Porsche Repair: heating problem 1/2 solved, heat measurement, good ol days

Question
hi dave iknow you  answer alot of questions.i hope you remmber me.about my question of my car over heating i replaced the sender screwed in the rad now my fan turns on before it over heats.before it would over heat then the fans would turn on.problem solved.now why would it heat so fast.highway driving theres no problem because i assume all that rushing air cools it just fine but city no rushing air and fans are constantly on.now let me thow this at you see if it sticks.have you ever heard of a water pump working only half assed.i mean it pumps but not as much as it should.there are no leaks in the cooling system.another thing i was thinking of was my car has a/c and that rad could be gumed up creating air resistance in the cooling rad.i was thinking of removing it any way and the compressor at the same time it would free up some horsepower.any thoughts/sugestions?

thanks rick

Answer
Hi Rick,

Sure I remember you and your hot-running 944.  

The water pump is driven by a cam belt so it really can't be performing abnormally.  I'm thinking there's one of two things at the moment:

1.  The problem is completely solved.  The heating fans now come on when they are supposed to and when you're on the freeway that cooler rushing air helps out tremendously.  Remember, for smog purposes, manufacturers purposely design the engines to run hotter than in the good ol' days.

or,

2.  I'd still like to see you check the condition of the radiator.  Some shops have a heat measurement device that can be used to roughly gauge if there are cold spots in the radiator while the car is running.  If a cold area is detected in an area where it should be hot, there's a blockage and you have less radiator performance than you're supposed to.  In the meantime, get an air hose and blow compressed air through both the a/c condenser and the radiator from both sides and see if you can clean up the finned areas.

Dave