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Nater1977 · 07-08-2025, **(Subject: Engine brake troubles need some input )**

I have a 2008 CM871 fresh rebuild (in-frame). Tuned correctly, With a new head as well, This is a w900. I use it mostly for towing with a DTU on it. And I also use it for low boy work as well. On these extremely hot days my coolant temps are running 180 to 205 oil temp is around 210-225 not loaded but when pulling hills. When loaded with total weight between 60,000-120,000 coolant around 195-210 fan comes on then stays around 200-205. The oil temp will run around 230-245, pulling hills. OIL PRESSURE IS ALWAYS AROUND 35-40+ I do notice my engine brake on the 3rd stage, When boost gets closer to 30 Psi it sounds and feels like I am loosing compression and the truck starts to have the misfire feel. (Skipping) Shaking the cab like a bad U-Joint, was getting worse at hotter oil temps. I have been chasing this down. Reading all posts I could find, I am thinking I am loosing head pressure. I have replaced all bushings on rocker arms, checked diameter of shafts, all in spec and detents are looking perfect. Checked engine brake rocker arms looks to be in spec but weary of the pistons in the rocker arms. Retest, getting oil up to 210 and still having the same issue. As of 06/27/2025 I Replaced all the engine brake rocker arms, The performance is 90% better but around 1500–1400 rpm and lower I can still feel and hear a very slight miss/loosing compression. As a technician, it's not right. I believe the oil temps are within spec from research, but I feel would they should be lower.
Any help would be great, I would appreciate it, thanks!

Mtvnrnv0805 · 07-08-2025, **(Subject: Engine brake troubles need some input )**

Following, I’m having a similar issue but with a 500 x15. No rebuild but if I use the Jake on Almost any stage it shakes like a son of a gun.

Rawze · 07-09-2025, **(Subject: Engine brake troubles need some input )**

A==> Copy out the program from the ecm and e-mail it to me to have it properly reviewed, if i have not done so already.

What is the engine ser#?>

Rawze · 07-09-2025, **(Subject: Engine brake troubles need some input )**

(07-08-2025 )Mtvnrnv0805 Wrote: Following, I’m having a similar issue but with a 500 x15. No rebuild but if I use the Jake on Almost any stage it shakes like a son of a gun.

what I said above about copying the program out of it for review + also do an injector leak test?.

copying program info: https://rawze.com/forums/showthread.php?...5#pid72945

leak test info (common rail engines) : https://rawze.com/forums/showthread.php?...3#pid75483

leak test info (IFSM engines) : https://rawze.com/forums/showthread.php?...8#pid67948

trucklogger2 · 07-09-2025, **(Subject: Engine brake troubles need some input )**

I had same Jake problem and changed both actuators which solved that for me.
You may want to check your motor mounts also,
Was 871 also. Member tuned

Nater1977 · 07-09-2025, **(Subject: Engine brake troubles need some input )**

(07-09-2025 )Rawze Wrote: ...
What is the engine ser#?>

79243033

Nater1977 · 07-09-2025, **(Subject: Engine brake troubles need some input )**

(07-09-2025 )Rawze Wrote: A==> Copy out the program from the ecm and e-mail it to me to have it properly reviewed, if i have not done so already.

...

Yes you have reviewed it, but I will pull it again just to be safe.

Nater1977 · 07-10-2025, **(Subject: Engine brake troubles need some input )**

Well, something strange is definitely going on here. I did order that 215° thermostat remove the old one and it was flopping around inside with the C clip dancing around in the tube with the thermostat. It’s not even installed correctly. Reading about as Rawze stated you cannot run an engine without this thermostat. It will bypass the cooler so I have to figure out what is going on here. Went to try to install the new thermostat and I can’t get it to seat. It’s like it’s almost too big. I have to get in there and investigate and see what’s going on. Maybe there’s a burr from the old one banging around. Also, the C clip seems to be too small that came out of it. And I believe this is supposed to be a dual cooler when it is a single, someone’s been in here messing around for sure. I know there’s a TSB on the Oil coolers in parts change.

Nater1977 · 07-10-2025, **(Subject: Engine brake troubles need some input )**

UPDATE:

This truck was equipped with a dual system, Someone changed it and screwed up the installation that's why the t stat was just bouncing around inside.

The problem was the updated cooler head that was not equipped with this engine has different sized tstat and retaining ring stated in tsb160085 have the correct 215 tstat and retaining clip on order.

Update on engine brake I have found incorrect part numbers on engine brake solenoids, getting them from Cummins today

SHITY PARTS CHANGERS THAT CAN'T FIX shi#t CORRECTLY!