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Tom
Tom, ASE Certified Technician
Category: Car
Satisfied Customers: 25954
Experience:  ASE Certified Master Technician
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Looking for expert advise on Land Rover Discovery 1998. Brake

Customer Question

Looking for expert advise on Land Rover Discovery 1998. Brake issue. Left front caliper locks up repeatedly. Have replaced booster, proportioning valve, both front calipers and rubber hoses. The vehicle had no brakes when it came to me. Now its has a great pedal until the left front caliper locks up? What is the cause of this??
Submitted: 4 years ago.
Category: Car
Expert:  Tom replied 4 years ago.
Hi I’m Tom and I’m here to assist you with your issue today. Before I get you a fully researched answer, I have to ask you a couple preliminary questions. Has the abs system been checked there are many issues with the abs pump/modulator causing this issue .
Customer: replied 4 years ago.
i removed all fuses and relays from the ABS system to take this out of the equation. I knew this could possibly be the cause.
Expert:  Tom replied 4 years ago.
Ok even if the fuses are out it still can affect the system unless you disconnected the abs control unit was this also done?
Customer: replied 4 years ago.
disconnect the harness from the system?
Expert:  Tom replied 4 years ago.
Ok so the entire abs system was not active or sure then correct just need to be sure to rule this out.Was all the fluid removed and fresh new fluid installed as well?
Customer: replied 4 years ago.
the fluid in the system is clear and pretty much new. when this vehicle came to me it had ZERO brakes. pretty much new system/ reman parts, front and back as of now.
Expert:  Tom replied 4 years ago.
Ok except the lines were the only items not replaced correct?
Customer: replied 4 years ago.
ot the steel ones. i did however remove the steel line on the left front, blew part parts cleaner through it along with compressed air. all seemed to flow correctly.
Expert:  Tom replied 4 years ago.
Yes these are what going to need to be replaced as long as the rubber lines are not crimped this will need to be checked next and your issue will be fixed.As you and I know there has to be a crimp or blockage in a line causing this issue then .I would start here next.Remember Im here if you need any further assistance for anything at all it will be for no further charge.Please rate excellent service so I can get credit for my help thanks.Bonuses greatly appreciated.
Customer: replied 4 years ago.
why replace the steel lines if there are no obstructions???
Expert:  Tom replied 4 years ago.
How can you be positive there are no obstructions just by the compressed air through will not guarantee that.Also the rubber lines can also be restricted.
Customer: replied 4 years ago.
i blew brake parts cleaner straight through the steel ones with no issue. the rubber ones i have already replaced
Expert:  Tom replied 4 years ago.
Crimp off with needle nose vice grips the rubber line going to the left front caliper and tell me if any other caliper locks up.
Customer: replied 4 years ago.
I'm going to try this now...If so, then where am I headed from here??
Customer: replied 4 years ago.
starting getting more pressure to right front
Expert:  Tom replied 4 years ago.
Ok what about the right rear?
Customer: replied 4 years ago.
the rear are fine. only the front seems to be effected
Expert:  Tom replied 4 years ago.
Ok so if you crimp off the drivers side brake line and it affects the passenger caliper that's telling you there has to be an issue with pressure. So it's either a bad master cylinder or there can still be an issue with the abs pump /modulator even though there is no power and it's not operating the fluid will always still run through the system and I believe that's the issue. I would focus there next. Remember that I'm here if you need any further assistance just let me know it will be for no further charge. Hoped this helped.Please rate excellent service so I can get Credit for my help thanks. Bonuses greatly appreciated.
Customer: replied 4 years ago.
i replaced the master last night with a new OEM. Is there a way to bypass the ABS modulator? If so, how??
Expert:  Tom replied 4 years ago.
Unfortunately there is no way unless you remove it and run just brake lines but that will take a lot of time to do that.Its possible the new master is bad but Im leaning towards that abs pump/modulator myself.Remember Im here if you need any further assistance for anything at all it will be for no further charge.Please rate excellent service so I can get credit for my help thanks.Bonuses greatly appreciated.
Customer: replied 4 years ago.
as far as the lines coming OUT of proportioning valve- which is for the front and which for the rear brakes
Expert:  Tom replied 4 years ago.
Why is it possible you installed them wrong ?I will see what I can find the correct diagram.
Customer: replied 4 years ago.
no, didn't install incorrectly. Giving serious thought into tying into the outlet lines from the valve and bypassing the ABS completely
Expert:  Tom replied 4 years ago.
Ok let me see what I can post although thats a lot of work .
Customer: replied 4 years ago.
If you can post a diagram that would be helpful!
Expert:  Tom replied 4 years ago.
This is the valve you have correct?
ClickHere
Customer: replied 4 years ago.
yes
Expert:  Tom replied 4 years ago.
The two with the red caps are for the fronts the other for the rear .Best of luck it should work.Remember Im here if you need any further assistance for anything at all it will be for no further charge.Please rate excellent service so I can get credit for my help thanks.Bonuses greatly appreciated.
Customer: replied 4 years ago.
from the pic you posted I can't see which ones are red...
Expert:  Tom replied 4 years ago.
The two in the front the ones closer together.