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mysterious overheating

 
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Old 11-01-2015, 07:22 AM
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mysterious overheating

Have been having overheating issues of about 2 months and I can't figure out why. It started a day after I replaced the oil cooler O-ring and a coolant line connected to the oil cooler the guy who built my engine said it was unrelated.

So far this is what I've replaced on the cooling system:
(1)water pump (less than 10,000 miles on it)
(2)new radiator+hoses
(3)new thermostat
(4)completely bled the cooling system
(5)new engine coolant temperature sensor+fan switch
(6)new cooling fan relay
(7)I also did a block test to check for a bad head gasket (several times to be sure) but the engine is fresh off of a rebuild so hopefully it's not that, plus the oil looks fine too.

The car is fine on short drives around town but will quickly overheat as soon as I get off the freeway after a long drive. The cooling fans turn on like they're supposed to when idling normally and the car can idle for hours without overheating as long as it hasn't been recently driven, but when the engine is already hot after a long drive they don't turn on until after the temp gauge is already indicating that the engine is overheating. I'm not losing any coolant either, but the coolant does look pretty dirty for being a few weeks old. I got a infrared thermometer and checked the temp of the upper and lower rad hoses when it was close to overheating and they were about 240 degrees.

I'm completely lost now, the only other thing I can think of is a vacuum leak. I found a loose vacuum line hanging down by the cold air intake and there was nowhere to connect it to so I just plugged it. (I think it was connected to the resonator but that's gone because of the intake). Car also has other symptoms of a vacuum leak like high/surging idle, power loss, and running rich even though there is no engine code.
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Old 11-03-2015, 03:56 AM
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Re: mysterious overheating

Are you using a thermostat from autozone or one from honda? I've always had bad experience with autozone/o riley thermostats. Do you have some fluid in the over flow resivor bottle? Need to have some in there if you dont.
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Old 07-16-2016, 08:04 PM
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Re: mysterious overheating

Quote:
Originally Posted by THM1000 View Post
Have been having overheating issues of about 2 months and I can't figure out why. It started a day after I replaced the oil cooler O-ring and a coolant line connected to the oil cooler the guy who built my engine said it was unrelated.

So far this is what I've replaced on the cooling system:
(1)water pump (less than 10,000 miles on it)
(2)new radiator+hoses
(3)new thermostat
(4)completely bled the cooling system
(5)new engine coolant temperature sensor+fan switch
(6)new cooling fan relay
(7)I also did a block test to check for a bad head gasket (several times to be sure) but the engine is fresh off of a rebuild so hopefully it's not that, plus the oil looks fine too.

The car is fine on short drives around town but will quickly overheat as soon as I get off the freeway after a long drive. The cooling fans turn on like they're supposed to when idling normally and the car can idle for hours without overheating as long as it hasn't been recently driven, but when the engine is already hot after a long drive they don't turn on until after the temp gauge is already indicating that the engine is overheating. I'm not losing any coolant either, but the coolant does look pretty dirty for being a few weeks old. I got a infrared thermometer and checked the temp of the upper and lower rad hoses when it was close to overheating and they were about 240 degrees.

I'm completely lost now, the only other thing I can think of is a vacuum leak. I found a loose vacuum line hanging down by the cold air intake and there was nowhere to connect it to so I just plugged it. (I think it was connected to the resonator but that's gone because of the intake). Car also has other symptoms of a vacuum leak like high/surging idle, power loss, and running rich even though there is no engine code.
Mine use to do that, My friend had a 92 who's temp gauge will also fluctuate. Mine will read overheating after the fans came on and sometimes it will go all the way till H. There was a time the temp never went down lol. I got a aftermarket gauge and the temp is normal, one day I decided to clean and sand down the ground from the battery to the chassis, and the one from the engine mount to the valve cover,not seemed the surfaces were covered in oil, cleaned them and sanded the surfaces and the fluctuation stopped.
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