S90 with a vacuum leak under the dash

lindy8_man · Post by **lindy8_man** » 29 Nov 2009, 20:22

Ok, so the first thing I noticed was that the cruise control quit. Then I noticed a faint hissing under the passenger side of the dash board. When I started paying attention to the hissing, I found that it would stop and no air would come out of the vents when the car is accelerating. I began adjusting the level selector to see if it was specific to one setting. The hissing only stops when I have selected defrost. I will check tomorrow if the cruise works with the selector on defrost.
I pulled the glove box out and the kick panel. I turned the car on and listened. I could hear the hissing from the area of the picture I posted below. I felt around for any noticeable air movement, in the area. I did feel a slight cool breeze in the area I marked with the Red Triangle on the second picture. When feeling along the colored tubes, I did not notice a change in that hissing sound.

Question 1. Any ideas where that vacuum leak could be?

Question 2. What is that box with all the colored hoses? Chilton manual gives no help on any topic under the dash...

Question 3. would the hissing stopping due to the selector being put on defrost indicate a diaphragm failure

lindy8_man · Post by **lindy8_man** » 02 Dec 2009, 19:01

No Joy. I tried to engage the cruise while in defrost mode and it started to engage then quit... Any help on tracking down this leak would be helpful!

Post by **billofdurham** » 03 Dec 2009, 12:49

There is a vacuum bellows on the rear of the heat exchanger/fan unit box, which is in the area of your red triangle. It controls the recirculation shutter. Apart from pipes passing through to other units it seems to be the only vacuum related thing there.

There is some information here relating to the 960 vacuum problems but it seems to be in the wrong area.

Bill.

reverend · Post by **reverend** » 21 Dec 2009, 11:58

I bet if you pinch the YELLOW hose, the hissing stops.

It goes to the DUAL bellow that is right above the gas pedal on the side of the airbox. You have to remove the cover under the instrument panel to get to it (real easy).

What you'll find is the yellow hose connects to the bellow and that's the side that is leaking. The bellow is about $40 new from Volvo, but is a bear to replace.

You can either do it the Volvo way and tear the entire dash apart and hope you get it back together without any rattles, or you cut a hole in the airbox and replace the baffle, then glue/caulk/duct-tape the 'cover' you cut out, back when you're done.

What I did (until I can brave the weather etc) is to just unplug the yellow hose and plug it with a little rubber nipple. The result is that I can never have "floor-only" on the vents. It'll always allow half the air up to the vents.

Here are a couple of pics I snapped from mine (not very helpful, sorry);
http://photos.robdiesel.com/viewer.php? ... 15&stage=3

lindy8_man · Post by **lindy8_man** » 08 Dec 2010, 11:01

OK Gang,

Finally bit the bullet and took the car to Swedish Auto AB in San Diego. Raphel is a master Volvo technician! My heater coil began failing, so the most expensive (in labor) volvo repair was iminent. The leak had persisted over the year also. I just did not have the time or the knowledge to take apart the dash to get the "Suit Case" out. Replaced the coil, the leaking vacuume relay (bellows/solenoid). The culpret was the dual control relay. While we were in there, we went ahead and replaced the other two relays. Now, we have no more vacuum leak, the Cruise Control is working, and no more slow coolent loss and sweet smell from the vents.

Life is good!

Post by **billofdurham** » 08 Dec 2010, 11:17

Thank you for the update.

Bill.

peteco · Post by **peteco** » 09 Dec 2010, 10:02

So how much did all that cost? Did you get a cost breakdown?