To diagnose a coolant leak on our m'home, I purchased a Sears coolant system pressure tester. It worked great for that purpose. Replaced leaky radiator and thermostat housing gasket... and all the hoses and the thermostat for good measure.

Since I also suspected a heater core slow leak in our 190E (persistant coolant smell in passenger compartment and outside, but very slow drop in coolant level over a few weeks), I next hooked the tester to the Benz. Surprise! - the leak was at the thermostat housing-to-water pump jumper hose. Tightened the clamps, and no more leak, system held pressure just fine.

Now, no more coolant smell, and no gutting the insides to extract the heater core. See what the right tool can do?

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7