1979-1993 & 94 Conv [Subscribe to Daily Digest] |
 | [Main C900 Bulletin Board | BBFAQ |
Prev by Date | Next by Date | Post Followup ]
Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Long response Posted by Saana88 [Email]  (#207)  [Profile/Gallery]
(more from Saana88) on Thu, 21 Dec 2006 18:21:39
In Reply to: Cabin heat puzzle, Arabiflora  [Profile/Gallery]
, Thu, 21 Dec 2006 00:14:18
Members do not see ads below this line. - Help Keep This Site Online - Signup
|
Now that's a puzzle!
Be sure you're not talking about the center air vents (between the controls and the glove compartment) which only blow cold air. A vacuum leak would make this pair of vents stay open all the time.
A vacuum leak will make your vents use the same setting regardless of the distribution switch setting. I'm pretty sure the vacuum leak setting is something like a face and defrost mix. The floor vent shutoff flap is spring-loaded so if you don't have enough vacuum to open it, it'll stay shut.
A good test for this is to try twisting the distribution knob when the engine is not running, pausing around five seconds on each setting. If you hear the familiar whooshing and wheezing noises of the servos working (you should be able to get 3 full cycles of the knob with a sealed system), chances are you have a system that holds vacuum. Otherwise, you have a big leak somewhere.
Check the rubber grommets and plastic fittings for vacuum lines on the intake manifold. A serious leak will make a rushing-air sound with the engine running, among other problems.
If you need to find a leak, first check the recirculation flap. With the car running and the hood open, push the recirc button and see if the flap over the cabin air intake closes. If it does, it works. If it doesn't you have a big leak somewhere, possibly in the supply line to the cabin vents (a vacuum line running from the intake manifold to below the AC evaporator at the firewall). Also check the line going from the firewall connection under the evaporator and air intake that goes to the recirculation servo.
Next, shut the car down in the defroster position. Let it sit for 30 seconds or so then switch on the ignition (two clicks, the run position, without starting the engine) and push the recircualtion button. If the flap under the hood grille closes (this is the fresh air intake box on the passenger side of the car) then you probably don't have a leak in the defrost setting.
Do the same thing with the floor setting (10:00). Shut the car off, switch the ignition on, and hit the button to see if that flap closes.
Repeat that for the face vents (8:00).
Tell us what happens on these tests. I'll try to monitor the board over the weekend.
Here's the maze of vacuum leaks I had with my '92 convertible when I first got it:
Rubber grommet on valve cover leaking ($4 even at a dealer)
Rubber grommets on intake manifold degraded, oil-saturated, probably leaking
Plastic pipe fitting that sits in one of those grommets and connects the vacuum lines to the intake manifold had a small hole in it, around 2 mm, right around the base
Degraded vacuum hose all around, especially the line that connects to the valve cover (this softens and degrades from oil fumes, part of the PCV system)
Leaking recirculation servo (flap wouldn't close)
Seeping distribution switch at rear of switch (reseated, fixed)
Throttle body gasket seeping
Throttle position switch seeping
One-way valve (1991 and later phase-in) in dash vent line installed backwards
Basically, if it could leak, it was. No wonder the poor thing wouldn't idle right and only got 26 MPG.
As long as that list is, all I had to do was reseat the switch body and all the lines (free), get all new grommets and fittings (most are special-order by now, and the one that didn't have a hole in it was almost clogged with oily deposits), get a recirculation servo from an '87 in the junkyard ($10), replace the throttle body gasket and switch O-ring ($10 total), change the check valve around (free, thirty seconds), and replace all the vacuum lines (it's really preventative maintenance even if they're not leaking).
Vacuum leaks may also occur at the cruise control pedal switches. If your cruise doesn't work, these may be seeping.
Need pictures or more details? Just ask.
, Thu, 21 Dec 2006 00:14:18, Thu, 21 Dec 2006 18:21:39 <-- Viewing This Message, Thu, 28 Dec 2006 14:15:42
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
