Here is another to add to the list. "Water pump failure". At 18 hours I noticed my water pump leaking
through the weep hole. This was a slow leak that I would have to add coolant after a two hour test flight.
Since this was the original pump on my 1986 13B I figured it was well past due considering it was 20 years
old. When I bought the new one at the Mazda dealer the parts department said they could only get
rebuilds.
This last Saturday at 72 hours on the engine I took off for my second test flight with a new IVO Magnum
adjustable prop. Excellent acceleration and better rate of climb than my home made composite prop.
However, with the old prop and 2.17:1 PSRU I was never able to get much over 5000 rpm. With the old
prop I would take off and climb to 1000 AGL then reduce power to let temp cool down to below 200 degrees.
It would hit about 220 in the climb. Oil temps have always been below 190.
At medium pitch on the IVO I was close to 6000 rpm and by the time I reached pattern altitude on both
the first and second flights it hit 230. On this second flight I did my usual reduced power and let it cool
down as I flew out to my test area over the sod farms. After 15 minutes of flight time I set power to 5000 rpm
and played with the prop control then worked my way up to 5500 rpm. At this point I am 20 minutes into
the flight when I notice my temps are back at 230. I reduce power to 4000 rpm and check oil temp is
still at 180-190. I turned back to the airport but the temp is still climbing. Reduced power to 3500 and about
90 knots. GPS says 10 minute ETE and now the oil temp is at 200.
I got a straight in to Rwy 33 and when I cut the power on final I had 260 on the water pump outlet sensor,
which was probably just reading hot air and 230 on the pump inlet sensor. Oil temp hit a hi of 230. The engine
never missed a beat the whole time. When I got off the runway and shut it down I had a trail of coolant
behind me. I pulled the cowl off and had coolant all over the bottom cowl where my over flow tube dumps out
but no sign of hose or fitting failures. Sunday after letting it cool overnight I swung the prop through and it still
has good compression from the sound of it. I started to fill up my expansion tank and after about 2 quarts of
coolant I could hear it draining back into my drip pan. The coolant was just running out the weep hole on the
water pump.
I would like to know if anyone else has had problems with water pumps and any comments.
Mike Perry
N981MP
Long Ez
Never had such a failure, never seen a water pump failure on another Mazda or any brand of race car, since 1973. Shifting at over 9,000RPM since 1980 when I went rotary.
You ran out of your own bad luck, and are using up somebody elses. Knock it off............
Lynn E. Hanover
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