ENGINE OVERHEATING (ODD HOSE PROBLEMS)

This Information was contributed by a Saab 900 owner

My 1992 SAAB 900 car would overheat and cooling fan would not come on. Fan tested good, Temp switch replaced, thermost replaced, fan runs when switch shorted indicating electrical good. Suspected radiator plugged preventing hot water not reaching switch or water pump defective causing same problem.

GUESS AGAIN!! Problem determined to be a PLUGGED Hose from top left of radiator to reservoir!
Unplugged hose and cooling system operates normally. This solution came after weeks of replacing switches and thermostats and MANY but scratchings and quite a few curse words. Suspect void developed around temp switch which is located directly below hose at radiator top,
causing no hot water reaching switch.

NOTE: We have seen issues like this on all models. Many hoses are dual layered hoses. If the inner layer of any cooling system hose fails then it will likely flop toward the inside (depending on the hose position). When this happens the flow of the coolant is interupted causing very odd cooling system issues. When this issue occurs it can be very difficult to diagnose. Replacement of the issue causing hose is the only cure.