I overhauled my 86 Sami and everything ran super for about a 1000 miles. Then one day 2 weeks ago I shut it off and when I restarted it a minute later it blew antifreeze out the overflow tube. It only was about two cups and then it stopped blowing out antifreeze. It only seems to do this if I shut it off and start it up before the engine cools down. My first thought was a bad radiator cap so I replaced it. Same problem. It does not overheat, and I checked the temperature sensor and the gauge and both of them are working good. I have started it up (cold) with the radiator cap off and watched the temp go up to normal and the thermostat opens and the radiator gets warm so I know the thermostat and the water pump are working. The antifreeze is not dirty and there are no bubbles in the radiator. The oil is good and clean. So now I am stumped, what am I missing?
Thanks, Bob

The only thing I can think of is pressure is building in the cooling
system, and that could be a leaking head gasket, so check/re-torque
the head bolts, other than that?

There is a test solution to test for exhaust in the coolant, you could
try that first before taking off the valve cover

Wild

Could be a cracked head/block too. How detailed was your "overhaul" did you have the head rebuilt?Was your overhaul due to a overheated engine or something else?

Update, I didn't see bubbles looking in the radiator with the cap off but I changed my pop can overflow to a plastic one that I could see into and it is bubbling constantly so I think you guys are correct about the gasket or head. I overhauled it because the rings were bad - smoked pretty bad but that is fixed , now this happens. It was a quick overhaul, honed the cylinders, checked clearances, new valves, rings, bearings, gasket set and threw it back together. I will retorque the head but I am sure I will be pulling it off and having someone check the head for cracks. I've had this one for 3 years and it never lost any antifreeze before so I assumed the head was good. But, you know what happens when you assume something.
Thanks for the help
Bob

If it was previously good I would not suspect the head
is cracked, but the question that comes to mind is did
you get back your head, or did a shop swap the head
without you knowing? I hate sending out parts, you just
never know what will come back, or if it's your old one

Wild

I always stamp a code in what ever I'm sending out, even taxidermy work, I mark it. So far I've had good luck but ya never know.

Was the head retorqued after the overhaul?  It should be standard practise to retorque after the first few hundred miles - if it was not done, that may be the source of your leak.

Hey all
I hope that it is just the gasket, it won't take much to pull the head and I should be able to see if the gasket is leaking. When I cleaned the head up I didn't see any signs of a crack and I would have thought that it would have shown up right away instead of 1000 miles later. I didn't send the head out because the didn't appear to be warped-checked with straight edge and feeler gauges- I put in new valves and hand lapped them and then checked them with prussian blue to make sure they were seating ok.
I didn't retorque the head because I asked the partsman about doing that and was told that it wasn't needed. I should have gone ahead and did it. Oh well, ya learn something new everyday.
That's a great idea -stamping a code in it so you know that your getting your stuff back, I'll have to remember that. Thanks.
I'll pull the head and check it out but I need to pull my transfer case out of my pickup and replace the seal in it. If it isn't one thing, it's another. Plus the wife is after me to finish the front step on the house. I think I need more hobbies. LOL!!
Thanks
Bob

The same thing happened to me, with the radiator fluid spewing out the overflow.  It was a simple trip to autozone getting a new radiator cap.  im not sure of the reason why it does it but when the spring in the cap is worn out and not making a good seal it will come out of the overflow.  after getting a shiny new $3 cap it hasn't posed a problem on my 87 sami.  Good luck!

Ok just had to add did you get your radiator serviced during the rebuild ?

I have had many radiators clog then clear then clog .... causing the same issues ...

just a possible problem ... good luck

Well, the Saga continues, today the upper radiator hose broke just as I got to work. I called the auto parts store and they had it in stock, how lucky was that? My wife picked it up and I put it on right after work and drove it home. Just another reason not to go with a cheap overhaul, I should have replaced all the hoses.
I did retorque the head today when I got home and that seemed to help. I'll still need to pull the head and replace the gasket. I will have the head checked and resurface it. I did find out that the previous owner bought the rig with a bad head gasket and he put a new one on.
This is getting to be fun!!
Thanks Bob

FWIW, make sure you have decent coolant/fluids; distilled water is preferred and a blend of anti-freeze, if you're where it gets cold enough. In the south, we also use "Water Wetter", by Redline, as an additive. Good luck.