C4 coolant fan mumbo jumbo
Thread Starter
Cruising
Joined: Mar 2026
Posts: 14
Likes: 0
From: Texas
C4 coolant fan mumbo jumbo
87 C4 once again overheating… a billion things have been fixed on this thing. Radiator replaced a couple years back, water pump replaced a couple years back, thermostat as well replaced, coolant flushed as well, temperature sensor switches also replaced for the passenger side one with the spade connector and the driver side one with the oval connector thing, lastly regarding the coolant parts a new fan relay installed. The coolant temp will get up to around 211 and the fan will turn on but it’ll just shut itself off a minute later. Does the same thing over and over while the temp climbs up and it never ends up cooling the actual radiator. Any ideas yall?
Instructor
Joined: Dec 2024
Posts: 217
Likes: 86
From: Phoenix, Arizona
Need more info. Are you talking about the main fan or the aux fan? Are you running the AC at this time?
Main Fan = Radiator Shroud
Aux Fan = In front of the AC Condenser
From the factory, the main fan isn't coming on until around 228*. Aux fan is closer to 236*.
Main Fan = Radiator Shroud
Aux Fan = In front of the AC Condenser
From the factory, the main fan isn't coming on until around 228*. Aux fan is closer to 236*.
Pro
Joined: Sep 2024
Posts: 526
Likes: 117
There are ways around this too. Lower temp thermostat will help, and then a standalone sensor/switch that will automatically kick on and off the fan and whatever values you purchase. Granted, you have to be ok with bypassing the factory stuff to do this. But you wire in a relay for the fan and the sensor in the head will trigger the on/off function of the factory fan. If you are interested, I can provide more details.
Le Mans Master
Joined: Jul 2004
Posts: 6,228
Likes: 698
From: Clifton Park, NY ............Clearwater, FL ... 85 Original Owner
87 C4 once again overheating… a billion things have been fixed on this thing. Radiator replaced a couple years back, water pump replaced a couple years back, thermostat as well replaced, coolant flushed as well, temperature sensor switches also replaced for the passenger side one with the spade connector and the driver side one with the oval connector thing, lastly regarding the coolant parts a new fan relay installed. The coolant temp will get up to around 211 and the fan will turn on but it’ll just shut itself off a minute later. Does the same thing over and over while the temp climbs up and it never ends up cooling the actual radiator. Any ideas yall?
Pro
Joined: Sep 2024
Posts: 526
Likes: 117
Safety Car
Joined: Nov 2009
Posts: 3,973
Likes: 341
From: Adelaide South Australia
My car uses a 3 row GM radiator, an aftermarket thermo front fan and the rear main fan is wired to a switch on the dash.
I don't let my coolant get above 180F and use the manual switch to control it.
I don't let my coolant get above 180F and use the manual switch to control it.
Safety Car
Joined: Sep 2001
Posts: 4,160
Likes: 554
From: Glenbeulah Wi
He is saying the fan turns on at 211 but then keeps cycling on and off while the temperature keeps climbing until the car final overheats. It appears to me the question is why is the fan cycling on and off as the temperature keeps rising.
Check the power at the fan and see if it is also cycling on and off, this will help you determine the next steps.
Check the power at the fan and see if it is also cycling on and off, this will help you determine the next steps.
Le Mans Master
Joined: Jul 2004
Posts: 6,228
Likes: 698
From: Clifton Park, NY ............Clearwater, FL ... 85 Original Owner
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