1997 n-14 460 e + CPL 2025 C brake from Jacobs- Model 455B New to us truck. KW t-800, came with the wiring cut off that went to the jakes. We've been trying to get the truck ready for the road and have some issues. Sometimes when you start the truck, it will run rough, and I think I've got that isolated to the front jake. It seems like this jake will stick partially open, and stay stuck on. Its like there should be springs inside the jake pulling it off. Its the only jake that will come on when you apply 12v to the solenoid, but then it seems like it won't go totally off. At times it will release all the way, and then the truck idles smooth, but if its stuck, it just kind of chuggs on the motor. Its not like the jake is totally on (which I can make it do with applying 12v), it just seems like something is slighly stuck. (maybe not totally releasing the valve?) The middle and rear jakes, when you actuate the solenoid, will simply pump engine oil where the blue arrows are in the picture. I'm assuming there's seals inside the "pistons", that are bad, and so they won't build enough oil pressure to make the jakes come on. They won't even try to come on when you apply 12v, and I can see the solenoid actuating. It just seeps oil out the top. Oil seeps out of the rear two where the blue arrows are, the front one does it a little bit, but not nearly as bad as the rear two. Also- I have no clue how to set overhead on this motor, is it best to get a cummins book for these, I've read that using a dial indicator is the way to go, but I'd be lying if I said I knew what I was doing.
I would definitely perform the overhaul on them. It's super easy. I used to set them running. It's not the right way, but the way I did em. Here's the right way.
Looks like I need kit # 3871704 from my cummins man? From what I'm seeing online from cummins- its around $600. And I'm guessing the jakes should come off- set overhead, then reinstall the jakes and set them after rebuilding?
Manual https://issuu.com/heydownloads/docs/cummins_n14_engine_service_repair_manual___1_
Good god almighty! Last time I did a set, the kit was about 225. Does the 600 kit include the little master valves and the solenoids or is that just for O-rings and snap rings?
Wonder why the wires were cut off, because of them not working, and the previous owner not wanting to fix it. I worked for a guy that removed the jakes from a truck because he figured it was hard on the engine. I remember seeing them in their stock room.
My dad told me about a local grain hauler/ farmer that removed all the jakes from all their trucks. His theory was that the jakes were hard on the rest of the driveline components, and he would rather buy brakes. I need the jakes.
Truck drivers sure come up with some strange theories lol.
It's the product of setting on their ass all day plus dreaming about what they would do if they were president.
was always told the complete reversal happens, when using jakes coming down a hill it keep the heat in the motor, dont know if this is an old wives tale but heard the older 335's used to scorn liners after cresting a good long hard hill then when going down the other side is when you wanted those engine brakes mainly for slowing down and keeping a little heat in the engine .most engine makers ,let's say the last big 3 at least , recommended jakes . its not all about brake lining, bet you will find more million mile + engines with jakes on them that are kept in good condition. fest
Do I need to remove the housings from the engine to install the kits, or does it all install from the top side?
They have to come off.
More than likely the control valves are bad, Do you have a solvent tank need to disassemble and flush the oil circuits. Once done setting valves and injectors which is easy-install jakes and you can set lash on any that have closed exhaust valves, then just bar engine till you find the rest with closed valves. Normally can set four then bar and get the last two.
When you get the Jakes off, it would be a good time to re-torque the rocker box. Sometimes the common stud backs off a bit when removing and you wind up with a leak and improperly adjusted overhead
Those C brakes don't use a rocker box stud, have their own 12 point bolt in center.
Thanks for clarification. I wasn't sure , I remember they improved the water manifold/ rocker box. Thanks TS
I've got a parts washer tank, but we just run old diesel in it, and its filthy. I can clean them in a separate tub if I need to. I'll get the kit ordered and here first before I tear anything apart. Is it likely that I need items that aren't in the rebuild kit?
You said when you applied power, one hit and 2 slobbered oil. So your solenoids should be working. Besides, if you do need a solenoid, they're serviceable from the top iirc.
Normally most just need a tune up kit. Master piston should be ok. The solenoids either work or don't, and are the same through various models, although expensive. after done hand scrubbing wash them down with brake clean and assemble hard parts in jake head with oil. Make sure all the o-rings on solenoids are replaced and if it uses a small green one on the bottom that those are removed and replaced. Those can stick in the bottom of solenoid bore in the head and missed.
I find it funny when they freak out when an engine revs up to 2,000 RPM.
It's hard to get it through their head a jake works best at 2000 to 2100.
https://www.jacobsvehiclesystems.com/sites/default/files/service_literature/021671.pdf
Works even better if the engine is going faster! Until it comes unraveled that is.
It can be a problem with inexperience at driving a AMT if it decides to down shift.
How so? I have never driven an AMT. Some Allisons come programmed to call for 2nd gear when you lift the throttle and the Jakes come on, which is very annoying. It will keep the engine near max RPM down to 2nd gear but not overspeed.
On a AMT you want to brake it down at the top of grade while in manual mode, lets say a 6% grade to 7th gear at 100K GVW. The jake will hold it to the bottom without touching the brake for how ever long the grade is and keep it at 38 to 40 mph. Or brake it down in auto mode till you hit the desired speed engage cruise control with jake on and it will carry you to the bottom at a constant 40 in 7th gear.
I was quite impressed with the jake on the DD13/Eaton 13 speed AMT. Heaviest load I hauled was probably about 85k gross and stage 3 on the jake slowed it down pretty quick.
Got some parts and pieces.... This was in the one that would act "stuck". I guess whatever pieces aren't floating around in here, hopefully are laying down in the pan. If they aren't clogging the oil gallery. Cummins had the rebuild kit, but I'm going to need some hard parts. I may go to my engine core guy and see if he has a full box to replace this one, the bore is pretty dinged up. It had the retainer snap ring about 1/4 of the way forced out of the groove on the bottom.
Those Robo-Lash cracks all the time, best way to check them is squeese them between your fingers and the crack will show up as an oil line on the pad section.
Not uncommon with auto lash those need to be set with feeler gage, don't really want to do it running. Unless the bore will clean up for the slave piston, possibly need a another jake housing.
Got a used jake housing, and have found two more suspect auto lashes. So we need a few more parts yet.
Not surprised, a 26 year old engine. On the Series 60's especially the 795 jake, when those get weak normally it's the oil control valve coming apart. Check the tops of solenoids where crimped to make sure those crimps are tight, have a tendency of getting loose.
I replaced all three solenoids- just so I knew they were good.
Put the old ones in your treasure trove for a while in case the new ones aren't as good as you think they are.