 100psi. Please help me figure this out if possible
Submitted: 1 year ago.
Category: Construction and Road Equipment
Customer: replied 1 year ago.
I have also changed all speed and transmission sensors which is four in total which the unit carries
Customer: replied 1 year ago.
I had a caterpillar guy take a look and tried to recalibrate machine but not having any luck
Expert:  catmastertech replied 1 year ago.

Hello, please post the full machine serial number so I can research the correct information.

What is the current pump pressure and steering pressures you are seeing?

How many hours are on this machine?

Have you rebuilt the final drives recently?

Do you have any fault codes logged?

Customer: replied 1 year ago.
The serial number is 3CR00344Machine hours 11700The final drives have not been rebuilt but brake seals have been changedThere are no fault codes loggedThe pump pressure at port P is 410 psi on low idle and 450 psi on high idleThe steering pressure is 325 psi and can be adjusted using service tool (4C8195)
Customer: replied 1 year ago.
Hey any ideas based on the info
Expert:  catmastertech replied 1 year ago.

I am assuming you have a manual?

I do not understand why the sensors were changed?

What other work has been done to this machine?

Have you replaced any of the brake solenoids?

Have you removed the brake valve and inspected for debris?

Do you have any active codes?

The brake seals is what I should have asked about instead of the final drive.

Did the hubs appear worn? (Where the inner seals ride?)

Have you checked priority valve pressures?

Brake pressure adjustment is mainly for feathering the application of the brakes to prevent harsh turning. It should not effect the high pressure, only the low pressure as the brakes are being slipped for turning.


Both brakes will not release.

Probable Cause

Electrical problem

Contamination in both brake pilot valves

Leaking seals on the brake pistons

Poppet assembly for the solenoid on the brake valve that is stuck open

Low pressure in the power train oil system

Customer: replied 1 year ago.
There are no active codes
All solenoids have been replaced on unit
Brake valve has been taken apart cleaned and new pieces put in except plate between two pieces which appears that be ok
Brake seals have been replaced all around
Priority valve pressures goes 350-400 psi at idle and full throttle drops to 120psi
Hub does not appear to be worn
Sensors were changed thinking that they were the simple fix to begin with
There has been no other work done except what has been mentioned
New alternator thinking that there may have been an electrical problem in that area
Speed sensors, brake sensors,all new solenoids
All new brake seals
When the parking brake is on the solenoids give a reading Of 75 % on the ET screen and off it drops to zero. Not sure if that means anything
Customer: replied 1 year ago.
Correction when parking brake is off its at 75% and on its at zero
Expert:  catmastertech replied 1 year ago.

WOW, that covers everything I have ever seen. I don't know of anything else that may help.

Have you contacted the dealer for technical support?

I don't recall the settings or readings on the ones I worked on.

The oddest problem I had was an early model that the check valve in the priority valve valves and it would loose brake pressure when traveling.

(It could throw you out of the seat if you weren't wearing your seat belt.)

What is the symptom that led to all this work? Did the machine just not move at all or would it lock when traveling?

Expert:  catmastertech replied 1 year ago.

This was the update for the check valve issue.

Check Valve Failure In Priority Valve


D5M (6GN, 3CR, 7LR, 5ES, 6AS),


Some reports have been received that the 9U-8076 Check Valve has failed in some priority valves. When the valve fails, oil is allowed to flow from the high pressure (controls) side to the low pressure (converter) side of the system. This scenario results in low system pressure available to the transmission and brake control valves. The general symptom has been that the brakes drag whenever the priority valve is at low pressure.


During proper operation, the priority valve raises the low pressure side to high pressure in order to supplement high pressure pump flow under the following conditions:

1. Cold oil (below 40 °C (104.0 °F)

2. Engine speed below 1300 RPM with the parking brake OFF

3. During a shift (speed or direction)

If the machine operates correctly when the priority valve is at high pressure, but operates poorly when the priority valve is at low pressure, then a failed check valve is the most likely cause of the problem. Inspect the 9U-8076 Check Valve within the priority valve. Replace the valve, as required.

Customer: replied 1 year ago.
It started when the left side would lock and it got progressively worse
Customer: replied 1 year ago.
Now both sides are locked
Customer: replied 1 year ago.
The steering pressure is at 325 psi and brake pressure is at 50psi. The steering pressure is able to be adjusted up or down but the brake pressure is not able to be adjusted. All that is done using program
Customer: replied 1 year ago.
Hope this helps to diagnose
Expert:  catmastertech replied 1 year ago.

I am sure you are right on top of this issue. It seems you have done everything I would check.

Since the problem started at one brake and then went to both, I would believe it is more to do with the steering and brake valve.

I do not recall any brake pressure adjustments with the program. Only the touch up pressure which is just the low pressure control to get smooth brake control when turning.

I am assuming the software is still the original and the ecm is correct?

What voltage do you see to the brake dump valves? Are they working correctly? Do you have another machine you could try swapping ecms?

Customer: replied 1 year ago.
I bought a new ecm and monitor. All seem to be functioning ok after they were flashed.
Expert:  catmastertech replied 1 year ago.

Ok, That was my last idea. I am lost on this one too. I looked through service letters and bulletins for all D5M brake issues and nothing came back other than the check valve issue.

I will OPT-OUT so, others can see your question and maybe help more.

Customer: replied 1 year ago.
All this was done thinking they were the problem
Customer: replied 1 year ago.
Thanks for your help

Related Construction and Road Equipment Questions