David_Quick

Well a while back i bypassed my heater core. now when i put coolant in it it still leaks. its not comming from the two hoses that i connected and now its starting to overheat. so what else could be wrong with it?

JA no Y

There has to be a leak somewhere.
The easiest way to find a leak is just look under the blazer when its parked and see if any coolant drips down onto the ground. Just trace it back to the spot its leaking from.
Look for any white spots on your engine. That can signal a gasket leak on the engine. Check your radiator hoses for cracks or other bad areas for possable leak areas. Check to make sure your hose clamps are not over tightened. That can cause the ends to flare out and not seal properly causeing a leak. There could be a small crack in your radiator. Look for any water spraying out after the engine warms up. Also check your oil dip stick and oil cap. If there is is a creamy colored oil on the under side of your cap or on the dipstick, you may have a blown head gasket or a possable cracked head.

Rick Norwood

Go to Autozone and borrow their cooling system pressure tester. It looks like a radiator cap with a small tire pump on it. Install it on the COLD radiator and pump it up to the pressure rating on your original rad cap. You should see any external leaks immediately. If you don't see anything leaking, you might have the traditional intake manifold gasket problem. But this is a good test to start with since it is free.