...So what's this infamous actuator valve on C15

I'm no mechanic. But I do have almost 2 yrs with a C15 ACERT motor and I can honestly say that I personally would never buy a truck with this motor.

Its great when everything is working right. But there are so many problems. The Valve Actuator is only one that you may or may not see.

The way I understand it the ( Someone correct me if I am wrong ) ACERT motors have VVT (Variable Valve Cam Timing). Under normal driving conditions the motor works in an efficiency mode with 1500 ft/lb trq. Then when needed the cam timing changes and the trq is increased to 1850 trq. Thats why the valves sound noisier at times and quiet(er) other times. The valves need to be serviced every 250k mi also.

In my opinion and as mechanics have stressed to me... "There is just way too much going on in that head".

Other problems I have encountered are Jake brake problems. Consistent regen issues stemming from anything from the ARD head, upper or lower temp sensors not seeing eye to eye. DPF filter issues. You name it.

I love the hill pulling torq. The low rpm pulling power. Good motor when everything is working right. But thats not very often in my experience.

 

I believe 3 per head

They are part of CAT version of EGR. They open the intake on the exhaust stroke to let exhaust back into the engine.

The main big problem with the actuators is they break studs. Then they bang on the top of the head and scar it. In worst cases they can ruin the head. But you will be able to hear it first usually. It will run rough and miss. About the only thing preventive you can do is check with CAT and see if the updated studs have been installed. I haven't had any trouble with the updated studs, yet. They will also break rocker arms and turbo studs just so you know.
If you hear something funny in the engine it will usually be an actuator, rocker, or a turbo stud


The most expensive actuator failure I have had was $2200 but that was including a stud update so it wouldn't happen again.

That being said mine have been OK motors. One pushing 900k and the other two about 800.

 

the valve actutators are on every cylinder incorporated in the jake housings.

 

The last two post hit the nail on the head, definetly check to see that you have the updated studs we have seen almost no trouble with the intake valve actuators after installing the update kit

 

I just got done installing the new updated studs, broke the ones in the middle rocker box and while I had it down I replaced all the studs, there are six studs and one bolt per rocker box. I also replaced both wiring harnesses,

the actuator codes are a lot of times a low voltage code, oil gets into the connector and throws a code, there is a updated connector that has a boot type seal that prevents this . at 833,000 mine nows runs like a new one smooth as silk. the odd thing is the updated stud is thinner than the old outdated stud right up under the six point area in about the middle of the stud
mine did exactly as stated, seems ed to lose a little power, then ran a little rough , and found cylinder 3 and 4 had broken all the studs, didn't hurt the head or anything else, they will sometimes drop a valve in this scenario.

 

Just to clarify some of the above posts. There are 3 actual IVA/jake housings in the head (2 cylinders share a housing) and on each housing are 2 oil solenoids (these are the normal wear items which along with wiring issues cause fault codes). The IVA housings DO NOT open the intake valves letting exhaust back into the intake. The IVA does not have enough power to overcome the initial seat pressure of the valve springs. It does however have enough staying power to hold the valve open during the start of the compression stroke letting some of the intake charge to flow back into the intake and "pre heat" it for better combustion. The whole ACERT engine is based off a modified Miller cycle combustion process (a different but similar 4 cycle engine process). Many of the associated problems with the IVA come from brittle wires, bad connections, dirty oil, and improper oil weight. Since the IVA uses engine oil it is vital to keep the oil even cleaner and the right viscosity so it flows through the small passage ways correctly.

 

the only issues I've had with my NXS C15 is I've had to replace the IVA oil pressure solenoid a couple of times. But then there is the problem with the right side of the engine being cluttered with the two turbos and other emmission related components that makes working on this side of the engine difficult. But if you never have any problems with the waterpump, oil cooler, exhaust manifold, or that silicon coolant hose behind the oil cooler you'll be fine.

 

Not sure if your saying they repaired the harness under the valve cover or the external harness. The internal harness is almost impossible to repair due to the heat and oil in my opinion its best to replace it if you have any trouble. On the outside it depends on where its damaged to the best way to repair it. If the resistance is altered much at all from the repair it can alter the data to or from the ECM. Weather pak terminals like the factory uses or sodier and heat shrink is best for external repairs.