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Fan clutch

Cussboy on Mon August 18, 2008 3:31 PM User is offline

Year: 1988
Make: Mazda
Model: B2200
Engine Size: 2.2
Refrigerant Type: R-12

Symptom, running hot at higher or freeway speeds, and sometimes at lower speeds, worse with AC on (extra laod).

Does this make sense to any of the experts here: my truck has been at the verge of overheating for three weeks, and when I stop it when hot, the fan clutch spins readily by hand. I replaced it with a free warranty replacement one (Hayden), and changed out the thermostat (cap is three months old), and no help. When I took the old one back to Pep Boys to get my refund, the mechanic there aimed his laser thermometer on the fan clutch and said the fan clutch was only reading 150 degrees F, not hot enough to actuate it, thought there was radiator internal blockage which was preventing any heat to be shed from it, and not warming up the fan clutch enough to get it to engage, and that the Hayden fan clutches seldom are bad right out of the box. He said this was also common with Nissan trucks as they get older. I'm borrowing a laser thermometer from work, does this sound like I'm just due for a radiator with a 20 year old truck?

CyFi on Mon August 18, 2008 3:46 PM User is offline

could be internal, but it could be external too, check for debris between the condenser and the radiator and check for bent fins on the condenser or the radiator

mk378 on Mon August 18, 2008 5:12 PM User is offline

First check the coolant is full, I'm sure you have already but you must check the radiator itself (engine COLD) and not just go by what's in the bottle.

Since overheating continues on the highway, I doubt it has anything to do with the fan. You get plenty of ram air at highway speed, unless as previously mentioned, the air passages are blocked.

Check if the outlet hose of the radiator is near ambient temperature (or at least much colder than the inlet), if so there is a water flow problem, probably a blocked radiator core if you're sure the thermostat is good. The radiator is cooling some water but it is not flowing enough to keep the engine cool. You can test drive with no thermostat installed to absolutely rule the thermostat out.

Cussboy on Mon August 18, 2008 10:36 PM User is offline

Installed new thermostat yesterday. Today I replaced the upper radiator hose, was soft and swollen, and re-routed coolant flow back through the heater core (I bypass it each summer), in case I need to shed heat in an emergency. It was OK driving home, AC on 103 F outside.

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