coolant flow direction
 

Does anyone knows if coolant flows from the top to the bottom of the rad or vice versa?? And if you have an aftermarket oil cooler (shape like a radiator), is it better mounted infront of the rad (between fmic and radiator) or behind the rad (between rad and electric fan)?

Top to bottom on a stock or aftermarket rad with the stock arrangement.

You really shouldn't replace the stock oil cooler with aftermarket. The FC oil cooler is far more capable than anything you can fit in. BUT that said, the aftermarket oil cooler would go in front of the rad, behind the FMIC.

Holly Joker, thanks for the reply (that's answer it)

the coolant flows from the bottom to the top. the hot coolant let into the radiator from the lower hose is cooled by the radiator and is waiting to enter a warm engine. the thermostat opens and allows the "cooled" coolant into the engine to cool it and shuts once the engine temps are under the t-stat temperature. the cycle is them repeated. the coolant is circulated by the waterpump.

Except for "the coolant is circulated by the waterpump" part, this is entirely incorrect.

From the FSM:
Attachment 710627

what's that point "B" on your diagaram?? ^^^

Clokker, thanks for the diagram.. Do you (or anyone) also have diagram for coolant flow for stock turbo system and heater system??

its the same regardless of turbo or non turbo. i'd been drinking last night and was all mixed up. forgive me for that (no more drunken posting for me lol).

but as you can see from the diagram coolant is flowing from the radiator which is the coolant that has been lowered in temperature by the passing air through the radiator then flowing through the lower hose and then through the engine. when the engine reaches the temperature of the thermostat, the wax inside melts and the thermostat opens, allowing the "hot" coolant into the radiator to be lowered in temperature and it then closes when cooler engine temps are reached and the cycle is then repeated.

Looks like the coolant return nipple from the stock turbo.

Yes you can see that there is essentially a coolant feed and coolant return port on the front iron where the water pump housing attaches. The one closest to the driver's side is the "feed" side that pumps the lower temperature engine coolant from the radiator into the combustion area by the spark plugs. As the coolant passes through the engine it picks up more heat. So as it hits the front rotor it picks up a bunch of heat from the combustion process and begins to lose efficiency.

So you have hotter coolant hitting the sparkplug/combustion area on the rear rotor than the sparkplug area on the front rotor due to prior heat transfer. Surely this contributes to the hotter exhaust temperatures that are typically found on the rear rotor under load. The rear rotor runs at least 100 F hotter than the front (depending on where the measurement's taken, AFR, timing, etc) based on my thermocouple readings. This design of the cooling system has got to be a major reason why the rear rotor blows more often than the front.

O'kay, I have a 20b and according to some folks the water flows in the opposite direction. Does anybody know the flow direction for each of the different engine versions of the 13 and 20b?

The 13b and 20b water pumps both rotate the same direction. All mazda rotarys spin clockwise, i assume the flow is going to be the same also. (flow into the bottom hose and out the upper rad hose)

water flow
 

But the diagram shows the water flowing into the top of the radiator and out the bottom doesn't it?

Yes, from the engine thru the top hose on the radiator.......thru the radiator......out the bottom hose........into the water pump housing..................ah just follow the arrows in the pictures.

Diagrams shows what *B* is.

I dont mean to hijack but I have a related question.

For those who remove ther heater core....what would the best way to rout the coolant commng out of the engine that would normally go to the core? I contemplated rigging some sort of small radiator to mount at the rear bottom of the bay and ductign seom air through it. Would the collant flow through by its self or would it need an electric pump? And finally where is the best location to rout it back to the engine?