Stock air intake on 2002 - Summer/winter box

[Happy Face]

I went to the parts bin and reinstalled the summer/winter air box piece back on, with the traditional air filter cover (sitting on top of a Weber 32/36).  The manual shows a second flexible hose going straight down from that box, presumably to the bottom area of the radiator, not really sure where that hose goes but it would suck up air in the 'winter' position.  The top hose fits right into the air filter housing (I'm presuming).  The manual says to keep the air box in the 'summer' position for temps above 50 degrees F.  That's pretty much 365 days a year here in south Texas.

 

I like the idea of 'cold' air going into the carb, like the original design, although not really sure if it makes a huge difference  Again, still don't know though where the bottom 'winter' hose goes to or if it just drops down to the bottom of the engine bay.

 

thanks in advance for any ideas/tips - dave

[Mike Self]

The "lower" hose on the winter/summer airbox is actually the winter inlet hose.  It leads to a collector box--cast aluminum on early cars, stamped steel on later ones--that's bolted to the cast iron factory exhaust manifold.  It allows the carb to pull warm air from around the manifold at the winter setting; as the engine warms up, the thermostatic spring inside the airbox gradually closes the warm air inlet and allows the carb to pull cold air in from outside. The summer setting locks the thermostatic spring and only allows cold air in.

 

Bet the collector box is missing on your car--it's a '72 so it would have been sheet metal, and they rust around the mounting bolts, and eventually will fall off.  Or you have a header manifold, not the factory one. 

 

mike

Edited January 25, 2019 by mike

['76mintgrün'02]

The bottom hose connects to the end of a heat shield on the exhaust manifold.

 

Some heat shields were cast aluminum

and some were pressed steel

 

I stole the images off of Google image search.

(using : bmw 2002 exhaust manifold heat shield summer winter box )

[Jeff]

The lower hose / winter mode goes to the exhaust manifold heat shield to warm the carburetor and keep it from icings up in cold conditions. Yes carburetors can ice up and the throttle can stick. I would use it and keep it in the Summer unless it gets very cold out.

[Conserv]

Here’s the lower hose hooked up on my ‘76.

 

The aluminum heat shield re-appeared on the 49-state 1976 cars — which is what my ‘76 is — as the manifold heat levels returned to more moderate levels after the thermal reactors disappeared.

 

Regards,

 

Steve

 

 

Edited January 25, 2019 by Conserv

[Happy Face]

fantastic.... that explains it and with some additional digging I found some previous posts about this.  I've got a Stahl header system so probably no real place to attach a 'winter' hose.  I think I'll just keep it in the summer position and try to get some 'cold' air into the air intake.  Thankfully we don't get really cold days down here!  Hoping the cold air intake will help on hot Texas days.

 

 

[stephers]

Just don't use any plastic hose for the bottom one, it needs to be a paper style one, original ones were brown

['76mintgrün'02]

1 hour ago, mike said:

the thermostatic spring inside the airbox

 

That spring also helps keep rodents from stashing nuts in your air cleaner.

(another borrowed image)

[stephers]

hot nuts