I've had the car 15 years and never run into a problem like this. I have a new radiator, new cap, fan works, NO thermostat, and no leaks. I checked to make sure the water pump was pumping and I had flow through the radiator. What could be causing the car to over heat?? Also no water in the oil. 1992 305 RS.

 

Why No Thermostat.

 

Runs cooler in the Texas heat.

 

Make sure that the air dam is in place under the nose of the car. Check the base distributor timing, should be set to 0* BTDC (retarded causes over heating issues).

Last but not least, remove the top plate the holds the radiator in place. Gently push the top of the radiator toward the engine and check the space between it and the A/C condenser.

Debris likes to build up in there blocking the air flow. After I cleaned it out I placed a piece of foam pipe insulation between the top of the A/C condenser and whatever is above it. That was done to prevent the debris from getting into that area.

RBob.

 

Retarding the timing will raise the exhaust gas temps and quite possibly make the overheating worse. I get that it may prevent detonation but go get some non-ethanol premium and don't retard the timing quite that far.

Get a shop to do a hydrocarbon test on the coolant. May be a head gasket, etc. I would do that first step to rule it out before you go throwing money around at parts. Don't troubleshoot with Visa.

If that comes back negative, find a shop with an IR camera to check the cooling system.

GD

 

Fan motor might be going out and not spinning as fast. You can replace the motor part.with any fan motor from a 4th gen camaro or firebird

 

Which is why I said to check & set the base timing to 0* BTDC. That is the factory stock setting. I see nowhere that the OP stated he retarded the timing to prevent detonation.

RBob.

 

OP; You need to install a 165 degree thermostat (with 3/16 vent hole) to slow down the coolant flow. Otherwise the coolant doesn't spend enough time in the engine to effectively transfer heat.

Good luck