Checking Antifreeze Electrolysis

Checking the quality of the antifreeze is one of the jobs that really should be done if you have recently purchased the vehicle. It is obviously important to check the PH but with a recently purchased vehicle it is also worthwhile checking the 'charge' of the Antifreeze, this is a simple but generally overlooked process, allow about 10-15 minutes to complete the check.

Equipment and Tools Required:-

The Jaguar service schedule recommends a change of the engine coolant every 5 years, however maintaining the effectiveness of the coolant is important. Incorrect or poor quality antifreeze, not using distilled water, or an electrical problem, can result in the fluid building up an electrolytic charge. This charge can result in substantial damage to soft metal engine components within the cooling system.


Checking the electrolytic charge of the coolant is not difficult and requires only basic knowledge of the use of a standard multi meter. Run the vehicle until the engine reaches normal operational temperature, then shut it off. Allow a few minutes for the pressure in the system to reduce, then using a cloth remove the cap of the coolant reservoir by unscrewing it until it rotates freely then pulling upwards.

Connections for electrolysis

Switch the multi meter to DC Volts and place the Positive (Red) lead of the multi meter into the coolant expansion tank ensuring that it is well submerged into the coolant. Connect the Negative (Black) lead to the engine or ideally the negative terminal of the battery.

DC V Range


You are looking for a voltage reading below 0.050V DC a reading above 0.150 VDC would be a cause for concern and would suggest that a full flush and replacement of the coolant is required.

Meter Reading

A reading slightly above 0.05V DC would suggest that the coolant fluid requires changing. The actual reading limits are not set in stone, with varying levels deemed acceptable by different vehicle manufacturers, it's worth remembering however that it should be zero and the higher the voltage the greater the likelihood of damage.

Causes of Electrolysis

The main cause of Electrolysis is lack of maintenance by not changing the antifreeze on a regular basis, but can also be due to chemical imbalance is caused by:-
  1. Not using distilled water.
  2. Not having at least a 50/50 mix of antifreeze and water.
  3. Using recycled antifreeze.
  4. Poor clean and flush of old coolant
  5. Using poor quality antifreeze that does not meet the manuafacturers specifications.
  6. Using coolant flush chemicals that are acid based.

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