I think that I would see air under the radiator cap if I had a compression gas leak?  I never see any air.

To check a piston engine for head gasket leaks, you would put the cylinder at TDC and pressurize the cylinder to about 150 lbs with compressed air and check the radiator for air bubbles…How do you check a rotary?

I will check the pressure sender against a mechanical gage. 

There is obviously a heating problem, but I think the pressure is higher than it should be until just ready to boil.  I shut the engine off at 210*, and at 22+ lbs, the boiling point should be well above 250*??

 

Thanks for the suggestions of where to look, guys…

 

Bill B

It is extremely difficult to remove all of the air from a rotary engines cooling system. It is also extremely important. If air is under the pressure cap in a static situation, it will remix with other coolant when the engine is at speed. The coolant moves very quickly through the system. The coolant volume appears to increase slightly because much of the air is reintroduced into the water. This coolant then becomes a poor conductor of heat. You need the anti foaming agent in Antifreeze. Just a bit, perhaps 10%. The system with the relief cap right on the radiator or filler point, starts to offload coolant as soon as the engine is started. It is in hydraulic lock, and has a small volume. The actual boiling point calculated for this coolant makes no difference at all. The cap opens a bit when the trip pressure is attained, the pressure drops to 22 PSI or whatever for your cap, and a bit more heating trips the cap again. It is exactly the same as most cars.

So, at first in each heat cycle, there may be no correlation between coolant temperature, and the actual amount of coolant dumped by the cap. This is only true closer to a constant operating temperature. And then pressure may be alarmingly unstable with power changes. The accumulator system makes pressure rock solid. 

 

 

Make the pressure cap into a filler cap, sealing only the top lip of the radiator or filling port. Connect only a  bleed hose and run it to the bottom of a recovery bottle, and put the pressure relief cap on that bottle. Keep the bottle about 1/3 full. Note after several heat cycles, the amount of water you need to add to keep that bottle 1/3 full is reduced each time. Once all of the air is out of the cooling system, no more coolant need be added to the bottle.

 

Heating and cooling of the system, makes sweeping changes in coolant volume. The air cushion in the bottle acts as an accumulator (used in thousands of aircraft) to maintain a constant pressure and coolant supply.

 

Race cars use a Rolairtrol or spin bottle in the hose from the top of the engine to the radiator. Water enters the bottle at about half height on a tangent and adds a spinning motion. Water leaves through a center hole at the bottom.

Trapped air pops to the top of the bottle and that is plumbed to the bottom of the accumulator as above.

You used to get the plans for this thing when you buy a Cosworth race engine. Does Cosworth know something you don't? 

 

Anyway, after about three heat cycles (operating temperature and back to room temperature) the coolant system will be solid coolant with all of the air removed. It will not be hydraulically locked against the cap.

It will have the relief cap pressure, and will hold that for as long as the engine is hot.

 

I have a Shrader valve installed in my accumulator tank, and before I start the engine I charge that bottle with compressed air until the cap relieves at 22 PSI. Now I know it has pressure, and I know it has 22 PSI.

 

This was the stock system on all Mazda cars in the 70s. I didn't invent it.

 

It is unlikely that you have leaking compression seals, unless there is coolant blowing out of your makeup tank, or coolant is running out of your exhaust system after shutdown.

 

My recovery bottle is mounted where the passenger foot well would have been. Even with the bottom of the engine. So long as the hose ID is less than 1/4" and the hose enters the bottle on the bottom of the coolant supply, it matters not at all where that bottle is located. There is a money back guarantee with this system. 

 

Lynn E. Hanover