I'm new to diesels, and I noticed today while driving down the street ~ 40mph a hissing noise coming from under the hood. When I lifted off the gas it would go away until the engine was at an idle and start hissing again. When I gave it gas to keep the speed up the noise would go away until the engine leveled off then it would hiss again.

From researching this forum I'm guessing a EBPV problem? If so what is the easiest way to confirm this problem?

The truck runs good but the hissing noise is loud enough to make it annoying...plus I dont like to let things go, if it requires replacement I'd rather do it now instead of it causing other problems elsewhere.

 

did it only do it when the motor was cold ? how long had it been running for? did it seem sluggish when it was making the noise?

 

the motor was up to temp while it was doing this. I never felt any power difference while it was doing this either

 

What is the outside temp? How long did you let your truck warm up?
Mine will do the same thing if I have to take off before it really warms up, but when it does warm up it stops.
When it's cold out and you start your truck can you hear that hissing? kind of like a jet taking off, well, that is the hissing sound. If you were to sit in the bed of your pickup you would hear that sound as you are driving. I talked to my wrench and he said I just need to let my truck warm up longer, remember these diesels love to be warm so does your trans. I installed a heater in my garage so I don't need to have my truck run so long in the morning.
I hope this helps.

 

You say it's hissing at IDLE? My EBPV never closes at idle at any time for any reason. It only closes at slight throttle settings below 2000 rpm and engine not fully warmed up. The only other time it closes is when the fast idle kicks in during the warmup cycle. But never at 600 rpm idle speed does it close for any reason. Could you be more specific on where the noise is coming from under the hood? Also if the EBPV is open all the way the lever will be pointing at about 2:00 on a clock face if you laid it flat under the lever with 12:00 pointing straight aft. Closed would be about 10:00

 

With my park brake on (6-speed) it will go to high idle with the valve closed. Never had a problem until it was about 8 below 0 and (farenheigh sp?) and was fully warmed up and I was going down the road and it would kick open and shut so I pulled over, shut it off and started again and it stopped. Came home and disconnected with no more problems.

 

So that is what the noise is when I drive on a cold day! The first time it did it, it scared me. It only does it at slight throttle, going about 10-15 mph, and the engine actually seems to lose a little power because the truck slows down. I would call it more of a muted roar then a hissing sound though.

I can either slow down to make the noise go away, or speed up and it also goes away. It only does it when it is cold, and the engine is first started for the day.

 

First I would like to say hi to everyone. This is my first post, but I have been visiting the site for about a month to learn everything I can about the PSD. I must say that I have really learned a lot! I have a 1997 F-250HD with a 7.3PSD in it and it also makes this same hissing noise. I do not think that it is the EBPV. I have driven the truck when it is cold (in the teens and twentys) and I know what sound that makes. On my truck it is more of a groan than a hissing noise. My motor will make the hissing noise at idle (it is faint), but it is more noticeable when moving at a constant speed (you can easily hear it with the radio off). It makes the noise when the motor is at operating temperature, and does not seem to affect the performance of the motor in the least bit. When you give the motor more throttle, it completely goes away instantly, and it is also gone when you are coasting. It is enough to drive me crazy. Does anyone know what this is? Do you think it will hurt my engine in the long run?

 

I forgot to give you all more info about the truck. It is bone stock with 168,000 miles on it. I just purchased it a little over a month ago. It is a 4X4 with a 5-speed. The dealer had just put on a new turbo before I bought it.

 

i think i have the same problem on my 99....almost sounds like the turbo is leaking......checked all the boots cant find anything.....its the worst between 1500 and 2000 rpm...any help appresiated

 

When was the last time you changed you air filter and fuel filter? Mine was making this noise before today, I had my truck serviced and asked them to change my fuel filter and put a new air filter in. Man it starts great, and I don't have that noise anymore. I do change my fuel filter ever other oil change.

 

not sure, i'm new to diesels also, but, mine made a similar noise and there was a leak in the flexible hose that came from the turbo. small enough to make a noise but didn't notice a change in performance,

 

tighten all blue couplers that feed turbo on top and down by radiator (both sides)they are always loose we have even had them pop off in some instances we had to take them off and degrease the pipe and coupler to get them to seal