944 non turbo overheating
04-21-2004, 11:10 AM
#1
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944 non turbo overheating
Hey guys. I have learned so much from everyone on rennlist and I wanted to thank everyone.
I currently have an overheating problem with my 1988 944 non turbo. I replaced the thermostat, bled the system so much that I can do it in my sleep and I still overheat.
The fans do not come on at all. (unless I turn on the AC, and the low speed comes on and this does not lower the temp.) I tested the fan circuit and I can get them to turn on high and low speeds by jumping the terminals.
The radiator was hot in spots and cool in spots so I had it power flushed and the radiator shop said that a bunch of crap came out but that they've seen worse. I put it all back together and now it takes about 20 minutes of driving to overheat even at highway speeds. I have replaced the head gasket, so I know it's not that. I don't think it's the water pump.
Could the radiator be so plugged that the fan temp switch is not getting any coolant by it and thus not turning the fans on.?
Your help would be greatly appreciated!
I currently have an overheating problem with my 1988 944 non turbo. I replaced the thermostat, bled the system so much that I can do it in my sleep and I still overheat.
The fans do not come on at all. (unless I turn on the AC, and the low speed comes on and this does not lower the temp.) I tested the fan circuit and I can get them to turn on high and low speeds by jumping the terminals.
The radiator was hot in spots and cool in spots so I had it power flushed and the radiator shop said that a bunch of crap came out but that they've seen worse. I put it all back together and now it takes about 20 minutes of driving to overheat even at highway speeds. I have replaced the head gasket, so I know it's not that. I don't think it's the water pump.
Could the radiator be so plugged that the fan temp switch is not getting any coolant by it and thus not turning the fans on.?
Your help would be greatly appreciated!
04-21-2004, 01:54 PM
#2
Race Car
Hmm, hot in spots, cold in spots... that's not good.
After about 15 minutes of idling, when my thermostat opens up, it takes about 30 seconds before my entire radiator is quite warm. Now, if your fans never kick on, try cleaning up the terminals on the thermofan switch. Use some emery cloth or very fine sandpaper to clean them until they are all shiney metal. same with the inside of the female connectors if you can.
I just thought of something, this may not be a good solution, but I think it's a good way to test this.
Try jumpering your fan switch, and taking it for a drive. See if it still overheats.
Obviously you would need to secure the wires somewhere, and you would be best off making a jumper with some #14 wire and 2 spade terminals, so it will last for the duration of the test.
If it doesn't overheat, then your cooling system is probably alright, and you can be about 90% sure the problem is the fan switch, if it still overheats, then you definately have a blockage somewhere in the cooling system.
You could be right about the coolant not circulating past the fan switch, but it's really a long shot. Are you familliar with how radiators are built? If you are not, let me give a brief explanation. There are 2 elongated tanks on each side, then all the passages between them (the bulk of the radiator). It would be awfully difficult to block up one of the tanks so bad that it would not heat the fan switch, especially given it's proximity to the water inlet on the radiator. In order for this to happen, all of the passages across the radiator below that point would have to be blocked, along with several above (pretty much the entire radiator), or else there would have to be a serious blockage in that tank on the radiator.
When you had the rad flushed, did they say anything about it seeming awfully blocked up (like it still didn't flow well after being cleaned?). If not, then you can be about 99% sure that hot coolant is getting to the fan switch.
When you say it's hot in spots, and cold in spots, do you maybe mean entire rows in the radiator are cold, or just that some patches in it are cold?
I'm just a little confused, so I'm tossing out ideas here.
After about 15 minutes of idling, when my thermostat opens up, it takes about 30 seconds before my entire radiator is quite warm. Now, if your fans never kick on, try cleaning up the terminals on the thermofan switch. Use some emery cloth or very fine sandpaper to clean them until they are all shiney metal. same with the inside of the female connectors if you can.
I just thought of something, this may not be a good solution, but I think it's a good way to test this.
Try jumpering your fan switch, and taking it for a drive. See if it still overheats.
Obviously you would need to secure the wires somewhere, and you would be best off making a jumper with some #14 wire and 2 spade terminals, so it will last for the duration of the test.
If it doesn't overheat, then your cooling system is probably alright, and you can be about 90% sure the problem is the fan switch, if it still overheats, then you definately have a blockage somewhere in the cooling system.
You could be right about the coolant not circulating past the fan switch, but it's really a long shot. Are you familliar with how radiators are built? If you are not, let me give a brief explanation. There are 2 elongated tanks on each side, then all the passages between them (the bulk of the radiator). It would be awfully difficult to block up one of the tanks so bad that it would not heat the fan switch, especially given it's proximity to the water inlet on the radiator. In order for this to happen, all of the passages across the radiator below that point would have to be blocked, along with several above (pretty much the entire radiator), or else there would have to be a serious blockage in that tank on the radiator.
When you had the rad flushed, did they say anything about it seeming awfully blocked up (like it still didn't flow well after being cleaned?). If not, then you can be about 99% sure that hot coolant is getting to the fan switch.
When you say it's hot in spots, and cold in spots, do you maybe mean entire rows in the radiator are cold, or just that some patches in it are cold?
I'm just a little confused, so I'm tossing out ideas here.
04-21-2004, 08:15 PM
#3
Instructor
It could very well be the waterpump. If it is not circulating the the coolant it might not get warm in the area of the temp switch. Though definately check out the easy stuff first.
