What does this hose do?

I recently replaced the heat exchangers & muffler on my '69 911E & have been having a problem finding the correct replacement for one of the associated hoses.The hose in question goes from the small (approx 20mm)take-off high up on the lefthand heat exchanger to a short metal pipe protruding from the underside of the lh side of the engine compartment. The hose which I removed was made of thick walled rubber (which had become hardened) which I would not have thought was correct. I can't find any picture or even mention of this hose in Automotion, Tweeks, Performance Products or Pelican's catalogues but Stoddard lists "hose from heat exchanger to regulator housing (w/mechanical injection)" part no.911.108.151.00 (on p.27). Is this the part I need & what material is it made from?
Thanks.
Andy (UK)
'69 911E

Andy,

That Stoddard part listing is the 2"(50 mm) flex hose for the hot air intake to the air cleaner assembly on '72-up MFI engines.

The part you need is indeed a heavy, multi-ply reinforced rubber hose, 25 mm ID x 440 mm long, pn# 999.181.212.50 ... and it does, as you surmised, connect to the twin-layer hose to the warm-up thermostat on the MFI injection pump!

While you are working in the engine area, you probably nshould remove the injection pump thermostat, disassemble, and thoroughly clean the stack of bi-metallic 'springs' with a degreaser/solvent ... the procedure is described in the MFI 'Blue Book' here in the Pelican archives ... if you don't already have a copy. A dirty thermostat causes the MFI pump to be too rich most of the time ... gas mileage and drivability problems are the result. Annual cleaning of that thermostat is recommended.

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Warren Hall
1973 911S Targa

Thanks Warren, will do.
Andy