Searched the forums last night and didn't really find an info on the problem I'm having...

Having an issue that seems like an intercooler pipe leaking, but I'm not conviced. Started last night, same problem this morning. All the connections seem to be solid. What's happening is there's a loud hissing noise when while driving down the road at a constant speed. I can make the same hissing noise while the truck is stopped as while...For example: While in neutral rev the motor to 1500rpm and hold it there. Motor will hold at 1500 rpm for a few seconds then the hissing noise starts and the rpm's drop with no movement of the pedal.

Turbo appears to spool fine without the hissing noise. The reason I'm unsure if it's a IC pipe leak is because on my SAAB SPG when I blow off an IC pipe you hear a rush of air when the turbo spools. I don't hear that same rush of air/hissing sound when the throttle is on with this problem on the truck.

Do our motors have a blow off valve? Could this be the problem?

The truck is a 99 350...Still trying to figure out how to add that to my signature at the bottom.

 

No blow-off valve on a PSD. Could be your EBPV messing with you now that the weather is cooling off. Look in the center of the valley for a 2 wire plug going to the turbo pedistal- this is the EBPV actuator. Unplug it and see if the problem goes away. Flip up the metal lock tab and pull the wires out.
On edit- a pic of the plug you need to find- right under the blue dot in the center of the pic. Harder to see with all the IC piping hooked up, but still not too bad.

 

No our PSD don't have blow off valves but we do have EBPV ( exhaust back pressure valve ) Its a flapper valve in the exhaust housing of the turbo it used to speed the engine warm up when these close your truck will start to sound like a jet . Was it cold last night ?

Chase beat me to the post I had a phone call.

 

Not too cold last night. Maybe high 20's on the way home. Truck was running for about 30 mins. Same issue this morning after the block heat was on from 4am-9am. Ran the truck for about 20 mins this morning. Shut it off after I could figure out the hissing/jet noise. What's the fix here? Am I damaging the motor at all?

 

does the hissing sound sorta sound like it's a Jet engine in your exhaust? And does it go away when you press the brake, or the throttle? It sounds like your EBPS (exhaust back pressure sensor) is working just like it's intended to. If it doesn't happen after the truck is warmed up, then that's it for sure

 

Just like Chase said though, it is a quick thing to check, just crawl in there and unplugg the EBPV and see if the noise stops..

 

20* is more than cold enough for the EBPV to close ,I would pull the plug that Chase showed you in the pic and see if that stops it .Get back to us and let us know.

 

Will pull the plug shortly and report back. Just need to finish one thing in the office. Thanks for the help guys.

 

As others have said, reach down in the valley under the intercooler piping and unplug the EBPV connector. Very hard to see but you can do it by feel. Just unhook the wire retainer clip and pull the connector toward the you. Just leave it unplugged and in the morning, no more hissing sound. It will not throw a SES light or anything. I keep mine unplugged. Can't stand the thing.

You have to go to your "User Control Panel" or "User CP" to edit your signature. User CP is located just below the thread title on the left. Or easy way is just click on the "Private Message" box on the upper right of the page and that will take you to your control panel. Edit signature is on the left side of the page.

 

He can't do a sig till he has over 25 posts.

 

Or unless he becomes a SUPPORTER. Then he can before 26 post.

 

I didn't know that supporter status superseded the 25 post rule good to know thanks.

 

Just plugged and unplugged the EBPV as reccomended above. The nosie went away when unplugged. Spot on.

Do I have this right in thinking that leaving the EBPV unplugged only slows down the warming process of the truck in the cold? Would the EBPV have stopped making noise last night or this morning if I let the motor run longer?

Also, what's happening here is standard operating procedure for the EBPV?

WRT to becoming a supporter, it's in the works. You guys and this site are invaluable!

Noticed a little oil in the valley. Is this oil blow by from the EBPV that people have talked about? Need to make sure it's motor oil. Doesn't appear to be fuel oil given the amount of grime that's built up in the valley. Again, the truck is new to be in the last month...still trying to work out all the kinks. Atleast I have a fair amount of past dealings with turbo charged engines with my chitshow SAAB SPG.

Thanks guys.

 

Leaving the EBPS unplugged could affect your mileage. It is used for more then just warmup. When it becomes clogged it kills mileage also.

 

It's plugged back in for now. How much do you have to take apart to clean it? Or am I going the wrong route here?