Brakes go to floor and brake light comes on

whipskipper · March 16, 2012, 01:41 PM

Hello I am a new member and have been having trouble with my brake system. My pedal goes to the floor and brake light comes on I was dealing with this last summer and found my front secession of master cylinder I filled it up and drove like that for a while. I could not find a leak anywhere except the front of my master cylinder is a little wet none of the wheel cylinders appear to be leaking I really don't know where to start as this brake system is a little more complicated than I am used to some kinda accumulator in front of master cylinder. It is on a 85 Chieftain 27ft 454 engine. Thanks for the help

Kevin

ClydesdaleKevin · March 16, 2012, 10:00 PM

You coach has a P-30 chassis, which will make this very simple for you to troubleshoot, and not all that expensive to fix, no matter what the problem ends up being.

A lot of the folks here are Mopar guys, but I'm definitely a Chevy/GMC guy when it comes to motorhome chassis at least....I think they are better designed, and since the P30 chassis was used for so many other things, like 1 ton vans, step vans, box trucks, etc...and was made well into the late 90s, the parts are available, cheap, and easy to find and look up.

Okay...you can't find a leak, but the master cylinder was empty, or one chamber of it was? That means that you do have a leak...somewhere. You won't have wheel cylinders on an 85 P30 chassis...you will have 4 wheel discs, front and back. So you will have calipers.

Look for breaks in your metal brake lines, and of course the rubber lines going to the calipers. It has to be going somewhere.

Now remember, the brake lines on RVs are LONG...so if you get air in the system, that air bubble can be huge, and it might very well STOP brake fluid from going back far enough to leak out of wherever its leaking.

With air in the lines, or in the master cylinder itself, or even in the calipers, your brake pedal can hit the floor, and your brake light will come on. With enough air in the lines, and the passage of time, it can make it really hard to find a leak!

So this is what to do. Invite a couple of friends over for some beers. One of your friends is going to sit in the driver seat...the other friend is going to be crouched down under the driver's wheel well, with a few big bottles of brake fluid. Take the lid off the master cylinder reservoir. Your friend in the driver's seat is going to pump the brakes...your friend under the wheel well is going to keep adding fluid to the reservoir. You are going to be under the RV looking for dripping brake fluid. Pump it long enough, and you will find the leak.

To expedite the procedure, which really can take a VERY long time, especially if your system is full of air, rent or buy or borrow a vacuum brake bleeder. Your friend in the driver's seat can take a break and drink a beer or two. Your friend under the wheel well is going to keep pouring brake fluid in the reservoir. You are going to go to the back passenger side wheel caliper, and loosen the bleeder screw, hook up the vacuum bleeder, and pump like there is no tomorrow. Its very important that your friend keeps the master cylinder reservoir full. When that line is free of bubbles, tighten the bleed screw, and move on to the next rear brake caliper, driver's side. Repeat the process. Then go to the front passenger wheel caliper, repeat, and finally the driver's side front, repeat.

I can't remember if there is a bleeder screw on the hydrolic booster, a big can looking thing about 6 feet back or so, around or under your steps...if there is, you'll have to bleed that too, and I think it gets bled first.

Now, all the air is out of the lines, the master cylinder reservoir is still full, and your friend in the driver's seat has to get back to work pumping the brake pedal...it should be back now, even with a small leak.

You will definitely be able to find the leak now! Wherever its leaking from, its going to pour out in spurts, now that there is no air in the lines.

Locate the leak, and fix it. Replace whatever is leaking, be it wheel caliper, brake booster (the one under your steps), master cylinder, or brake line/lines or hoses.

Once you fix it, bleed the whole system all over again, using a vacuum bleeder, until you see no more air in the lines.

You brakes should be fixed once the leak is fixed. Its a good time to inspect your brake pads while you have the wheels off to access the brake calipers...they are cheap and VERY easy to replace, front AND rear...no drums on these things!

If you can't find a leak but you are loosing fluid somewhere, then its probably leaking into the brake booster canister. You'll have to replace the whole unit with a new/rebuilt one...again, super cheap comparatively on these things!

If you can't find a leak and you are NOT loosing any fluid, then either your brake booster is bad, or your master cylinder is bad. The amount of bleeding required for these things negates the necessity to bleed the master cylinder itself...the amount of fluid going through just doing a regular brake bleed, coupled with a friend continually pumping the brakes, would bleed a brand new empty unbenchbled master cylinder, although if you have to install a new master cylinder, its a good idea to bench bleed it first.

There is one other possibility as well...if your power steering is also out, this could be the root of all your problems. The brakes on P30 chassis are hydrolic assist, and they power steering pump ALSO provides hydrolic pressure for the brake booster.

Hope that helps!

Kev

ClydesdaleKevin · March 16, 2012, 10:05 PM

Oh yeah...because the bleed process can take a VERY long time, you are going to go through a lot of beers.

Wait until the next day to test drive it.... :)rotflmao

Kev

DaveVA78Chieftain · March 16, 2012, 10:43 PM

QuoteI really don't know where to start as this brake system is a little more complicated than I am used to some kinda accumulator in front of master cylinder.

Are there power steering hoses going to that accumulator? If so then you have a hydroboost system rather than a vacuum booster. Bleeding sequence is the same however power boost is via the hydroboost unit.

Do you have a tag axle? Though that is doubtful for a 27ft rig. If so, then there is even more to this.

Dave

Lefty · March 17, 2012, 01:50 AM

I got an '87 Georgie Boy 28' on a Chevy P-30 chassis, and mine is a Hydroboost front disc/rear drum set-up.. NOT 4 wheel disc.

I just recently had the master cyl. replaced. Due to a limited timeframe, I chose to have a local shop replace it for me. I purchased the master cyl at NAPA for about $65 bucks (new, not rebuilt.. and a lifetime warranty), and paid the shop $125 for labor to install it and bleed the entire system.
It was money well spent.. it stops on a dime now and has a very nice firm pedal.

ClydesdaleKevin · March 17, 2012, 10:04 AM

Wow! I thought all the P30s had 4 wheel disc! Even my old 77 did. So I guess there are always exceptions to every rule!

Kev

whipskipper · March 17, 2012, 01:22 PM

Thanks Kevin for all the detailed info. I as well have drums in the back and not 4 wheel disk that would be nice though. I will get to that bleeding done real soon I spent a day last aug bleeding and never could find anything just ended up toping off master and continued using rig. I replaced my front calipers rotors and pads last spring prior to driving up here to alaska from california. Anyways my rig has not moved since late October so I think i could be a static leak. The main problem is we have so much snow still on the ground I can't really get under the rig to do much inspection. Trying to get ready for a memorial day camping. I will keep you posted on my results. As for the brake booster that is what runs off power steering so if I have no power steering issues can I rule out brake booster??

I think I may just replace master cylinder if I can't find a leak again. it seems to be the only place I can see wetness do to fluid.

tiinytina · March 17, 2012, 08:32 PM

gone did the same thing last year.. hot hot July day in traffic.. brakes to floor with a semi in front of me at a red light.. Pumped pedal like a maniac.. stopped.. phew.. brake light on.. pulled over did full inspection no leaks anywhere.... got back on road after long discussion with my awesome mechanic. stopped bought fluid, refilled well (was near empty). got to campground and my mechanic drove out with a new master next day but we have hydroboost which is special order... but.. we drove Gone around campground and I had brakes again... the heat of the day, heavy use in traffic (4 wheel disc) bad hydroboost = brake light and no brakes.. the cylinder was in essence boiling the brake fluid.... Was able to drive the 40 miles back home on a sunday morning, no traffic, cool temps no problem... New hydroboost $65 and while at it total brake job. Old lines were just old. One cylinder also bad...

Tina

ClydesdaleKevin · March 17, 2012, 11:46 PM

Yep...if you have rear drums it could very well be a bad wheel cylinder, and unless you pull the drum, you might not be leaking enough to see brake fluid coming out of the drum...or it could spin off while you are driving and then you might miss the mess that would indicate a leak.

Drums aren't that hard to pull, but you'll have to pull the drive axles as well. When you get that far, if you have any questions on how to do it, let us know. Its daunting and they are heavy, but its pretty simple and easy if you know the tricks to it.

Kev

whipskipper · April 03, 2012, 01:12 AM

So I did more investigating since the snow here has melted mostly so I can work on my rig. I opened the master cylinder and found my rear half was bone dry from statically leaking in driveway I had filled it up last fall. So I focused on rear wheels and got her jacked and on stands to work on safely. I so far have pulled the passenger rear drum and found my source to be wheel cylinder for sure looks like both rear wheels are leaking as there is a stain on inside wall of tires. I pulled axel as well was no big deal except an impact was required. My local Napa carries the parts I need. I am debating on doing the shoes while I am in there since I hope to not have to do this again for along time. One thing I did notice was my front shoe is worn down more than rear is this normal??

Also if there are any tricks to doing the shoes let me know I plan to start tommarrow morning. I was also planing on using my mighty vac brake bleeder to suck out all old fluid in lines first then put fresh in and bleed brakes last.

tiinytina · April 03, 2012, 06:53 AM

you may just want to replace all the brake lines as well while at it... That way all new etc.. having the brake light go on as the pedal hits the floor is not fun...

Tina

DaveVA78Chieftain · April 03, 2012, 10:58 AM

Both shoes should wear fairly evenly. What may have happened is someone may have changed them before and mixed up the Primary and Secondary shoe. The asbestos lining on the Primary shoe is shorter than the lining on the secondary shoe. On each side of the vehicle, the Primary shoe goes on the forward side of the backing plate. In a floating shoe "self-servo' design, when the brakes are applied, the front (Primary Shoe) gets pushed into the drum which then gets wedged into the drum due to rotational force. This rotational force gets transfered to the rear (Seondary) shoe via the star wheel adjuster at the bottom. The secondary is then wedged into the drum (combination of rotational force and wheel cylinder expansion) however the anchor point at the top prevents continued rotation of the shoes. This expansion/rotational/wedging force produces the braking friction to stop the vehicle.
It is inherent to the "self-servo' design that the trailing brake shoe actually provides most of the stopping power. Hence, the trailing brake shoe (rear side of drum) will wear faster than the leading brake shoe, and that is also why there is more brake pad material on the trailing shoe (A way to tell them apart).

Dave

whipskipper · April 08, 2012, 02:09 PM

Ok so yesterday I finished my brake project it worked out great. I am glad I did this job my self it always feels better than paying a shop to do the work and I learned a lot. Took her for a test drive yesterday and the brakes now work great I still get a a flicker on brake lite when I hit a bump so that must just be an electrical problem. Thanks for all the help.

jbefumo · April 25, 2019, 08:50 AM

Quote from: ClydesdaleKevin on March 17, 2012, 10:04 AM
Wow! I thought all the P30s had 4 wheel disc! Even my old 77 did. So I guess there are always exceptions to every rule!

Kev

Hmm -- my '86 does -- I was surprised.

jbefumo · April 25, 2019, 08:54 AM

Quote from: whipskipper on March 16, 2012, 01:41 PM
Hello I am a new member and have been having trouble with my brake system. My pedal goes to the floor and brake light comes on I was dealing with this last summer and found my front secession of master cylinder I filled it up and drove like that for a while. I could not find a leak anywhere except the front of my master cylinder is a little wet none of the wheel cylinders appear to be leaking I really don't know where to start as this brake system is a little more complicated than I am used to some kinda accumulator in front of master cylinder. It is on a 85 Chieftain 27ft 454 engine. Thanks for the help

Kevin

Semi off-topic, but -- there's a sheet metal shield inside the driver-side wheel well that must be removed in order to replace the master cylinder ... What is that part called, and is there supposed to be a corresponding component on the passenger side?

Mine does not have one on the right side, and it got me wondering if I should be searching for the part, and if so, what it's even called.\

Thanks,

Joe

tmsnyder · April 25, 2019, 09:10 AM

Those keep air moving past the motor, helping cool the exhaust manifolds so they don't warp and crack as bad. Shrouds maybe?

Rickf1985 · April 25, 2019, 09:16 AM

There were a couple threads about the passenger side shroud, it was a factory part that was usually removed for access and never put back because service people "figured" it was not needed. It was actually there for the reason mentioned above and also to help keep the plug wires from cooking off the plugs. In those posts and even from Winnebago I think are the diagrams from reproducing that shroud.

HandyDan · April 25, 2019, 01:24 PM

Somewhere in my computer hard drive I have a template for that shroud. It was not installed by the factory and is a owner made part. I'll see if I can dig it up.

circleD · April 30, 2019, 11:18 PM

I know this is late but my 84 had 4 disc but the TAG was drum. I thought they only had the secondary cylinder under the walk through door if there was a TAG. I also bleed my brakes and it helped. I finally replaced master cylinder and rebled the system. WOW the difference.
Using a hand vacuum I discovered that I had a front flexible brake line sealed up on the inside. I replaced it too.

Rickf1985 · June 29, 2020, 09:58 AM

If you become a full member there are the wiring diagrams available for the Winnebago in that year. I don't know how well they will translate over to the Rambler though.