miataman

I am losing engine coolant slowly and don't find a leak.

I let the truck sit for 24 hours and cranked it over with the spark plugs removed. No coolant was expelled from the plug holes. All plugs looked fine.

I then installed the plugs and wires and started the truck. Approximately 1/2 cup of rusty water was expelled from the tail pipe.

Any ideas what would cause this?

Thanks.

sam29078

The converter will make water and spit it out at times.

How much coolant are you adding and how often?

Have you put pressure to the cooling system?

Chris_1

iTrader: (1)

Get a cooling system pressure tester and pressure test it cold. Sometimes you can't see the leak because it's vaporizing when hot.
Coolant out the exhaust (head gasket) shows as sweet smelling white steam coming out the exhaust.
Rusty water coming out the pipe is more likely just condensed vapour from in the exhaust system (the reason why your exhaust rusts from the inside out).

miataman

I think you're right. I caught some in a cup today so I could look at it. Just rusty water.

I'll look for a pressure tester.