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Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 5428
Experience:  17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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I have a Komatsu 420-1. I replaced the hose from the

Customer Question

I have a Komatsu 420-1. I replaced the hose from the reservoir to the brake valve on the centre of the rear diff. I suspect some dirt got inside the hose. Now when I use the brake the back left side wheel locks up and won't release until I bleed the nipple. Is there any way to fix this without removing the valve. Regards
JA: What is the complete model and serial number of your machine?
Customer: Komatsu WA420-1 Serial number 20136
JA: Anything else you want the equipment mechanic to know before I connect you?
Customer: No thank you Regards Wilf
Submitted: 10 months ago.
Category: Construction and Road Equipment
Expert:  Dan replied 10 months ago.

Hi Wilf, My name is***** the brake is sticking it is likely in the master cylinder causing the problem or a restriction as you suspected. You will need to remove the lines and blow through them with an air blow gun to be sure they are free of restrictions. Then bleed the system. Let me know