HYDRA SYSTEM light on dash lights cluster

[Brent Harte]

Hello,

We purchased our 2001 Beaver Monterey Seacliff 3 years ago with 58K miles.  When you pressed the brake peddle a red light with the text "HYDRA SYSTEM' would come on.  In the last 3 years we have put about 10K miles on the Coach and the light came on every time the brake peddle was pressed.  The brakes performed fairly well.  However we are now having break problems.  So can anyone tell me what this light indicates.

looking forward to some wisdom.

[Eric Maclean Co-Admin]

Brent
Your coach has a hydraulic brake booster with an engine driven hydraulic pump ( commonly the power steering pump ). the light is a warning that the hydraulic pressure for the boost system is low it should also be accompanied by the sound of an electric pump.
That light is controlled by a pressure switch at or near your brake pedal valve.
Most of these systems have an electric backup pump the pump should run with the engine off and brakes applied to test it's operation.

Could you give us some more detail on your current brake problems symptoms etc.

Eric

[Brent Harte]

The brake pedal never had smooth even resistance when applied and the braking force was uneven during the travel of the brake pedal.  This was the case for the past 3 years.

Before our last trip I was trouble shooting small air leaks on the ride level valves and one guy wanted to press the brake pedal to the floor with the emergency brake off (we where attempting to see if braking was a cause of any air leaks anywhere).  Note: We where not trouble shooting anything to do with the BRAKES. 

We started our trip and the RV was driving and braking normally for about 5 miles, we stopped for gas and I left the engine running, I had to back up to to leave the gas station.  During the slow drive out of the gas station I could hear excessive squeaking from the rear tires while driving forward out of the gas station parking lot.  When I tried to accelerate on the road the RV would not accelerate past 25 miles an hour and as soon as I let off the gas the RV would stop as if the brake where being applied. I tried a few more times to accelerate and the RV would behave exactly the same, and then I smelled the brakes heating up, I felt the center hub cap on the rear tires and it was very hot, one side was quit a bit hotter than the other.

I called a mobile diesel mechanic that lifted the entire back axle of the ground and spun the tires by hand, and they turned freely, so we decided to drive the RV slowly back home, the RV brakes only briefly gave resistance during the initial acceleration then let loose and the RV drove normally for the 5 miles back.

The diesel mechanics are returning on Monday to trouble shoot and repair, however they are unfamiliar with our RV's breaking system.  FOR THIS REASON I would truly appreciate any guidance in overseeing their work.  Note:  The mechanics are highly recommended by Cassones RV -Mesa AZ, So I think with a little oversight I should get the right fix, but I'm OPEN to suggestions.

[Eric Maclean Co-Admin]

Brent
I am assuming nyou have a hydraulic over hydraulic boost disc brakes
That helps a lot the hard brake application test you refered to may have extended the a master cylinder beyond it's usual travel into a section of it's bore that is not usually used in doing so the bore may have some dirt build up in it which has caused the rear piston in the master cylinder to stick when this happens the bypass port in the master is covered and the rear brakes can not relieve the pressure from the calipers and the rear brakes will drag .
Unfortunately the cure is a new master cylinder
To test this get the system to duplicate your problem and then loosen the rear brake line at the master cylinder ( that would be the farthest one from the brake pedal if this is the problem by loosening the brake line to the rear brakes the pressure should be relieved and the brakes should release.

If it turns out you have air operated disc brakes we are looking at a whole different problem.

Hope this helps
Eric

[Brent Harte]

Ok the posted information is extremely helpful.  To add further clarity and maybe solicit additional advice, the following is what I have found out.  I have hydraulic brakes, and I believe a Hydro-Max Hydraulic Brake Booster and Master Cylinder (See Attached Picture).  Besides any additional advice, would it be advisable to just have the entire part replaced or trouble shoot the original?  And does this part utilize air in any way? And is there a way to get a part # for Booster without looking at the current part on my RV?

[Eric Maclean Co-Admin]

Brent
The hydromax is what I thought you had it uses the hydraulic pressure provided by the engine mounted power steering pump to boost the brakes there is no air involved.
The system uses a backup electric pump mounted to the hydromax to provide boost when the engine stops or hydraulic pressure is lost.

The following link should help diagnose your problems

https://pdf4pro.com/amp/view/hydro-max-hydraulic-brake-booster-and-master-cylinder-2f2bb4.html

Read that link and understand the system so you can talk with your mechanic and get a proper fix.
With the price of labour being what it is and the age of the unit it might be wise to consider replacing both the hydromax and master cylinder.
Unfortunately there are many variations of the hydromax unit it's important to get the right one for fitment.
Making it important to remove the existing unit to identify the proper unit
The link below may help you identify the proper unit.

https://www.powerbrakeservice.net/noname.html

Hope this helps
Eric