Hi, so I have a 2005 Toyota Matrix XR with 180,000 miles and have a slight problem with running a little hot occasionally.
So this problem of running hot occurs intermittently and seems to be when using the A/C AND when I'm not going highway speeds, 50+ MPH, at the same time. Also have noticed the A/C seems kind of weak at low speeds as in not blowing cool enough air. This is the problem and now I'll get on to what I've done for diagnosis and replacement.
I've replaced the radiator cap, and replaced the thermostat and thermostat gasket, there are no coolant leaks, the coolant is at proper level, also tested both #1 and #2 fan relays extensively, the cooling fan works(but more on this in just a second), I've checked Engine Coolant Temperature Sensor resistance values at HOT, but not COLD, and the resistance values are in spec for HOT and there is a 5volt reference signal when backprobing the connector, and the water pump bearing/pulley, with the drive belt off, spins with a little bit of resistance and smoothly.
More on the cooling fan subject now, so it's a single cooling fan and the cooling fan seems to be working and turning on as it should at idle(turns on when A/C is full blast and when the temperature reaches a certain temperature). But my concern is that the cooling fan seems to be running at a MUCH slower speed than I've seen before. I've compared it with another family member's Toyota Matrix of the same year and theirs seems to pull air MUCH more. You can also tell this by feeling the air pulled through the condenser and the sound is much louder like it should be. The weird thing about this is at idle it doesn't overheat, only when driving at non highway speeds.
I have not backprobed the relays for the fan either so I'm wondering if it could be the electric fan motor, but I'm not sure how to properly test it. I'm wondering what you're opinions are on this matter.
Well you don't even need a cooling fan when you're going 60 MPH the wind cools it so for my experience 99% of the time that is just a worn out radiator they're plastic and aluminum in the aluminum corrodes inside and does not dissipate heat correctly especially at high speeds or when the AC is throwing hot air from the condenser right in front of the radiator making the radiator work harder
So I was able to figure out what it was. It turned out to be something internal with the fan. The male and female part of the fan harnesses aren't corroded or loose when connected. But, when I push/tug/wiggle on the connector, it must affect the wiring that goes into the fan motor because the fan starts to run full speed, but when I let off it reverts back to super slow speed(like maybe 120 revolutions per minute). I think when it even gets hot enough, there's some resistance to some loose connections inside and causes the fan to stop when hitting bumps. I just recently caught the fan not moving for the first time when I happened to look... That was one thing I didn't check.
Also check your radiator cap and perhaps a stuck thermostat.
Radiator cap and thermostat was changed