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Daniel Wilson
Daniel Wilson,
Category: RV
Satisfied Customers: 5568
Experience:  Owner at DJ Wilson
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I already went through this but lost my connection. I have a

Customer Question

I already went through this but lost my connection.
I have a 2003 Holiday Rambler Ambassador 38PST Roadmaster chassis with cummins 315 ISC.
The Park brake light stays on upon release of park brake.
2 months ago I drove 1200 miles before the light stayed on. I had a mobile mechanic check the system and he could find nothing wrong after charging me $300. He said all mechanical brake parts were working fine and suggested I replace the park brake switch. I replaced the switch with the same exact new part. the light remains on There is a white wire attached to each master cylinder and 2 white wires attached to the brake pressure switch. Nothing in the manual refers
to any thing about the light except the park brake switch.
Submitted: 9 months ago.
Category: RV
Customer: replied 9 months ago.
2 weeks before I left on my last trip, I was topping off fluids and accidently put ATF in the bottom master brake cylinder.
I did not turn the engine on or apply the brakes before evacuating the contaminated brake fluid by sucking it out of the master cylinder and then flushing and bleeding that master cylinder by a diesel mechanic. He assured me I should not have a problem.
But about 1200 miles later the parking brake light started staying on and also hear a noise when applying the front brakes.
according to the roadmaster chassis manual there are lots of moving parts that may need lube. I just do not want to have a problem as I drive on a lot of mountainous roads.
Expert:  Randall replied 9 months ago.

Hi! My name is ***** ***** I can assist you with this. I may need some additional information from you first in order to give a complete answer.

Expert:  Randall replied 9 months ago.

I don't do brake questions, but we have several techs here on site that do. I will opt out of this and allow one of them to provide an answer. Not sure when that might be as they come and go all during the day.

Expert:  Daniel Wilson replied 9 months ago.

Hi John, My name is***** will be glad to try to help. I recommend flushing the system further and bleeding the system thoroughly. If a new switch did not correct the light it means that there is air in the system still or you are losing brake pressure for some reason. Bleed the system further until you can get the system to pressurize enough to turn the light off. If this does not resolve you either have a leak in the system, air in the system or a faulty master cylinder. Let me know

Customer: replied 9 months ago.
None of the literature on the dash brake light says anything about a warning for the master brake cylinders having a problem
So I assume the white wires at the master cylinders is a pressure sensor or low fluid sensor. There are 2 white wires running to the pressure switch. Am I correct in this assumption?
Customer: replied 9 months ago.
I will check it out this week and get back to you with the results
Expert:  Daniel Wilson replied 9 months ago.

Yes there will be a brake pressure switch and if there is air in the system the pressure switch will trip. Try jumping the pressure switch for test purposes to confirm its the switch triggering your light to see if it goes off and on when connection and disconnecting the jumper. If that is the case it means electrically its working but you have low pressure in the system.... This can be airbound from the flush and possibly only require more thorough bleeding.

Customer: replied 9 months ago.
How do I jump the switch? I do not know exactly how to do that
I have the manual for instructions to bleed the system
Expert:  Daniel Wilson replied 9 months ago.

on a two wire switch you use a jumper wire to connect the two terminals. Connecting and disconnecting acts as a switch to open and close the connection .

Customer: replied 9 months ago.
OK got it I will try in a day or so when the weather here clears,
There are 2 white wires to one terminal, so do I need to test one at a time to locate which cylinder?
Expert:  Daniel Wilson replied 9 months ago.

you will be jumping one terminal over to the other terminal. The switch just makes that connection.

Customer: replied 9 months ago.
I jumped the terminals on the brake pressure switch and the light remains on. When I apply the brakes there is a noise coming from the area of the master cylinders. It is a mechanical sound like something is binding. My guess is one of the master cylinders may be malfunctioning. I turned off the engine and repeatedly applied the brakes and only lost a small amount of air at each application of the brakes. Every time I applied the brakes there was a mechanical thumping upon applying and a lighter noise upon release of the brake pedal
Expert:  Daniel Wilson replied 9 months ago.

Thanks for the update. So you are getting a small amount of air instead of straight fluid? That is enough to throw a light.

Customer: replied 9 months ago.
is my next step to bleed the brakes ? Both front and Back? I only flushed and bled the bottom cylinder which I think is the rear brakes.
Expert:  Daniel Wilson replied 9 months ago.

Yes. Bleed starting at the furthest away from the master cylinder to the closest. Two people. One pumping the pedal then holding, the other then opening the bleeder until the pedal goes to the floor, close the bleeder and then lift the foot from the pedal and go again keeping an eye on the fluid level until there is no air. If the switch and wiring are good and this does not get the air out try having them pressure bled at a shop. Now this is for a brake system fault light. If the service brakes are okay and it is the park brake indicator staying on let me know. That will be a problem i the park brake circuit.

Expert:  Daniel Wilson replied 9 months ago.

Hi John, Did you get this resolved? If so please take a moment to rate my service as that is how the site credits my time for helping on the site.

Customer: replied 9 months ago.
Not yet. I am in Ensenada Mexico and my mechanic helper did not show up over the weekend.
Hopefully he will show up this coming weekend.
Will keep you posted
Expert:  Daniel Wilson replied 9 months ago.

Thanks for the update. Let me know

Expert:  Daniel Wilson replied 8 months ago.

Hi John, Just checking in so your question does not get lost in the archives. How are things going?

Customer: replied 8 months ago.
The weather has been too bad to do the work. I am a fair weather guy
Expert:  Daniel Wilson replied 8 months ago.

Thanks for the update. I understand. We have a lot of ice and snow where I am and freezing temperatures. Unfortunately for me I have to go out in it if there is a call. Keep me posted.

Customer: replied 8 months ago.
OK finally got a break in the weather. The problem is the master cylinder that I had contaminated a year ago with accidently putting ATF in the master cylinder instead of the hydraulic jack reservoir. Now my problem is finding a new or used master cylinder or a master cylinder repair kit. Today's search turned up nothing in Ensenada Mx or San Diego Ca.
Trying on line search tomorrow.
Expert:  Daniel Wilson replied 8 months ago.

Thanks for the update. click on this link for the locator for your nearest parts vendor.


Keep me posted