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Discussion Starter · #1 ·
I just replaced the water pump, however the needle used to climb to half way before that. The primary fan does not kick on until the needle goes to nearly 3/4. The primary fan will turn on with AC/Defrost. Neither fan will turn on if I unplug the harness at the temp sensor in the water pump. Resevoir cap is a few years old, same with thermostat. I know I have bled the system repeatedly on an incline. Car is a 96 SS. Radiator is maybe a year or two old. The block was pressure tested and was leaking at water pump gasket before replacement.


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big airbubbles in system maybe??
 

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I would first replace the temp sensor, being sure the electrical contacts are clean and corrosion free. Bleed the system again, both fans should come on after you disconnect the sensor! It may take a few seconds. Fan relays could be faulty also.
 

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...The primary fan does not kick on until the needle goes to nearly 3/4. The primary fan will turn on with AC/Defrost.

Neither fan will turn on if I unplug the harness at the temp sensor in the water pump. ...
The primary fan is performing as it should.

As others have have suggested, try disconnecting the ECT with the engine running. They should turn on within 10 secs.

In practise the secondary is very rarely known to turn on during normal usage.
 

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The primary fan is performing as it should.

As others have have suggested, try disconnecting the ECT with the engine running. They should turn on within 10 secs.

In practise the secondary is very rarely known to turn on during normal usage.
Actually Oldtimer is right. It sounds like the primary fan is working properly. But I thought the secondary fan should come on when A/C is turned on.
If the primary comes on at around 3/4 temp and the car cools down this is good. If the car doesn't over heat, and again both fans don't come on when sensor is unplugged. We are back to a bad sensor, at least that's where I would start. I would say a bad secondary fan but neither coming on is not right.
 

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Check the fan relays in the underhood fuse box. If the plastic is scorched around the pins, replace the relays and the fan motors. These fan motors don't fail all at once - they gradually just get slower and slower, building up resistance all the while which burns up the relay. If the relay is burnt and you don't replace the fan motor, it will just burn up another $40 relay.
 

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Discussion Starter · #8 ·
Both fans come on when I unplug the connector at the water pump. I checked both relays and there were no burn marks on the plastic. Fuses also checked out ok. No dealer in the area had the temp sensor or resevoir cap in stock.
 

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That is the wrong unit, that's the sender for the guage. This is the ECT sensor: http://www.autozone.com/autozone/ca...&navValue=15900113&itemId=113-0&parentId=59-0

As for the cap, be wary of parts store replacements. I bought one at O'Reilly and took it back because the threads fit loosely and it would pop loose instead of tighten down. Your best bet is to buy an AC Delco one from somewhere, like RMS: http://www.rmsautoparts.com/proddetail.php?prod=RC87
 

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Your right I got the wrong one on that sensor, it is the sending unit. As far as the cap, I bought one from Kragen and it's last more than two years.
I should have double checked that gauge sender better, but I did rush trough the site.

Sorry!
 

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Your right I got the wrong one on that sensor, it is the sending unit. As far as the cap, I bought one from Kragen and it's last more than two years.
I should have double checked that gauge sender better, but I did rush trough the site.

Sorry!
I agree that the secondary fan comes on when the gauge is quite high like 3/4 or more and the factory gauge is not that accurate anyways...on my 96 9C1
 

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I just replaced the water pump, however the needle used to climb to half way before that. The primary fan does not kick on until the needle goes to nearly 3/4. The primary fan will turn on with AC/Defrost. Neither fan will turn on if I unplug the harness at the temp sensor in the water pump. Resevoir cap is a few years old, same with thermostat. I know I have bled the system repeatedly on an incline. Car is a 96 SS. Radiator is maybe a year or two old. The block was pressure tested and was leaking at water pump gasket before replacement.


Thanks
Its been a while since I had a similar problem but we confirmed it was okay hooking up the scanner at the shop I work at part time.....you can see the computer command the fan to come on I still think it may be that the dash gauge is inaccurate in comparison to the fans temp on time
 
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