So, for the last 2-3 months, I've sometimes noticed a smell of coolant around the engine bay of my 2013 Fit after running the car. The car has 55,000 miles on it and no notable performance issues or changes. I took the car to a mechanic back in late March. They did a pressure test and inspected the radiator closely, but no leaks were found. The coolant levels in the radiator and reserve tank were normal.

Fast forward to this week: I smell the coolant again and I decide to check the levels again. This time, I notice that there's a very small puddle on the pavement, directly beneath my coolant reserve tank. A smell test reveals that it's coolant. I pop open the radiator cap and the reservoir cap. The coolant level in the radiator is normal, but the coolant level in my reserve tank has gotten pretty low, hovering right around the MIN mark.

My immediate thought was that I probably had a loose clamp or a pinhole leak in a hose. But upon taking the car to another mechanic today, they weren't able to find the coolant leak with a pressure test or an undercarriage inspection. I don't know how much of a factor this might be, but it rained quite a bit last night and the underside of the car was damp, so maybe this made it harder to find the leak by sight or touch? I'm going to bring it back on a drier day for another look, and I figure I'll add some coolant to the reserve tank in the meantime.

Has anyone dealt with anything like this? Slow coolant loss, visible coolant puddle under the car, but difficulty finding the leak?

 

No leaks of any kind :/
Do you top off fluids on occasion? You or your mechanic? Could it be possible that coolant was added to the reservoir before it had opportunity to drain back into said reservoir after running the engine?​​​​​​

 

Personally I would take your car to a specialist- a radiator shop and not to a regular mechanic. I would drive the car there and get the engine up to running temperature. Ask the radiator shop to remove the radiator cap and attach their pressure tester to the radiator neck. Pump the system up to the pressure that the radiator cap has printed on it. With the engine warm and the radiator cap pressure applied to the system, any leaks should appear. If no leak, I would suspect either the overflow rubber hose from the radiator neck to the overflow tank has a leak, or the overflow tank itself might have a crack/hole that only leaks when the overflow system is working and the coolant level gets high enough in the overflow tank to reach the hole. Remember the radiator and cooling system are under pressure at operating temperature, but the overflow bottle is not.

Post back what you've tried and what your results are.

 

I'm thinking that going to a radiator shop might be the best approach too. My current guess is that the reservoir tank itself has a leak that only appears under certain operating conditions. I'll post the latest result when I have it.

 

If you think it's from the coolant tank, you can put some of that water tape or water paste on the tank. It changes color in the presence of water. Not expensive.

 

Do you park on a hill?

 

Try a new radiator cap. If the cap is losing pressure (1.1 bar) the car will lose coolant slowly. My car had the same problem but I never saw any puddle under the car and the problem was a defective radiator cap. Best of luck, Clay

 

While my car is a 1st gen, not 2nd, it to had a slow coolant leak. Replacing the radiator cap solved it, and been fine since.