2 blowby tubes? Help!

Loopy84

New member
Feb 20, 2023
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0
1
so here's my question. I'm having smoke coming from underneath my truck. The rubber hose that hangs down occasionally has always dripped a little bit, but I have smoke puffing out of a second metal tube that seems to originate from closer to the alternator than where that valve is. I'm a little confused as to what it even would be for. My coolant level has not dropped, oil level has not went down noticeably and there doesn't seem to be any fuel in the oil. I just did my injectors about 10k miles ago so I'm pretty confident it isn't that. Are there two breathers on some of the lb7s? I'm really at a loss because while I did drip a little oil before, I last drove my truck 2 days ago and prior to it sitting it didn't smoke at all like this and definitely not enough to be able to see it smoking without even crawling under. Help!
 

DAVe3283

Heavy & Slow
Sep 3, 2009
3,727
296
83
Boise, ID, USA
I've never seen a rubber hose hanging off the bottom of a LB7 before. That might be an aftermarket PCV reroute?

The metal tube you describe sounds like the factory PCV system. Visible smoke from it is not a good sign. I'd check for excessive crankcase pressure. You open the oil fill cap, then flip it upside down and place it on the oil fill tube. If things are healthy, the cap should just sit there, but if something is wrong the excess blowby will cause it to dance around or even push it off.

I'm curious what the rubber hose is. If you follow that back up, where does it go?

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