Recently, I bought a motor off an importer. Compression on all rotor faces was around 100psi ish. I did some coolant mods such as welding the rear iron nipple shut, getting rid of the top barb on on the waterpump housing, replacing some barbs with npt tapped holes for my an fittings. It was time to pressure test the coolant system for my peace of mind. The last thing I want to do is pull the engine out.

I had some npt fittings, 1.5" pipe, vacuum plugs laying around. I had to buy a ball valve from home depot for 8$. Total cost $8 =) I'm pressure testing at about 16psi. I'm going to leave it overnight and check for a drop in pressure.

 

Good idea! I have one of Pineapple Racing's cooling system pressure testers -

http://www.pineappleracing.com/cooli...estercspt.aspx

I've used that on engines to pressure test prior to installation to make sure an O-ring didn't get pinched.

You do need to wait overnight, I discovered that once the hard way. Built a motor, pressure tested it, it read rock-solid. Got it in the car and fired up, car was drinking coolant. Pulled it back out, tested again, same deal. BUT, if I left it overnight, the pressure would drop. Since there was still coolant in the engine, I could look through the exhaust port and see a puddle of coolant in the front rotor. Ooops!

It was one of the aftermarket coolant seals, it had jumped the groove and was pinched by the rotor housing. I now use only the Mazda OEM seals .

If you are losing pressure, you can add coolant into the motor and re-pressurize and check through the exhaust ports. Hopefully it's not the case here, looks to be a solid motor!

Dale

 

hm this is odd. after 4 hours it dropped to 10psi.. but after 10 hours its still sitting at 10psi..
hmmmm..

 

how old is the cap? and is it a 13psi or 16psi cap?

 

the cap on the filler neck is not pressurized, its got about 29k miles on it. I've repeated the test, and after 5 hours its been steady at 14psi.

 

thats a damn good idea... considering I worked in the Natural Gas industry for a while I should have thought to do this :P....


good job.. i'll be doing the same thing to my motor now...


J.