I still know all of that stuff, I just cannot remember it.

 

The Mazda and many other engines use a closed loop cooling system when cold.

 

Where coolant is free to move through only the engine block during warm up. This keeps hot spots from forming and keeps the block from growing too big on the hot (exhaust) side. It also gets the engine warm quickly so the total HC is low enough to sell the cars in the Peoples Republic of California.

 

In a conventional system, most thermostats have a little bubble valve and that allows some coolant (and bubbles) to move out of the engine and pull some coolant in from the radiator. This makes the warm up last longer than is good practice. In the Mazda version the thermostat from the Rube Goldberg shops has a conventional looking top to block coolant from leaving to the radiator, and a plug valve that is open when cold to divert coolant around only inside the block. When the coolant warms the top opens and the plug valve closes off the bypass port in the pump body forcing coolant out the norice to the radiator.

 

You can modify the pump casting by tapping the internal (plug valve hole) for a pipe plug. Then use a conventional American thermostat.

 

I use a 160 degree thermostat with three 1/8" holes drilled around the perimeter. In the event that the thermostat should fail, just reducing power allows the three holes to pass enough coolant to save the engine. On very cold days, the thermostat never opens and the engine cools only through the 3 holes and runs about 150 degrees. For those days we taped off much of the radiator. We have a big radiator.

 

The rotary has dozens of nooks and crannies in which it hides air bubbles to use to stop the water pump with an air lock when you need it the most. It can run for weeks with the bubbles in place and when you rev it up for say a race start, or a take off, zoom there go the bubbles swept along to the suction side of the pump, followed by no more pumping and then no more engine. All of this is the same as any engine, however the rotary has the water pump mounted very high on the block where the bubbles can have the maximum effect on producing cavitation.

 

All of the air must be removed from the system. Mazda did all of the engineering for that in the RX2-3 and 4. The make up tank on the fire wall (plastic crap that no American relief cap fits very well) has the pressure cap on it. The cap on the radiator is just a lid to seal the radiator and has no pressure relief function. Bubbles popping to the top of the radiator are forced up the hose to the pressure bottle, then pop to the surface inside the bottle. With any pressure reduction inside the block, resulting in only pure coolant returning to the block. The pressure bottle need only be filled to 2/3 capacity allowing a compressible air volume on top of the coolant. After 3 heat cycles you will need to top off the bottle as the coolant will be in the block and the recovered air will be in the bottle. Works great. Works every time. Designed by Mazda. Works on Mazda, Cosworth, Chevy and even Ford racing engines and airplanes.

 

This was no genius move by Mazda. This is just an Accumulator.

These are used in all kinds of liquid systems to provide bubble removal and as a back up supply of that liquid. And to maintain a specific pressure. As in 3000 pound flight control hydraulic systems in airplanes.

 

The make up tank or bottle need only have a filler neck that will fit an American style relief cap. (Stant lever cap 17 to 22 pounds) Consult you radiator manufacturer for maximum pressure. Taller and thinner is better. Hose to the radiator top out the lowest point in the bottle. Cap accessible so you can top off the coolant. The actual location of the make up bottle is not at all important. It need not be the highest item in the coolant system. The hose needs to be about 1/8" in ID however.

In the racer the Mazda make up bottle from an RX-2 sits on the passenger floor, and works just fine since 1980. I put that or similar in every race car I ever built. Never a cooling problem.

 

If you use a thermostat, keep in mind that they seldom fail in the open position. They fail by the bellows cracking and loosing the alcohol in the bellows (or whatever they use now) and the damn thing snaps shut. They do not die slowly in order to give you a warning.

 

Many racers use restrictions in the water outlet to limit flow rate to the radiator. This is so the restrictor is the main restriction to flow and not the radiator. You do not want any cavitation occurring inside the radiator. Notice that the bottom radiator outlet and hose is much larger than the top (high pressure) hose. Notice also that the bottom hose has an internal support spring installed to prevent collapse. Deduce then that it is possible to collapse the bottom hose via a dynamic pressure difference between the water pump outlet and the water pump inlet even though the pressure cap is in place an fully functional.

 

They (radiators) die quickly. If you run the rotary up to 8,000 rpm while listening to the bottom radiator hose through a stethoscope,

you will probably install a restrictor after changing you Depends.

 

Notice that some aircraft installations run fine with 1" ID radiator hose to and from the radiator. That is a lot of restriction. And still it works.

All of my coolant must pass through a 5/8" sharp edged 1/8" thick restrictor. And still it works.

 

For low RPM installations such as airplanes, a restrictor is probably of no value.

 

Lynn E. Hanover

 

 

 

I have been searching the archives but to scant successes regarding thermostats use or lack of use for cooling.

I have been having issue with cooling lately. I use to be able to idle on the ramp for over an hour in the middle of a Houston summer with adequate cooling. However, lately temps are rising faster and higher.

Yesterday, while troubleshooting this issue I noted that after about a ten minute taxi that the mounting location of my coolant temp probes was reading about 220 degrees measured with a handheld thermo gage, close to what was being indicated on the panel  However, the top of the radiator was cool to the touch. The handheld thermo gage read 45 degrees.   Ok. Seems to be a flow/thermostat/pump issue. I will be Looking into this ASAP.

This got me to think about thermostat usage. I have one. I know some do not use them.

It is my understanding that if you remove the thermostat you have to close some passage off. What passage is this and why does this need to be done. Also, what is the accepted method.

While researching I also saw discussion on restrictive plates. While I am not considering a restrictive plate, the thread discussed drilling holes in the thermostat itself. Lynn mentioned do it caught my interest.

It seems this is something I use to know but now forget where I saw it. I just finished reviewing my partial scan of Tracy's conversion manual to no avail and my archive search is giving me hundreds of returns.

Thanks,

Chris