Many car owners and DIY mechanics wonder if the temperature of engine coolant affects the accuracy of coolant testers. We decided to investigate this question practically, especially as temperatures dropped below freezing. Is it essential for a coolant sample to be at a specific temperature for an accurate reading, or can you test coolant directly from your car’s system regardless of its heat?
To find out, we conducted a simple experiment. After my Alfa 146 sat in sub-zero Celsius temperatures, a coolant sample was taken. Initially, the sample was around -2°C. The coolant tester’s instructions indicated optimal performance at 21°C, raising concerns about reading accuracy at such a low temperature.
Bringing the cold sample indoors where the ambient temperature was a comfortable 23°C, the sample was allowed to warm up gradually. After reaching room temperature, the coolant test was performed again. The result? Absolutely no discernible difference in the reading was observed. This initial test suggested that starting coolant temperature might not be a significant factor.
To explore this further, we proceeded with additional tests using water to understand the tester’s behavior in more controlled conditions. Water serves as an excellent medium because its freezing point is predictably around 0°C, depending slightly on pressure and wind chill.
First, the coolant tester was immersed in hot tap water, approximately 70°C. In this hot water, the tester sank completely to the zero mark. Next, the test was repeated with cold tap water, around 10°C. This time, the tester only descended to the -7 mark on the glycol side of the scale.
These water tests revealed a crucial insight: testing hot liquid significantly impacts the reading. The hot water test indicated a potential misreading of approximately 10°C compared to the cold water test. This margin of error is important to consider when testing coolant immediately after the engine has been running and the coolant is hot. It’s also worth noting that different glycol formulations could potentially exhibit varying results under temperature changes.
Concerning the original coolant mixture from the Alfa 146, the tester reading suggested it was in good condition. The float within the tester did not fully sink to the bottom of the scale, making a precise reading difficult. However, based on where it floated and the previous tests, we estimate the coolant’s freeze protection to be around -70°C. This deduction is based on the tester’s behavior in our temperature experiments and confirms the coolant is providing adequate protection even in very cold conditions.
In conclusion, while the initial temperature of a cold coolant sample doesn’t appear to drastically affect the Coolant Temperature Tester reading, testing hot coolant can indeed skew results, potentially by as much as 10°C. For the most accurate assessment of your coolant’s freeze protection, it’s advisable to let the engine cool down before taking a sample and performing a test with a coolant temperature tester. This will ensure a more reliable reading and help you maintain your vehicle’s cooling system effectively.
