Well....I pulled my air box out of my 97 850 n/a to do this modification to have a cold intake setup and found that it doesnt have the temperature dependent valve but a similar valve which is operated by vaccum. I pulled the other side of the vaccum line from top of the air box and sucked with my mouth on it and found the flap moving. So, basically I put everything together without any real work done but have a quick question and that is :

Do all the thermostat valves you mentioned above were only temperature operated or they also had this vaccum operated diapharm on them OR this is just something that volvo come up with in 97's? I have no running problems with mine other then that I notice some pinging during hot weather with stop n go traffic conditions - which might be normal.

 

I'm not sure, this is my first Volvo so I'm just going with what I find on it -- my guess is its a later invention since mine is a '95 - wait for tech or someone to clarify for sure though.

Just to make it clear, my 1995 850 GLT has the airbox thermostat controlling the valve but no vacuum control for the valve at all.

 

Yeah, same valve here on my 96 850 n/a. No idea how is this suppose to work (vacuum and temperature) Old setup seem to be simpler

 

i just took my flap and pushed it to the cold side an put a sheet metal screw in the bottom of it just in front of the flap to stick up in the way of the flap so it cant close to the hot side.

 

Hi Black brick,
I see a nipple for a vaccum line on the valve in pictures . The round thing is the vaccum diapharm. So if you will put a small tube on that nipple and try to suck air thru that tube, you will se the flap moving.