By Tom Jelly, procedure designed by Paul Yaw
One seemingly fatal malady that will occasionally strike even a well cared for wankel is a leaking o-ring condition, where a small leak occurs in the o-rings that seal the flat side housings to the rotor housings. The characteristics of such a leak are continuous ejection of coolant from the radiator cap overflow tube, and white smoke while running or heavy white smoke during startup (usually accompanied by bogging during the first few seconds of runtime until the coolant is out of the combustion chamber) Usually the car will run well otherwise, but consume coolant.
Until now the only way to repair such a condition was disassembly and a rebuild - very costly, and a real bummer on a low mileage or recent rebuild.
My original engine has over 90k miles on it, and I had been planning on a rebuild, even to the point of buying a core engine to rebuild so I would have one to go in when the time came - I figured mine would eventually just puke an apex seal or something because of the high mileage. At the beginning of the '01 driver school season I was on my way to Gingerman and stopped at a gas station in MI for a final fill up before getting to the track. The car blew tons of white smoke and bogged at startup- I had developed a classic o-ring leak. Not wanting to believe it, I just kept the engine full of coolant at the track, and noticed another telltale sign of the condition- a thermostat housing mounted coolant temp gauge will read very erratically between 140 and 180 deg when you KNOW the car should be at a solid 180-205F. This is because of the airspace in the thermostat housing resulting from the ejected coolant.
BE CAREFUL HERE, REMEMBER THAT WITH A LESS THAN FULL SYSTEM WITH AIRPOCKETS YOU WILL GET LOCALIZED BOILING THAT MAY LEAD TO MORE SEVERE ENGINE DAMAGE.
After the run home I left the car in the garage for a week pondering what to do. I have been planning a rebuild for a while, but it was the beginning of the season and I really wanted to postpone the inevitable to the winter if possible so I started looking around for answers. I found out that Paul Yaw had done a procedure that had fixed a few of these problems over the years and one of them was still working fine after 2 years! I decided to give it a try.
You will need 3 bottles of CRC Block Weld available at Pep Boys. This stuff has copper powder of different sizes in a clear silicate fluid, and the bottle says you cannot over treat with the stuff. I looked after treatment and it really looks like the copper stays in suspension even after treatment, and the silicate stuff seems to get into areas of leakage where capillary action is the means of leakage-there was evidence of the stuff where I had installed a coolant flush kit in the lower heater hose coming off of the water pump. It was ONLY where the hose overlapped the nipple. This indicates to me that there really is no way the stuff could clog your radiator.
You will also need a gallon of purple power degreaser, again available at Pep boys.
This will allow residual cooling
system pressure to force blockweld toward the combustion chamber thru the
leak point, keeping positive pressure on the leak until the stuff has a
chance to work and cool.
We have not yet
determined if it makes a difference if you leave the block weld in the
system; I plan on leaving it in there till the end of the season and then
running distilled water and 25% prestone.
(This comment was added later after Tom had some time with the fix in place):
I would suggest draining and flushing out the blockweld mix if you left it
in and the car was fixed - my waterpump seal just went ( the car has over 90k
on the original, so that might not be what caused it) as a precaution. No
big deal, the pump was an EASY replacement and cost $100 from pepboys. I'm
still happy w/the fix, BTW.
This procedure will probably be scoffed at by some on the list as a band aid hack job, but the fact that it solved the problem speaks for itself. At least 3 others did it while I was doing it, all successfully to my knowledge. My radiator remains unclogged. Car runs great, temps same as before. I figured I would give it a shot because I’d be rebuilding anyway, but now I may run the thing as long as possible just to see how it holds up.