924 Mystery..

[DLA]

My car is behaving terribly. She's a 1979 924 of whom I love dearly. I'm no professional mechanic, so bear with me. When going down the road, the car would quickly overheat anytime that I took my foot off the accelerator or if I was at a steady speed. It would run cool anytime that my speed was increasing. It overheated at idle. There were no coolant leaks. I changed the thermostat, radiator cap, flushed the radiator, checked the hoses, etc. and it didn't fix the problem. No chocolate milk on the oil cap, and no exhaust smoke. One night, having to drive it, it was overheating as usual and I added some fluid. For some reason, she ran perfectly for several days. Started overheating again and I changed the head gasket for lack of ideas. It still didn't fix the problem. Same thing. Every once in a while, adding fluid made her drive cool and perfectly. I found a small dip in the head and took it to the shop to have it re-done. Now I'm still having the same problems. She drives fine every once in a while for no good reason I can think of. I'm also noticing something unusual with the radiator. The fluid is being suctioned down into the system and gives the appearance that she's out of fluid. Once she cools, the water level is normal. Maybe she was supposed to be doing that all along, but she never did before. Any ideas?????

[DTP]

What Ratio are you mixing your coolant? I have had this problem with several cars not just my Porsche. My Dad who has owed a sports car almost all his life except during my teenage years(smart man) reccomends if you are using a 50% distilled water and 50% coolant ratio change it to 40%Distilled Water 60%coolant. It has worked for my other cars and I have never had a problem with my 77 924 once I used this mixture.

[DLA]

Thanks for the advice. I have been using a 50% ratio. I'll give that a try. I'm seriously running out of ideas here. Thanks again.

[Martin Taylor]

Sounds like there is still air in the system, it has to be bleed properly or it will not circulate at low rpm.
The mixture is richened as the throttle opens, a richer mixture runs cooler also.

[DAVES]

My wifes 78 924 overheats in traffic, and boils over after I turn the car off. I was worried about it, so I put a rocker switch in the console just behind the gearshift. It is connected to bypass the radiator fan switch. Now when I'm in traffic or city driving I just hit the switch, the fan comes on and starts cooling the engine down, before it gets too hot, I leave it on until I am no longer in traffic or driving on city streets.

[DLA]

Thanks for your reply..... I actually did the same thing to my 924. Worked great for awhile and then suddenly one day smoke started pouring into the car. Seems I fried one of the fans....