Hose to PCV valve goes flat - a problem? - Fuel Economy, Hypermiling, EcoModding News and Forum

Ecky · 07-24-2012, 03:00 AM

I have a frankenstein Honda motor with parts from various mid 90's Integras and Hondas, but the block is a 1993 B18A1. It has a breather-box on the back (which I believe is the PCV valve equivalent) that has a vacuum line that runs to the intake manifold. When the car is running this line goes flat from the vacuum. When I noticed this I was worried at first... but isn't the PCV "positive crank ventilation" ? If the line is going flat from vacuum it's probably not a problem right?

Do I need to fix this or can I leave it?

user removed · 07-24-2012, 11:34 AM

Positive crankcase ventilation means keeping the crankcase below atmospheric pressure. A collapsed hose indicates the valve is plugged or the hose is not PCV hose which is stronger than typical hose to allow some vacuum inside the hose without collapsing. Try sucking on the end of the hose that is not connected to the PCV valve. If you can't pull air through the hose then the PCV is clogged. If it is not a PCV valve then there is some clog in the passageway to the crankcase.

I learned this in the 1960s. I used to buy 1963 Valiants that appeared to be using a lot of oil. The owners would sell the car cheap becasue they thought the engine was bad at 40k miles. Removed the PCV and the hose cleaned both out with some gas and voila, oil consumption went from a quart in 400 miles to a qaurt in 1500 + miles.

regards
mech

user removed · 07-24-2012, 11:37 AM

Without crankcase ventilation (required by law in 1963) you have pressure building up in the crankcase. This can push oil past the rings and make you think the engine is burning oil becasue it is worn out, when like my old Valiants, you just need good crankcase ventilation.

regards
Mech

drmiller100 · 07-25-2012, 12:19 AM

old mechanic is right.

replace the hose.

Ecky · 07-26-2012, 09:15 PM

Thanks all. I replaced the hose I had on there with something beefier and it doesn't go flat anymore.

I sucked on the hose and air moved just fine through it, but I heard what sounded like a little bit of fluid(oil) gurgling in the breather-box on the back of the motor when I did.