I found the post below after researching the noise I have been experiencing. His description of my noise is right on. I saw some comments this may be related to the exhaust back pressure valve. My question, is the noise I hear just the valve functioning as designed during cold weather or is something broken or out of adjustment? Besides the hiss, the engine also sounds different while the hiss is happening.

"Old post"
This is stumping me... it only happens when it is cold out.. like below 40. Then, the colder it is, the worse it is. The symptoms go away when the engine warms up, unless it is below like 30 then it stays longer. Didn't happen all summer, now that it is getting cold again, it is back. It sounds like a really bad vacuum leak, and only during light acceleration or "maintaining" speed. If I accelerate hard, or back off to idle, it goes away. Today, when the sound came on, I tried to make it go away by accelerating and it was like there was no response to putting the pedal down for a while. I had to put it all the way to the floor to get more power-- and then it went away- until I went back to maintaining speed. I don't seem to be able to replicate it unless I am driving so it is a bit hard to diagnose. Ideas?

 

there basically is a butterfly valve in the exhaust side of the turbo that is the EBPV.
The whooosh and hiss sound are from it closing.
The reason the motor sounds funny is because its essentially running on natural aspiration instead of forced air.

You will have basically no power until it opens up because its blocking the turbo from spooling.
Since its oil operated in the turbo pedestal, its not instantaneous when it opens and closes thus thats why its so weird to drive when you have the issue.

 

Best thing to do, while the truck is cold, is to reach behidn the turbo and unplug the EBPV sensor and just wire the EBPV open with some wire.
That will stop it from trying to accuate it.
You might get a CEL on the dash, (dont remember)

The system is really ... well, bad.
It's a huge potential leak, plus the issues you are seeing.
Most of us just delete it.

 

And it's normal for the sound to stop when accelerating and to resume when you let off the gas? Also stops once the engine gets really warm.

Thanks

 

If it truly is the EBPV butterfly valve,what you are hearing is exhaust back pressure against that butterfly. Letting out of it there is very little exhaust pressure therefore the noise goes away. When the truck warms up the valve will stay open therefore alleviating flow.

Think of the EBPV like jamming a set of fish nets in your tailpipe, but rather up near the down pipe. The truck will make very little power since it can not exhale properly, but blocking the exhaust gasses assists in warming the motor. The EBPV solenoid should open the butterfly (actuator rod&piston) once it see an increase in oil pressure from idle, if its not opening unplug and wire open the butterfly, or replace the seals on the solenoid. I'd suggest deleting the entire unit and using a deleted pedestal if you go that route. Its actually cheaper than replacing the components with OE parts.

 

Thanks but like the original post, If I accelerate the noise goes away, it's when I let off or just hold steady in normal city driving that it occurs. Sine it goes away after the engine gets good and warm is it functioning correctly?

Thanks

 

as mentioned, you accelerate/increase Engine RPM...oil pressure increases actuating the butterfly to open. If a seal has completely failed, then the exhaust pressure is opening the bf and the solenoid isn't doing anything. Unplug it and wire it open and see if this helps, takes a matter of 10 minutes.

Do I think functioning correctly, probably not since it was not doing this before, correct?

 

What happens is the cylinder, the huge round thing on the turbo pedestal, ovals out and the seal on it starts to fail or not work right.
Then the EBPV starts to malfunction.

Thats why 90% of us have removed it.

 

I didn't appreciate mine much when i had to dump 4 gallons of oil in to get home.

 

Nope, won't set a cel on our trucks, but it will on a super duty.

Just do your self a favor and unplug it. If you ever have the turbo off, delete it. It's easy.

 

Yes, everything you describe is normal.

 

Thanks for all the good information gentlemen. As this seems to be normal functioning behavior, I will probably leave it as is until I have the turbo off to delete the valve. Is there a part that needs to be purchase in order to do this correctly?

 

You can delete the pedestal yourself or buy one: Garrett TP-38 Blank/Deleted Pedestal - 7.3L Ford Powerstroke 94-97

You will appreciate a deleted pedestal come next time you have to take it out....

 

unplugging it wont hurt anything and will save you a ton of headaches while driving like you're already experiencing.

 

You planning on keeping the stock turbo or upgrade it down the road? I say this because if you have your turbo out you can always upgrade to an e99 set up like I did( I have no intention on changing my turbo I like my set-up as is) use an e99 pedestal or buy a deleted one and buy the turbo center cartridge of a gtp38 turbo, rebuild yours and you will have something like this





Easy to take off, im planning e-fuel in the not so distant future