fan radiator problem

[carzboyz]

Hello I have problem with my fan radiator. My car is a dodge shadow ES with a v6 engine with an A 604 tranny. I Tested the fan relay and it work great ! When I unplug the coolant temperature senosr the fan goes on. But when the engine is very hot the fan doesn't start and the engine start to overheat. I removed the coolant sensor and warm it with a torch and the fan start very well ? I don't know what is the problem ?

[lookin]

Since the fan motor, the relay and temp sensors all check out, it may the thermostat. That is unless the water pump is gone, or on the way out, and the pump isn't circulating enough coolant.

Also, that 'torch test' you did, really doesn't rule out a malfunction of the coolant temp sensor. It may not be triggering, at a low enough temp, even though the torch could get it to do so.

[c2xejk]

The check for a faulty themostat would be, does the radiator get hot? If not, then the thermostat is bad.

My other thoughts on the subject are "how do you know?" It could be the coolant temp sender used by the gauges (seperate from the one used by the ECU.) Second, it could be the CTS (used by the ECU) is not reading in range. Rather than a torch, you might put it in pot of boiling water (known temperature.)

Alternatively, install an aftermarket coolant temp gauge and check the accuracy of the factory gauge.

[lookin]

You can feel the radiator return hose also. Squeeze it a tad to see, if it is both hot 'and' firm and or pulsing, to see if the thermostat is allowing hot water to pass and whether or not the pump is pushing any water.

[carzboyz]

the engine doesn't overheat when Im on the highway its only when I drive slowly and both radiator hose are hot and the radiator is hot and when I squeeze a radiator hose witn my hand and I smash the trottle the hose become hard it seem that the water pump pump the water into the system. The engine overheat but it take a very long time and if the fan start it will never overheat. I putted the car into P after a good ride and I checked the temperature it goes very high after 5 to 6 minutes then I started the fan manually and the temprature go to the normal operating temperature. The problem is the fan system, is not able to start when its the time to start.

[lookin]

OK. That's good diagnostic info.

I would change the coolant temp sensor, both of them if they are the original ones, and I bet that will fix your problem. If it doesn't, then I am thinking you must have a bad connection, from the temp sensor that triggers the fan.

[carzboyz]

I replaced the coolant temprature sensor and the problem is still there? I checked the connection between the sensor and the logic module and they seem to be good, all the wire are plugged correctly and have a good contunity I don't understand? When you unplug the coolant temp senor when the engine is running the fan start immediately. I think the problem is the logic module ? It could be the problem ?

[Ondonti]

He said the fan turns on when he puts a torch to the sensor...
So obviously not a good test but gives an idea that the sensor probably works. Putting it in a pot of boiling water might be a better test of the sensor because that is a temp range that the sensor should be freaking out (but not 600 degrees like that torch).

I have my own radiator problems in my P body and I hope mine is not so ridiculously difficult/contradictory/confusing.

[lookin]

Could it be a ground issue? Like a ground from LM to chassis, or something else, ... I don't know anythings about? If you disconnect the senor the fan comes on, and so maybe a broken ground keeps it from coming on, when it is still connected. Try switching the relay with one of the other known good ones. They are tricky buggers. I always have a couple of spares in the van.


Hope you get your radiator problem sorted out Brent.

[lookin]

Where's Ed? I bet he can figure this out.

Yo .... Ed Kelly!

[jory]

Mine does the same thing. It's not as noticeable when it's cool out but if I'm in traffic on a hot day I have to turn on the A/C to get the fan to kick on. The radiator gets hot and the hoses have pressure. CTS is new, fan relay maybe?

[c2xejk]

If the ECU is able to turn on the fan, then it is not the relay. What I am curious about right now it, what is actual temperature your seeing. Factory gauges are not the most accurate.

The best/easiest way is to use a scantool to see what the ECU is seeing. The other direction is to install an aftermarket coolant temp gauge. (or both.)

[lookin]

Couldn't part of the relay, be bad though, since there is more than one simple on off circuit in them? I mean, my relays, all have 5 contacts on them. Are the older style relays different?

[carzboyz]

I tried the sensor in a pot of boiling water and the fan doesn't start ? I tried an other sensor and this is the same story but with an higher temperature than the boiling water the fan start ? I tried 2 other fan relay and theres no difference.

[carzboyz]

does it can be the firewall ground (wire from the engine to the firewall) mine is missing ?