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Coolant smell

I can smell coolant when I first turn my heater fan on then I goes away I have a 96 gmc jimmy just changed the thermostat.heater works good no leaks that I can see no coolant on passenger floor and no residue on windows does anyone have an answer for me

You may have a very small pin-hole leak. Or a seal in the heater leaks a small bit when cold. Leave it alone a while and see if it gets worse or leaves a deposit where you can see or feel it. It is never a good sign to smell coolant.

If I were in your shoes, I’d check the coolant level, add coolant if necessary, and drive it to the shop to have the vehicle’s cooling system pressure-tested. The results of that pressure test will tell you everything you need to know.

Leaving it alone a while to see if it gets worse will increase your chances of overheating the engine, being stranded, and paying towing charges. I prefer to take care of these issues before they become a problem, even on a vehicle as old as yours.

I had a coolant smell I chased for nearly a year in my Ford. Just every now and then, but the smell was undeniable Then, I started to notice a loss of coolant, very slow at first. After a couple of months and no visible signs of a leak, I put some UV dye in the system. First day, I noticed a small trail of green that did not reach the bottom of the block on the front side of the engine. I started thinking timing cover seal, intake manifold seal, or even head gasket seepage. The leak started getting worse, then, within a week, finally let go. Turns out the lower thermostat housing, made of plastic or fiber-resin, developed a crack at a heater hose fitting that took a long time, over a year, to blow out. It took removing the upper intake manifold to reveal the lower thermostat housing.

I am a fan of those uv dyes

I use them all the time in ac systems. For slow leaks, it takes awhile for the dye to show up, though

It’s very helpful for the next guy that has to diagnose the ac system