Airbox thermostat failure...

[DARK_BLU]

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.

No problem, Matthew. I have more part replacements in mind and will certainly do my part to support this site. I knew nothing about this Volvo 850, when I got this car last year. Thanks to you, your site, and others here, I've learned a lot and the car continues to run strong. Much appreciated.

[JennyQ]

I have what seems to be the same problem on my 2000 S40. The vehicle has almost 200K miles on it. The engine air filter has 25K miles on it and looks new out of the box every time I check it. This vehicle is a turbo. How is the air controlled? Where do I start looking?

[erikv11]

Pardon me if this was already accounted for but: to check the air filter, you have to lift the filter up and look underneath, that is the side that accumulates any dirt/debris. The air comes in from the bottom of the filter box, then goes out the top to the engine intake.

Sorry, I don't know what the airbox looks like on an S40 so I don't know if it has a flap and hot air intake.

[blkdrgn18]

Ok, so I have a real conundrum for you guys. I have a 1993 Volvo 850 GLT. It doesn't like to start up when it is cold outside unless I turn on the ignition for several minutes. I thought it could very well be just the battery going out but I just replaced it and it still does it. Any ideas?

[850Rick]

I have a 1996 850 spd with the same issue. Mine was also stuck in the preheat mode. I used to electrical cord connector caps to block it open. I'm going to call around in the morning and find out how much a new thermostat will cost. It's simply jerry rigged for now. It will be interesting to see how much of a power and mileage increase I will get now. It was bogging bit at 4500-5000 rpm on hill climbing in 4th gear. Never used to do that, in fact I could take it up to red line with no issue and this car has over 325,000 miles. Just running over to get gas it already seems to have a bit more power.

[oragex]

This is my understanding how this thermostat works
In cold weather (perhaps below 5C/40F), the thermostat pin is retracted and the flap lets all warm air from the engine plus about 25% to cold air from the air duct in front of the car (even when the flap is fully letting warm air, some cold air still gets into the engine). If the car drives faster, more air needs to come from the front grid, so the vacuum hose will open the flap more for cold air.
In warm weather, the thermostat pin extends and completely closes the warm air from the engine and fully opens the cold air from the duct in front of the car. So basically in winter there is about 25% cold air and 75% warm air, while in summer there is 100% cold air getting into the engine. This is important because it greatly affects the gas mileage.

[scot850]

I am still confused by this and your explanation. It is not that you are wrong, but maybe my thermostat is just not getting your message.

Now outside temp is 5-7C today and just took the 2000 project V70 base (NA) for a run of about 5-6km. I was trying to warm the trans up so that I could try (yet again) to get a proper level of trans fluid once the trans was hot.

To get to the dipstick it is best accessed by removing the intake air tube from the front of the car. First thing I notice is while the engine was registering normal hot on the gauge in the speedo cluster, the air thermostat in the airbox was still almost fully closed. It was open maybe 8-10mm max from the fully closed position.

I know when I had the airbox in the fridge the flap was fully closed at an ambient temp of 5-6C:

Temp reading of thermostat

You can see it is reading 5-6C. Below is the flap position (remeber the vacuum(?) line is not connected).

Position of flap at 5-6C

Thermostat flap position after running hair drier

After running a hair drier on the thermostat at an ambient 21C this is the open position.

So my confusion here is what are the expected flap positions based on the cold air intake temps rather than the engine temp?

Neil.

[s3bi]

I'm currently also working on the hot air flap, started because the vacuum hose connector broke but when I remove it, it looks like this:

If I understand it correctly the piston in this part should press the hot air closed and the vacuum can pull the hot air flap open.
So this is not fully closed and therefore the thermostat that runs that piston that closes the hot air flap should be replaced, right? (I looked up the part number 9142616, it's available for 17€). However I have no idea how to get it out.

Now I bought a really cheap used airbox, which seems to have the same problem but I can tinker around with this one and if I break it it's not so much of a problem. Also I could fix the hot air closed on this one and repair the other one until it's winter time.

I've also looked on the one of a V70 which has clips on the outside, this one seems to be sealed so I can't access the part which should be replaced from there.

[scot850]

The unit you picture above has what looks like a load of 'barb' plastic clips. If you clean off the dirt Along the straight ledge running down the unit as seen in the picture above on the RHS it may split open.

Neil.

[Francisco86]

I'm currently also working on the hot air flap, started because the vacuum hose connector broke but when I remove it, it looks like this:
ansaugluftvorwärmung.jpeg
ansaugluftvorwärmung2.jpeg
If I understand it correctly the piston in this part should press the hot air closed and the vacuum can pull the hot air flap open.
So this is not fully closed and therefore the thermostat that runs that piston that closes the hot air flap should be replaced, right? (I looked up the part number 9142616, it's available for 17€). However I have no idea how to get it out.

Now I bought a really cheap used airbox, which seems to have the same problem but I can tinker around with this one and if I break it it's not so much of a problem. Also I could fix the hot air closed on this one and repair the other one until it's winter time.
ansaugluftvorwärmungaussen.jpeg
I've also looked on the one of a V70 which has clips on the outside, this one seems to be sealed so I can't access the part which should be replaced from there.

Hey there,

Have you managed to open this? I am facing the same issue here. Bought the thermostat but I don't know how to open this thing

Anyone with this configuration done the mod? Working well?

Thanks