Hey everyone. Im looking to get some insight on some things going on with my truck. Not sure if they are issues or just things I never heard before.

After putting the fuel bypass on, the under hood noise was cut down by about 70% and Im now hearing strange things. Also recently did the CCV bypass. Have not installed my homemade oil collector yet so its just an open hose tucked inside the frame.

1. Every now and then, correct speed and rpm, the injectors (I think) get into a rhythm and almost seem to surge. Speeding up or slowing down changes it. Its not often and Im unable to induce the behavior.

2. When floating (holding constant speed) theres a "ssshhhhhh" sound from under hood. If I let off or slightly accelerate it stops. This is repeatable.

I have no vacuum leaks and there is no fluid leaking. I checked all the intake hoses and everything is tight. Not sure if theres any holes in any intercooler hoses though, need to check/replace them. I was also thinking about putting a Big Head wastegate actuator on it. Not sure how to test mine but its the original. There does not seem to be any performance issues. Unfortunately, I have no diagnostic tools or gauges yet.

All mods should be in my sig. Currently 176k on the clock.

I know the local diesel guru but hes tough to get time with. Thought I would try here first. Thanks in advance.

 

Moved over to the 7.3L PSD forum.

Stewart

 

The shhhh sound is more than likely your 6637 talking to you. I am not understanding the "surging" description. You may want to build a leak detector just to make sure.

 

You might be talking about when the Engine Oil Temperature is crossing a threshold from cold to warm. The injectors make a freaky noise for a short time, then it's gone as the oil warms even more. Could that be it?

 

Im thinking this could be it. It does occur about half way to full operating temp. I'll keep an eye on the temp and driving time when it does happen. Thanks.

Now for the air noises. Looked at the leak detector deal, may build one. I do need to get some gauges on it though.

 

Could the "ssshhhhh" sound be the EBPV closing & opening while cruising? I saw this come up in another thread recently, is why I'm asking. And it seems to fit. Also thought it could be the 6637 at first, but doesn't make much sense that it stops when you accelerate.

 

That makes sense. The 6637 make noise with the turbo spool, sort of a whistle up and down. What Im talking about is on and off so I bet thats it. At least I know its working and not an issue.

Thanks for the input.