Vehicle is a 1982 GMC K1500 6.2 diesel. It's got a 1987 6.2 diesel engine in it swapped by some previous owner (there were many). The truck has sat for a while since I didn't really have time to work on it. Recently I bought new batteries for it and started it up. Fired right up but I noticed the coolant begins to bubble within ~60-90 seconds of the truck turning on.
Video: https://i.sstatic.net/CoiCE.jpg
The coolant isn't hot at all at this point. I have a Chilton manual and looked through it but didn't find any info on bleeding air from the coolant. Most of my mechanical experience is with newer foreign cars (BMWs) so I wasn't sure of what the procedure is that I should be following to bleed it? Just remove the rad cap, turn heat on and let it idle for a while until the bubbling stops?
I'm worried it could be the head gasket but want to eliminate other possibilities first. There doesn't seem to be any oil in the coolant. Any other suggestions welcome.
Thanks.
