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JDL billet coolant pressure tester bolted to a Mazda rotary engine, with gauge and Schrader valve
Back of the JDL billet coolant pressure tester plate, showing the O-ring groove and ports

Mazda Rotary Coolant Pressure Tester — 12A / 13B / 20B / Renesis Billet

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A billet pressure tester that seals off the coolant passage on a freshly built Mazda rotary engine, so you can pressurize the water jacket and find leaks before the engine ever runs. Gauge included.

After a rebuild, the coolant seals (O-rings between the housings and irons) are the parts you most want to confirm. If one is pinched or rolled, you would normally find out the hard way — coolant in the oil, or white smoke on first start. This tester lets you check on the bench instead.

How it works

  1. Bolt the plate onto the engine's coolant opening — the O-ring groove seals it.
  2. Pump air in through the Schrader valve with a hand pump or regulated compressor to 18–20 psi.
  3. Watch the gauge. If the needle holds steady, the cooling side is sealed. If it drops, you have a leak to find before install.

What's included

  • CNC-machined billet aluminum test plate, JDL MFG logo machined in
  • 0–30 psi liquid-filled gauge
  • Schrader valve fill port
  • Machined O-ring groove for a positive seal

Reusable — test every engine you build.

Fitment

Fits all Mazda rotary engines: 12A, 13B (including REW / FD RX-7), 20B and RX-8 Renesis.

Made in-house by JDL Manufacturing.