ok, my friend just bought an 87 base with 110k on it, and since i know more about rotaries than he does, im helping him out with it. the guy before him took good care of it, the body, interior and engine bay are real clean the the motor runs really good. the previous owner doesn't know if the engine has been rebuilt or not but i suspect it has because it pulls real smooth and idles rock solid. only problem is coolant bubbles into the overflow bottle when the car is ran. it used to overheat so he had every exterior part of the cooling system replaced; rad, hoses, fan etc, and it still overheated. he took it to a local rotary shop, and they said coolant in the filler neck is foamy and measured 141 ppm hydrocrabons. they concluded that it needs a new engine. my guess is that it just needs a new coolant seal? the car runs better than it should for 110k miles, so im guessing it was rebuilt, and the coolant seal was just seated wrong or came unseated or somthing like that. but im unsure because like i said it has a rock solid idle and pulls really hard. is it a blown coolant seal or could it be something else?

edit: it also bubbles out in the overflow bottle, as wells as fills it but doesn't drain it. it also floods when cold.

 

Have you checked for a leak somewhere in the system? Check for fluid leaking anywhere through-out the cooling system. Make sure the coolant cap is holding pressure. It could be something little like that (hopefully). Tells us what ya find out from there.