2003 2.3L 236K


I have driven this truck very little this year. About three times now I have topped the radiator and reservoir to the max line, run it up to temp driving around on errands, let it cool it off and topped off again. Maybe a month and 200 miles later, the level is down at the min line. There are no obvious leaks at radiator or houses or fittings, the exposed parts of head gaskets look dry and normal, the only fluid on top or under floor mats I've found is rain (rear window leak). There's no coolant in the oil. Where else should I look?

 

You can add a UV Dye to the coolant to find the leak

There are kits that come with the UV dye and a UV Flash light.

What is most likely happening is there is a small leak that only leaks under pressure, so only after engine is hot.
Coolant is evaporating before it can drip to the ground or any noticeable place.

UV dye will be left behind so you can see it and follow it to the leak point.

Hopefully it is not the rear coolant fitting on the head, have to drop transmission to get to it.

The 2.3l Duratec is the Mazda L 23 engine, designed for Front wheel drive and transverse mounting, so this fitting would not be hard to get at if engine was mounted side ways

 

One note on the UV dye, dont do what I did and spill any when pouring it in. Its super concentrated and doesn't wash off easily lol. It works awesome though even for the smallest seeping leaks. It also turns motorcraft gold coolant green so if you have the gold stuff dont forget years from now and put green coolant in by mistake.

 

Thanks Ron and Apex, the dye sounds interesting. Already have a UV from the pet store. Never shine those things on bathroom walls around the toilet!

 

Or on hotel beds...............................

 

Ewww

 

Check the coolant return line tee peice, it's plastic and is 95% always this part when it comes to coolant issues on this engine

 

Reply to old post: The heater valve (vacuum operated) and in line with heater hoses to the left of the valve cover will drip when turned to heat as I finally found out.Took me awhile to find it,bought a Chinese equivalent part that leaked the same as the worn out original,Finally replaced with an equivalent metal bodied part that was originally used in an Aerostar if I recall.