MVS Forums member and new-to-Volvo SUNRG shows us how to modify the 240’s airbox to make it reliably pull in fresh air. Instead of a “factory” fix that would fail in a similar way down the road, he chose to engineer his way around this. Good work!
So I recently changed the air filter on this new-to-me car and of course found that the 240 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. 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). 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. 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. The screen prevents leaves and anything sizeable from entering the airbox while allowing virtually completely free air flow.