Airbox thermostat failure...

[fn42]

just wanted to say... holy cow what a difference. I checked today and mine is in fact sticking closed. This should be on the stage 0 checklist!

[matthew1]

FN, you're absolutely right. I just added it.

[Faheyk1981]

So i've driven about 800 miles since this mod/fix and i can definitely see a difference is fuel ecomomy. No exaggeration but i'm seeing a 16% improvement in fuel economy. Thats a lot more than i thought i'd ever get!

[dosbricks]

Due to early and unusual cold weather for mid-November (a frigid 39 degrees forecast for tomorrow morning here in coastal South Texas)--I didn't like the longer time it took for the engine to warm with the full cold air mod because the freeway is only about four blocks from my house. I just prefer to have the engine up to temp before hitting that on ramp.

I use a 5/16" dia. dowel on the intake side to prop the flapper open with a dab of Gorilla Glue to affix it. So I popped the 1-1/4" piece out and installed a 3/4" length to give a roughly 50/50 mix of warm and cold air.

I must admit closing off the manifold heat last summer was way better than any tune up I had ever done as far as enhancing performance. So I'll be taking the 20 min. to switch back to the full cold dowel next spring (mid-February in these latitudes).

I'll see how the wagon performs and warms over the next few days and post back for the benefit of you all up in the Midwest who are freezing your butts and might want to consider modding your mod.

[erikv11]

Agreed. On my NA I remove the hose and pop a dowel/wedge in there every spring, then restore the factory setup every fall. I actually had the throttle body freeze up twice when I used the airbox mod during the coldest winter months. Kinda scary, especially when my wife was driving (alone).

[Faheyk1981]

I just wanted to give an update on this mod. As i'm now in the winter months i decided to readjust the air intake to 20% hot air and 80% cold air. Having it 100% set to cold air was taking too long to heat up during winter months. When summer hits again i'll go back to full cold air.

Or i was thinking that i'll just buy a new airbox thermostat but i seem to be finding it hard to find one for a 1999 V70 N/A 2.0 Litre Petrol. On ebay & on other sites, they appear to have them in stock up to 1998 and they state the 1998 thermostat will not fit 1999 model.

Would anyone think/know if the 1998 airbox thermostat would fit the 1999 car? I would just go ahead and buy one but its gonna cost me about 80e for it with p&p so i want to make sure before i go buying it that it will work. I'd prefer to have a working thermostat than using this mod.

Thanks, Kevin.

[DARK_BLU]

So driving a 99 v70, (1984cc N/A automatic with 147k miles) thats meant to go 0-60 from the factory in 12.1 secs. I was curious since i purchased the car 2yrs ago why it feels very slow on take off and felt under powered while overtaking. And from doing my own 0-60 tests i was only getting 0-60 in 15.5 seconds.

Other than this the car runs smooth and is 100%, no cels, regularly serviced, seafoamed etc and minded very well. And with UK MPG averaging 25mpg, thats driving highway 40% and town 60%, i felt thats not too bad. BUT i still always felt the car should be giving me more power.

So i found this post which suggests testing the Airbox thermostat. Because if it's broken and stuck all the time in the HOT air position, then your car will be sucking in just HOT air and feel like it's pulling a truck behind you. After inspecting the airbox thermostat i found it was indeed always in the HOT air position regardless of running temperature. To be certain I took it out of the car and stuck it in the freezer and then in front of a heater for a while but no movement what so ever going from hot to cold. So i knew it was broken.

Instead of replacing the thermostat, i decided to force open the flap in the COLD air position as others have done in this posting. I done this by using just 1 screw as shown below. I know i could of opened the air box thermostat housing and cut it out like other N/A drivers have done, in order to let more air flow through but i wanted to have the option to go back to the original factory format. Just in case something went wrong in the future. I also didn't bother inserting tin foil in the hot air part of the housing like some of you have done but the hot air pipe is still attached. Now the flap feels secure open in the cold air position.

So whats the verdict???

Well i re-done my 0-60 test and i'm now getting 0-60 in 14 seconds. Instead of the 15.5 seconds i was getting before i done this mod. Its still not the 12.1 seconds that the car should be getting since it was new but it is 14yrs old now and with nearly 150k miles. I'll see over time if i'll get any improvement in MPG. I certainly feel the car is now more zippy on start off and better on overtaking. It's still no rocket ship but it is a good improvement and it was worth doing.

And all thanks to this site!

I was going to replace my air box thermostat until I found this thread. I decided to do this, instead:



Flap now permanently open to allow only cold air in. I'm pulling pre-heater tube off the hot side, as it is not needed any more. And no hot air will be coming through the other side, as the door now blocks it. When winter comes, I'll just let the car warm up a bit longer before going.

[erikv11]

If you are in a cold climate and this car sees freeway speeds, I would at least replace the pre-heater tube in the winter.

[DARK_BLU]

I am in Atlanta, GA, USA and the summer heat is high for us here, this year. We may get some cold in the Winter, but we are a long way from that. It so happens that when I ordered replacement 02 adapter harnesses and an oil filter from eeuroparts.com, I also ordered a replacement pre-heater tube, since my existing pre-heater tube is the original that came with my 96 850 and it's falling apart. So, I can put that pre-heater tube on when it arrives. Is there a special link to use for eEuroparts or a special code that gives Mathew's site credit for the purchase? I try to buy from site supporters and want to insure that Mathews site is getting some sort of credit for my site sponsor purchases. I've also been going to Voluparts, which is located here in Atlanta, so if I'm supposed to tell them something that gets Mathew's site some credit for purchasing from a site sponsor, I need to know that too.

[matthew1]

Thanks for thinking of MVS, Dark. eEuroparts has a "Coupon" box on the cart page to get 5% off with code "MVS". But I think there are codes out there that are more than 5.

Either way, there should be a comments box somewhere you can mention MVS, coupon or no coupon. That would be super. Thank you.