Urdone

Hi all, just purchased my 1st '83 944 with 115k miles with no records, so on the safe side I decided to :
Replaced all front seals, installed new updated water pump and timing and balance belts on my own. car started on first try, no leaks and runs smooth, except this:
After bleeding all air out of coolant system car still gets hot, temp gauge will hold steady in middle for a while then climb to near hot until fans kick in and cool engine. a continuos cycle of cool to hot back to cool back to hot.
as far as I can tell no air in system and no leaks sucking air into system. both upper and lower hoses are warm, telling me the coolant is cycling thru motor
Am i overlooking something ?
Thanks for any input

V2Rocket

your fan switch sounds suspect.
the fans should be turning on by the time the temp gauge gets to "middle".

as a test, make a jumper wire with a 1/4 female quick-connect terminal at each end.
unhook the factory fan switch wiring from the fan switch, and hook one of your jumper terminals to a switch terminal.
let the engine run and warm up to temp, then connect the other jumper terminal to the other terminal on the switch, this will force the fans to run. watch your hands near the belts and fan blades!

does the engine stay at a steady temperature?

Coloradoguy

Welcome, Undone. My 86 has the exact same symptoms.

Mine came with records but I can find no recent attention to replacing the coolant, which should be done every two years. It runs fine but after warming up the temp gauge creeps up past the last white line towards the red at every stop light. The fan eventually kicks in, but way too late. I always crank the heat and blower motor way before then. I ordered a new fan switch, thermostat, and coolant. As soon as the weather warms up a bit I'm going to do a complete flush of the cooling system and with the new parts I hope it fixes things.

The switch is a simple screw in but not the easiest place to get to under the top left radiator hose. Good luck on fixing this all-too-common 944 problem.

joejoe

What is the actual temperature? Porsche gauges can be quite a bit off. All my 944's show different temps (on the gauge) but in reality all are within 4 degrees at temp and idle. The same is with my 928's. An infrared temp sensor on the themo housing will give a better idea of what's going on. Also congratulations on :1 your purchase and 2 tackling the major necessities right off!

Urdone

Thanks for the info ..
V2rocket..the switch seems to be bad, definitely the passenger side fan due is not coming on when a/c is turned on, and the drivers side doesnt come on til almost in the warning area. I will replace it
if that doesnt solve the problem then I guess its flush time

Next question, noticed 3 different temp switches, 75c, 80c and 92c. My thermostat is 76c. so I'm leaning towards the 80c would that be the correct one to use?
which manufacturer is reliable, heard wahle has had issues with thermostats and these switches

V2Rocket

get the fan switch closest to your thermostat in temp rating.

if you do go to flush coolant, do yourself a favor and remove the radiator from the car.
you can use a garden hose to "backflush", stick the hose in the lower rad hose outlet and plug the other holes with fingers/thumb and force the water to come OUT the upper rad hose inlet. you wont believe the crap that comes out. i did this a while back and my avg running temp dropped 20 degrees.

Urdone

Ok, after replacing temp sensor switch(82C), It still does the same thing, but now only goes up to the 3/4 mark then the drivers side fan goes on, cools down then back to the 3/4 mark . roller coaster with the temp. Plus now the passenger side fan does no engage, poop.
Next logical step is to back flush radiator and I'm going with the 75c sensor. But why isn't the passenger fan engaging? even when turning a/c on only the drivers fan works...
both fans worked before disconnecting them to remove fan assy
can't do these tasks til I get back from vacation in 2 weeks, but any advice would help with the fan issue , thanks

th535is

Could possibly be the fan relay. I believe there is a failure mode where the relay can be bad but the fan still kicks on at high enough temperature.

I'm dealing with a similar issue and have ordered a new fan relay to test this.

Also, oddly enough, relay number X which in the manual is supposedly for the intermittent windshield washer also seems to affect the fans working or not. Have been dealing with it buzzing intermittently and when I push on it I can get the driver side fan to come back on. Have a replacement arriving in the next few days. Hopefully that will fix it.

NEXT DAY UPDATE:
The two new relays fixed the fan and relay buzzing issues