Brake Trouble

[FIRE UP]

Originally Posted by cimplexsound

I'm fully aware of how the brake system works. Done a lot of work on automobiles of all kinds. We have determined a bad vacuum booster. The pedal won't go to the floor when the motor is started. Then of course the brakes lock up after several depressings of the brake pedal. So the check valve is gone. The only thing left to do is replace the booster

cimplexsound,
I hope I didn't offend you with my long winded explanation of the brake system and the basics of how things worked. I sometimes get carried away with stuff like that. It's just my intent to make sure that when I suggest an answer to something like a problem you were/are having, that everyone is on the same page and, to try and reason things out so that my suggestion makes sense.

Some guys are way more into all the mechanics and operations of their coaches/cars/pickups/motorcycles/boats etc. than others. Unless I've communicated in one way or another with a particular individual and know his/her capabilities, I kind-a go back to basics in explanations so that we're on the same page.
Scott

[Murf2u]

Originally Posted by cimplexsound

I'm fully aware of how the brake system works. Done a lot of work on automobiles of all kinds. We have determined a bad vacuum booster. The pedal won't go to the floor when the motor is started. Then of course the brakes lock up after several depressings of the brake pedal. So the check valve is gone. The only thing left to do is replace the booster

Before you get too excited throwing more money at it, try, as was suggested above, checking and replacing flex lines.

This is a VERY common problem. Take a test drive with an infrared thermometer. When the brakes start to drag pull off and check the callipers, I'll bet you find one is very hot.

[FIRE UP]

Originally Posted by Murf2u

Before you get too excited throwing more money at it, try, as was suggested above, checking and replacing flex lines.

This is a VERY common problem. Take a test drive with an infrared thermometer. When the brakes start to drag pull off and check the callipers, I'll bet you find one is very hot.

I have never experienced issues with the flex lines deteriorating on the inside, but, I'm sure it could happen. The reason I don't see his issue as a flex line problem is, as soon as he removes the retaining nuts from the master cylinder to the booster, and the piston is allow to return to the fully retracted position, his brakes let off and are free.

I would think logically, if it was a flex line issue, and they (any of them) were acting like a check valve, then releasing the retaining nuts for the master cylinder would have no effect because the problem would be lower in the system, not up high. At least that's the way I'm thinking.
Scott

[Hikerdogs]

Originally Posted by cimplexsound

I'm fully aware of how the brake system works. Done a lot of work on automobiles of all kinds. We have determined a bad vacuum booster. The pedal won't go to the floor when the motor is started. Then of course the brakes lock up after several depressings of the brake pedal. So the check valve is gone. The only thing left to do is replace the booster

If it's really only the check valve that's not working correctly it can be replaced without replacing the entire booster. A check valve usually costs less than $5.00.
http://www.summitracing.com/parts/rn...FUQdgQodzfEDDg

[cimplexsound]

Originally Posted by Murf2u

Before you get too excited throwing more money at it, try, as was suggested above, checking and replacing flex lines.

This is a VERY common problem. Take a test drive with an infrared thermometer. When the brakes start to drag pull off and check the callipers, I'll bet you find one is very hot.

The brakes were heating up. But the whole brake system was locked. This RV has proportional valve rather than a check. The power booster is factory sealed. So when the valve goes out the whole thing has to be replaced.

[cimplexsound]

Originally Posted by FIRE UP

I have never experienced issues with the flex lines deteriorating on the inside, but, I'm sure it could happen. The reason I don't see his issue as a flex line problem is, as soon as he removes the retaining nuts from the master cylinder to the booster, and the piston is allow to return to the fully retracted position, his brakes let off and are free.

I would think logically, if it was a flex line issue, and they (any of them) were acting like a check valve, then releasing the retaining nuts for the master cylinder would have no effect because the problem would be lower in the system, not up high. At least that's the way I'm thinking.
Scott

I tried the hard pedal test. That foul proof test you do to see if. By pumping the pedal several times with the engine off, then seeing if the pedal will go to the floor when the motor is started. The check valve was fine but The power booster failed the hard pedal test. It did not work.

[TeJay]

You still did not mention the year and make of your RV. FIRE UP's long answer was very good but mentioning your experience and coach year would have aided in a better answer more to the point. Also knowing if you had discs, drums or 4 wheel discs would have helped.

One thing that FIRE UP did not point out is the fact that on the newer caliper systems, which is very common to have 4 wheel disc brakes on newer units, rebuilding the calipers is also advised. The interior square cut seal around the caliper piston is what pulls the piston back away from the spinning rotor when the brake pedal is released. As the seal gets older it won't withdraw the piston which creates a .005 clearance between the pads and rotor. That will causes more heat to build up. Now you have a snow ball rolling down a hill and things go sour quickly. That issue is fixed with new or rebuilt calipers.

With a total picture (4 wheels locking up) of complete symptoms this should have been some what more simple to diagnose.

"The brakes were frozen" was your description of the symptom. One can assume you meant all 4 wheels or just the fronts, or just the rears. We didn't know. Sometimes good diagnosis gets into trouble when a tech ASSUME'S something.

With all 4 wheels locked up that just about points to the MC or PB unit. All 4 wheels would have been roughly at the same temperature which would have been very hot to the touch. Even the potential to burn and blister you very quickly. A very important diagnostic point to not zero in on immediately. I have had one rotor locking up which caused a pull and one rotor much hotter than the other front one.

That facts above would have avoided posters mentioning that flexible hoses could be an issue. Yes I have seen the interior of flexible hoses completely close up but it is very unlikely that it would happen to more than one hose at a time. Knowing the age of the coach would have also avoided those answers. It is very, very unlikely that a hose would fail unless it's at least 8-10 or more years old.

You did mention power booster. We can assume (again) vacuum. Most F-53 chassis use a hydraulic not vacuum PB.

Do yourself a favor and replace the MC and PB unit because you do want your brakes to work. If the hoses are more than 8-10 years old also replace them as preventive maintenance. While you are at it it's time to also flush the entire system. In the last 10 to 15 years that has become a new service procedure to be performed usually every 4-5 years.

Best of luck with your repairs.

TeJay

[twinboat]

He owns a 1979 Dodge Tioga.

[FIRE UP]

Hey TeJay,
How is ya Pal? Question for ya. Not being all that well educated in the latest automotive technology, you mentioned the fact that there's a "seal" in many of todays disc brakes that has the ability to "retract" the pistons to draw the pads away from the discs, correct? If so, how would a simple seal be able to do that? I mean, I'm just looking at it simply. A seal is a seal.

Unless that seal flexes outward as the brakes are applied and, due to it's own desire to return to it's relaxed state, it will pull the pads back. Would that theory hold some water.

One more thing. The OP mentions a procedure for dead engine-hard pedal multiple applications and then, when the engine is started, the pedal should go to the floor???? I don't think I've ever seen ANY brake pedal go to the floor unless there's a severe problem with the brakes, i.e. waaaaay out of adjustment, massive leak(s) etc.

I mean, even with the Ready Brake system, that definitely bleeds down any stored vacuum while you're towing. Then, when we get in the vehicle to move it after we've towed and, our pedals have NEVER GONE TO THE FLOOR. I think I'd panic if my pedal had gone to the floor, AT ANY TIME.

Scott

[TeJay]

Scott,

Hi!!!! Yep you are 100% spot on with the square cut seal. When an O-ring is cut you see a circle (O). When a square cut seal is cut you see a rectangle. When the piston moves out the rectangle distorts. When pressure is released it assume its original position pulling the piston back and allowing roughly .005 clearance between the brake pad and spinning rotor.

When the seals go bad they look OK or just the same but lose their ability to assume their original position when distorted. When that happens the pad drags against the rotor causing more heat and hence the snowball rolling down the hill effect.

As far as the brake pedal test it won't drop all the way to the floor but drops a lot. That's one of those tests that is not often done. I'd have to do some research to determine exactly how it's done and what results to expect. When things like this come up very infrequently I forget the exact procedures. I mean when's the last time you had a vacuum booster go bad. I think I changed maybe 2 or 3 in 40 years.

I know that's not much of an excuse but. About three months ago I ran across my first ever proportional valve that was blocked by some brake flexible hose deterioration allowing small particles of rubber to flow through the system. One of my X students called me after he had done all he knew and we hashed it over for a bit. He explained a few things and he actually thought of it and we discussed a few ways of determining that it in fact could be the issue. He applied some air and blew some rubber bits out a hole and all was well.

I've got an issue with my TOAD wiring but I'll send you a PM later tonight. Got chores to do.

Hope all is well with you and yours. Our Son moved back to LA so we might be heading out that way some time.

TeJay

[cimplexsound]

Originally Posted by TeJay

You still did not mention the year and make of your RV. FIRE UP's long answer was very good but mentioning your experience and coach year would have aided in a better answer more to the point. Also knowing if you had discs, drums or 4 wheel discs would have helped.

One thing that FIRE UP did not point out is the fact that on the newer caliper systems, which is very common to have 4 wheel disc brakes on newer units, rebuilding the calipers is also advised. The interior square cut seal around the caliper piston is what pulls the piston back away from the spinning rotor when the brake pedal is released. As the seal gets older it won't withdraw the piston which creates a .005 clearance between the pads and rotor. That will causes more heat to build up. Now you have a snow ball rolling down a hill and things go sour quickly. That issue is fixed with new or rebuilt calipers.

With a total picture (4 wheels locking up) of complete symptoms this should have been some what more simple to diagnose.

"The brakes were frozen" was your description of the symptom. One can assume you meant all 4 wheels or just the fronts, or just the rears. We didn't know. Sometimes good diagnosis gets into trouble when a tech ASSUME'S something.

With all 4 wheels locked up that just about points to the MC or PB unit. All 4 wheels would have been roughly at the same temperature which would have been very hot to the touch. Even the potential to burn and blister you very quickly. A very important diagnostic point to not zero in on immediately. I have had one rotor locking up which caused a pull and one rotor much hotter than the other front one.

That facts above would have avoided posters mentioning that flexible hoses could be an issue. Yes I have seen the interior of flexible hoses completely close up but it is very unlikely that it would happen to more than one hose at a time. Knowing the age of the coach would have also avoided those answers. It is very, very unlikely that a hose would fail unless it's at least 8-10 or more years old.

You did mention power booster. We can assume (again) vacuum. Most F-53 chassis use a hydraulic not vacuum PB.

Do yourself a favor and replace the MC and PB unit because you do want your brakes to work. If the hoses are more than 8-10 years old also replace them as preventive maintenance. While you are at it it's time to also flush the entire system. In the last 10 to 15 years that has become a new service procedure to be performed usually every 4-5 years.

Best of luck with your repairs.

TeJay

Mine is a 1979 Dodge Fleetwood Tioga class C Dodge 440ci 7.3 liter v8. 25 foot.
The Vacuum booster was in fact the problem. We checked everything else including the check valve. All systems are a go. Put the new booster on the brake pedal went down, no more sticking brakes and plenty of brake power. Quickly and accelerates to freeway speeds. So unless it sticks again the problem is in fact solved.

[TeJay]

Good news on the fix.

We've got a bit more in common than one would have guessed.

You've got your work cutout for you keeping a 79 RV up and running. We had a 78 23' Tioga Class C by FW with the Dodge 360. That was our first RV. We had a great time with it. The 440 was the other engine choice at that time but we spotted this unit at an RV show and with the rear bunks it was a perfect fit for the 4 of us.

Since then we've had a 1999 34' Dutch Star on the F-53 chassis and now a WBGO 31' also on the F-53 chassis. The old Tioga with the rear bunk beds actually slept the 4 of us much more comfortably than either of the next two bigger coaches.

Enjoy your travels.

TeJay

[cimplexsound]

Originally Posted by TeJay

Good news on the fix.

We've got a bit more in common than one would have guessed.

You've got your work cutout for you keeping a 79 RV up and running. We had a 78 23' Tioga Class C by FW with the Dodge 360. That was our first RV. We had a great time with it. The 440 was the other engine choice at that time but we spotted this unit at an RV show and with the rear bunks it was a perfect fit for the 4 of us.

Since then we've had a 1999 34' Dutch Star on the F-53 chassis and now a WBGO 31' also on the F-53 chassis. The old Tioga with the rear bunk beds actually slept the 4 of us much more comfortably than either of the next two bigger coaches.

Enjoy your travels.

TeJay

Yes, but my RV has been very well taken care and she runs like a champ. No mine is not hard to keep up. It is in very good, has been well maintained, and it only has 92,000 miles on it. So over in great shape.

[cimplexsound]

Thank you all. It was in fact the vacuum booster. Put in a new vacuum booster, master cylinder and she is as good as go. I made it to Pahrump and she ran like a champ the whole way. So thank you for all the input. Problem solved