i recently picked up a 240 wagon in what i felt was solid condition. a lot of small things but nothing i thought major until i tested the voltage of the antifreeze.

i do not do this often but here and there and after checking this car i will now do this regularly on all cars that come my way. the test is simple. remove the cooling expansion cap and place a multimeter probe in the coolant and the other probe on a chassis ground. the engine block works or even the negative battery terminal. set the meter to DC and use the 2 or 20 volt setting. now read the voltage.

in the case of this wagon the voltage shocked me when i read just under 1 volt..... (.91 to be precise)(normal non destructive reading in my experience are between 0 and . 1 to .2 volts...give or take....much above .6 is cause for worry). this is easily high enough to eat away the heater core, the radiator, the freeze plugs in very short order and really got me worrying if a heater core was in my near future. i was afraid if i flushed the cooling system a now covered over leak would open up. having no real choice i flushed and replaced with fresh coolant and now will pray the core is sound. i could pressure test the core but do not yet have the guts to find out how the story will end.

for those who perform this test i also STRONGLY suggest you perform at the same time this test to determine if you have any voltage leaks into the coolant from the various electrical systems on the car.

to test for voltage leaks into the coolant

1. use probes as described above
2. have some else start the car while your measure the voltage..if no voltage changes take place no leaks
3. if voltage rises you have a leak into the coolant form a poor ground somewhere
4. to narrow it down do this.turn off everything you can, start the car and measure. if it is higher you have a start motor leaking voltage into the coolant. if not turn off the car and turn on every accessory you have and the restart the car
5. measure voltage...... now turn off one accessory at a time until the voltage drops. the last one turned off should be the source system for the leak

here is something you can do to mitigate voltage leaks into the coolant. find yourself a piece of zinc rod or small plate. drill a hole in it and suspend this in the expansion tank. any stray excess voltage will eat away FIRST the zinc rather than the radiator, heater core or freeze caps.