Saturday, April 6, 2019

924S Cooling System. Testing Why Radiator Fan Doesn't Come On

I lost the water pump at the end of a nice country-drive and had a long 100 mile tow to get home. (about $500!) With the water pump now replaced, I am not seeing the radiator fan come on unless I flip the air conditioning on.

Once the car is powered off, Coolant seems to be leaking from under the engine close to the water pump, but at a slow trickle.  There is no sign of white smoke from the tail pipe or of frothy oil.

Facts:
-> During period that water pump failed, I continued to drive the engine "hot" to get to a safe place. I refilled the coolant once and then stopped a second time. After the tow, I didn't restart the engine until I had replaced the water pump. However, the engine tends to overheat and it seems that the coolant is not circulating. Fan Resistance: Drivers Side: 400 Ohm, Passenger's: 1300 Ohms.

-> When I replaced the Water pump and removed the M6-1.0 studs, most broke in their holes. I therefore replaced the studs with 1/4" 20 tpi stainless bolts. The torque spec used was lower, and the waterpump gasket seal may not have been torqued down sufficiently as a result. That would explain the coolant loss from around the waterpump gasket.

-> Following this Clark's Garage procedure, the fans can power on in both low and high modes.
http://www.clarks-garage.com/shop-manual/cool-01.htm

-> The thermostat was reused and not tested before assembly.

Next Steps:
-> Remove the water pump a second time, test the thermostat and check the gasket for signs of leakage. Use some sealant and correct torque spec for bolts and reinstall.

-> Bleed and Retest the Cooling System

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