I was leaking coolant pretty fast and now i replaced the water pump and the leak is gone but now its overheating faster. is it possible the thermostat is opening or what. any help welcomed

 

If the thermostat was stuck open you would run cool. If its stuck shut then you heat up. Did you get all the air out of the system? Did you flush out the system afterwards?

 

all i did was drain the the radiator and change the water pump and fill it back up

 

I usually leave the cap off while the engine is running, let the thermostat open. When it does, the coolant level should drop looking inside the radiator. I always just keep it full until the fluid level stops sinking getting out all the air.

 

I ran it with cap off but it wouldn't go down. And stupid question does blazers really take 5 gallons of antifreeze

 

You start with "overheating faster". This leads me to believe you had an over heating problem that started this pump change and coolant drain, correct? You say the leak has stopped but its still overheating. With the cap off and the motor up to temp you should see movement in the coolant. I'm not saying up or down but movement. If you do not your water pump is doing absolutely nothing, highly unlikely or highly likely, your thermostat is stuck closed and you need a new one. This may well have been the start of your problems.
I do not have the speck sheet's in front of me but your right five gallons sounds like alot. But possible.

 

I would check to see that your thermostat is working like spittybays suggested. You can tell it is opening when the vehicle is up to temp by feeling your upper rad hose. It will get hot to the touch when it is open. If it is opening I would be sure you don't have an airlock. I like to elevate the front end to ensure the rad cap is the highest point in the system and let it run with the cap off. You should be able to see the coolant moving or your rad is plugged up. If your coolant is moving and after you burp the system I would put a new rad cap on too. No one ever replaces them and they should. If everything above checks out then have a look at your fan clutch. It should turn by hand (with the motor off) with some resistance. It should have not play in the bearing. It you need a new one get an OEM one as I have never had any luck with any of the aftermarket brands. I would check your rad too. Make sure it is clean and not plugged with mud. Run your finger gently across the cooling fins. They should not collapse or be brittle, if they do your rad is toast. If all this checks out you may have a bad headgasket. If you have overheated in the past you can destroy one easily.

 

I hope its the thermostat bc its an easy fix. I was frustrated when I had to get the fan clutch off bc the tools the gave me didn't work and I didn't even think about flushing the system but I was satisfied that it was no longer leaking but I Will change the thermostat today and see. My temp has never gone over 210 until yesterday and when it did I turned my truck off