ISL400 second stage brake not working

[amxalan]

I have a 2005 Monaco with the Cummins ISL400 with an engine brake issue. The second stage engine brake does not work. The switch lights up when turned on
but where is no noticeable difference in braking beyond what the first stage does.
I took the coach to a local mechanic who replaced the wiring harnesses for the brakes located under the valve cover . Issue was not resolved. I took the coach to a Cummins dealer and their diagnosis was as follows:
CAUSE:No codes logged. Looked up brake test procedure. Removed ECM to check wiring for engine brakes. Checked pins, 8, 18, and 34 per the diagram. Only pin 18 is there. No pin 8 which is the other leg of the circuit. Pin 34 is not there as it is the return.
CORRECTION:OEM needs to run a ground wire from the dash switches

The Cummins dealer would not run the ground wire as they stated it is a coach issue and they are not trained for such work. I took the coach to the Monaco factory service center in Indiana but they had no clue on this diagnosis or how to proceed either. Looking for recommendations to fix this issue.

[Smitty77]

It say's Post # 1, if this is accurate - welcome to the gang!!!

A question, and a few comments:

Question - Is this a new to you coach? And if so, had the High (2nd Stage) ever work?

Comments:
-The 8.9 is not a larger displacement engine, so the braking Horse Power is not as dramatic as say a ISM, ISX BIG BLOCK engine. Unless you are towards the upper RPM 2000-2600 (2600 Redline for Jake, on my engine) when the Jake is activated - the difference between Stage 1 and Stage 2 is not all that dramatic!
-Our 2004 coach we bought used with low miles on it at the end of 2010. As I was test driving it, I could detect no difference between Stage 1 and Stage 2 (Low/High). As part of the PDI, I paid to have Cummins do a Dino Test of the engine, look everything over, check the chassis and Allison for me too. They found a few recalls that had not been done. They also agreed the Stage 2 was not fully working. So part of my condition to purchase was for this to be addressed, as well as all recall items, and a few other engine/chassis related.

The end result was that the Cummins Service Writer called me to explain that a mistake had occurred during manufacturing, and the Stage 2 (The second closing of valves on the last three cylinders.) had never worked. He said they had corrected the problem, and also adjusted the Stage 1 too, to validate it was properly engaging.

====

So if it's a new to you RV, and you do not know the history. Perhaps your engine too had had a mistake during the manufacturer process - worth a check!!! If not, either way, if it's not an electrical problem from the switch to the ECM to activation of the Jake... They'll need to open the valve cover and check the valve train Jake control!

Sure hope it's something simple for you. And again, welcome to the gang,
Smitty

[A Traveler]

There is one other “test” that can determine whether the high range is working. It’s called the “Cummins shake.”

If the Jake Brake is working on all 6 cylinders (high) there will be no noticeable vibration as the engine slows to 1,000 rpm (at approximately 15 mph in 2nd gear) where it will disengage.

If the Jake Brake is only using 3 cylinders (low) there will be a pronounced and rapid vibration for a couple of seconds at that 1,000 rpm point, just before the Jake disengages.

[amxalan]

Originally Posted by Smitty77

It say's Post # 1, if this is accurate - welcome to the gang!!!

A question, and a few comments:

Question - Is this a new to you coach? And if so, had the High (2nd Stage) ever work?

Comments:
-The 8.9 is not a larger displacement engine, so the braking Horse Power is not as dramatic as say a ISM, ISX BIG BLOCK engine. Unless you are towards the upper RPM 2000-2600 (2600 Redline for Jake, on my engine) when the Jake is activated - the difference between Stage 1 and Stage 2 is not all that dramatic!
-Our 2004 coach we bought used with low miles on it at the end of 2010. As I was test driving it, I could detect no difference between Stage 1 and Stage 2 (Low/High). As part of the PDI, I paid to have Cummins do a Dino Test of the engine, look everything over, check the chassis and Allison for me too. They found a few recalls that had not been done. They also agreed the Stage 2 was not fully working. So part of my condition to purchase was for this to be addressed, as well as all recall items, and a few other engine/chassis related.

The end result was that the Cummins Service Writer called me to explain that a mistake had occurred during manufacturing, and the Stage 2 (The second closing of valves on the last three cylinders.) had never worked. He said they had corrected the problem, and also adjusted the Stage 1 too, to validate it was properly engaging.

====

So if it's a new to you RV, and you do not know the history. Perhaps your engine too had had a mistake during the manufacturer process - worth a check!!! If not, either way, if it's not an electrical problem from the switch to the ECM to activation of the Jake... They'll need to open the valve cover and check the valve train Jake control!

Sure hope it's something simple for you. And again, welcome to the gang,
Smitty

Thank you for your response. I purchased the coach used with 52,000 miles on it. I can not say stage 2 ever worked although it seems strange prior owners did not notice. At time of purchase driving around the dealership area there were no long grades I could test the second stage on. Being new to 2 stage braking I didn't know the difference at the time. Here's my test: descending a 6% grade in stage 1 at 65 mph and gaining speed I turn on the rocker switch for stage 2 and there is no difference in speed.
Meaning that I continue to gain speed and then apply foot brake to get back to the 60/65mph range. Is it possible you can supply me with more details as to what was actually fixed/corrected on your engine brake issue? So far I have not found a shop willing to run the ground wire. I could run it myself but am concerned I could cause a computer issue if not done correctly.

[amxalan]

Originally Posted by A Traveler

There is one other “test” that can determine whether the high range is working. It’s called the “Cummins shake.”

If the Jake Brake is working on all 6 cylinders (high) there will be no noticeable vibration as the engine slows to 1,000 rpm (at approximately 15 mph in 2nd gear) where it will disengage.

If the Jake Brake is only using 3 cylinders (low) there will be a pronounced and rapid vibration for a couple of seconds at that 1,000 rpm point, just before the Jake disengages.

Thank you for your response. I will give this a try.

[A Traveler]

On a 6% grade you will have to downshift to 5th gear at 65 mph to hold speed, even in high mode. There’s not quite enough braking horsepower available in 6th gear at that speed.

If the Jake will not hold your speed constant on a 6% grade at 65 mph in 5th gear, it is not in high mode.

[BrianGlenn]

Originally Posted by A Traveler

There is one other “test” that can determine whether the high range is working. It’s called the “Cummins shake.”

If the Jake Brake is working on all 6 cylinders (high) there will be no noticeable vibration as the engine slows to 1,000 rpm (at approximately 15 mph in 2nd gear) where it will disengage.

If the Jake Brake is only using 3 cylinders (low) there will be a pronounced and rapid vibration for a couple of seconds at that 1,000 rpm point, just before the Jake disengages.

Agree. I can fell this difference on my 400ISL with hi/Lo Jacobs brake.

[Smitty77]

Originally Posted by amxalan

Thank you for your response. I purchased the coach used with 52,000 miles on it. I can not say stage 2 ever worked although it seems strange prior owners did not notice. At time of purchase driving around the dealership area there were no long grades I could test the second stage on. Being new to 2 stage braking I didn't know the difference at the time. Here's my test: descending a 6% grade in stage 1 at 65 mph and gaining speed I turn on the rocker switch for stage 2 and there is no difference in speed.
Meaning that I continue to gain speed and then apply foot brake to get back to the 60/65mph range. Is it possible you can supply me with more details as to what was actually fixed/corrected on your engine brake issue? So far I have not found a shop willing to run the ground wire. I could run it myself but am concerned I could cause a computer issue if not done correctly.

Sorry I missed this message! And I do not have my receipts from that period with me to review. But from memory, the 2nd stage was not working due an assembly problem when the engine was built. I believe he said it had to do with the rocker arm control of the three cylinders making up the 2nd stage. Assume it was related to the Exhaust valve not opening to allow the built up compression strokes of the 4 cycle action, to release. This then removed these three cylinders added displacement into what I describe to my wife as the 'compressor effect' when Jake is activated. (Fuel delivery off, and control of the Exhaust valve to open at a different time point, basically turns the cylinder into a large air compressor.) They had to remove the valve cover to change the settings, and at the same time, he said they also reset/validated the 1st Stage control of the Exhaust valve were set within parameters too.

Not much help, but it's what I recall...

Best to you,
Smitty

[amxalan]

I have had the opportunity to try your suggested test several time now .Results: Slowing down on a level road surface in either low or high engine brake and the result is the same. The engine brake noticeably disengages around 1200 rpm but there is no shake from the engine regardless of wether brake is in low or high.

[A Traveler]

It should not disengage until 1,000 RPM. You won’t feel the “Cummins shake” at 1,200 RPM.

Time to take it to a pro for diagnosis.

[shootist]

Did you ever get the engine brake working properly?