Honda Civic Coolant Mix Corrected After a Previous Service Got It Wrong
A Honda Civic came into us here at Platinum Vehicle Services after the owner had a nagging feeling something was not right with the cooling system. He had recently had the car serviced at another garage and noticed things just 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.
What we found on inspection
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.
Why the mixture matters and what can go wrong
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 actually 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 can put unnecessary strain on the cooling system, cause overheating under load, and potentially damage components like the water pump, thermostat, and radiator. It is the kind of thing that does not announce itself with a dramatic warning light straight away, but it quietly works against the engine until something gives way.
How we put it right
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 with a cooling system problem 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 we see customers from across the West Midlands, so whether you are local or travelling a little further, you are welcome to bring your vehicle in and we will tell you exactly what we find.
