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Technical Administrator
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Preventing Against Repeat Heater Core Leaks​

Issue:Some vehicles may exhibit repeat heater core leaks. This may be caused by a chemical reaction called electrolysis. Electrolysis involves an ion exchange between the heater core and engine coolant which can result in a breakdown of the heater core material. This is similar to the operation of a battery.

1. To check for electrolysis use a DVOM set on DC volts. Place the pos (+) probe in the engine coolant and the neg (-) on the neg battery post.

2. Adjust throttle to 2000 RPM to get the flow going and true electrolysis voltages.

3. If more then .4V is seen, flush the coolant and recheck.

4. If there is still excessive voltage present check the body/battery grounds. Also, verify proper grounding of aftermarket stuff that has been installed.

5. If the condition is still present after the grounds have been checked, it may be necessary to add extra grounds to the HEATER CORE and engine. I replaced the weak school engine grounds with thick SS straps from Summit on each side of the motor. A hose clamp can be used to secure a 16 AWG stranded copper wire to the heater core inlet tube. The other end should be secured to an EXISTING FASTENER on the body sheet metal. Extra grounds should be attached between existing fasteners on the engine and body sheet metal. Verify continuity of any added grounds to the neg (-) batt terminal.

6. If the condition is STILL present, add a restrictor (PN F1UZ-18D406-A) on the inlet hose with the arrow facing the direction of coolant flow (toward heater core). Cut the line and install it as close to the engine as possible (not near the heater core itself).

I would think this would be good PM for our cars. You need to make sure all the trapped air is removed for the cooling system. If you don't know the right way to fill the coolant read on...

Coolant Fill Procedure:

1. Disconnect the heater hose at the right or front of the engine.

2. Remove the T-stat and housing.

3. Fill the engine with coolant mixture until it is observed at the engine side heater hose connection.

4. Reconnect the heater hose and install the T-stat and housing.

5. Fill the degas bottle to the fill mark.

6. Run engine until it reaches normal temp and select MAX blower speed on the climate system.

My tip 'O D day,
-Dr. Frankencougie
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