Paul,

   Good news!  After spending many, many months (years) trying to
get my oil   temps down, I finally discovered that the problem was a
defective oil   cooler.  It appears that the only oil cooling was
from the oil/water   exchanger.  While temps were too high for
comfort, especially during  summer,   it did cool the oil well
enough to keep me flying throughout the Texas   summer.  After just
recently discovering the defective cooler, I replaced  it   with a
Modine of similar size & style and flew it for the first time
today.   WOW!  What a difference, possibly enough to remove the
oil/water exchanger   altogether (more testing is requried).
 Addimitedly, the OAT was in the  mid   40's, the return oil temp
was down in the 150*F range, when it had been   around 210 - 240*F.
On today's flight, in cruise configuration, the  coolant   was 165-
170 with cowl flap closed.

   Also, it appears that Lynn Hannover is correct (big surprise)
about the  best   horsepower being produced at around 160*F oil
temp.  I saw an extra 11  knots   IAS today over my typical cruise
speeds.  I'm sure it wasn't just my   imagination as the fuel flow
was also higher.  (Gotta take the bad with  the   good.)

   So, if you want to go fast(er), work on reducing those oil temps.

   Mark S.

   That has happened before. Was it a 2nd gen Mazda cooler?
   What was wrong with the old cooler? Was the oil thermostat still
in there?

   Paul Lamar

  If you hadn't installed the oil-water exchanger, you would nearly
  immediately known that your primary cooler wasn't working at all..

  Matt-

  We need to do a check list for this stuff as this type of oil
cooler  failure  never occurred to me. Do's and don'ts. The second
gen cooler that  works so well is a two pass.

  Paul Lamar

Paul,

A checklist of possible causes of poor cooling would be a beneficial
tool for many builders.  When trouble-shooting a problem, it is easy
to "assume" things to be true that are not, such as in my case of
the swollen oil cooler end tanks.

I don't know exactly when the oil cooler failed, but I feel that the
oil/water exchanger allowed me to continue flying, albeit with slightly
higher oil temps.  At least I didn't have to do an emergency landing
out in west Texas somewhere.

Also, the TES o-rings are probably the reason there wasn't any
engine damage from the higher than normal oil temps.

Mark S.

Back in the old days you could destroy a set of neoprene cooling O-
rings in an instant. I know! It happened to my brand new 12A powered
RX2. I wish I had that car back. It only weighed 2500 pounds and had
a lot of room in it. It is 500 pounds lighter than my RX8 with less
room. Your tax money at work. This is one I saw at Seven Stock. It
had a 3 rotor in it. I have a 3 rotor sitting in the hangar waiting :)

Paul Lamar
-
I wonder if they upgraded the brakes. My '73 RX3 had the same brakes as the
Boing Boing engined 808. Heart stopping a few times. Just over 2100#.I would
like to have it back now also.

Dale Davies