My car runs about 10 degrees cooler at idle than it does on the hiway. When I'm going down the hiway I can clutch it in and let it coast for about 5 seconds then let out on the clutch and keep going and the temp will drop a few degrees. Whats the deal?? Air pocket? Not enough airflow? The engine is still a bit tight from the rebuild. The thermostat is out and radiator is brand new Fluydine unit.

 

The only thought I have is that with the thermostat out, the coolant is flowing through the radiator so quickly, the air doesn't have time to remove the heat. As the engine slows down, naturally the pump turns slower allowing more heat to be removed. Try it with a thermostat installed. I would think you would want a 'stat in ther albeit a lower temp.

 

Yeah I would put the thermo back in.

Remember MAZDA OEM one only. The other ones are junk.

Santiago

 

http://www.aaroncake.net/rx-7/cooling.htm

 

The thermostat has TWO valves.

There is a spring loaded disc thst sits about 1" below the main stat valve, that blocks off a bypass port down inside the the pump housing.

If you ever have to run without a stat, you need to plug that bypass hole.

 

The bypass has been tapped and a plug screwed in. It does make since though, i'll put new thermostate in and see what happens. Good article Aaron.

Also, I use an aftermarket gauge from Greddy and the temp at after idling for 5 minutes will be about 188, the temp going down the hiway at 75-80 in 5th gear with no boost is about 197-203.

 

So is the consensus that without a thermostat even though the return hole has been pluged it will cause overheating?

 

bump..

Maybe the coolant is flowing faster than it should?

 

If the bypass hole has been plugged, you should be fine. However, the thermostat provides a restriction of flow to the radiator. If the water is moving too quickly through the rad, it will not be as effective in transferring heat. However, I doubt this is the problem. Why not just put the thermostat back in?

 

Yes try and put the thermostad back on and see if that fixes the problem. if that doesn't work check out your stock fan.

with the car warm but off, flick the fan with your finger its should rotate only about an inch or so any more than that and you fan clutch is most likly worn.

 

I'm using a permacool 2800cfm fan and it does have a shroud around it. It's sucking air in and moves it well. I'll order a new thermostat (the old one has holes drilled in it) and see what happens.

 

Cooling issues at speed have nothing to do with the fan since it is only used at idle and during low speed driving. I would suspect the water pump next, assuming the rad is good as is the thermostat. The vanes might be corroded down to almost nothing.