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Heater Core Failures and Electrolysis
By Blog Admin on November 7, 2008 4:07 PM |
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Most heater core failures are caused by high flow rate or poor quality coolant. But there's another culprit for repeat heater core failures: excess voltage in the coolant, which leads to electrolysis.
When stray electrical current runs through the cooling system, it can cause metal to be removed (pitting, scarring) from the heater core and result in leaking within the core. Electrolysis may be caused by a lost ground or if the coolant has become corrosive.
To combat the damage caused by electrolysis, ACDelco heater cores use a one-step brazing process to strengthen the joints for high corrosion and erosion resistance and durability.
If the heater core is leaking, examine the location of the leak. If the leak is on the inlet or outlet tubes, it is most likely due to high flow rate. Review the appropriate Service Information, which may call for the installation of a restrictor on the inlet hose, facing the direction of the coolant flow (toward the heater core) and close to the engine block.
If any leaks are found in the heater core itself and there are no signs of physical damage, the coolant inhibitors may be depleted and require a check for electrolysis. (Fig. 7)
Voltage Reading
Generally, electrolysis is possible with a Digital Multimeter (voltmeter) reading of 0.3 or higher.
To determine if electrolysis is present, with the engine running, take a voltage reading with the voltmeter negative lead grounded to the battery and the positive lead suspended in coolant, making sure it does not contact any metal part of the cooling system.
Both AC and DC voltages should be checked. Vehicles normally have DC voltages, but a faulty engine block heater or faulty diode in the alternator can produce AC voltages.
Although coolant is lost due to heater core failure, try not to dilute the original coolant with new coolant during testing if possible.
Flush the Coolant
If the voltage in the cooling system is greater than 0.3 volts, indicating electrolysis, perform a cooling system flush using a coolant exchanger, which can replace virtually all of the old coolant with new coolant.
If the cooling system is restricted from scale, rust or other debris (Fig. 8), only an exchanger with a back-flush procedure will be effective. A vacuum-fill exchanger also will purge any trapped air in the cooling system.
Check the Grounds
The most likely possibility for electrolysis is a poor ground somewhere in the vehicle electrical system, such as a cooling fan mounted to the radiator.
Check the grounds on the battery, engine/transmission and body sequentially with the voltmeter negative lead.
Also check various accessories by watching the voltmeter while turning each accessory on and off and also by engaging the starter motor, but not starting the engine.
Next, perform the same checks with the engine running at a fast idle, about 2000 rpm.
Remember, you must check all three grounds (battery, engine/transmission and body) with each accessory and keep the positive voltmeter probe suspended in the coolant. The voltmeter reading is unlikely to drop to zero, but should clearly drop below 0.3 volt. The accessory with the drop has a bad ground.
One other item to keep in mind is that if the vehicle is equipped with an electric cooling fan it should be cycled during the testing and voltage monitored with it on and off.
Don't Ground It
The final word, plain and simple, is do not ground the heater core. If the heater core is grounded, a path is provided for electrolysis to pass through the heater core, which would allow any stray voltage to use the coolant as the ground path.
- Thanks to Dennis Kissack
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About this Entry
This page contains a single entry by Blog Admin published on
November 7, 2008 4:07 PM.
Tire Pressure Monitor Sensor Service Tips was the previous entry in this blog.
2009 MACS Convention is the next entry in this blog.
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burning smell too..2010 ss.. the other morning listening to smoke on the water really loud.. turned the heater on and the car filled up with pink steam..fluid out the vents.. Heater coil!! yep, they have to pull the windshield to replace.. my main worry is why it went out. 35k on the car...this might be your burning smell. i thought my daughter was smoking in the car.. but this might be the problem. see below