Airbox thermostat failure...

Post by **MadeInJapan** » 18 Feb 2007, 09:06

Hopefully this will help with the PCV: http://volvospeed.com/vs_forum/index.ph ... 29650&st=0
Not really sure about the 02 on the '93 but you can measure the resistance on the wires and determine if it's really shot...I believe it's suppose to be .1volts. Others will add their knowledge.

greasefingerss · Post by **greasefingerss** » 18 Feb 2007, 12:14

On most Bosch O2 sensors, one can check for continuity across the two white wires. This is the heating element only. If you see an ohm or two then the heater element is working.

The other two wires (black & brown I think) are the output of the sensor. The output is a sinewave of voltage vs time, so a voltmeter is not the correct tool for this. But if one were to back-probe the sensor (measure in-situ) and test it with a hot running engine, you will see the voltmeter swing from about 0.1 to 0.9 volts. It swings quickly so if the voltmeter has a min & max feature, then use it to extract the two data points.

An oscilloscope or a proper scanner is the best way to test it.

Some have a narrower swing (like 0.3 to 0.7v)

What you don

TacklaNHL · Post by **TacklaNHL** » 12 Jan 2008, 14:00

Hey guys - just found this little discussion - quite interesting.

My 1995 850 GLT Wagon (2.4L 5-Cyl. N/A) has been getting poor gas mileage as of the last year. I cleaned out the throttle body, replaced the vacuum tree and flame trap, and still... about the same gas mileage. My PCV is the next big project, but it seems like a big one, so i'm trying to prevent doing it.

So, I took my airbox out and removed the thermostat this morning. I haven't even driven it around much yet, but the engine sounds good and seems to be running great.

When removing the thermostat the silver pin just came right out - is this normal?

Does this mean that my thermostat was bad anyway?

My big question is - I live in Denver, Colorado. During the winter almost every morning I'll be driving the car in sub-freezing temps (around 17-30 degrees F usually) - is having the cold air flap constantly open going to put me more at risk than other people?

And what are the risks? A new MAF sensor? What does that do anyway?

Thanks for the help - this site rocks!

Post by **Ozark Lee** » 12 Jan 2008, 17:05

I just jammed mine open and didn't actually remove it so I'm not sure about the pin. Make sure that your damper is forced to the cold air side after you removed the thermostat.

It won't hurt anything to not have it. At worst the car will take an extra 1/4 mile to warm up on the coldest days.

...Lee

rchotrod · Post by **rchotrod** » 12 Jan 2008, 21:50

Ive had my 97 volvo 850 non-turbo (5sp!!) for a few months now. My thermostat was fine in my intake but I just decided to go to all cold air to see what would happen. On the "Y" piece that houses the thermostat and warm/cold intakes, I just pushed the door back all the way to all cold and marked the spot. I drilled a small hole and threaded a screw in to hold the door to all cold. The system has worked flawlessly for a few weeks now. I have noticed considerably more 'pep' and increased city mileage by 3mpg!

ps. I think i have a good system figured out for a true cold air intake as well; Ive ordered some parts that should be in soon. Ill post pictures as soon as I get the parts in and get them on.

97 Volvo 850 5sp, 115000 miles

Post by **MadeInJapan** » 12 Jan 2008, 22:38

Keep us posted on the CIA for your non-turbo. You take pictures, we'll post your write-up in the repair database and you'll be FAMOUS!!

Post by **tjts1** » 13 Jan 2008, 11:29

I completely gutted mine to free up some air flow.
Before

after

leftovers

If you are interested in picking up much sharper of throttle response do this.
http://volvospeed.com/vs_forum/index.ph ... try1168946
It makes a world of difference on a 5 speed where throttle response determines your clutch engagement point.

We did a 1900 mile road trip over new year break from San Francisco to the San Juan islands in Washington state. The 855 averaged 26.5mpg for the whole trip including 2 stretches with chains on and about 200 miles of local driving. Highway only fill ups came to 29mpg on 87 octane.

Post by **MadeInJapan** » 13 Jan 2008, 11:50

Very cool. Let's hear some more comments on this. If this is a viable thing to do long term on your N/A 850's I'll pin this in the repair database.

cn2000 · Post by **cn2000** » 24 Feb 2008, 13:55

I just wanted to add that when I was in the shop we used to replace these t-stats on cars which failed the NOX portion of the smog tests. The cars with a "hot-air postion" stuck t-stat or hot-air leak will produce dramatically elevated NOX emissions due to excessive combustion temperatures. That little sucker is not to be understimated. So you're even helping the environment by replacing it!

vroller · Post by **vroller** » 01 Apr 2008, 22:15

Hello there,

I'm new here and like many others before me I must say this is a really great site (thanks Matthew!).

Last night, I found the flap that blocked 'straight-on' air intake from above the radiator and having removed it, the car does seem more eager off the mark

But like some others who drive a T5, I found no hot/cold air flap in my airbox nor in the air intake plumbing.

A K&N filter is next on the list. I've been holding off on aftermarket/improvement stuff for fear of 'adding problems' to what is already a rather complex and not inexpensive to maintain/rectify car, lol but thru this forum I've found the confidence to do so.

On another note, we have an indy over here who supplies reconditioned ABS control units in exchange for faulty ones for RM400 (approx. USD120) plus labour with a 3-month warranty. Great find especially in view of the cost of a new one (RM2,000 plus) and the fact that I don't have the tools to saw open the casing and re-solder (not to mention a fair amount of skill and patience) the bits in the motherboard.

162,000km on the clock