West Valley BMW Repair

8335 W. Sherman St Suite 200 Tolleson, AZ 85353

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Cooling System Electrolysis

Electrolysis process. On passing electric current the cations move towards the cathode and get deposited. Simultaneously the anions move towards the anode. galvanic cell element. Experimental set up for electrolysis

This month – We are discussing an important issue – Electrolysis in vehicle cooling systems. Over 70% of all vehicles we see at Ultimate Auto Repair Service have electrolysis in the cooling system…as low as 50,000 miles!

First, Let’s Define Electrolysis.

Looking at the above picture gives a simplified visual of how a basic 12 volt lead acid chemical automotive battery works. Two dissimilar lead plates (positive / negative) are connected in series (cells) and submerged in water & sulfuric acid, AKA “electrolyte”. The chemical reaction between the dissimilar plates and electrolyte creates voltage AKA EMF. Connecting a circuit creates current flow. Voltage is electric potential or force. Current is actual electrical energy “flow”. This chemical reaction between the water electrolyte and metal plates is always present inside the battery. A result of this chemical reaction is degradation of the metal plates gradually over the course of years as the electrolyte AKA Battery acid eats away slowly at the plates. This is expected in a battery and why they have a lifetime after which a new battery is required. This should not be expected inside your engine!

However, that is exactly what electrolysis in an engine cooling system does. Normally, coolant has additives that prevent electrical current and protect your system… Electrolysis when used in terms of engine cooling systems is a term used to describe when the coolant/water mixture inside your engine has actually become electrically conductive, like electrolyte inside a battery, and is causing a similar chemical degradation of the metal components in your cooling system. Including but not limited to your radiator, water pump, thermostat, and internal engine passages or cylinder head passages. This can cause a very premature failure of any or all cooling system components as the electrolysis continually attacks the metal components in your cooling system. There are a few causes and reasons for electrolysis, but it can all be summarized in this: not properly replacing your engine coolant on a regular basis.

The How’s and Why’s of Electrolysis:

1. The simplest is this: Coolant has chemically degraded and is no longer effectively protecting your engine and needs to be replaced with new coolant.

2. Using ANY water BESIDES distilled in your cooling system. Distilled water MUST be used in your cooling system. As a process of vapor distilling, there are zero sediments or minerals left in the water. Using regular water, ESPECIALLY phoenix tap water, has all kinds of sediment and minerals that make the water more conductive to electrical current. Distilled water has very few ions left so it is a poor conductor in comparison (as an instructor once said, “anything becomes a conductor with enough voltage – the human body becomes a conductor with 100,000 volts.

3. Most Vehicle Manufactures for some time have mandated “long life” 100,000 mile coolant with “no maintenance interval”. Before I explain how wrong this is I’ll preface it with the understanding that we can’t all blame the Manufacturers too much…There are several factors at play:

A) Increasing environmental mandates breathed down their throats to meet continually rising standards so they are forced to look for new “long life chemistry” coolants and set longer “recommended” maintenance intervals.

B) Competition. All it takes is for example, is if the standard mileage for a coolant flush was say 40,000 miles, Ford comes along and says “we have an 80,000 mile coolant interval”. Well if Chevy doesn’t buck up, are you going to buy a Chevy? Of course not! Regardless of what is truly best for the vehicle, Manufactures have several factors from environmental mandates to reasonable or unreasonable competitive claims that force them to recommend maintenance intervals that are in their best interests along those lines, NOT the vehicle’s best interest. A brief understanding of these realities is necessary to provide both an understanding and validity to why maintenance intervals that are best for your vehicle long term are often not the same as “factory maintenance scehudles”.

4. Arizona is considered a “severe” climate by ANY definition in any vehicle’s owner manual. Meaning maintenance is required sooner and more often due to chemical breakdown that occurs from high loads and stress from a severe climate.

So what should you do?

1. The resolution to electrolysis is to completely flush the system with a flushing chemical additive, completely remove all coolant from the engine cooling system, and refilled with new coolant / distilled water mixture and a preventative / electrolysis reducing agent.

A) SPECIFIC COOLANTS ARE REQUIRED FOR ALL VEHICLES, ESPECIALLY VW / AUDI. Chemical dissimilarities between “universal” or incorrect coolants and proper coolant can create a sludge like coolant that plugs heater cores and radiators.

2. Always used distilled water to top off your cooling system in an emergency. A gallon is less than $1 to keep in your trunk. Always buy the specific coolant for your vehicle. Typically this is only a $10 difference for a concentrated gallon compared to cheap coolant at a parts store.

3. You can test your system for electrolysis if you have a voltage meter: put 1 lead on battery negative, the other lead into the cooling system radiator or expansion tank without touching any metal or components in the system except the coolant. Anything 0.1 V or higher indicates electrolysis is actively present.

Contact Ultimate Auto Repair Service today to have a complete cooling system flush performed properly to resolve or prevent electrolysis from happening in the first place. We recommend flushing your cooling system every 2.5 years or 50,000 miles – whichever comes first.


Auto Repair