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dukealumni · 09-24-2019, 09:05 PM

Brake light warning came on, went to Les Schwab who diagnosed low brake fluid in the master cylinder. Refilled it and said the light should go out when the sensor engaged some 20 miles. Stayed on, another Les Schwab could not fix, said probably the master cylinder float is stuck, second break inspection. Chevy dealer said either that or the parking brake would likely be issue. Any thoughts? Thanks all!

Jim_HiTek · 09-24-2019, 09:22 PM

What I remember about the Bendix MC on a '94 Bounder was that there was a low fluid warning sensor screwed into the side of the MC. Those sensors can go bad, and even more likely is the wiring from the sensor to the idiot light on the dash.

MinntoMich · 09-25-2019, 08:51 AM

Deleted earlier reply as I have a couple of questions... Reading your previous posts is this a 1993 or 94, a class A Brave 24' or something else? When you say "parking brake" do you mean the emergency brake or transmission brake?

If its just the master cylinder low brake fluid warning light than I think Jim_HiTek is right. If its your AutoPark light, that's a different, seperate system.

dukealumni · 09-25-2019, 09:31 AM

It's really a 93, thee was some question about that when I bought it. Anyway, it's a 24 foot Brave with Chev chassis. And it's not an issue with the manual parking brake that registers as PARK on the dash, though I understand that if that is not totally released that may also set off the brake warning light. The master cylinder is located under the driver's side wheel well making access difficult. Think I will have to replace the whole thing.

Jim_HiTek · 09-25-2019, 11:29 AM

Changing MCs isn't that hard. Mine was in the drivers wheel well too, but I had a front jack so I could jack the RV up enough to get to it easily. Well, sort of easily. In your case, since it's only a 24 footer, it might be fairly easy to jack up the front, and pull the wheel. Do the job yourself and the savings will more than pay for a floor jack from Harbor Freight or Craigslist.

While I was researching mine, I found that the brake system parts usually have a casting number embossed on the metal. And those numbers can lead you to the part online when you're ready to buy. Mine was over $500 for new but no one was rebuilding MCs for that big of a chassis at that time.

With a new MC, a MC kit from CarQuest, and a friends help, it doesn't take long to do a MC change and a brake fluid change.

I know our chassis' are different, but maybe the brake job article at my blog might be some help: Brake Job

Good luck. It might not be the MC and looking at the wiring should be on your list.

dukealumni · 09-25-2019, 09:39 PM

Good information, thanks for that. Don't know if I can trace the wiring, but my hunch is it's the master cylinder. Folks at Les Schwab said fluid level was low, probably set it off. I may try to tap it just to see if the float is stuck but not hopeful.

RickNC · 09-25-2019, 09:42 PM

Quote:

Originally Posted by dukealumni

It's really a 93, thee was some question about that when I bought it. Anyway, it's a 24 foot Brave with Chev chassis. And it's not an issue with the manual parking brake that registers as PARK on the dash, though I understand that if that is not totally released that may also set off the brake warning light. The master cylinder is located under the driver's side wheel well making access difficult. Think I will have to replace the whole thing.

We have the same little bus. There is no float or other sensor on the master cylinder to indicate a low fluid level. The brake warning light is coming from the proportioning valve which is mounted to the frame near the master cylinder. Likely the level got low enough to allow air into the brake lines which cause an imbalance in the brake force . You will need to bleed the brakes to get the light off. But first you need to find out where your brake fluid leaked from. If the master cylinder is leaking, there is a small hole between the hydraulic brake booster and the master cylinder, check for wetness or signs of leakage. The master cylinder isn't hard to remove.there is a shield covering it that you remove.then the bolts to the frame are right in front of you. The bolts holding the master cylinder onto the brake booster are not hard either. BTW Life is easier if you remove the front wheel.

dukealumni · 09-26-2019, 09:26 AM

Great information. Thanks much. Did have two different Les Schwab outfits tell me that they saw no leaks in the mc, they turned the tire hard left and looked with a mirror. But maybe a simple break bleed could do the trick, certainly worth trying.

twinboat · 09-26-2019, 10:00 AM

It's a dual master cylinder. Did you notice which compartment was low ?

The larger one would be the front disk brakes.

Sometimes a quick hard kick of the pedal will reset the light, otherwise you need to bleed front or rear to get it centered again.

Brake fluid doesn't evaporate, it leaked somewhere, or with disc brakes the pads and rotor are thin and the caliper pistons are pushed way out.

Did you feel any difference in the brakes when the light came on ?

Were you stopping or using the parking brake when it came on ?

dukealumni · 09-26-2019, 01:27 PM

Matter fact, I did have to use the parking brake on a steep backward hill just a few minutes before it came on the Les Schwab folks didn't say which compartment was low.

twinboat · 09-26-2019, 02:15 PM

Put the parking brake on again and pop it off. See it that puts the light out.

There is a switch, somewhere on the pedal, that may be sticking.

The low brake fluid may have been normal due to brake wear.

dukealumni · 09-30-2019, 03:08 PM

Hey all, thanks for.all the feedback. After being ensured that our breaks were all good but the dash warning light was not operating correctly, the light went off yesterday morning, started the rig and had a clean dash. Some 500 plus miles after Les Schwab topped off the fluid in the mc. Thought I would share this,