3 replies to this topic

[Parity]

I have a persistent coolant leak I can't seem to resolve on my '90, 1.6. I've already installed a new gasket and tried RTV black. I removed the neck and sanded it flat to within .002". Still no luck. Park the car overnight and there's a puddle in the morning with coolant drips hanging from the lower edge of the cast neck. Any suggestion?

[Keith Novak]

If you have a new gasket, the surfaces are flat, and you've tried RTV, I'm guessing that's not where it's leaking from. It's leaking from somewhere else and making it's way to where you see it dripping from. Probably above that since water doesn't usually leak upwards. I'd suspect either the thermostat neck o-ring or the water pump gasket. I'd try the o-ring first and use a Mazda one since I found the store bought ones don't fit well...and leak in a way that makes you think it's coming from somewhere else.

[Ken SM94]

I had the same problem and discovered the small 1/4" nipple on the water neck was leaking at the welded joint.

It was rusted from the inside.

Good luck!

[Johnny D]

^^ That would be my guess.
J~