MAF Sensor dead Air box thermostat broken flap

dosmainframe · Post by **dosmainframe** » 22 Apr 2012, 17:55

Hello I recently ordered a MAF Sensor (2nd one so far) picked it up for a good price on Ebay, I also did a little research on this site and found out I had to replace the air box thermostat in my car as well, after a bit of struggling with this damn thing I finally got the original air box thermostat out, it was about 2 inches shorter than the new one I purchased, the air box was stuck on the hot side and it killed my maf sensor, in the process of getting the original (broken) air box thermostat out bits and pieces broke off of the flap that opens and closes the hot air and cold air intake, my question is will this allow hot air into the intake and kill my new MAF sensor? is there any way to just simply keep the air box permanently stuck on cold air only? I live in FL and don't think I really need the hot air at all. The flap seems to function correctly now only allowing cold air in but the broken bits have me worried, I don't want to have to buy yet another MAF sensor, any insight would be appreciated. The car is currently not being used because I need to replace the O2 sensor and Coolant temp sensor as well, so I won't be using it until I get those two parts changed out I'm hoping that these will fix my issues and I can finally have a normal functioning car again.

ed7 · Post by **ed7** » 22 Apr 2012, 18:46

Volvo actually recommended disabling the air box flap so that it would only draw air from the cold side.
I recall pulling the thermostat out of its holder and lodging it under the plastic that held it.
It was explained in the Haynes manual. Also remove the hose to the heat riser.
Ed

dosmainframe · Post by **dosmainframe** » 23 Apr 2012, 15:57

Hmm do you know what page in the haynes manual tells you how to do this? it's not that I don't believe you I would like to get a second opinion before I remove the hose I was thinking of super gluing the flap down to make sure it never opens the hot air side open anyone else ever tried this before?

ed7 · Post by **ed7** » 23 Apr 2012, 16:07

Page 100, 101 of the 740, 760 1982-1988 models.
The hose just ducts hot air off the heat riser to the air cleaner.
Ed

dosmainframe · Post by **dosmainframe** » 23 Apr 2012, 17:36

So it seems those instructions are about removing and or renewing the air box as a whole, so let me ask you this did you just disconnect the metal hose? did you pull the hose out completely on both ends? I'm really interested in doing this to ensure my MAF doesn't get fried again, also if you either pull the hose out altogether or disconnect it do you have to plug up the open outlet on the air box? would that hose pumping hot air do any damage? so many questions, such a poor design, I just want this thing to work right let me know what you think I really appreciate it.

ed7 · Post by **ed7** » 23 Apr 2012, 18:24

It's really a paper hose with foil on it- and it screws on.
With the flap deflected to suck cool air from the fender side there's little hot air coming through.
I think this whole thing was discussed on the Brickboard. They also have good info on the 700s and 200s.
http://www.volvoclub.org.uk/faq/FAQSummary1.html
Yes- you can plug the hot side. Then forget about it.
Ed

lummert · Post by **lummert** » 24 Apr 2012, 20:12

I removed the metal shield parts from the downpipe and also the thermostat from the air box 2 years ago. I used a small bolt and 2 nuts to lock the flapper in the cold air position. I have since found the block off cap for the hot air side of the air box, but haven't removed the flapper and installed the cap yet. Later 940 Turbo's evidently had a different air box bottom with no flapper and a cap to block off the hot air tube.

I haven't noticed any problems with winter driving in Indiana with my 1988 Volvo 760 Turbo Wagon since this change.