Jake Stopped Working

[Ben]

My jake brake has suddenly stopped working today. Going down steep hills/mountains I'll be in 4th gear with the Jake on High and the bus just keeps going faster and faster... it would easily head to 65 or higher. I have to ride the brake in order to keep it at 60mph. My boost gauge is only at 3 when it would usually raise when the jake is on.

Any idea how I can trouble shoot this?

In the past, I could always tell if the Jake is working by simply turning it off and I'd feel an immediate speed increase. Now there is no difference so I know it's not doing anything.

My turbo has also done a weird thing three times over the last two days. I'll be going up a hill and I'll notice my power fluctuating and the turbo not being steady.... it will go down a bit for about two seconds before coming back to normal strength. It might do this 3-4 times one after the other and then return to normal.

Other questions:

1) How long is it safe to ride the brakes while going down steep mountain passes. I'm driving South on I5 in Oregon towards California and will be heading to San Francisco (if this problem doesn't mess me up too much).

2) Is there any kind of indication of when my brakes might start to overheat? How long does it take to let them cool down?

3) Any other driving suggestions would be greatly appreciated.

[merle&louise]

Ben,

Sorry, I can't help you on the jake brake problem. But I can suggest down shifting your transmission to slow down. By selecting a lower gear to descend the hill you will use your brakes much less. If there is a highway sign warning of a steep grade it will usually have a suggested speed. I slow down to that speed at the crest of the hill and then downshift from 6th to 3rd or 4th gear. I use the brakes only to keep the rpms from exceeding 1800. After a little practice doing this, you will only need to tap your brakes to stay within a comfort rpm range.

Hope this helps until you can get your Jake brake fixed.

[Ben]

merle&louise (or is it Tuga & Karen?)

I know about down shifting... I tried to start in 3rd... have to start very slow to do that (four ways flashing on the shoulder kind of thing)... that only lasts for about a minute before the tranny shifts into 4th. It just doesn't feel safe to stay that slow and I have to ride the brakes more in trying to do so. I can stay in 4th, but have to hit the brakes every 15 seconds or so to keep it around 50-55. I'm trying not to ride the breaks for long periods, assuming that using them on and off will give them a little chance to cool.

I'm pulled over right now between grades to let them cool down. I'll be parked for 10-15 minutes and then continue.

With no Jake, the bus just wants to continue speeding up and the brakes in 4th is all I've been able to come up with.

My rpms are often between 2000-2300... I try to not let it go above that. My manual states to keep it under 2450 rpm.

Of course this had to happen the day before thanksgiving when shops are busy and will be closed tomorrow... and when I need to get to San Francisco for Thanksgiving. I'm willing to miss Thanksgiving with friends... more concerned with safety than getting there, but through I might be able to make it since I looked at a topo and it looks like there are not all that many overly steep passes between here and SF.

[Jon Wehrenberg]

Ben, I suspect the jake on the series 60 is like the 8V92 in that Prevost has a terminal or two in the rear electric box for the Jake solenoid valves. Call Prevost and find out if they do, and assuming they do they can give you the terminal numbers for your serial number coach. With the engine idling, jumper between each terminal and a 24V (12? ask please) power terminal. That will actuate the solenoid valve, bypassing the lowspeed cutout, and you will hear the engine bog down. Do it on both terminals. Assuming both cause the engine to lug down you have ruled out anything internal to the engine and the problem lies with the push button control most likely.

Brake firmly going down hills until you are about ten MPH below your target speed and release the brakes until you exceed your target speed by around 5 mph. Stay in the same gear or lower that would have been appropriate to climb the hill. If you think the brakes are getting hot, pull over and stop and allow them to cool. Hot brakes will fail.

Higher RPM makes the jake work more effectively, but I would try to keep the RPM between 1500 and 2100, and no higher.

Try to flash your codes because I think your turbo boost sensor may be acting up and it should show up as a code. If not indicated as a code pull off the big tube going into the turbo (between the turbo and the air cleaner) and slowly spin the impeller in the turbo. Make sure it is not wobbling, making metal to metal contact and especially that it turns freely and smoothly with no drag or spots that feel different than other spots.

[dreadnought]

All good advice Jon. I've driven many a loaded truck with no Jake in the mountains and was taught to go down the hill in the same gear it took to climb it, and to brake firmly to bleed off speed rather than ride the brakes. Basically if you use a lower gear to hold your speed down and brake only to keep from over revving the engine you should be fine. The other thing this does is let the block cool gradually from the heat of climbing the hill which is much better for the engine. Another thing worth mentioning along these lines is to never switch off as soon as you stop. A engine running a pyrometer temp. of 900 degrees or better needs 3-5 minutes of idling to cool the block evenly. Otherwise it will just get hotter after you turn it off!

[Coloradobus]

Ben.

We have an intermittent Jake Brake probem, too. The check engine light will no longer come on. The Jake indicator activation light stops working and we can feel the Jakes have cut out.
Have you tried shutting the motor down and then restarting it? At first, we thought it to be a loose wire on the DDEC. Try to trouble shoot it with S and S, we determined if we shut down the engine, let it sit for a few minutes, start it back up, all resets and we have Jake again. Our September trip of 3,500 miles, the Jake only cut out when we were in stop and go traffic in Vancouver, BC. Other times, it has cut out off of Loveland Pass, Yeeow!! Know what you mean. I don't care at the speed. When the Jake cuts out, we go down a hill either in the gear we climbed or a lower one so we don't have to punch to service brakes so much. I just stab them, and slow the coach down as Jon described above. This way, the brakes stay cooler, and you don't run out of air.

[Ben]

I belive that my turbo fluxuation was actually a gear change that I didn't notice... I think it switched gears for a few seconds and then switched back (which would also cause the turbo pressure to change quickly).

I made it through the hills and am now about an hour from San Francisco. That means I'll make Thanksgiving without a problem. I'll troubleshoot more the day after.

I toured Marathon on my way through Oregon. I spent a few hours going over their whole operation. I was surprised to see that they don't use the lightweight materials I saw at Liberty and Millennium (at least it looked like plain old plywood). Nice coaches and a nicely put together operation.

I saw an H3 that had tipped over and slid down a hill before hitting a telephone pole, which is the only thing that stopped it from sliding. A few windows on one side where smashed, but otherwise the side didn't look all that bad. There was a dent in the roof caused by the pole it slid into. It sounds like it was because of a deer... people where going around it on the shoulder, but once the Prevost went on the shoulder, it sunk in, tipped over and started to slide. They said the interior didn't get much damage, but the fridge did come loose (it was on the side that ended up becoming the "ceiling"). The driver had his seat belt on and got out by kicking out the windshield.

If you're ever passing by, they are more than happy to let you hook up for a few days and give you a personal tour (just call a manager instead of the front desk, otherwise they'll tell you that tours are at 11am each day instead of giving you a personal one).

Jon... thanks for all the info. I'll give Prevost a call as soon as Thanksgiving is over.

[matsprt]

Ben,
Engine brakes (Jake brakes) stop working 8 out of 10 times because of electrical connection issues, the other 2 times it's mechanical and expensive to fix. :(
Jon knows the Prevost scheme and will send you in the right direction.
Ref your turbo issue, first question I have is how do you know it's the turbo ?? Sounds like it could be several things (turbo included). Would like to know the boost pressure readings and pryo readings when the problem occurs.
The braking question... I guess that old saying about down in the same gear as you climb up in is "ok" as a guideline only. My experience is the go ups are never the same as the go downs. But having said that you almost can't start too slow at the top. Easy to let it pickup speed as you get to the bottom, not so easy to slow down if you let it get away from you. Flip on the flashers and don't worry about anybody else until you are down the grade safely. They'll go around.
I'm one of those that disagree with the stab the brakes method....mostly because in the "old" days the CHP used to say slow steady pressure...now they have changed their minds. I will say it's a multi-faceted relationship between weight, grade, speed and applied braking pressure. Point in reference, I could go north on I-5 in California and descend the "grapevine" at 80K, no Jake, hold speed at 25-27 MPH and hold a steady 5-7 pounds of applied brake. Never smoked the brakes and never played in the sandbox.
If you start stabbing the brakes too much you will build heat, feed nice fresh Oxygen into those hot brakes. Get enough and you'll have fire.


I just checked Ashland weather, light rain down in Ashland, so I expect the pass to be snowing. You'll find that all across until you make Redding. If your in California and can make Redding your mountains are over. If your past Ashland maybe stop in Weed and spend the night. Tackle the "canyon" (down through Shasta) tomorrow in the daylight.

Michael
Flame proof suit on....

[matsprt]

Opps, I see you made it...Happy Thanksgiving !!

[truk4u]

Ben,
Could you have a cruise control problem killing the Jake?

[matsprt]

Ben,
Could you have a cruise control problem killing the Jake?

Tom,

Cruise control ?? These things have cruise control ??
WOW!!
I knew there was a reason I wanted one !!

Michael
:D :D :D :D

[Coloradobus]

Ben,

The tipped over coach is 589, a 2000 "H", an HWH 2 slide equipped bus. It was being used in Alaska on the "Extreme MakeOver TV show and was being driven back to the lower 48,
Up to this show segment, Marathon had provided the driver. This time, it was not a Marathon driver. We heard several differnet stories as to what exactly happened. A Deer, soft shoulder, driver error, whatever it was, the service crew said once the insurance thing is hashed out, the coach rebuild was a future winter project.
Glad you are making it to SF. It was 73 degrees here in the Front Range today. Heard they had snow flurries north of Leesburg, Fla.:D

Happy Turkey!

[truk4u]

Michael,

Yep, we got em, what are you waiting for?:p

With all due respect, I have to disagree with your braking suggestion of slow, steady pressure. That is exactly what will cause fade and a trip to the dirt or WORSE. Being a trucker for the last 40 years (ya I know, I'm getting old) I have watched smoking, fading brake drivers get in bad situations. I think the buses are much more prone to this problem without the jakes, as the brakes pretty much suck from the get go. I'll take 80,000 lbs and five axles anyday downhill, provided the brakes are adjusted, rather than the bus. Maybe it's because of a combination of drum on the drive, and disc on the steer and tag, I'm really not sure.

For those not familiar with the Commercial Drivers Manual, here is a piece from the Proper Braking Technique:

Remember: The use of brakes on a long and/or steep downgrade is only a supplement to the braking effect of the engine. Once the vehicle is in the proper low gear, the following is a proper braking technique:

1. Apply the brakes just hard enough to feel a definite slowdown.

2. When your speed has been reduced to approximately five mph below your "safe" speed, release the brakes. (This brake application should last for about three seconds.)

3. When your speed has increased to your "safe" speed, repeat steps 1 & 2.

[matsprt]

Tom,
I like you have a long history with trucking (also like you, longer than I care to remember). I can tell you that "my" method had worked for me until Jakes became commonly installed on trucks. At that point going downhill was much easier. I can still remember "setting" new brake shoes with a good long downhill.

I agree with everything you say. However one can find themselves in trouble no matter which method you use. Going downhill is a carefully thought out mixing of weight, speed, grade, length of grade. You know that the "bad situation" you find yourself in at the bottom was caused by decisions made at the top.

If one uses the now taught (there was no teaching in the "old" days-except by veteran drivers :D ) method and you start down a hill too fast the results will be no different.

About buses, I've just started reading all your complaints about braking. Thats interesting. It seems a common complaint in the MH world. Tom is right about taking 5 axles worth of brakes and 80,000 pounds with a Jake and running hills. It's a no brainer (well for most anyway). But that said, I find the weight of most MH's is just barely above that of an empty truck and empty trucks are a snap to get down hills.

My current coach is just below 40,000 pounds with the toad. I can flip on the exhaust brake, and let it ride down the grapevine (I-5 north out of LA - 5 miles of 6% grade) and NEVER touch the brakes. It will hold 53-55 mph all the way down.

I-5 north coming down into Ashland Or., same type of hill only a little longer and has some parts that are steeper than 6%, I hit the brakes 4-5 times lightly to trim off speed in those sections. (the stabbing method ??)

Your buses weigh more but Jakes create more braking power than the exhaust brakes. Net even ??

Michael
Still has a CDL (and actually got to use it last Tuesday !! Yeah !!)
They don't let me out too often in a truck anymore...:(

Happy Thanksgiving to all !!

[Jon Wehrenberg]

We're bouncing around a little here, but it is all related because if Ben doesn't have supplemental braking like a jake or retarder he has to pay attention to advice like Tom's. Tom also brings up a good point and should be added to help Ben with his problem.

The cruise control may or may not be a part of the problem. I think Ben has to rule out the mechanical aspects by powering the solenoid valves with the bus idling. I find it very difficult to imagine both solenoids failed at the same time, but it is possible one has failed and Ben was unaware, and when the second one failed he realized there was a problem. If they are functioning then Ben needs to look at the controls, and Tom is correct in suggesting the cruise may be a factor.

I hope JDUB can jump in here, but if my memory is correct, DDEC can be programmed to allow the use of the Jake with the cruise engaged, or to prevent the use of the Jake when cruise is engaged. That provides another point to look for a problem. I don't think flashing the codes would tell Ben anything on this, but a DDEC reader may give some clues.

[Ray Davis]

If it's anything like my jake issue (8v92), the DDEC required a zero throttle signal, and then it would send the signal to the jakes. I don't have the schematics in front of me, but we could measure (on mine) 12V at two lugs in the electrical panel (under the driver), and again back in the electrical panel above the engine. In my case, the signals made it all the way to the back electical box, but the spades had been removed for an engine service, and forgot to be replaced. Doubtful that's Ben's issue, but I'd be more than willing to see if I can get the terminal numbers from my manuals. Might be the same on Ben's unit.

[Jon Wehrenberg]

I think the terminals are specific to a particular coach. The Prevost guy I spoke to when chasing my problem said they are usually X and Y, but when he looked up my serial number they turned out different.

[Jerry Winchester]

Jon is correct in that the codes related to the Engine Brake are cruise control specific.

If the CEL (Check Engine Light) or SEL (Stop Engine Light) are functioning correctly and there is no indication of a fault, then it is unlikely that the issue is anything other than a wiring harness or fuse problem.

As the Jake Brake is an added system to the engine, the DDEC only seems to deal with it as a function of Engine Overspeed (Engine Brake Engaged) or the Cruise Control (setting it up to keep the Jake Brake from coming on when you are following Anal-1 thru the hills in South Florida with the cruise control on :eek: Hey, I'm not making this up :rolleyes: )

[JIM CHALOUPKA]

Ben, Was there ever a conclusion to your Jake Brake issue?

[Ben]

It worked fine the next day and has ever since. I think I just needed to re-boot the coach... shut it down and start it up again... I happen to keep it running all day while driving from OR to CA.

[JIM CHALOUPKA]

Thats good to know. If that ever happens to me I'll try to remember that on the way down. :D :eek: