Coolant out overflow

[Thedivingpirate]

My 77 runs great, but every time I shut her off she spits some coolant out of the coolant reservoir.
Replaced the rad cap with a new 16 pound safety cap. Old one looked pretty worn out.
She does not run hot at all.
She does have a puff of white smoke out the left tail pipe at start up.
NO coolant in the oil.
Coolant level in the reservoir is about 4 inches from the top.
The pic shows a huge spot..just changed out my daughters thermostat housing. The spot in red is all that spits out.
Whats the next thing to check out?
Thanks for your time

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[Preston]

I would just keep an eye on it, may check your spark plugs on the bank that’s smoking could have a bad plug, wire or low compression on 1 cylinder. Has the truck been setting for a while? Are you loosing oil?

 

[C10MixMaster]

the coolant level is about 2-1/2 inches from the bottom cold. if your 4 from the top cold your probably over filled

 

[Thedivingpirate]

Thanks

 

[Madhorn]

I would just keep an eye on it, may check your spark plugs on the bank that’s smoking could have a bad plug, wire or low compression on 1 cylinder. Has the truck been setting for a while? Are you loosing oil?

What Preston said. Check the plugs for discoloration. I had something like this happen with my 77 when i bought it 20 years ago. It gurgle coolant in to the coolant over flow tank. No oil in water and no water in oil. I did find a plug that had a green tint (green coolant) to it so I pulled that head. It took a while but I ended up finding a hair line crack in the combustion chamber.

 

[Thedivingpirate]

not loosing any oil, I drive it everyday. I will pull the plugs this afternoon and check them out. Thanks

 

[Thedivingpirate]

pulled all 4 plugs from the drivers side, side that has the puff of smoke. They seem fine to me. Wires are not damaged.

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[Madhorn]

Just an observation. Second plug is a lot cleaner than the other three. May be nothing, but it is.

 

[Madhorn]

Just had a thought. Yes it hurt. Put one the dirty plugs in the cylinder the cleaner one was removed from and check it in a couple days and see if it changes.