2003 7.3TD has started to exhibit several behaviors at 48,600 miles:

1) When cold (at idle or when driving), turbo waste gate is opening and closing (you can see the arm moving), and making a hissing (vacuum) sound, 2) The usual cold temp high idle rpm is working intermittently, 3) there is a loss of power when this hissing occurs, 4) I'm the original owner and these behaviors are new. Any help figuring what to address would be appreciated.

 

Are you sure you're looking at the wastegate arm and not the EBPV arm? The wastegate is on top & rear of the turbo, the EBPV is on the bottom. I would guess that the thing is cycling in & out of warm-up mode, which is usually a symptom of a plugged or cracked EBPS tube. I'd start there....

 

Yes, I believe it is the wastegate arm. The arm I'm looking at is on the top of the turbo. What does EBPS stand for, and what is it's functin? Not familiar enough with the engine. Thanks for the quick reply. Bob

 

Something is up then. It usually takes quite a bit of boost pressure to push on the diaphragm in the canister to open the wastegate. If it's opening at idle (no boost pressure), the it could be a bad wastegate head...

 

EBPV stands for Exhaust Back Pressure Valve, there is a rod that comes out of your turbo pedestal and connects to a flapper valve in your exhaust outlet and during cold starts it will close to help worm the engine up faster it will cause the hissing sound your are referring too. It will also come and go while you are go down the road until your truck is up to running temp.

 

What's throwing me is how I didn't hear this hissing or experience the other symptoms until last winter, which was my 8th year driving this truck. I had a 4" Banks turbo back exhaust professionally installed May of 2007, could this somehow be related?

 

I belive it could, because mine got a louder when I Installed my 4" turbo back. I thank it might have something to do with the strait thru muffler.

 

It seems unlikely that the exhaust system install would bugger up the wastegate actuation. As previously stated, it is more likely the wastegate actuator. The actuator is the cylinder that the wastegate actuation arm sticks out of. That cylinder contains a spring that opposes the boost pressure piped into the actuator. When the boost pressure overcomes the spring pressure, the wastegate opens. The spring can weaken over time and allow the wastegate to open at lower than optimum boost, but I haven't heard that this happens at idle.

The spring tension on the actuator can be increased by removing the retaining clip on the wastegate arm and turning the arm to lengthen it. However, it is likely that you'll lose the retaining clip in the process of undoing it, so have a spare handy.

 

It is absolutely and totally impossible to hear the wastegate opening on these trucks. So right there, you can completely rule out the wastegate.


What you are hearing is the EBPV. It's cold, the engine is cold, that's when it's supposed to activate. It works during idle (which you are experiencing), and during low load driving (which you are also experiencing). It makes a hissing noise, and there is always associated with it a loss of power, since it's shutting off the exhaust and putting an additional load on the engine.

Couple that with the fact that you installed a larger exhaust prior to noticing this.

So there's you're answer, it's the EBPV, and not the wastegate.

 

^^Yeah what he said...

 

Thanks guys, I appreciate the feedback. Bob D

 

Is it possible the EBPV is malfunctioning somehow, perhaps due to a bad vacuum hose of sensor. Ever hear of either of these failing. The truck has only 48,600 miles on it.

 

Have you only started hearing this sence the weather has got cold?

 

The EBPV functions off of oil pressure. The actuator that controls the rod for the EPBV is actually located in the turbo pedestal, directly underneath the turbo. There is an electrical connector on the front of the pedestal that controls when the rod is extended to close the EBPV. It is directly controlled by the PCM.

The PCM gets it's input from engine oil temp, ambient air temp, and the exhaust backpressure sensor. When temps are low enough, the PCM will activate the EBPV. The control of the EBPV while activated are governed by two things, the backpressure sensor and the brake pedal. Touching the brake pedal automatically disengages the EBPV. Also, if the PCM sees higher backpressure (such as during acceleration), the EBPV is commanded to open.

This is the one place where issues arise most often with the EBPV.... in regards to the exhaust backpressure sensor. It's located at the front of the engine behind the idler pully. There is a metal tube under the sensor that leads to the passenger's side exhaust manifold. That tube can get clogged with soot, causing the sensor to not accurately read exhaust backpressure.

If you still want a functioning EBPV, and are having trouble with it choking your engine down as you drive, you'll most likely need to clean out that tube. Here are instructions for how that's done: Welcome to guzzle's Exhaust Backpressure Sensor Cleaning Maintenance Web Page

If you are tired of the EBPV and don't want it to engage, simply unplug the electrical connector on the front of the turbo pedestal, directly under the turbo. When it's unplugged, the PCM can no longer command the EBPV shut.

 

The only thing I'm concerned with is that he said the rod was moving at idle ON TOP of the turbo. Something has to be very loose for that to happen. It takes A LOT more pressure than what you see at idle for the wastegate rod to move...

Could be two issues happening here...