Hi all,

01 Chevy Blazer, 4 door 4wd here. Apparently the previous owner of my vehicle put Stop Leak in the coolant system. I've since replaced the radiator, and most all of the coolant hoses, along with 2 real flushes by a mechanic. However, the heater core has been plugged from time to time which I usually cleared with a reverse flush from a garden hose. However, currently the heat doesn't seem to work as well as it has before, and I suspect a clog in the core that the hose flush won't fix safely. There can't be many places left in the system to hide stop leak remnants, so I'd like to get this core flushed for good. Any chemical flush ideas to clear out the core that won't involve the rest of the system? (ie Chemical cleaners in my brand new radiator...) Thanks for the help!

 

This stuff comes highly recommended but you'll want to flush your entire coolant system after using it.

https://www.amazon.com/Irontite-Thor.../dp/B00JJ1FB28

 

My experience with stop leak is you use it in an emergency to get where you can fix it. If it's in longer then that be ready to replace every part of the cooling system. IncludING the heater core and the LIM gaskets if they are still the oem plastic ones.

 

This is why stop leak is the worst. Flushing the heater core is actually pretty easy. What I did was grab a roll of heater hose from Advance, not expensive. Disconnect your heater core. Get a funnel and hook it to your heater core with a hose, you could probably just use your stock hose. Get a bottle of CLR and pour it in there and let it sit for about 15 minutes. Now, hook a water hose to your core using something like this. hook the role of heater core tubing to the other side and run it into a bucket. Now turn the hose on until the water runs into the bucket clear. Then switch the hoses and run the water through again in the other direction. I did this with mine and when the water first came out it was black. I have had good heat ever since.