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?