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Car Forum / Porsche / Porshe 944 / June 2006Overheating
Hi, On a long fast trip yesterday my '86 2.5l Lux was overheating. I used the interior heater to keep the engine temp down (at the expense of roasting myself even with the windows open). On testing the system today: Coolent is correct Radiator is <2 years old and no blocked fins System holds pressure Now here's the interesting bit, the cooling fan comes on at the right temperature but I dimly think I remember it used to have two speeds. Is this right? Am I imagining it? It comes on at what appears to be the lower speed but this is insufficient to stop the temperature climbing further. Turing on the cabin heater hot with 1 speed on the interior fan redresses the balance and the engine temp settles down correctly. What should I test next? If there is a higher fan speed what triggers it and how can I check the circuit? Many thanks in advance Chris Is the thermostat fully opening when it gets hot? A blockage restricting coolant through the radiator would cause your problem. If your radiator fan has only 2 wires then it probably only has 1 speed. 3 wires should give the fan 2 speeds. Is the radiator fan moving/pulling the air through the radiator in the correct direction? And you are sure that there is no debris blocking fresh air through the radiator? later, dave (One out of many daves) > Hi, > On a long fast trip yesterday my '86 2.5l Lux was overheating. I used the [quoted text clipped - 19 lines] > > Chris I had a similar problem with my '89 some years back. Someone online suggested I open the bleed screw on top of the thermostat housing and blow into the tank until coolant starts coming out. This blows out the air in the system. Of course my first thought was "where's the camera?". I did it and realized cooler temps immediately. Give it a shot.....it doesn't cost anything. Let me know how you make out. Best of luck, Fred > Hi, > On a long fast trip yesterday my '86 2.5l Lux was overheating. I used the [quoted text clipped - 19 lines] > > Chris The 944 has two radiator fans - one fan comes on for cool down after you shut off the engine - and both fans will come on when needed when the ac is on, or while running and hot. A good test - is to put the AC on - then check to see if both fans come on for maximum cool down. Putting the AC on will actually help cool down the radiator faster - like in stop and go traffic. BUT - if you are traveling fast - you dont need the fans - they actually get in the way of the airflow at high speeds. I bet thermostat - and/or bleeding the system with a good blow job (did I say that?)  Signature______ joliett >I had a similar problem with my '89 some years back. Someone online >suggested I open the bleed screw on top of the thermostat housing and blow [quoted text clipped - 30 lines] >> >> Chris Oh you so did go there. > The 944 has two radiator fans - one fan comes on for cool down after you > shut off the engine - and both fans will come on when needed when the ac [quoted text clipped - 46 lines] >>> >>> Chris Thanks for all the advice! Some I will take with a pinch of salt (or mouthwash). I discover through fiddling around today that my fan's higher speed now works again. I cleaned the insides of the relay and instead of only getting the low speed when it hit temp I got the full blast. It should therefore be ok. One thing disturbs me tho and that is the overheating was happening at 80 to 90mph so plenty of air would have been getting to the radiator anyhow. Perhaps I'm just being oversensitive about how high the needle normally goes? It did not get into the red but there was clear space above the upper mark. Is this actually just normal? For good measure I did bleed the system btw. I preferred to do it by giving the hose a good squeeze! I guess the thermostat being stuck half way open could cause the problem. Is this possible? Cheers, chris > Oh you so did go there. > [quoted text clipped - 48 lines] >>>> >>>> Chris You might want to invest in a new rad over the years they do clog up with rubbish. Or take it out and back flushing it might help! Not a good idea flushing them out with radiator flush product as there is a good chance it will unblock ok, including any old self sealed holes. leaving you with a calender for a radiator. > Hi, > On a long fast trip yesterday my '86 2.5l Lux was overheating. I used the [quoted text clipped - 19 lines] > > Chris Having same problem with 84 944. Current radiator is twenty years old. I am considering installing a new radiator. Can they last twenty years? I don't think so. I already have a new radiator - about 18 months ago. I'm going with the assumption that if anything it is a partially stuck open thermostat. I'll let you know how I get on. Chris > Having same problem with 84 944. Current radiator is twenty years old. > I am considering installing a new radiator. Can they last twenty > years? I don't think so. Check out www.clarks-garage.com. It sounds like you may have an air pocket in the system. Need to incline the car with engine running and open vent plug to get all air out. Also, recommend using "water wetter" coolant additive. I dont recommend any water wetter agent. If it's not in the Porsche owner's manual - don't use it...it's all BS anyway. Signature______ joliett > Check out www.clarks-garage.com. It sounds like you may have an air > pocket in the system. Need to incline the car with engine running and > open vent plug to get all air out. Also, recommend using "water > wetter" coolant additive. Radiators last the life of the car - as long as you DON'T put diesel oil in it. (Dont ask!) My new one lasted 400K miles - and 25 years. The gauge can go anywhere it wants - as long as it's not in the red. Signature______ joliett The temp gauge should normally hover around mid scale. Water wetter works to increase the heat transfer from metal to water. I changed my radiator at 120k and it made a huge difference in dropping the temp. It always now runs in the bottom of the middle band no matter how warm the air is and if I am stopped in traffic. I had replaced fan switches, thermostat, water pump, etc, but the radiator made the biggest difference. I think they slowly corrode over time if they don't flushed periodically. > The temp gauge should normally hover around mid scale. > Water wetter works to increase the heat transfer from metal to water. |
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