Flushed everything last fall, replace coolant with new G12 SF. Had great heat that has gradually gone away. Flushed the crap out of my heater core on Sunday and I now have great heat again. I wish I had taken picture but I kept getting particulate in the fresh water that was about the color of popcorn husks but much smaller. No, it's not stop-leak unless someone broke into my car and added it sometime in the last 100,000 miles.

If I spent 2 days of my life putting in a new heater core, I'd be back to where I am in a few months. So what part of my system could keep producing this brownish particulate? It does not look like any corrosion. If it was a deteriorating water pump gasket I'd be leaking by now. Is there anything in the after-run coolant pump that would deteriorate and produce particulate?

 

The only other thing I could think of, is that the interior of your radiator is slowly deteriorating and pushing that stuff out into the system....that's all I got off the top of my head...you could install some small 'screens' on the inlet and outlet of the coolant reservoir and see if it catches any of the particles....done the screens a few times for various reasons....

The last heater core I did was due to the owner putting in 'stop leak' but he swore he never ever did - and yeah, one day of my life and about 2000 zip ties.....Pics attached so people know what that 'stop leak' does to your heater core and what kind of crap it puts into your engine....Even after completely flushing the system over 10 times, by passing the heater core etc...I put screens on the inlet and outlet hoses of the coolant reservoir to catch stuff, as well as the inlet of the heater core once hooked back up, told the guy to come back once a week for a month and he did, screens kept picking up more and more stuff - it NEVER goes away once it's in your engine folks!!!!

 

Couldn't agree more on that stop-leak stuff. It is pure evil.

Your radiator idea is worth playing around with. Might take it completely out of the car and flush it both ways with a hose this spring. I think the only two materials in it are aluminum and the plastic ends though.

 

If it's not your radiator, the only other thing I could think of was the heater core itself. What kind did you put in? OEM? Aftermarket?

It also always begs the question, why do heater core's get clogged in the first place? Where does THAT gunk come from in the first place if you take care of your car....?

 

It's the original one, straight from Inglostadt.

That is the question. Only had G12 in it, all cooling system original. I'm just going to have to take out the radiator, after-run pump and oil cooler this summer and flush the hell out of it.