390 engine

I replaced the pcv valve and the hose with new hose clamps, but the hose still collapses.

its as though there's too much vacuum for the pcv valve to keep up...could it be the wrong pcv valve?

 

Are you using heater hose? The actual PCV hoses are much more rigid than heater hose. If you don't want to track down a new hose you can slip a piece of copper pipe in the hose to keep it from collapsing

 

As has been mentioned, its not heater hose. There are a couple sources for the right hose. I bought mine from www.mansfieldmustang.com. Check out the hose they have listed for 69 390 GT. The one I bought had a ford part number on it. May still be available from Ford as well.

 

That's what I get for going to autozone. I didn't even think about using heater hose. I just ordered the proper stuff. thanks!

 

Anybody else use fuel injection hose for their underhood vacuum hoses?
3/16" took some looking. :)
And no, my vacuum leak wasn't a hose. ;)

Alvin in AZ

 

When did this problem start? Is this a fresh engine/plumbing set up?........AND what type cap do you have on the other valve cover?.....The PCV has to be able to draw air from somewhere, and it sounds like your system is air tight, or the PCV valve is in backward????????.......aMP

 

Uh, one thing I noticed about this...

The PCV valve system has a BREATHER on the valve cover opposite the PCV valve.

You should not build enough vacuum to collapse even heater hose.

At least, that's the way the stock setup works. If you want a vacuum in the crankcase, then you have definitely achieved that

 

With the hose collapsed the is no air movement from the drivers side breather thru the engne to the PCV and then into the manifold, which pretty much defeats the purpose of the PCV system.

 

But it keeps the oil leaks under control with a high crankcase vacuum.
Out needs in replacement, i've run heater hose over 800K trouble free miles.
Old school here with rebuildable PCV valve, same one over 36 years and million miles.

 

Are we talking about the hose from the PCV valve to the carb (manifold vacuum) or the hose coming off the breather?

The only reason for the hose (from the carb to the PCV) to collapse is either the PCV valve is clogged or somehow stuck closed, or the breather on the other valve cover isn't a breather

I'm going on what I've seen on late 60's autos w/PCV and my '74 highboy. Was there ever a case where Ford put on a PCV system and had an air-tight cap on the other valve cover?

 

Yes on the tight air cap, it was plumbed to the dirty side of the air cleaner. Another stupid idea, why not to filtered air?
Before this the bottom of the cap was vented to the atmosphere.

 

I have the same problem. 1967 352 2bbl, 3 on the tree, 2wd, stock, leaks oil & needs to be rebuilt. Got new PCV valve, new breather cap w/new hose to new air breather. I collapse heater hose and molded PCV hose. What is stopped up between breather cap & PCV valve?

 

Start pulling hoses,the cap/breather on the other valve cover whatever. And see if you get a sigh of relief from somewhere...17to21 lbs of vacuum psi can seem like a lot more when it's contained. I saw a hose that was'nt the proper material delaminate the layers, the inside layer callapsed and blocked off the hose...all the while looking fine from the outside.

 

Mine, with the truck running, hose in my hand & pcv valve in the end of the hose, I can see the pcv valve close & stay closed, collapsing the hose. I have tried 3 valves from 3 different parts stores, all look the same as when I bought the truck.

 

And that's with the PCV valve in the vertical (installed) position, not upside down or something?

Mondo Bizarro...

Carl (Beemer Nut), when I said "air tight cap" I didn't mean the type with the hose going back to the air cleaner. My '74 had that setup. A '67 390 I have in the garage had just a vented cap (with filter media inside).