Radiator - Flush or replace?

[JTH1972]

Okay, I had planned on changing my thermostat today, but instead of coolant coming out of the drain, I got this brown sludge slowly dripping out (and I do mean slowly!). Coolant on the top is nice and green, but this stuff is... ugh. I'm wondering how bad the rest of the system is.

So besides the obvious flush to clean out the block, should I try my luck and see if the rad will flush out too, or am I further ahead to just repalce it if it looks this bad?

 

[cr_the_machinist]

I'd say just flush it. That coolant will start to break down after a while if it is not flushed out with new coolant. If you have not had any running problems just flush it out and clean out the radiator.

 

[Sasquatch_Ryda]

Run some rad flush in it for a while, then drain it and back flush the rad out.

 

[LearjetMinako]

Use a radiator flush, then take a garden hose and just keep flushing it with clean water until it comes out clear. Do this with the engine running and heater on. And back flushing the radiator helps too.

Did this on my mom's 96' Blazer. I didn't realize how far broken down the dex-cool became until I saw the brown color coming out. Won't happen again, no more dex-cool. Go old fashion Prestone green coolant for all makes.

 

[JTH1972]

ok I'll give that a try first. thanks for the replies. Hopefully it'll get out most of the rust and crap that's clearly in there. Is there any way of cleaning out the drain petcock?