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Volvo 240 Airbox Mod & Air Filter Thermostat Delete

Help, Advice, Owners' Discussion and DIY Tutorials on all Volvo's "mid era" rear wheel drive Volvos.

1975 - 1993 240
1983 - 1992 740
1982 - 1991 760
1986 - 1991 780
1990 - 1998 940
1990 - 1998 960
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SUNRG
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Year and Model: '93 240 Wagon
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Volvo Repair Database Volvo 240 Airbox Mod & Air Filter Thermostat Delete

Post by SUNRG »

I've been into european cars my whole life, but I only relatively recently became a 240 owner ... and I'm in love. What a fantastic car!

So I recently changed the air filter on this new-to-me car and of course found that the airbox thermostat was non-functional, and the engine has only been drawing air off of the exhaust manifold for who knows how long ... the bottom of the old air filter looked like toast.

IMHO the thermostat is an unnecessary weak link, if (when) it fails it's horrible for the car in many ways ... so I:
  • deleted the whole valve
  • cleanly blocked off the warm/hot air intake port
  • removed the snorkel to guarantee loads of free-flowing cool air
  • added a coarse screen, to prevent anything sizeable from entering the airbox, thereby enabling the air filter to do what it does best ... remove tiny contaminants from the air to promote long healthy MAF and engine life
I'm not recommending that anyone do this, but, I personally believe that these mods are positive steps in 240 engine health, performance and longevity.

Part 1 - Pull the airbox, remove the valve and thermostat and block-off the warm/hot air port:
Airbox with pre-heat hose removed.
Airbox with pre-heat hose removed.
From your local hardware store, pickup a 1.5 inch plug.
From your local hardware store, pickup a 1.5 inch plug.
Slide plug / cap over the warm air intake port and secure with hose clamp (commonly comes with the cap).
Slide plug / cap over the warm air intake port and secure with hose clamp (commonly comes with the cap).
Use a rubber mallet to close the end of the pre-heat hose.
Use a rubber mallet to close the end of the pre-heat hose.
This is just a free way to use your old pre-heat hose as a plug.
This is just a free way to use your old pre-heat hose as a plug.
Use common fiberglass screen material, use a coffee can or similar to cut it in the shape of a circle larger than the cool air intake port, place it over the port and secure it with a hose clamp. IMHO you've now got a safer for your engine high performance airbox. Reinstall with a clean filter and enjoy.
Use common fiberglass screen material, use a coffee can or similar to cut it in the shape of a circle larger than the cool air intake port, place it over the port and secure it with a hose clamp. IMHO you've now got a safer for your engine high performance airbox. Reinstall with a clean filter and enjoy.
With the snorkel and its base removed you'll get loads of cool air easily reaching this huge air intake port. Because this big air port is behind the headlight no big debris will ever enter the airbox (or clog the snorkel) so the air filter's flow and filtration efficiencies should be improved.
With the snorkel and its base removed you'll get loads of cool air easily reaching this huge air intake port. Because this big air port is behind the headlight no big debris will ever enter the airbox (or clog the snorkel) so the air filter's flow and filtration efficiencies should be improved.
The screen prevents leaves and anything sizeable from entering the airbox while allowing virtually completely free air flow.
The screen prevents leaves and anything sizeable from entering the airbox while allowing virtually completely free air flow.
Previous: P1800, 760 Turbo Diesel, 760 Turbo Wagon, 940 NA Wagon
Current: '95 850 Turbo Wagon, '93 240 Wagon
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93Regina
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Re: Volvo 240 Airbox Mod & Air Filter Thermostat Delete

Post by 93Regina »

SUNRG wrote:Pull the airbox
Keep It Simple....just take the hose inserted into exhaust-manifold's bracket and point it into radiator.
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matthew1
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Re: Volvo 240 Airbox Mod & Air Filter Thermostat Delete

Post by matthew1 »

SUNRG, great write-up. Scheduled for inclusion in the Volvo Repair Database.
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woc2
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Re: Volvo 240 Airbox Mod & Air Filter Thermostat Delete

Post by woc2 »

Keep it clean, I hate that dirty stupid hose anyways. This is the project for this weekend. Im also going K&N filter, just to have a sticker that says K&N LOL.
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Re: Volvo 240 Airbox Mod & Air Filter Thermostat Delete

Post by matthew1 »

I put my sticker on my laptop. I needed the speed boost more with it than my 850 ;-).
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woc2
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Re: Volvo 240 Airbox Mod & Air Filter Thermostat Delete

Post by woc2 »

matthew1 wrote:I put my sticker on my laptop. I needed the speed boost more with it than my 850 ;-).
I have put an apple decal on top of the sony Vaio sign on my laptop, i noticed 50% increase in boost. :P
SUNRG
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Re: Volvo 240 Airbox Mod & Air Filter Thermostat Delete

Post by SUNRG »

Update / Improvement: Just remove the whole lower heat shield/director the hose attaches too. This is cleaner and it opens up this side of the engine bay enough so that you can easily change the oil filter from the top!

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Previous: P1800, 760 Turbo Diesel, 760 Turbo Wagon, 940 NA Wagon
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Re: Volvo 240 Airbox Mod & Air Filter Thermostat Delete

Post by 93Regina »

SUNRG wrote:Update / Improvement: Just remove the whole lower heat shield/director the hose attaches too.
I use the Motorcraft Oil Filter FL1A, and sometimes remove the heat shield, but I always put shield back on.

If I lived in a warm environment, I might remove it, but in colder environments, no: I bought an Acurite wireless weather thermometer and inserted wireless sensor into air box. On highway driving, around 32°F (0°C) at 55 mph, inlet air was running around 100°F (38°C) on level ground, and upto 111°F (44°C) in hilly terrain with air box hooked up with defective thermostat.

Cold inlet air temperature will increase the fuel burn



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SUNRG
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Joined: Tue Sep 18, 2012 11:38 am
Year and Model: '93 240 Wagon
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Re: Volvo 240 Airbox Mod & Air Filter Thermostat Delete

Post by SUNRG »

@93Regina - your experiment proves the importance and value of this delete mod!

at 32F in hilly terrain your airbox temp was 111F - imagine how crazy scorching hot the airbox temp would be if outside temps were 80 to 90F!

i've done the delete to numerous 240s since the original post this mod has been flawless and it keeps the air filter cleaner longer.
93Regina wrote: Fri Nov 06, 2015 4:41 am
SUNRG wrote:Update / Improvement: Just remove the whole lower heat shield/director the hose attaches too.
If I lived in a warm environment, I might remove it, but in colder environments, no: I bought an Acurite wireless weather thermometer and inserted wireless sensor into air box. On highway driving, around 32°F (0°C) at 55 mph, inlet air was running around 100°F (38°C) on level ground, and upto 111°F (44°C) in hilly terrain with air box hooked up with defective thermostat.

Cold inlet air temperature will increase the fuel burn
Previous: P1800, 760 Turbo Diesel, 760 Turbo Wagon, 940 NA Wagon
Current: '95 850 Turbo Wagon, '93 240 Wagon
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93Regina
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Year and Model: 93:240/940
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Re: Volvo 240 Airbox Mod & Air Filter Thermostat Delete

Post by 93Regina »

SUNRG wrote: Wed Jul 24, 2019 12:30 pm @93Regina - your experiment proves the importance and value of this delete mod!
Experiment was done with a defective thermostat.

I've installed new thermostats....but in warmer weather, I disconnect tube going to header so non heated air enters it on my 240s..

On 1993-940, radiator supplies heated air to air box...year round.
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