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dieseldan55
dieseldan55, Mechanic
Category: Construction and Road Equipment
Satisfied Customers: 754
Experience:  Road Mechanic for Volvo Construction Equipment.
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Volvo l90b wheel loader hydraulic problems. anyone up to it?

Customer Question

volvo l90b wheel loader hydraulic problems. anyone up to it?
Submitted: 12 days ago.
Category: Construction and Road Equipment
Customer: replied 12 days ago.
owner has replaced what i beleve is the servo pump and also replaced 2 sensors on the brake valve. equipment worked well for almost a full day after changing the pump but has now returned to low brake pressure warning lights and only occasional use of the lifting and tilting cylinders. applying brakes does stop the unit. fluid is full.
Expert:  dieseldan55 replied 12 days ago.

Hello this is Dieseldan, I will try to assist you. Are you able to tell me the pressure readings on the main and brake systems?

Expert:  dieseldan55 replied 12 days ago.

kinda need to know if they replaced the brake/ servo pump and if so check the servo pressure and brake system pressure to make sure pump is working. You can adjust the pressures and if you need info on that let me know. Possibly a piece of debri is in the relief valve causing the low pressure so you should be checking as well. Be aware you need to release the brake pressure in the circuit before working on the systems. Let me know how I can help

Customer: replied 12 days ago.
I figured you was going to say that. Means I have to purchase pressure gauges and fittings and start from the pumps work to the valves etc. I am guessing either they changed the wrong pump (but then why would it work good for almost a day?) Or the #9 non return valve is sticking closed and not allowing other hydraulic functions. Not looking forward to purchasing gauges as directions recommend several gauges to monitor multiple functions simultaneously. Was hoping the symptoms would be a give away to the problem. Well thanks anyway.
Expert:  dieseldan55 replied 10 days ago.

Well when troubleshooting you will want to make checks before tearing apart. Sounds like if they replaced the small pump which is the servo and brake pump. Its possible there's a piece of debri in the relief valve and they should be removed to look at the seats. One is in the footbrake valve and one is in the servo block under the a/c housing. Once you verify the servo is about 500 psi then if you still have no hydraulics it could be a bad main relief or faulty main pump. It sounds like it could be just a debris in the relief but that's why we put a guage on then start at a reference point to see if we make improvements upon cleaning or replacing parts.

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