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When my engine is warm and idling, I watch the temp slowly climb up to 230, then as soon as it hits 230, it drops rather quickly down to 200, where it begins the slow climb to 230 again. Is this the result of my fan clutch kicking in and out? Does this sound normal?

I have my coolant temp sensor in the passenger side cylinder head. I have a mild 350 with headers. and a stock fan/radiator/shroud.

Thanks for any help..

nervous nova newbie with first engine.
 

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It SOUNDS more like that the temp cycling is from the thermostat opening and closing.

What temp thermostat are you running?

Where is the location of the temp sending unit?

And are you using a quality temp gauge?

Do you have a fan shroud?
 

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what temp thermostat are you running? My understanding is at low speeds the clutch is engaged on the fan and the fan is working...it is only at higher speeds (RPMs) that the clutch disengages and the fan free wheels...I think that is how they work...
 

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Maxturbo said:
It SOUNDS more like that the temp cycling is from the thermostat opening and closing.

What temp thermostat are you running?

Where is the location of the temp sending unit?

And are you using a quality temp gauge?

Do you have a fan shroud?

he says the temp sending unit is in the passenger side head...
 

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Discussion Starter #5
sender is in pass. head will that make difference?

Maxturbo said:
It SOUNDS more like that the temp cycling is from the thermostat opening and closing.

What temp thermostat are you running?

Where is the location of the temp sending unit?

And are you using a quality temp gauge?

Do you have a fan shroud?
Max T

The sender is in the passenger head, and I am using a shroud. I'm not sure what thermostat was in there, it is what the guy at the parts counter handed me for a 71 350, at the time I didn't know enough to even ask more than that.:(
 

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NovaNate said:
Max T

The sender is in the passenger head, and I am using a shroud. I'm not sure what thermostat was in there, it is what the guy at the parts counter handed me for a 71 350, at the time I didn't know enough to even ask more than that.:(
If it's the "standard" temp thermostat it's probably a 195. Snatch that sucker out of there and stick in a 180 and you should be O.K.

Sorry that I missed the temp sender location earlier. That one being in the head can attribute to a higher than normal coolant temp READING (closest to the heat source) compared to the intake manifold placed sender that houses the thermostat.

And if I had taken my time in re-reading your post, 69NovaSS would have beaten me to the answers (again). :( :p
 

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If it is a thermostatic fan clutch it will work off both temperature and RPM. So it could still be a defective fan clutch. You could test the fan. Tie a light string from the fan blade to the frame or something that will not move. Do not tie it to a hose or something that will break or tear away. Start the engine when cool and see when the clutch fan kicks in ( the string will break at the temp the clutch is set at )
 
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