I was wondering what the flexible stainless steel hose that runs from the front of the car past the oil filter and towards the back of the engine is called? It broke near my filter about a year ago. Also, what function does this hose serve? Can I mend it myself easily? Thanks for any suggestions and happy holidays, Mate
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Mate ('90 244 165K)

That is the hose which directs heated air from the exhaust manifold to the air filter box. When a cold car is started, the heated air helps the cold engine to run better. As the car warms up, a flapper valve thermostat in the air filter box is supposed to close the flapper, shutting off the heated air and allowing unheated air through the air filter. Many believe the failure of the thermostat on the flapper valve leads to continuously running hot air into the air mass meter thus shortening the life of that expensive part. You can replace that metal hose fairly easily or just patch the break with metal tape. Many disconnect the hose to prevent damage to the air mass meter. A disconnected hose might make your car fail an inspection though. If you live in a really cold climate, you might want to fix the hose and also check the air filter box thermostat to be sure it is working. A new thermostat is around $20 US. Here in Oregon, I've just disconnected the air hose on one of our 240's and will probably do the same on the others.

You mean the metallic flexible tubing, about 1 1/2" diameter? Made of foil covered paper? That's the preheater hose, for warming up the car a bit sooner when it's cold. By a thermostat in the air box controlling a flap, it pulls the air from that tube, which gets preheated from the exhaust pipes.

It's not something that absolutely needs to be there (unless there's a visual inspection during smog checks), and if the air box thermostat isn't functioning correctly, can fry some things along the way (namely the AMM, if so equipped).

As for patching ... I have two segments of these spliced with a drink can and hose clamps. It works well enough to pass here in California, so.

-- Kane ... I suppose duct tape would work too.
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Blossom II - '91 745Ti/M46 ... Bubbles - '74 144GL/BW35 ... Buttercup - '86 245GL/AW70 ... The Wayback Machine - '64 P220/M40