The '93 245 I just bought still has the hose...I've read a bit about how the air box has a damper that is supposed to reposition, etc. The metal ducthose is supposed to "preheat" the incoming air, right? I have my '86 and '89 240s w/o the ducthose..and no problems have occurred. Should I buy replacement for them? I live in the south near Nashville. Any insight would be much appreciated. Thanks
Cabbie2169

I kept the preheat pipe and and I gor rid of the whole thermostat mechanism from the air box. Its help in with 3 snap in tabs. You have to remove the whole airbox to get to it. Then I stuffet a big ball of aluminium foil into the pre heat hose. No more preheat, no more intake restriction. I also removed the top part of the intake tube in front of the radiator.

BB consensus from my research (lurking on BB for a couple of years) seems to be: protect your AMM by disabling the pre-heat system; particularly in the warmer climes where engine heats up soon enough after starting. I like BC's solution no. 2 as you still have the cosmetic apperance of a stock 240. My '88 wagon had already had pre-heater disabled by PO in this way but then my mechanic removed the ductwork completely. No discernable change in performance at start up but feels kinda naked now! Your choice. Good Luck. YMMV.
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Mike's 'Indobrick' : '88 245 250,000kms; RIP: '84 360GLT 200,000kms.

Inside the air filter box is a large flap, controlled by a temp-sensitive device. When the incoming air is warm enough, the flap moves to close off the duct hose from the exhaust preheater.

OK, AMM warms up quicker, EPA is happier, and your emissions test folks see the hose hooked up and are happy with that.

It's the temp-sensitive device that fails. It quits with the flap fully open to heated air, sending the AMM to the toaster. Everything looks nice, so the above-listed folks are happy, but you own the dead AMM problem.

Solutions: (1) Disconnect the air hose at the exhaust heat area. Hook it up for your emissions test - if they check that in your area. (2) Install a block of wood in place of the temp-sensitive device so as to keep the flap closed all the time. (3) Install a new temp-sensitive device. Same labor as #2, will need another replacement in the future.

You choose. Protect the AMM.

Good Luck,

Bob

:>)
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240s: 1986 244GL, 1988 244GL, and 5 others.