1992 Explorer v6 reservoir boiling

[jhow1]

we recently purchased a 1992 explorer. Test drive went fine. Runs and shifts fine. Few small leaks but for the price (trade for an old riding mower) we weren't expecting much. We drove it for over an hour home and it did fine. It was all highway.
Once we pulled into the driveway we heard bubbling. Opened the hood and the reservoir was boiling and steamy with rusty water. However the temp gauge always stayed in perfect range and the motor seemed at normal temp. I have never in my life seen a car boil over but not overheat.

I'm going to put some real antifreeze in and see if that changes anything
Any ideas? I can handle replacing the head gaskets but I'd rather exhaust my other options first.

 

[natenkiki2004]

Flush the system and start with a new radiator cap. If I were you, I'd give a try of some water and a bottle of radiator flush. Drive it for a while to clean it out and then do the regular garden hose flush. But follow the instructions on the bottle.

For what it's worth, I remember when I yanked my engine and got everything back together, I used one of those spill-free fill funnels. I guess being a newbie, I ran the engine too long and it ended up boiling over out of the funnel violently. The engine is fine, no major head gasket issues. I don't use any noticeable amount of coolant or have any issues now that the system is sealed back up.

 

[jhow1]

Thanks I'll give it a try