Sunday, January 29, 2023


Why do my RV’s brakes feel spongy and weak?

Dear Dave,  
I recently bought this motorhome (55k miles) and the brakes are low and braking power is slow to the point that it feels like the motorhome won’t stop. It looks like the fluid is full, but it is difficult to see the amount. I’m hoping the problem is simple like bleeding the brakes or low fluid. What advice do you have for me? —Josie, 1994 Spartan Georgie Boy

Dear Josie,
From your RV description, I believe you have a 1994 Georgie Boy with a Spartan chassis. That is a diesel pusher platform rather than a gas chassis, which would have been available in either the Ford F-53 or Chevrolet P30. Depending on the floor plan and length, if it was a gas version I would say the longer length and weight would be challenging for both!

However, since it is a Spartan diesel chassis, the braking system should be adequate for whatever length and Gross Vehicle Weight Rating (GVWR) of your rig. From the info I can find on the internet it is most likely the Mountain Master Chassis and most likely the 400 hp and 34,000 GVWR, unless it has a tag which would put it at 43,000 lb. GVWR.

Get the rig weighed

The first thing I would recommend is to get the rig weighed so you know where you sit with all fluids and cargo. I would doubt you are over GVWR, but it is still a good idea to check it out. Go to a CAT Scale at any Flying J or Pilot and for $10 you can get axle weights and total weight. Place the front axle on the first pad and the drive axle on the second pad. You should have a data plate inside the rig on the driver side wall that has the Gross Axle Weight Rating (GAWR) as well as the GVWR.

Flush and refill brake fluid

Since your rig is almost 30 years old, I would flush and refill the brake fluid. Most chassis manufacturers recommend changing the fluid every 3-5 years, depending on the mileage and usage. The brake fluid can break down as well as develop condensation, and this would contribute to weak braking. This is a handy brake fluid tester that owners can use to verify good fluid. You can find one on Amazon here.

Then you need to have someone pull the wheels and check the pads and braking system. I believe the Mountain Master has air brakes, so a qualified technician can inspect all the components and pad thickness. It could be an adjustment required on the slack adjusters or even a leak in the air chamber. Most of these troubleshooting issues are not a DIY procedure. Get your VIN or chassis serial number and call Spartan to get a service manual for your chassis.

 You might also enjoy this from Dave 

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25 days ago

Hard to diagnose a problem without the full specifications. You did a good job covering the options available whether Ford, Chevrolet or Spartan and I am not sure where the Mtn Master came from…. is that a Spartan option? Anyway you covered the options Josie might have and recommended getting a shop manual specific to the VIN. Good job Dave.

25 days ago

IF a standard brake system with brake fluid also CHANGE THE RUBBER BRAKE HOSES to the calipers and rear brakes when you change the fluid. The hoses alone could be the source of your spongy brake problem.

I suggest you upgrade to better stainless aftermarket brake hoses such as those with stainless steel outer shield.

Jesse Crouse
24 days ago
Reply to  bull

Brakes IMO are not a ” do it yourself” maintenance item. A licensed, insured professional who gives you an invoice for the work done is the way to go.
In my profession- Plumbing & Heating- you never ask a friend or yourself to do the annual maintenance on your heat source. The newer equipment is more complicated and “must have” a combustion test done annually. That’s why I spent $1500.00 on a combustion analyzer.

25 days ago

Going on about flush and refill brake fluid. Then saying the RV probably has air brakes?

Bob p
25 days ago
Reply to  Bob

The flush and refill pertains to gas powered vehicles, and I doubt very few people even think about that. Yes if it has air brakes which most diesels have, it may have been years since they were checked, a 29 year MH with 55K they could be very corroded. Air chambers could be corroded and slow to work. Without regular maintenance and draining condensation from air tanks that moisture goes through the braking system and corrodes all the parts. Modern air brake systems have automatic drain valves, I doubt a ‘94 model has that.

25 days ago
Reply to  Bob

Bob, I agree. If a person doesn’t know much about the different braking systems, this answer could be quite confusing jumping back and forth between the two.

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