Coolant could very well be outgassing from a simple small leak that has not developed into a noticable leak yet (dampness around a hose fitting) so don't rule this one out yet. You could try to disconnect the heater hose from the aux. water pump and ride without the heat (using a 12v electrical heater) to confirm or deny this as the culprit.

This case reminds me of the Army brass at Ft. Benning that had his engine replaced in his Cadilac. When he got the car back, he started to smell a foul odor, and couldn't find the cause. Since he car-pooled (and drove his Caddy) each morning he would have a car load riding to the base with the windows down, and it was winter time (cold, but in Georgia). His wife told him to sell it or she would not ride in it anymore.

He took it to a car wash and they removed the back seat looking for the cause, and found a dead mouse that had crwaled into the car and died while having the engine replaced in the shop. The Caddy had leather interior, which is pourous, so the stink was aweful, even after two trips to the car wash at $200! I could hardly stand smelling it before I placed my air purifier in it, and the windows had been down all day! So, the army brass told me that if my machine worked, he would buy one for his home. It worked, but he didn't make a purchase, because the problem was gone.....that's how the government works sometimes, huh?

Hope you locate your source of headaches. It seems to be air related.

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'87 300E | 2.6 engine
Artic White - Navy blue interior, chrome rims, very clean and sharp!
91 300E
89 300E


The rest of my collection are just cars and trucks...no more "automobiles"...