Gurgling in the heater core, (in the dash), is caused by air in the cooling system. That should work its way out fairly quickly. If it continues, or if there is bubbling in the reservoir, I d be more worried about a leaking cylinder head gasket. That is an expensive repair, but a pretty common one on any car brand.
After thinking about this some more, I suspect the logical conclusion might be the transmission cooler, which is usually just a pipe running through part of the radiator, corroded through, and the sudden increase in pressue caused the radiator to pop. Had that happened slowly over, say an hour or more, you would have noticed the transmission slipping. I think the cooler let go abruptly. That would explain why the overheating showed up right away, AND the transmission was so low but you didn t have time to observe the additional symptom.
Naturally you couldn t tell the mechanic the transmission was low, because you didn t know it. An experienced mechanic should have put two and two together, but a lot of them have never run into this.
One good peice of news, I suppose, is GM usually runs transmission fluid through their coolers at more than 15 pounds of pressure, so it s higher than the coolant. When the transmission cooler leaks, that higher pressure can damage the radiator. Some manufacturers run the transmission fluid in the cooler as low as 5 pounds, so when there s a leaking cooler, coolant gets forced into the transmission. If you catch it right away, you can flush the transmission and save it, but often the symptoms take days or weeks to show up to the point you realize a serious situation is occurring. That can result in a failed transmission, which is a real lot more expensive than a radiator.
Tuesday, July 19th, 2016 AT 8:57 PM