After a week of not driving my 86 I thought I'd gor for drive to pick up some lunch. After letting the car warm up for about 10 minutes I began to hear a strange gurgling sound. I lifted the hood and and noticed coolant flowing out of the overflow tank. I shut the car down and pulled out my phone for a quick video.
http://youtu.be/SSTyRh2z1_k

Any ideas what could cause this?

 

i used to have that problem it was terrible i was so annoyed, when i drilled my thermostat the problem went away, i think you have air trapped on the coolinG system , did you burp the system ? Check for coolant in the oil as well. let us
know !

Check THIS THREAD and THIS THREAD

 

The funny thing is that your overflow is doing it's job. It's just supposed to take on coolant when there is an overpressure. Instead of being a heating overpressure, your blockage is putting back pressure on your radiator and just dumping coolant. Your coolant is already going to be REALLY low, so I would just do a flush. That way you know it's done properly and you can burp away to get all those darn bubbles out. And drill the hole while your at it. Stupid fluid dynamics and their vortex vacuumes.

 

Yes,Navy is right, you might get outta coolant like that causing more damage,it's really annoying, the drilled thermostat made the trick for me

 

with navy_vette your block has some type of an internal coolant blockage. Pull the radiator & overflow caps and take a pics of the inside of the tanks.

Looking at the video, orange (appears to be the result of mixed Dex-cool and the ol' green polly stuff - which is non compatible by the way) spots of "goo" can be seen below and around the radiator components. In my opinion, more than likely the orange "goo" is the issue...getting it all out of the block, heads, heater core, hoses, pump and radiator will be near impossible.

 

I would try to burp the system first.
There are many threads with the procedure. The thermostat may be stuck causing an overheating condition.

What does your temperature gauge say when this happens?
On and the cat is also pretty sweet (^_^)

 

A weak radiator cap can cause the same issue.

 

Thank you all for suggestions and advice. I am working today but will have some time tomorrow. By the way the radiator is just a year old this month. My temp gauge has not worked since I have owned the car. As matter of fact I just purchased the part to get it working two weeks ago. Was going to put it in this weekend.

(The Kitten I rescued,it had been abandoned by it's mother kitty. Kitty is now thriving in a loving home!)

 

Turns out it was the Radiator cap. Thanks all!!!

 

i'm very happy to read that outcome !
Congrats !!!