Mystery Part

[sh'maal]

While changing spark plugs on my 91 Mazda Navajo, I noticed a broken piece of black tubing running from a capsule looking thingie on the evaporator. It's under the number 3 in the Typical engine compartment layout - 4.0L pushrod V6 picture on page 1-3 of Haynes. I suspect it has something to do with inlet air temp control. It has one tube that goes to a three port foil wrapped gizmo. the foil wrapped gizmo has one tubethat disappears down into a wiring harness (the broken line) and another line that goes over to the vacuum manifold. Two years ago while troubleshooting a hissing sound I noticed that the vacuum manifold had an open port. Using the end of a Bic pen I was able to close it up. Tracing the end of the tube on the foil wrapped gizmo it was trapped behind the window wiper motor. I'm supposing that it blew off and got wrapped behind the motor, possibly when the other tube broke. Any enlightenment on what this capsule looking thingie does and whether it not being attached has any effect on operation of the car would be appreciated.

 

[sh'maal]

Mystery part is still a mystery

Here it is November and despite multiple views, the purpose of my mystery part is still unknown. My daughter's boyfriend believes it to be some sort of vaccum accumulator for an air inlet damper. The small (5mm) diameter hoses have become brittle and easily snap in two. The car seems to knock more thatn it used to, perhaps the change in temperature. The piture in the Haynes manual captures it best, if I have to I can take a picture with my digital camera and post.
Thanks for any advice.

 

[Blee1099]

Its best to post a picture of the line..

 

[Glacier991]

The old adage: "A picture is worth a thousand words" was never truer. More and more folks with digital cams are putting pics in their posts, which personally I find to be a GOOD thing! (Course I guess I am probably a little prejudiced as I have more pics uploaded in the gallery here than anyone... but I think they really add to posts - either asking Q's or showing something.)

 

[MrShorty]

From your description:
1) The capsule thingy on top of the evaporator is nothing more than a vacuum reservoir.
2) The foil wrapped gizmo is nothing more than a "T" connector with a one way valve in it.
3) The vacuum tube that goes into the wiring harness goes through the firewall and under the dash.

From what I've been able to gather on my '92, that whole collection of stuff doesn't do much. The only thing I've been able to determine is a small part of the HVAC system: the "doors" that control the MAX AC setting. All of the other HVAC settings appear to be cable operated. The reservoir is there to "store" vacuum when the engine load increases causing a loss of engine vacuum and the one way valve is there to keep the vacuum in the reservoir from being lost when the engine vacuum goes down -- all so that small part of the HVAC system will work smoothly regardless of engine load. On later models, they removed cables from the HVAC system and turned most if not all of the HVAC controls to vacuum operation. On these later models, problems in those vacuum components show up as problems with the HVAC system (stuck in Def position, or intermittent going to defrost under load. Def is the default position on these later models).

In short, I don't think you're losing much with that vacuum reservoir disconnected, unless yours has something else coming off of that tubing.