View Full Version : Vacuum line running to the valve cover?!

04-20-2003, 03:52 AM
*Happy Easter everyone! I hope you have a great spring whilst you are revving up those SCs!*

...also, I was wondering if anyone has the vacuum diagrams for the 1994 SC. I have two shop manuals and I couldn't seem to find them in either book. Hmmm... ?!?! There are lots of wiring diagrams though!

I need them because I have a found a vacuum line (I think it's a vacuum line) corked by a screw towards the bottom of my engine compartment on the passenger side. It's pretty much ran along the fender well directly under the tube connecting the MAF sensor and the throttle body . I traced the tube back to the valve cover, I think... if so, is this even a vacuum line? The tube is rubber for about two inches then turns to metal for about ten inches. It snakes it's way back to the passenger side valve cover, as previously stated.

Any suggestions/comments? Thanks for the help again guys!

04-20-2003, 10:29 AM
thats your pcv(positive crankcase ventalation) system

(i know i can't spell)

i disabled mine by putting a couple of k&n valve cover breather there
note: if your state has emisions tests you will fail without a functioning pcv system

04-20-2003, 10:51 AM
Hmm... okay. This makes sense. But what does the tube run to from the valve cover? I know it's not supposed to be corked up by a screw... is it? Also, how much are those breathers?

04-20-2003, 01:32 PM
But what does the tube run to from the valve cover? depending on your year it run to either the hose between the maf & tb
or the inlet plenum for the sc

I know it's not supposed to be corked up by a screw... is it? no and being pluged up can be harmful for your motor

Also, how much are those breathers?
i paid 18.00 a piece for them (you need two) from a local race shop they are k&n rubber top push in breathers for a 3/4 in hole

04-20-2003, 02:02 PM
without the PCV functioning, pressure builds up in the crankcase, and some guys have even had oil pushed up out the dipstick tube.

A proper functioning PCV has NO negative impact on performance, so I'd recommend re-connecting it. If you can't get the info to do it yourself, it should be pretty cheap to have a shop do it, even if you need a new valve.

XR7 Dave
04-20-2003, 02:07 PM
That line is supposed to be connected to the intake tube. It is not a vaccum line, it is a breather line that is supposed to be connected after the MAF. If you have it connected to a filter then you are allowing unmetered air into the intake system which may have some small effect on idle mixture calculations in the EEC. Having the line plugged does not disable the PCV system, but it's not right either.

04-20-2003, 05:55 PM
This is perplexing.... you see, I only see one spot where that type of line can be hooked into the air intake pipe (I guess that's what the pipe connecting the MAF to the throttle body is called), and that spot is already occupied by a pipe running to Lord knows where. There aren't two PCV valves, are there?

04-20-2003, 07:44 PM
Don't worry about it....cap the fitting on your intake tube and buy a breather for the valve cover. I bought a small APC breather for under $10.

04-21-2003, 01:01 AM
also what's with the anti-disable pcv people

yes i put breathers on,yes i took the egr off,yes i took off the cats from my car

i did it because i don't like any of these systems and they are considered a ~~~~ by most people

and no i dont have emmisions tests here

( puts flame suit on and grabs bucket of water)

04-21-2003, 07:08 PM
That's not a PCV line. The PCV valve connects to one "T" arm, the other arm connects to the inlet plenum. The shaft of the T meets and rubber hose, runs down to the fender and is the fuel vapor hose that connects to the purge valve which leads to the gas tank. This valve opens when gas tank pressure is too high and vents back into the PCV system. If you have the Ford service manual, look on pages 3-13-5 (fuel vapor hose) and 3-08-4 (PCV "T" fitting). Yours is most likely dry-rotted like mine was. Replace with a new hose, along with the PCV hose going to the intake hose as these can leak vacuum or boost (most likely boost) and possibly throw a code, but not always. Make sure when you're all done that the inlet plenum fitting is secure as these almost always leak. Try running your engine without it connected and you will see what I mean.

04-21-2003, 09:59 PM
without the PCV functioning, pressure builds up in the crankcase, and some guys have even had oil pushed up out the dipstick tube. I resemble that remark!!!!

yeah the pcv can and will make the car run like azz if its not connected to the inlet plenum properly

XR7 Dave
04-21-2003, 10:57 PM
Scotte, disconnecting the PCV system is just plain dumb. It has little to do with emissions. The PCV system was designed long before emissions were ever a concern. PCV systems have been used since the 50's, and the main purpose of them is to evacuate condensation from the inside of the motor. Want your motor to get all caked up inside with deposits? Leave it disabled.

Regarding the connections to the valve cover, first of all, you need to understand that there are two PCV connections, not two PCV systems. The connection on the passenger side valve cover is at the rear of the valve cover under the throttle body. This is the vacuum side of the system and this is where the PCV valve is located. It DOES go to a T connection that connects to the back of the inlet plenum and the charcoal vacuum canister. This connection is subject to vacuum only not boost. There is no boost condition between the throttle body and the supercharger where this connection is made. Nonetheless, it was not my understanding that this is what you were talking about.

My understanding of the hose in question is the hose that runs from the drivers valve cover into a tube that snakes under the nose of the supercharger over to the passenger side and terminates at the back of the DIS. A hose then connects that tube to the rubber intake tube that goes between the throttle body and the MAF. There are no other connections in this line. This is not a vacuum line at all, but rather the breather line which in the old days was just a filter on the valve cover.

This line is plumbed into the intake tube because any air that is sucked into the motor (in this case via the PCV valve) should be metered by the MAF and not drawn from the general atmosphere. I am not saying that the car won't run this way, I am just saying that is how it was designed and there are reasons other than emissions for it to be connected that way. There should be no other connections on this line.

04-21-2003, 11:29 PM
thumper said passenger side fender. Fuel vapor hose.

XR7 Dave
04-22-2003, 11:38 AM
Actually he said passenger side valve cover too. So ya, it would be for the fuel vapor recovery. :rolleyes: