Hissing Diesel Engine

[Dave Shepard]

Most brakes now are using the variable vane turbo instead of an add on like the pacbrake.

 

[sotc]

That would be efficient, I know at least one of the turbos is variable on that truck

 

[NickfromWI]

So a weird thing happened.... We started up the truck to try and find the source of hissing. Everything sounds fine and dandy. Odd...

We proceed by shutting off the truck, lifting the cab, then restarting it.

Again- we didn't hear anything.

We left the engine running while me and one of the guys start eye balling things looking for something not looking right.

We found a small hose- maybe ¼" in diameter right on too almost front and center on the engine that was not connected. We plugged it back in.

Not sure what it was- I'll post pics later- but the hissing is gone.

The weird part is that even with the engine running we could unplug that hose and still not hear the hissing. Hmmmm


love
nick

 

[BlackSmith]

Don't ya just hate it when ya fix something and don't know how? heh...

 

[sotc]

MAYBE you do have an exhaust brake and the switch got flipped in the cab...

 

[toyotadadon]

On my isuzu the exhaust brake came stock its toggled by the wiper stick and runs automatically works real nice between the 6 spd manual and the exhaust brake it will slow even a max 26k load. Model is isuzu frr...do u have the 6 cylinder diesel or the 4? Mine is the big six i can take pic if u need referencing off mine....

 

[NickfromWI]

http://youtu.be/X1vz6kNrwJc

There it is. We can see more or less where the sound is coming from, but can't pin-point it


love
nick

 

[NickfromWI]

The part in the green square is the basic area where the sound is centered.

The orange circle is a hose that was disconnected yesterday but was immediately reattached




love
nick

 

[BlackSmith]

Wastegate?

 

[NickfromWI]

?


love
nick

 

[greengreer]

Check all the hose clamps and connections between the turbo and the intercooler (the black pipe at the bottom of your picture). Also check for a crack or leak in the vacuum line on the wastegate, just left of the green outline. If you have some starting fluid.or propane you can carefully fog those areas and listen for a response from the engine.

 

[FireFighterZero]

Nick, a wastegate bypasses exhaust gas around the turbine wheel when the compressor side (fresh air) actuator senses too much boost.

When the exhaust gets re-directed it does not act on the turbine wheel, thus lowering the power available to turn the compressor side and that limits and lowers the PSI of boost until the pressure drops enough to close the wastegate.

Its a governor of sorts. Too much boost can be bad for an engine, stresses the head bolts, gaskets and bottom end.

 

[NickfromWI]

Ahhhh

You guys are smart at this


love
nick

 

[MasterBlaster]

Heck yea we are!

 

[pantheraba]

Yeah....Jim beat me to explaining that whole exhaust gas flywheel wallopin' rod wastegate pressure drop thingy.

 

[NickfromWI]

Major update!!!!

So I had a diesel mechanic come take a look at it. Took him about 30 seconds to diagnose the issue. He peeks in and goes "there's the prob. You can see the carbon tracing..."



You can see the black patch in the middle. He said the gasket under that piece is wore out. He's ordering parts and will be back next week to fix it all.

Hopefully that takes care of the issue!


love
nick

 

[sotc]

Not as easy as a turbo hose but still not too bad.

 

[FireFighterZero]

Didnt really sound like an exhaust leak. Most times they sound like a knock, rather than a hiss.

Glad he found something though. Would leak worse when cold before the metal expands.

 

[pantheraba]

So did the hissing hot gases erode the metal there? Am I seeing that right?

 

[SouthSoundTree-]

Gary, I think that is black spot is soot.

 

[pantheraba]

OK...that is the carbon track then...I was looking for a thinner trail.

 

[greengreer]

Wouldn't have guessed exhaust leak either from the sound of it. Interesting. Glad you got it figured out.

 

[NickfromWI]

Well we THINK it's figured out.

We'll find out come Saturday


love
nick

 

[SouthSoundTree-]

Did you try to put something over that leak to plug it for a minute, and listen?

Maybe a two part problem. Hopefully not. Might be easy to do before the day of, and skip a second repair session.

 

[NickfromWI]

Hmmm... What would it take to plug it up for a minute?


love
nick