I have a 2006 caravan, used to leak about 1 qt of coolant per week, I used a sealer, it worked, but now while driving temp on guage shoots way high,
then comes down, it repeats on and on , oil good and no loss of coolant, any ideas?

 

Because you used a sealer and now have clogged possibly the entire cooling system. That stuff is pure junk. Need to try flushing the cooling system and see if that helps.