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+--- Thread: Question about Jake brakes on a cm2250 (/showthread.php?tid=8222)
Question about Jake brakes on a cm2250 - ahrenbenjudah - 05-11-2022
Hey guys, I'm back with another one.
One of our trucks (2013 KW T800 with an isx15 cm2250) recently had a new reman head from cummins installed at our southern shop. The driver immediately noticed that his Jakes weren't as good as they were before. He claims that going down a 5% grade at 270k lbs he used to be able to hold it in 4th with the occasional brake touch.
Now, the truck won't hold him even in 2nd on the same run with the same load.
Our southern shop brought the truck back in and opened it up and confirmed that the exhaust brakes were within tolerance. They adjusted one, and sent it back out. My driver brought it back up north and lived with it for a bit and then started complaining again.
I went with him for a drive and noticed that it was vibrating more than it should but its hard for me to gauge whether or not they're working from the butt dyno way of looking at things because I'm a mechanic, not a driver. I brought the truck in and checked the resistance on the solenoids and they were in spec, but barely.
Last Friday, I pulled the cover off and put new solenoids in, found one had a slightly torn o-ring. I went ahead and replaced the harness since they're not that pricey and its good insurance. I also threw an engine brake overhaul kit at it as well since I knew that our southern shop just swapped everything over from the old head.
After I was done, I double checked the clearances on the exhaust brake rockers and buttoned her back up. Driver told me the vibration was gone now, but the braking is the same.
Driver also stated that before the head swap, when he was on the high setting with his jake brake, his boost pressure would hit 30 psi during a sustained engine brake. Now it only hits about 20. I can't find specs on what pressure it should be hitting on a cm2250. I have read that the 870s are only about 12-15 or so. Because of this, I took a look and his turbo is working as it should, boosts to about 36-38psi on a hard pull, vgt is working as intended, everything is good on that side.
What i've done:
Confirmed the switch works.
Confirmed that the solenoids are good and working as intended.
Engine Brake overhaul kit.
New injector harness.
Oil change is less than 5k miles old and pressure is good.
So I guess my question is, what should the boost pressure be during exhaust braking, and, is it just in his head? At this point, I've almost wondered if his jakes were messed up previously and hitting too hard.
RE: Question about Jake brakes on a cm2250 - Rawze - 05-11-2022
First and foremost.. is this truck de-mandated (deleted)?. If so then having the programming reviewed to ensure it is safe for the engine etc., is priority #1.
next, Will the engine pass a rail leak-down test as shown in this video?...
http://rawze.com/forums/showthread.php?tid=7915&pid=69262#pid69262
* Has anyone bothered to ensure there are no intake, CAC, or other boost, egr piping, or exhaust manifold leaks?. Maybe use some block-plates on the turbo front and back then pressurize the whole engine up with 10 - 30 psi of shop air and check for any. The allowed leakage rate for the intake system (at 30 psi) is no more than a 10 psi drop in one minute.
* Has anyone checked to ensure the overhead cam has not slipped.
* Also has anyone verified the part# on the head to ensure its part# matches exactly for what is required according to the ser# of the engine?. There are different heads that are required for for different tier engines out there.
RE: Question about Jake brakes on a cm2250 - ahrenbenjudah - 05-11-2022
(05-11-2022 )Rawze Wrote: First and foremost.. is this truck de-mandated (deleted)?. If so then having the programming reviewed to ensure it is safe for the engine etc., is priority #1.
next, Will the engine pass a rail leak-down test as shown in this video?...
http://rawze.com/forums/showthread.php?tid=7915&pid=69262#pid69262
* Has anyone bothered to ensure there are no intake, CAC, or other boost, egr piping, or exhaust manifold leaks?. Maybe use some block-plates on the turbo front and back then pressurize the whole engine up with 10 - 30 psi of shop air and check for any. The allowed leakage rate for the intake system (at 30 psi) is no more than a 10 psi drop in one minute.
* Has anyone checked to ensure the overhead cam has not slipped.
* Also has anyone verified the part# on the head to ensure its part# matches exactly for what is required according to the ser# of the engine?. There are different heads that are required for for different tier engines out there.
It is still in its original form other than being bumped up from 500hp to 600hp. This was done by KW a few years ago from what I'm told and has ran great ever since.
I haven't ran a rail leak down test on it as of yet. It wasn't showing any fuel related faults and doesn't have issues running or idling.
I did check the CAC but did not check the EGR or intake/exhaust for leaks. I did not see any prominent soot indicating an exhaust leak.
I have not verified if the cam has slipped, I took for granted that outside of the exhaust brake, the truck runs great.
I also did not verify the correct head, maybe to my detriment, I assumed that our southern shop verified it when they put it on, and since it was running well I didn't even think about that part.
The head was swapped due to leaking cups and coolant getting in to the fuel. I was informed that it was more fiscally prudent to just get a new reman head than to repair the old one.
RE: Question about Jake brakes on a cm2250 - Rawze - 05-11-2022
(05-11-2022 )ahrenbenjudah Wrote: ...
The head was swapped due to leaking cups and coolant getting in to the fuel. I was informed that it was more fiscally prudent to just get a new reman head than to repair the old one.
THE OLD isx HEAD SHOULD never BE REUSED, repaired, re-worked.. etc.! - A BRAND NEW ONE ONLY (not a reman) is recommended.. and of not, then only a certified reman from cummins if that is all that someone can get a hold of as a last stitch thing.
sounds to me like you have a lot more testing to do. Perform the things that I mentioned. Start there and confirm all of them!. making half-arsse assumptions is exactly why people chase their tails and waste money and time.
RE: Question about Jake brakes on a cm2250 - ahrenbenjudah - 05-12-2022
I'll pass the information along to my south shop as they're the ones that are tearing back in to it. Thanks Rawze!