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Airbox thermostat failure...

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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wheelsup
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Re: Airbox thermostat failure...

Post by wheelsup » Wed Apr 01, 2009 6:05 am

Also keep in mind you probably don't need any sort of tin foil, screws, washers, bolts, etc. to hold it open. There is a little tab where you push on it and it holds the vent closed. Much easier than shoving tin foil in there and it can be done without removing anything except the air filter. Mine has stayed closed for close to 6 months now.
1995 850 GLT Wagon w/ 185,000 miles

tjts1
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Re: Airbox thermostat failure...

Post by tjts1 » Wed Apr 01, 2009 9:52 am

wheelsup wrote:Also keep in mind you probably don't need any sort of tin foil, screws, washers, bolts, etc. to hold it open. There is a little tab where you push on it and it holds the vent closed. Much easier than shoving tin foil in there and it can be done without removing anything except the air filter. Mine has stayed closed for close to 6 months now.
The reason why I used aluminum foil in mine is because I removed the whole trap door mechanism. The door is still there, flipped upside down. The aluminum is there to act as insulation and help stabilize the door that has been glued into place. Even with the door in the correct position, the plastic bracket that holds the mechanism in place restricts airflow. Breathing cold air is one thing. I wanted to build the most efficient intake possible with minimum expense and effort.

The 3 way junction as it comes out of the car. Looking at it from the airbox end.
Image

Remove the top half. As you can see, mine was stuck on the hot air side.
Image

I removed the spring, thermostat and door from the Y junction.
Image

Then using some pliars and brute force, I cut out the plastic bracket that kept the thermostat in place. The door was then reinstalled backwards and glued into place using epoxy. You can see the bits and pieces of plastic that were removed on the left.
Image

Then I added the balled up aluminum foil to the hot air side. This is the part that everyone seems to focus on. I don't know why. In hindsight, it was probably not necessary but I feel better knowing that its there.
Image

With the top half of the Y intake in place, you can see a clear shot for the air to travel through from one end to the other.
Image

I hope this clears up any confusion about the aluminum foil in the airbox. This was just 1 of 4 changes I made to the intake. The others being the 960 throttle plate which has been thoroughly discussed here.
http://www.matthewsvolvosite.com/forums ... a&start=14

Like I've done on all my cars, I removed the MAF screen with no I'll effects. Before
http://farm4.static.flickr.com/3584/340 ... 8587_b.jpg
After
http://farm4.static.flickr.com/3648/340 ... 878f_b.jpg

I replaced the restrictive airbox snorkel with a 3.25" piece of flexible tubing I found in the McMaster catalog.
http://farm4.static.flickr.com/3417/340 ... e014_b.jpg
http://farm4.static.flickr.com/3582/340 ... 242e_b.jpg
You might notice in the pics I also had the injectors out for a good cleaning. I use these instructions to clean my injectors at home.
http://www.fordfuelinjection.com/?p=82

Thats about it. I suppose I could go into adding smooth underside plastic panels to reduce drag but I'm already getting way off topic. Our 96 base 855 5 speed has 190k miles, gets 32mpg at 75mph on 87 octane and is quicker than any NA 850 has the right to.
cheers
Justin
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polskamafia mjl
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polskamafia mjl

Re: Airbox thermostat failure...

Post by polskamafia mjl » Fri Apr 03, 2009 2:03 pm

Thanks a lot guys. I was looking at it and there are two hoses hooked up to it. I guess one is the MAF. What is the other and do I need to disconect both? And finally how do I disconnect them and reconnect them? Sorry for all the questions hahaha...
'All my money is gone and I have an old Volvo.' - Bamse's Turbo Underpants

Current: 1995 Volvo 850 T-5R Manual - Bringing it back from the brink of death
Previous: 1996 Volvo 850 GLT - Totaled

Ozark Lee
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Re: Airbox thermostat failure...

Post by Ozark Lee » Fri Apr 03, 2009 5:02 pm

One goes to the cold air intake that routes to the front of the car and the other is the silver flexible line from the cover over the exhaust manifold. The MAF line comes off of the top of the airbox.

...Lee
'94 850 N/A 5 speed
'96 Platinum Edition Turbo
Previous:
1999 V70XC - Nautic Blue - Totaled while parked.
1999 V70XC - RIP - Wrecked Parts Car.
1998 S70 T5
1996 850 N/A
1989 740 GLT
1986 740 GLT
1972 142 Grand Luxe

polskamafia mjl
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polskamafia mjl

Re: Airbox thermostat failure...

Post by polskamafia mjl » Sun Apr 05, 2009 3:36 pm

If the thermostat in the airbox is broken or removed won't that set off the check engine light or anything?
'All my money is gone and I have an old Volvo.' - Bamse's Turbo Underpants

Current: 1995 Volvo 850 T-5R Manual - Bringing it back from the brink of death
Previous: 1996 Volvo 850 GLT - Totaled

2volvoken
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Re: Airbox thermostat failure...

Post by 2volvoken » Sun Apr 05, 2009 4:15 pm

I have removed the t-stat, and using a dremel tool all of it's mounting plastic, with no ill effects. The car runs great! I live in northern Indiana and ran my '93 in -30 degree temps and It ran great......I did not use foil I just used a sheet metal screw to screw the door shut in the cold air position.
'93 850GLT na 155,000 '98 V70XC 115,000 '99 C70 126,000

Craigd2599
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Re: Airbox thermostat failure...

Post by Craigd2599 » Sun Apr 12, 2009 5:35 pm

Okay...second tank of gas through the car after the airbox change...23.3 MPG. I have owned this car since July '08 and NEVER got more than 20 MPG around town. That's up 3.3 MPG. Wonderful!
Craig D
Philly Boy in Lynchburg VA
2007 S40 Previously: 2 850's and an S80
Waiting for that "R" model barn find

tjts1
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Re: Airbox thermostat failure...

Post by tjts1 » Sun Apr 12, 2009 5:55 pm

Excellent :D

Is this car manual or automatic? I never logged my FE before and after the airbox fix so its nice to get some solid data.
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Craigd2599
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Re: Airbox thermostat failure...

Post by Craigd2599 » Sun Apr 12, 2009 8:21 pm

Automatic N/A 155K miles, no alterations to anything
Craig D
Philly Boy in Lynchburg VA
2007 S40 Previously: 2 850's and an S80
Waiting for that "R" model barn find

jasonaileo
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Re: Airbox thermostat failure...

Post by jasonaileo » Tue Apr 14, 2009 6:27 am

Just a little FYI on this topic. I have a '99 V70 non-turbo and I did the above mentioned mod. I used a small piece of 1/2" copper pipe about 1" long (length measured to fit/jam tight into the air intake). My mod worked great at forcing open the fresh air intake and forcing closed the return exhaust intake. About a month or two after the mod, I got a check engine light (CEL). I had the codes read at AutoZone and got a P0420 Rear Bank Sensor Efficiency Error. I think that by closing the return exhaust may have created a backup where the excess exhaust that used to cycle back into the air intake was now forced past the rear O2 sensor and triggered the CEL. I took out the mod, reset the CEL and it has not come back on. One way around this may be to simply leave off the exhaust return line from its connection into the back of the airbox. This of course would be just releasing the exhaust into your engine compartment and the environment. There may also be an issue with exhaust pressure or something, but I don't know enough about this stuff to tell you if it would be harmful in the longterm. Your call.

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