Jake break? Sometimes.

My Jake has been acting up for a little while now. Started maybe a few weeks ago. Here are the symptoms:

Driving down the road, everything is great, jake is working in hi and lo. No problems. Then all of the sudden, I find myself picking up speed going down a hill and notice the Jake isn't kicking in. So I step on the accelerator and let it back up and wham, the Jake kicks back in.

Once, I stopped, and lubed up that little wheel under the pedal and blew the spring out with some compressed air. Seemed to make it work better.

Some variations on the same theme.... jake no go, step on accel. and jake turns on, then off, then on then off, etc. It is almost as if the sensor thinks I'm keeping my foot on it ever so slightly. Ya know, how you can keep the Jake from coming on by just laying a slight amount of weight on the pedal?

Tonight, all was well, other than an obscene amount of driving today. Then, late at night, all of the sudden, no Jake. This time, I couldn't get it to come back on at all. We were not in the mountains any more, so it didn't matter... other than that we will again be in the mountains... soon!

Any thoughts? The previous owner had replaced that little square sensor that hooks to the pedal. I'm wondering if he did it because his Jake wasn't working. Maybe I'll email him and ask.

Thanks for any help.

Best,

Adam

Didn't know the Jake had any sensor at the gas pedal.

Always thought the Jake was controlled through DDEC, which sent a 12 volt signal to two terminals in the rear electric box which in turn energized the two solenoids in the head.

This is something a tech with a DDEC reader should check. I wouldn't be oiling or messing around under the pedal. The throttle position sensor is under there and that sends a signal to the DDEC computer.

I just spoke with Ste & Ste about checking my Jake brake issues.

I was told the majority of issues with the jake working or not, are not computer controlled at all, but mechanical. He stated one of the two stage jakes may not be working, and it would have to be researched under the valve covers, NOT just by hooking up to a computer?

While there is some electrical issues involved, between the Jake and DDEC, it sounds to me like a lot of money involved to check why mine doesn't work as well as I believe it should work. CRAP Not what I wanted to hear.:(

Gary S.

When I had a jake issue in my CC, I pulled out the schematics. At least in the case of my 93 CC, the jake required that there be a signal from the DDEC which indicated zero throttle.

This is a wild guess, but I'm thinking that if you have to jiggle the throttle position, then there is a sensor that that is either not calibrated, or is mal-functioning.


If you had a DDEC reader, I would think you could see if you're getting zero throttle?

Ray

Quote:

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Originally Posted by Jon Wehrenberg

Didn't know the Jake had any sensor at the gas pedal.

Always thought the Jake was controlled through DDEC, which sent a 12 volt signal to two terminals in the rear electric box which in turn energized the two solenoids in the head.

This is something a tech with a DDEC reader should check. I wouldn't be oiling or messing around under the pedal. The throttle position sensor is under there and that sends a signal to the DDEC computer.

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Jon, I guess what I meant was that the Jake comes on when the pedal is in the upmost position. Since, I can often times get my Jake to come back on by "flicking" the pedal and letting it spring back up, it makes me think that my Jake is not cutting on because it thinks the pedal is not in the upmost position. See what I mean?

As for the lubricant, I was only lubing the little roller which wasn't rolling smoothly. I was careful to confine the silicone spray to the the roller axel and only used a very little. It made a big difference though. And, all of the sudden, the jake worked again.

By the way, I'm really not a very big fan of intermittent problems. My Webasto was working perfectly the other day. Now it is back to its old tricks.

I'll talk to Prevost about the Jake.

thanks for the input!

Adam

Adam, If you pedal is not "returning" you can tell. With the coach in neutral operate the pedal and release it as you would when driving. The tach should show it dropping down to idle speed every time. If it returns to the 600 or 650 idle speed every time the computer should work the Jake.

Your accelerator pedal is doing nothing more than sending an electrical signal through a sensor to the computer. You're going to love this: They call the sensor located under your pedal a throttle position sensor. If the normal idle is experienced every time then it is not a question of the pedal returning because it is returned when the engine RPM is the normal idle.

However, if operating the pedal occasionally causes the idle speed to remain above the normal idle speed, you are correct in that the bus does not know the foot is off the pedal and it will not engage the Jake until it thinks your foot is off the pedal.

Talked to my Prevost rep. He said that he was almost positive that it was a faulty throtle position sensor. This was based on my description of the problem. I hope he's right. I have a new one on the way and will put it on before our huge upcoming trip through the mountains. Will post and let everybody know if that does the trick. Keep your fingers crossed.

~Adam

Adam,
I can confirm what the Prevost Rep told you. I had the exact same issue and screwed around flipping the throttle position sensor by hand. Get the new part and install it. It only takes a few long grades with no Jake to make someone a believer. What is happening is that the Jake will not come on until the computer is positive you are not on the gas pedal. The failure is the throttle position sensor is not coming all the way off. Simple to fix.

Adam: Just curious if your bus is equipped with a Pro Driver? and if so did it indicate a TPS failure? Or it just hasn't failed completely yet?

I once had a failure of the TPS and for such a tiny gizmo, it stopped us from our merry way.

This too should probably be added to the list of items that can shut you down. You can start the engine but it will not accelerate therefore - no go.

I wonder if this throtle position sensor could be my problem as well ?

Gary S.

Quote:

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Originally Posted by jimshoen

Adam,
I can confirm what the Prevost Rep told you. I had the exact same issue and screwed around flipping the throttle position sensor by hand. Get the new part and install it. It only takes a few long grades with no Jake to make someone a believer. What is happening is that the Jake will not come on until the computer is positive you are not on the gas pedal. The failure is the throttle position sensor is not coming all the way off. Simple to fix.

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Jim, I don't know why I didn't just call you first. I mean, it seems that every problem that crops up for me, you have already dealt with and fixed. Buddy, when am I going to be able to start helping you out?!

Better watch out... with seven kids, I might start calling you for parenting advice too. (Especially since your kids are so great!)

Thanks for the encouragement. I ordered the part and will install it on Thursday.

Thanks!

Adam

Quote:

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Originally Posted by rfoster

Adam: Just curious if your bus is equipped with a Pro Driver? and if so did it indicate a TPS failure? Or it just hasn't failed completely yet?

I once had a failure of the TPS and for such a tiny gizmo, it stopped us from our merry way.

This too should probably be added to the list of items that can shut you down. You can start the engine but it will not accelerate therefore - no go.

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Yes, I have Pro Driver. And no, it did not indicate any sort of Failure. However, I called the previous owner of the coach, and interestingly enough, about a year ago, he had gotten a tps failure code. So, he replaced the tps. He never noticed that the jake, or anything relating to the tps wasn't working. But the code said to replace the tps and he did. Here I am a year later with massive tps symptoms, but no code. I'd say the whole thing is a little strange. And, as Jim mentioned, going down a big mountain without a Jake is a problem. But an even bigger problem is going down a big mountain and thinking you have your Jake on and working, only to find yourself accelerating towards 80 and needing to slow down. Let's just say that one might not only leave skid marks on the road.

~A

Adam your last post made me cringe. Don't do stuff like that.
Even if I were familiar with that piece of road and was jakeless I would have done it slower. Never having done it you never know what is around the next bend.

Adam,

I like the pun. Jake "break" for a broken Jake brake. Nice. Keep up the good work. When is the tour coming to Houston?

Loc

Adam,
I may have fixed a lot things, but you are the King of driving the Beast.

Loc, Adam and his group are only getting as close as Lake Livingston.

His concert is on March 21, 2009 7:30pm according to his web site.

Peg and I hope to be there to see his show.

http://www.pianafiddle.com/calendar.html

Quote:

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Originally Posted by Loc

Adam,

I like the pun. Jake "break" for a broken Jake brake. Nice. Keep up the good work. When is the tour coming to Houston?

Loc

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Oh, I'm so happy. My quest for coming up with witty, creative, and eye-catching titles is not falling on deaf ears.

Yea, we are playing in Livingston. Also playing in Palestine. They like us there. We were just there last year and they wanted us back. Nice big civic center to fill up with people. Over 1000 seats if I remember correctly. And plenty of bus parking in their massive lot. So come on down. I'm sure we can all camp in their lot. In fact, I think that show is on a Sunday afternoon, which means Sunday dinner at a really nice Mexican joint near the hall. Mmmmm, fresh made flour tortillas. Gotta love central Texas!

~Adam

Hey Adam, where in Livingston, TX is your concert?

Is there plenty of bus parking there too? That is closer to Houston, and is on a Saturday night, which is great for Peg, YOU Know, her working all the time. Her working really gets in the way of doing fun stuff :D

Gary S.

Quote:

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Originally Posted by Gary & Peggy Stevens

Hey Adam, where in Livingston, TX is your concert?

Is there plenty of bus parking there too? That is closer to Houston, and is on a Saturday night, which is great for Peg, YOU Know, her working all the time. Her working really gets in the way of doing fun stuff :D

Gary S.

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I think it is at the high school performing arts building? Maybe not the most exotic venue we've ever played, but parking should be good:-)

See you there... if not before. Please email me with your ticket order about a week or so before the show so we can leave the correct amount of tickets at the door for you.

Adam

Jean & I are searching for Buster 2.

We are looking at a 2000 H single slide. I asked for the weights on the three axles. Front. Actual 18,940 vs. 16,500 rated.Actual total 53,180...rated 52,060. Drive and tag were below rated.

Is the overage a game stopper. It was posted on here you could get a ticket if over and your insurance would be void if you ever had an accident.

Any insight would be greatly appreciated.

I would be more concerned about SAFETY than the legal issues!!

Chances are, you will not likely get ticketed for being overweight. The real concern is tire pressures, braking distance and the potential damage to the components of your suspension system....

Simply put, how much risk are you willing to take with full knowledge that you are operating a vehicle that substantially exceeds the safe handling limits?

Buster,

There are better things in life than driving a coach that may be a handling nightmare.

The way Prevost rates the axles is based on the capacity of all the components, not just the tires or wheels. Air bags, brake pad surface area and application force, bushings, bearings etc. all are a part of the total and while conservative driving and luck may allow you to enjoy years of enjoyment, the flip side is that coach is likely to wear out front end bushings, bearings and brake pads, but it also will be slow to raise to ride height, and with the heft of the front its braking forces on rain slicked roads may be compromised.

I'd walk. There are a lot of choices out there.

Mike, I would have the coach re-weighed after the ride height, and tag bag pressure had been checked. We have seen some significant variances in scales, and we had a Newell that we sold, and by adjusting the ride height & tag axle pressures were able to correct a 1,500lbs. overweight on the front end. This coach went to Newell, and they also re-rated the front end for an additional 2K lbs. with different front tires. I would also check with Prevost to see if they will tell you what the limiting factor is. It is not a big deal ($4K) to put the 365 upgrade on the front end. That will get you closer but if the axle is a 16K axle you are significantly over. And as John stated you will likely have other components that may be undersized for that weight. If you love the coach, you may check to see what the cost would be to change the front end to the current configuration. If the coach still has the beam front axle (98 chassis & older on an H) it would likely not be possible.

With all due respect for Steve there is a common belief that air bag pressures can be modified. They are modified constantly while driving, but only to maintain the ride height under the varying road conditions.

The air bag pressures are a function of the weight on a given axle. The unsprung weight is the tire, wheel, brake disc, calipers, etc. The air bag does not lift that, but it does lift the chassis and everything in the chassis including the people. For a given size air bag the air pressure required to position the bus at ride height is dependent upon the weight which must be lifted. The only way to reduce the weight on any axle is to move the weight elsewhere in the bus or remove it from the bus.

The ride height valves only serve to control when the flow of air into or out of the bag is necessary to place the bus at a specific distance above the road. They adjust pressure, but only to the extent necessary to raise or lower the bus height. But in the end, if the bus is sitting on a level surface, and the pressure in an air bag is raised or lowered, the only change will be to the height of the bus. It will have no effect on the weight on a given axle.

John, on the Newell that we had the tag axle air pressure is adjustable via a regulator in the engine bay. We had the coach parked, and running with the steer axle on the scale. You could adjust the air pressure on the tag axle and watch the weight raise or lower depending on how the tag was set. The drive axle acts as a fulcrum, and the coach will gain weight on the tag & steer if the tag pressure is reset. Remember that the rear ride height is determined by the drive axle ride height valves. There are not ride height valves on the tag axle. That is why you can increase the weight on the tag, which will also increase the weight on the front, and decrease the weight on the drive axle. The front ride height valve, or valves will compensate for the increased weight by increasing the front air bag pressure to bring the coach back to the ride height. In my racing days we would set up our race cars by corner weights. The car would be set on a level plane with individual scales @ each corner. We would adjust the individual ride height via coil over shocks to set the individual corner weights to where we wanted them. You would be amazed at how significant of weight change you can achieve with minimal adjustments in ride height. If we were racing on a predominantly right hand turn track such as Lime Rock we would set the car up asymmetrically to achieve the best balance in right hand turns. A coach is no different if you were to raise the tag axle pressure (same thing as adjusting a coil over spring) on only one side (I know that is not possible with the standard air system) it would transfer weight to the opposite side on the front. The Newell that we were referencing went to Newell in Oklahoma, and I saw the print out of the new corner weights. It was completely different then what we had when we weighed the coach in CA. If you doubt what I say, park your coach on a scale with only the front axle on the scale. Now raise the tag axle, and see what happens to the front end weight. That is the reason that some coaches with heavy front ends need to lift the tag to speed up the achieving of full ride height on the front end.

Steve, I am well aware of how the tag affects the steer axle weights.

That is how the overloaded Marathons get to raise the front end to road height. They pick up the tag.

However this is not something that is adjustable on our coaches. The rear ride height valves supply or exhaust air from the three rear airbags per side simultaneously. There is no pressure regulator to control air bag pressures anywhere on a Prevost.

Steve,
Why does Newell allow the tag axle air spring pressure to be adjusted? Sounds like a formula for disaster. Prevost surely does not allow that, and there must be a good reason. I have heard Newells are heavy and among other things need the 600 hp get down the road? On a Prevost, all three air springs on either rear corner will have the same pressure in them. Both front air springs will have the same pressure. I just can't believe Newell would have a user adjustable air spring pressure.
Jon, Which Marathons are having that problem getting the front to road height? Do you know if it is a particular model or year? Or is it the possibility that the front axle may be overloaded?

Jim,

There was a period of time when some Marathons exceeded the Prevost front axle limits. At the time they were configured with the generator and I believe batteries in the first bay.

They are not alone. There are other converters whose front axle weights are in excess of the ratings. I do not know if the problem continues to exist but I suspect some, especially with slides are close if not over

In about 1992 or 1993 Bill Campbell, one of the three owners of Prevost at the time gave a dire warning to owners about observing weight limits during a PP seminar. He was cautioning owners not to overload their bays, but he was also sending a not so subtle message to a few of the converters at that time. He apparently got spanked by the converters for doing that because from that time on we never heard a word from Prevost about converters exceeding the limits.

That was when Prevost did a retrofit to larger air bags in the front because some coaches had to come up to full air pressure just to get the front up to ride height. If my memory serves me the four shock absorber set up was also retrofitted because with the excess front axle weight some coaches had so much rebound over bumps they were bottoming.

Jim,

My 97 Marathon XL would not lift the front end without dumping the tag and it was at gross weight with little weight in the front bay.

My Liberty is also at gross on the front (I thought they did a better job on the weight distribution), but will lift the front very easily.

40 footers are a bitch to get the front light. There is very little weight cantilevered beyond the rear axles so the front shares every pound in the bays. The 45 footers with the long rear overhang have less of an issue if the converter keeps the heavy stuff back towards the drive axle.

An entertainer coach with the same overhang as a 40 footer in the rear is almost guaranteed to be front axle heavy.