Honda Civic Coolant Mix Corrected After a Previous Service Got It Wrong

A Honda Civic came in recently after the owner had a nagging feeling something was not right with the cooling system. He had just had the car serviced at another garage and noticed things did not seem quite as they should. Rather than leave it and hope for the best he brought it in so we could take a proper look. It was the right call.

Every Ball in the Hydrometer Floated to the Top, Putting the Reading Firmly in the Not Safe Zone

The first thing we did was carry out a coolant check using an antifreeze hydrometer tester. This is a simple but reliable tool that draws a small sample of coolant from the reservoir and tells you whether the mixture is sitting at the right concentration. When we tested this car every ball inside the tester floated to the top. On the scale that reading sits firmly in the not safe zone. The coolant was far too concentrated, which pointed to one likely explanation. Whoever topped up or replaced the coolant at the previous service had used pure undiluted antifreeze and had not added the water that needs to go with it.

Pure Antifreeze Without Water Actually Freezes at a Higher Temperature Than the Correct Mixture and Transfers Heat Less Efficiently, Putting the Cooling System Under Unnecessary Strain

A lot of people assume that more antifreeze means better protection but that is not how it works. Coolant needs to be mixed with water, typically in a ratio of around 50/50, to do its job properly. Pure antifreeze on its own has a higher freezing point than the correct mixture, so it offers less frost protection not more. It also transfers heat less efficiently, which means the engine cannot cool itself as well during normal driving. Over time running with an incorrect mixture puts unnecessary strain on the cooling system, can cause overheating under load, and potentially damages components like the water pump, thermostat, and radiator. It is the kind of thing that does not announce itself with a warning light straight away but quietly works against the engine until something gives way.

Coolant Mixture Corrected to the Right Concentration, System Checked Over and the Car Back on the Road the Same Day

Once we had confirmed the problem we corrected the coolant mixture to bring it back to the proper concentration. The system was checked over to make sure everything was in good order and the owner left knowing the cooling system was doing what it is supposed to do. It was not a complicated job but it was an important one. A straightforward oversight at a previous service had left this car running on a mixture that was not fit for purpose, and catching it early meant no lasting harm was done.

If your car has recently been serviced elsewhere and you have any doubt about whether the work was carried out correctly it is worth having someone take a second look. Signs to watch for include the temperature gauge running higher than normal, the heater not working as well as it should, a sweet smell from the engine bay, or visible coolant loss over time. If you notice any of those things do not put it off. We are based in Walsall and see customers from across the West Midlands. Bring your vehicle in and we will tell you exactly what we find. Book in at platinumvehicleservices.co.uk or come in and speak to us directly.