Cooling issues.. ideas?
 

Alright so one day my rad blew and what not, ended up getting kinda hot and crap by the time I let it cool and got home.... so I ended up having to change a thermostat and rad... now I seem to have this problem and i'm confused on what it could possibly be...

While driving (has to be at least 20-30 mins MINIMUM of driving) before signs of any kind start. The temp guage starts to move up....and than down... than up higher etc... etc. Highest is gone is around 3/4... BUT when its gotten like this and i've stopped and looked (at my friends since I was on my way there)... the fans aren't even on, they work, and do come on... but like my friend said if it was overheating, they'd be on all the time. The coolant obviously boils over and goes into the overflow when it gets hot like that... any ideas what it could be? (tried bleeding it a few times as well)

So when your rad blew what did you do? Did you replace it?

get a new rad cap or test it to make sure it holds the correct pressure it raises the boiling point, could be a faulty cts so its not kicking your fan on. Make sure you have no air in the sytem 100% before you test these and run 50/50 straight water or straight coolent could cause it aswell.

well it kicks the fan on, just it doesn't keep it on if it really is getting really hot, but the problem is... I can keep driving, and than the temp ends up after a while going back to normal...

i've been told it could be bubbles, thermostat (even tho its brand new), cts, or even a headgasket

head gasket or crack in the cylinder walls will do that because you are getting air in the coolent happend to my budies car. you better do a compression test to rule out the engine .

alright so I drive around with the heat on, and the needle doesn't move at all... BUT if I don't turn the heat on, after a while of driving, it starts to bounce around... and normally when i've checked it, the overflow starts to get exactly that, more overflow... But when I drove around with the heat cranked, got home and checked, there was NOTHING in overflow, any ideas if that may be something other than a headgasket or cts? or is that still the ideas you'd get from these?

You are losing coolant somewhere....

But once it cools down, all the coolant is back in overflow...