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manbridge 74 manbridge 74 is offline
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Join Date: Jul 2011
Location: CO
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Start at the heat exchanger on the left side. The big thick rubber type hose goes from forward area of heat exchanger fitting to engine tin by cylinder 2. Other side of tin from this is where your smaller double hose connects, other end going to t-stat. Also present in 73 are the hoses from intake pre-heater one underneath at cyl 3 tin area. The other comes up from rear of exchanger through tin in area just in front of left side chain housing.

Porsche put some thought into the thermostat system. One of the parameters is the rate of heating of the air hoses to the thermostat. Changing the type of hose changes the heat-up characteristic of the thermostat.

The best place to start is stock. Most changes involve getting the thermostat to turn off sooner. This can be done with an aluminum hose inside the stock rubber hose. There is a VW hose that can fit over the double concentric hoses from the tin to the thermostat.

Big issues are that there aren’t any air leaks at the heat exchanger or hose to the heater control box.
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74 911, #3
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Old 09-23-2019, 11:57 AM
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