Cm570 engine brake vibration and weak jakes

[Marat]

Hey everyone, this is my first post so hope I’ll be able to share a video to show you guys what Im dealing with.

On stage 1&3 there is a noticeable vibration, overall jakes feel weak and havent made more than 10psi on stage 3. Ive done the overhead myself and am confident enough I didnt screw anything up there. Measured detent with a dial and they were all around .070” give or take.

So today I pulled the valve cover off and manually engaged the solenoids to see whats happening.

Is it normal to get some oil leakage out of the top of rocker arms where the piston sits when jakes are on?

Solenoids seem to be only leaking from the bottom which Im guessing is a drain hole and seems normal?

#1 cylinder seems to be the main problem. It doesnt engage with 2&3, only time it engages is if i hit the first solenoid and even then the engine sound does not change at all. So 4-5-6 turn on when i hit the back solenoid, 2-3 come on with the middle solenoid. What I did is swap the piston and spring from another rocker to see if problem moves, but no change #1 seems to be kaput.

https://youtube.com/shorts/DBmFg_84K0s?s...q3O0VNQ2AC

[Rawze]

The overhead valve adjustment does not set/adjust the strength of the engine brakes. The valve adjustment is either correct .. or incorrect and that is all to be done.

Inspect the overhead cams for flaking etc. and ensure no lobes are damaged or worn down.

It also looks to me anyways, like all the rockers are functioning/operating just fine.. though I don't make it a habit to play with them like that. Activating the jake solenoid that only controls one single cylinder IS going to be very different than the solenoids that operate 2+ cylinders at a time.

When they are fired by the ecm instead of by hand, do they activate properly?.

What someone needs to do as equally important, is an injector leak test, to make sure no injectors are leaking fuel into the cylinders during jake operation.

Here is how it is done:
http://rawze.com/forums/showthread.php?t...8#pid67948

I am no expert on digging into CM570 engine brakes specifically, however, I do know that an old 570 with a non-VG turbo is going to have a significantly weaker engine brake overall, than anything more modern... especially at lower rpm ranges. If that turbo is weak, mis-matched to the engine, or has damaged turbine then the engine brake will be effected by that as well.

Just my own thoughts on it any ways.

[Marat]

Appreciate your input Rawze

Cams and rollers all look great no flaking or any damage to anything there.

Brakes do activate by the ecm as well, however Im just not sure if cylinder one is doing anything at all. What concerns me is that the other 5 rockers have a good amount of oil coming out of the caps but number one looks very weak.

Im wondering if that is because number 1 is meant to come on with chlinder 4 5 and 6 for it to function properly or if something is actually wrong with it.

Im planning on doing the injector leak down test today as well as test all 3 solenoids maybe swap them around as well.

Turbo is original, I had it out recently when I replaced the manifold/turbo gaskets and had a look in the turbine side couldnt see any damage to the wheel.

Im just scratching my head about that cyl 1, if someone can confirm what its doing is normal then I could just leave it alone and move on.
My thoughts were that if that cylinder isnt working with the rest it could through everything off balance and be one of the reasons for the vibration Im getting.

[Marat]

So I did the injector leak test. Cylinder #1 failed.
Going to replace that one. However That cylinder still doesnt fire at all when jakes are engaged. Wether its from inside the cab or doing it manually, the rocker moves around but not like the other ones. I tested the solenoids all 3 are within soec at 8-9 ohms. All 3 click the same when given 12v. I even swapped out the solenoids to no change. Took out the plunger/pistons from that rocker and a good working one. Engaged jakes to compare oil flow, its as good as the other ones. Im pretty much at a dead end now. Probably gonna have to pull the rocker shaft off and inspect further. Definitely gonna change that one injector as well

[Rawze]

Maybe bearings in the head worn enough to make lower than normal oil pressure up there?.

just a thought.

[Marat]

So I fixed one thing but chasing a new problem now.
Changed out all 3 solenoids now the engine brakes work great.
Changed injectior on #1 cylinder and bubble tested again, im still seeing bubbles.
The bubbles push out right at damper marking C. So I figured maybe I made a mistake and its actually cylinder #2. Changed that injector with the one I took out of cyl #1 before wasting money on another new one. Im still getting bubbles at the same mark. From the first time I bubble tested its at the same mark, lookslike it’s between b and c but it happens so close to c that it could be c and a. Regardless I changed out both injectors im still getting bubbles. It has a bit of a rough idle especially when cold, mostly clears up once warmed up.

Any idea why I’m still seeing bubbles?

[tree98]

Are they genuine cummins injectors?

[Marat]

The old ones yes. The new one in there is rebuilt. I find it unlikely for the new one to be as well, I shouldve tried moving that one to another cylinder see if the bubbles moved with it.
Aside from the injector, is there anything else that could make it fail this test?

[tree98]

(10-09-2023 )Marat Wrote:  is there anything else that could make it fail this test?

The bubble is compression being pushed back through the injector......... so I would say no.

Put genuine cummins injectors in and I bet it doesn't leak. Injectors seem to be a total crapshoot if you use aftermarket/ rebuilt. Although I will say a 570 Injector would be more forgiving than a common rail engine Injector.