Re: overheating blazer
My vote is the thermostat. It sounds like it's not opening until the coolant gets too hot. Then when it finally opens, everything goes back to normal. It closes back up, and the vicious cycle starts over. If you have already changed the thermostat, has the problem gone away? One tip - drill a small (1/8") hole through the thermostat flange. That way, when you fill the system back up with coolant, any air bubbles will be able to pass through the thermostat, but it won't let a lot of coolant through and defeat its purpose. The thermostat is usually the highest point in the cooling system before it opens, and if an air bubble gets trapped under the thermostat, it has to turn to steam before the thermostat will open. By that time, the coolant will be way too hot. I pegged the temp gauge in a Turbo Laser once, and this trick has prevented this problem.