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Contributor
Location: Webster, Wisconsin | I'm working on the brakes of #426. The shoes look new and so do the brake springs. I've put in all new bleeder screws and a master brake cylinder that I bought from Leslie at MCR.
I've got a vacuum pump that draws 27". I've followed both Leslie's and Jim Black's recommendations on the bleeding process. After bleeding several times (the FMC, not me) I have the following problem.
The first time I hit the brake pedal it goes to the floor. If I immediately hit it second time the pedal goes about half way and stays there, no matter how much pressure or how long I push it.
Has anyone else run into this? How did you resolve it? I have gone though almost a gallon of brake fluid and repeated the procedure a half a dozen times and still no brakes on the first pedal.
Greg
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Expert
 
Location: Cottage Grove, OR | Well Greg, it sure sounds like some air remaining in the system somewhere. With the canted brake cylinders, it is a persistant problem. I had the problem of the first stepping of the brake pedal going down about half/two thirds of the way, and the second staying hard. I will tell you what I had done, but am not reccomending it per se as many people have achieved solid braking without doing what I had done. It did resolve my brakeing situation.
I had a chance meeting with an FMC owner from B.C., Canada who was on his way back north. During our visit he mentioned what he had done that solved his braking problems.
Our coaches have two cylinders per wheel with the brake line for the fronts going to the lower cylinder and for the rears, the line goes to the upper cylinder. When bleeding the fronts, the brake fluid goes into the bottom cylinder and pushes the air up to the upper cylinder and it is then bled out of that cylinder. This follows the natural flow of fluids and gases. Gasses rise to the top of fluids. However, with the rears this natural situation is not followed. The brake line is attached to the upper cylinder and so how does it push the air out of the lower cylinder? The Canadian had RVS install longer brake lines on the rear and attach them to the lower cylinders in the rear like they are in the front. He said it gave him good, solid brakes. Based on that, I had RVS do the same to mine. I now have good, solid brakes on the first stepping of the brake pedal.
Now I hope others will advise how they bleed their brakes and get a good solid pedal without doing what I had done. One thought I had was to park it (with wheels adequately blocked) on a steep uphill slope which would help flatten the cylinders and then bleed them! |
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Contributor
Location: Webster, Wisconsin | Hi Stephen,
That's a good idea. The front brakes make sense as lighter materials rise so the air goes to the top cylinder & you just push or suck it out.
But when I started working on the back brakes I wondered what FMC was thinking of when they attached the hose to the top necessitating bleeding from the bottom cylinder. Doesn't make sense.
I'll take a look at mine & see about getting longer hoses & rerouting to the bottom cylinder. I've been futzing with the brakes way too long now. Aggravating to say the least.
Greg Furtman
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Expert
Location: Cottage Grove, OR | Greg,
I might add that the reason for attaching the brake line to the upper cylinder in the rear may have been to keep it away from the axel drive shaft. When putting the longer lines on mine, Jim B. welded a small bracket to the backing plate to secure the brake line and keep it away from the axel. If the the two componets come to gether, it would not be good!! Jim had a bit of a problem finding lines made of DOT approved material of the right length. If you decide to do this, you might give him a call. |
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Veteran
Location: Illinois | Have you ble all 8 bleed screws with the screw opened no more than 1/8th turn????
Then have you bled all 8 bleed screws with the engine running??? After each wheel, the brake pedal should be cycled one time.
Also all 8 brake adjustment screws should be locked and backed off 5 clicks.
HAPPY TRAILS - Leslie Hoagland |
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Contributor
Location: Webster, Wisconsin | Honest, really Leslie. I've done exactly what you told me to do & when I hit the pedal the first time it goes to the floor. Ah, but the second time it only goes about 1/3 to 1/2 the way and no further, no matter how hard I push.
I'll check the adjusters again & see if that makes a difference. |
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Veteran
Location: Illinois | Greg -
Are you certain that you have drawn sufficient fluid on each wheel cylinder to be sure that air has been elliminated???
HAPPY TRAILS - Leslie Hoagland |
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Contributor
Location: Webster, Wisconsin | Just a quick update on my spongy brakes. Last summer I had a pair of brake hoses made for the rear and attched them to the bottom cylinders. Now I can bleed from the top. It made a big difference! Much less travel in the break pedal before I get resistance.
I hope to get #426 on the road this summer, if I can afford gasoline. I've had other projects the last two summers ( actually my wife's projects but you know how that goes) so I see myself finally having enough time to finish the few things I feel should be done before taking #426 on the road. |
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Expert
Location: Cottage Grove, OR | Greg,
Good that you are going to make it back on the road. If you come from the East and I come from the West, we can catch the Colorado Coach Caravan event the first of August! |
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Contributor
Location: Bowling Green Ky. | I have had the same problem. I have some brakes on the first stroke. But usually have to hit them a second time for solid pedal. I have replaced everything but the pedal ( in 2002). I have got used to the feel. What you are saying makes good sense. I replace all coponents and went with silicon brake fluid as well. This might be the piece to the puzzle.
Thanks Darrell Dubree |
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Extreme Veteran
Location: Ignacio Colorado | The first thing to do is readjust the shoes. Make sure they are adjusted up properly. Also remember there is an adjuster for each shoe. It doesn't take much extra shoe travel to get the 2 pump brakes. If all the adjusters are a little bit too loose it turns into 8 times that much travel.
Good luck and keep us informed.
Bill |
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Contributor
Location: San Clemente, Ca. | I had the same issue with #621. Finally figured out the problem was the nonmetallic hoses in the brake line. Replaced them and I have never had better braking. |
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Contributor
Location: Bowling Green Ky. | Thanks for the repy.
I am not understanding. Nonmetallic hoses in the brake line? Are you referring to the flexable rubber hoses. What did you replace, and with what type? Are you refferring to what Mr. Heinrichs suggested on the location of the rear rubber flexable hose attachment location?
Have a great day!
Darrell |
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Contributor
Location: San Clemente, Ca. | They were flexible rubber hoses but in the front.
Ron |
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Contributor
Location: Bowling Green Ky. | Very good.
Thanks for the reply.
Darrell |
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Spongy Brakes