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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / August 2006Overheating problem
Hi, I have a 2000 Daewoo Nubira, and it has an overheating problem. It overheats on the freeway, after about 10-15 miles of driving at sustained freeway speed. When exiting the freeway, the gauge creeps up another couple of notches when I come to a full stop, then cools down to 1/2 way on the gauge when I start back up again (never goes down to where it should be though - half way is the coolest it gets). This is what I've done to date to solve the problem * Installed a new radiator * Installed a new thermostat * Installed a new waterpump (and while it was disassembled I also had installed a new timing belt) * Two separate pressure tests * PH Balance test (whatever that is) * Verified that no steam is venting from the exhaust pipe I've spent 1100.00 so far, and I'm still at square one. Car still overheats. It doesn't quite peg the temperature gauge, but it creeps up to near 2/3 to 3/4 of max after driving for 20 minutes or so. Any suggestions would be most helpful. I've combed the 'net looking for ideas, but everything I've read so far are things it looks like I've already had done. Thanks kindly, Matt Is your coolant really hot? Are you losing coolant (boil over)? Gauges are mechanical devices which may not be correct. Yours connects to a sensor in the coolant stream. If you are not losing coolant use an IR gun or a touch type thermometer and see how hot the coolant is. Your cooling fans should turn on low speed at 199 degrees and go to high at 207 degrees. The PCM will shut them off at 194 degrees. > Hi, I have a 2000 Daewoo Nubira, and it has an overheating problem. It > overheats on the freeway, after about 10-15 miles of driving at sustained [quoted text clipped - 23 lines] > > Matt > Is your coolant really hot? Are you losing coolant (boil over)? Gauges > are mechanical devices which may not be correct. Yours connects to a > sensor in the coolant stream. If you are not losing coolant use an IR > gun or a touch type thermometer and see how hot the coolant is. Your > cooling fans should turn on low speed at 199 degrees and go to high at > 207 degrees. The PCM will shut them off at 194 degrees. I don't know this car but there may be 2 separate temp sensors - one for the gauge sand one for the computer. So there are several items not on his list that should be checked to see if they are working correctly. But it seems unlikely that will be the source of the problem. If we can assume that the OP has described the problem correctly then it seems he can drive around all day in town (stop and go traffic) without it overheating. That indicates that all of the sensors gauges and fans are working as they should. It's seems oily when he drives at highway speeds for more than 12 mins. that it overheats. The fan doesn't add much to the cooling capacity at 65 mph. So I would look for something that is restricting the air flow or coolant flow at high speed. Did he forget to remove that piece of cardboard he stuck in the grille when it was -20° last winter? Maybe the suction side radiator hose is collapsing at high speed. Also late ignition timing coupled with high speed can cause excess heat generation. -jim Thanks for the replies and the suggestions. > But it seems unlikely that will be the source of the problem. If we can >assume that the OP has described the problem correctly then it seems he [quoted text clipped - 3 lines] >for more than 12 mins. that it overheats. The fan doesn't add much to >the cooling capacity at 65 mph. It's hard to demonstrate that it doesn't overheat due to excessive city driving, because I do so little. Most is done on the freeway. But once off the freeway, the little bit of city driving I do does cause the temp to cool down to about half way (although still higher than what one would expect). As for any type of obstruction, e.g. cardboard in the grille, I just bought the car last month (from a private seller), and in that time I haven't added any jury-rigged devices, and I haven't discovered anything that might have been installed by the previous owner during all the tests and replacements thus far. Interesting note on the ignition. I'll have that checked too. Thanks. Re: the previous poster, thanks for the tip. No I don't seem to be losing coolant. I'll see if I can get a temperature reading on the coolant while it's running hot. > Thanks for the replies and the suggestions. > [quoted text clipped - 10 lines] > the freeway, the little bit of city driving I do does cause the temp to cool > down to about half way (although still higher than what one would expect). So you don't actually know that it is overheating? For all you know half way is right where it is supposed to be. I would still be concerned a little about it going up when driving at highway speeds, but the gauge could be very sensitive in that temperature band so it's possible that could be just a few degrees elevated. -jim > As for any type of obstruction, e.g. cardboard in the grille, I just bought > the car last month (from a private seller), and in that time I haven't added [quoted text clipped - 11 lines] > Message posted via CarKB.com > http://www.carkb.com/Uwe/Forums.aspx/car-maintenance/200608/1 > Hi, I have a 2000 Daewoo Nubira, and it has an overheating problem. It > overheats on the freeway, after about 10-15 miles of driving at sustained [quoted text clipped - 8 lines] > * Installed a new waterpump (and while it was disassembled I also had > installed a new timing belt) Did you reverse flush the block with a garden hose or some such when you did these replacements? > * Two separate pressure tests > * PH Balance test (whatever that is) > * Verified that no steam is venting from the exhaust pipe > > I've spent 1100.00 so far, and I'm still at square one. Car still overheats. Before doing anything more you need to do a cylinder leakdown test on all cylinders and/or check for the presense of exhaust byproducts in the coolant, there are test strips for this, to eliminate a failed head gasket. I am not sure why you think a failed head gasket would always result in steam out of the exhaust pipe. Ted Have you verified that the fan is pulling the air thru the radiator? I had a used Honda with the same symptoms and the fan had been wired backwards, even though the connector was keyed, someone had forced the plug together backwards. At highway speeds the fan would counteract the air coming thru the radiator causing it to overheat, only on the highway. Just a thought, good luck. >Hi, I have a 2000 Daewoo Nubira, and it has an overheating problem. It >overheats on the freeway, after about 10-15 miles of driving at sustained [quoted text clipped - 23 lines] > >Matt |
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