Keeping Her Cool – Coolant Replacement

Being smoking hot inappropriately is not appropriate.

Depending on the type of the factory-filled coolant. Coolant replacement interval can range from 30,000 to 150,000 miles. In the SX4, Suzuki recommends 30,000-mile interval. We were way overdue on this.

As part of the big 60K celebration, we changed the factory-fill.

We selected Prestone Extended Life 50/50 Pre-Diluted Antifreeze. It is universal, and compatible to different types of coolant, and cooling systems per Prestone. It also claimed the coolant is good for up to 5 years or 150,000 miles. We have been using the Prestone coolant for years and years in our daily driven and track proven Nissan, and Mazda cars. We never experienced any problem in terms of incompatibility.

Function of Coolant

The number one purpose of coolant – a.k.a. antifreeze like it’s term has suggested – is to prevent freezing. Coolant is a mixture of chemical additives that lowers the freezing point of water to prevent formation of ice in the engine that could cause catastrophic mechanical failures such as cracked engine block, cylinder head, and/or set loose the core (freeze) plugs.

Second but also critical purpose of the coolant is to prevent electrolysis occurring in the cooling system.

In theory, electrolysis is a chemical reaction that involves ion exchange between dissimilar metals in cooling system. This ion exchange process has the tendency to cause dissimilar metals to dissolve and migrate via coolant throughout the cooling system.

This migration is caused by a mild electric current flow and that is caused by dissimilar metals being suspended in a water-based liquid. This metal dissolving behavior leads to deterioration and erosion of materials in the cooling system.

A cast iron block and aluminum head engine (bimetal) with a copper radiator is more vulnerable to electrolysis corrosion than an all aluminum engine with a plastic-aluminum radiator based on the ion exchange in dissimilar metals theory. However, aluminum corrodes much faster than iron. So in bimetal engine, the corrosion is first seen at aluminum parts.

The electrolysis processes are in proportion to the amount of electrical current flow through the coolant. A smaller current flow in the coolant creates a slower corrosion. A greater current flow creates a more severe corrosion. But neither one can be tolerated and neglected because a slower corrosion can also cause major corrosions over time.

Typically, electrolysis happens in the cooling system is due to improper grounding from engine to vehicle body and/or from electrical components to body. The electricity travels through the coolant based on the fact that the metallic impurities in the coolant create a favorable circuit for the electricity and since the electricity has the tendency to find shortest path with the least resistance.

Therefore to eliminate cooling system corrosion due to electrolysis is by ensuring the vehicle has proper grounding, and to make sure the coolant has sufficient corrosion inhibitor and free of suspended metals.

Changing the coolant periodically is the best method to replenish the corrosion inhibitors, and get rid of the impurities.

How to Do It

There are numerous ways of replacing the coolant:

  1. By coolant flush machine at a shop
  2. Open both engine block drain plug, and radiator plug
  3. Radiator plug only

Based on the condition of our SX4, as we didn’t see any corrosion or oily deposit. The cooling system is in top notch condition. We opted 3. but with a trick. We drain and fill the radiator three times for a complete flush.

Tools needed for the job is minimal. Just some rags or towels to soak up any spill, a drain pan that holds about 6 quarts, and about a gallon of coolant per flash. So 3 gallons in our case.

It took us about 2 hours to complete 3 flushes excluding the cool down time in between.

Cost: $8 (on sale) per gallon of Prestone Extended Life 50/50 Pre-Diluted Antifreeze. Our total cost is $24.

Here is the Process


Use the information here at your own risk. We take no responsibility and will not be held accountable for any safety issues, or any problems whatsoever.If you are not mechanically talented or never open a hood before, please do not try this on your own. Seek help.

  1. With engine at room temperature, locate the corkscrew at the bottom of the radiator. Turn it open to empty the radiator. Open the radiator cap will help speed up the flow.
  2. While coolant is draining, remove the reservoir and clean out the content. Reinstall and fill with new coolant to full mark.
  3. Once coolant stops dripping out, close the corkscrew. Fill up the radiator with coolant, and squeeze on the lower hose then upper hose to release air pocket as you are filling up the radiator with new coolant. Fill radiator to full and reinstall radiator cap.
  4. Turn the HVAC temp control to fully hot. Drive the car until it reaches normal operation temperature for 5 minutes.
  5. Shut off engine and let it cool to room temperature.
  6. Repeat Steps 1 thru 5 at least 1 more time.
  7. Flush complete. Make sure the coolant level at the reservoir is full. Re-check its level daily for about a week with the engine at room temperature. It is normal for coolant level to deplete initially as the air pockets in the system is being filled. Just add more coolant to the reservoir as necessary. The coolant level should stabilize after a few days unless you have a leak.


Coolant replacement is probably the only maintenance item that you don’t feel the different in driving. But it makes the inner us feel good knowing the cooling system is protected.

Lamzgarage Health Tip

Dispose coolant properly. It is highly toxic to any form of life.