My car has had a very slow, almost undetectable burn off of coolant which has been ongoing over the last couple of driving seasons. There is no visible wetness/pooling anywhere. However, when the car is fully warm and idling there is a distinct smell of coolant burning off, from somewhere. Over time, the level in the overflow tank has slowly reduced so there is clearly a leak.

I am not sure where to begin my search for the source of this leak (busy job and short on time...don't want to start pulling things apart with no plan).

Any advice on where to start first and/or common weak points in the system would be appreciated.

 

You might want to check the head gasket.

 

The plastic coolant overflow tank is a known age-out point. 25-year old radiator cap is another.

Hopefully not the head gasket!

-- Chuck

 

under the intake manifold. there are orings that go bad. can leak on the starter and down to the chassis ground below.

 

chuckie,
I just replaced my cap. What’s the deal on the overflow? Plastic crack causing a leak from the tank?

 

Silicone coolant hoses by any chance?

These permeate coolant molecules. Odor, and evaporating coolant

 

Possible clues here from nine (9) years ago:

https://www.s2ki.com/forums/s2000-un...-tank-1150879/

-- Chuck

 

Thanks everyone. Didn't think to investigate the overflow tank because i didn't think there would be any burn off/smell if that were leaking (given location away from engine/exhaust). Fingers crossed that is all it is.

 

this, under or at the rear of the intake manifold

 

Plastic overflow tank is common. The radiator also has plastic end tanks which don't last forever.

Different car, but I had a hose develop a pin-hole leak. Took forever to find since it was tucked in the V of the engine (2006 Mazda6 wagon V6).