When standing outside and the truck is idling, it sounds like a HUGE vacuum leak and it looks like it puffs smoke down there. Prev owner told me its the oil overflow pipe?

Matt

 

smoke coming out of the vent would indicate HUGE amounts of blowby. Check the band clamp on the downpipe or maybe the downpipe is cracked. Have someone rev it with the hood open and check it out.

 

Hissing and black smoke should only ever happen near the tailpipe opening!

 

Exhaust leak or lots of blow by. How many miles on it?

 

It has 255k miles... which isn't a lot for any diesel let alone a Cummins.

So why is it making that hissing noise? Is it normal? I DO have a front cover leak, if that means anything, and as far as I know thats the only place where oil is consumed.

How do I test this? It seems to be coming from the rear of the motor, almost where the trans sits maybe.

I'll go check the dp real quick

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Ok so I checked it out a little better, it doesnt dump black smoke or anything, but there is clearly smoke coming out of that rubber tube if you look underneath.
I THOUGHT that was whats creating the hissing, but it might be something else. It sounds loud looking under the truck (its snowy; i'm not climbing under), but it's also kinda noisy underhood on the drivers side too. The IC lines looked good, no rot or poor clamping.. wtf is this?

 

idk bout the hissing, but the rubber hose is the blowby tube. at 2**,*** miles, u can expect some blowby.

 

Yes exactly I can live with some blowby.. no biggie. Just wondering what the hell is hissing, like a vacuum leak (though diesels obviously have no vacuum), and if its normal for smoke to puff out of that line.

 

actually you could check vac pump on the front of power steering pump. pretty sure 97s didn't have hydroboost?

 

I'm pretty sure this has hydroboost? Though I could be wrong. What's the big purple cylinder thing?

 

is it smoke or steam on cold days its steam your seeing from warm ingine air hitting cold air so no worrys