We changed my coolant today and I'm running the Fleet Charge stuff now, 50-50 with distilled water. While the radiator was empty, I took the opportunity to look inside, and when I saw it, I had to get a picture.

The previous owner told me he used a stop-leak product in the past. The green stuff that came out was perfectly clean, like regular ol' antifreeze, and no gunk came out when we drained the block. The mechanic thinks the deposits inside were caused by the stop-leak, but I'm thinking it's hard water deposits. What do you guys think?

For what it's worth, the truck has zero cooling problems and the heater blows inferno, so nothing's plugged up, it just looks ugly. This is also the radiator the truck came with, it's never been replaced.

 

For a 300K mile radiator that looks pretty doggone clean!

 

if you got the rad out use CLR to clean the scale out, and if it is still in the rig you can use a flush, follow the instructions carefully and rinse it one extra time, for go measure.

 

I don't have much of a frame of reference for what's good and not good. I just looked inside and to my untrained eye, that looks like "Holy $#!%, how has this not exploded yet"

OH! Before I forget! Chevy_Eater, you know how you're always posting that picture of the unused block plug when people ask where to stick a temp gauge sender? Other people may not listen to you, but I did, that's where I hooked up my new temperature gauge. Very helpful, thank you very much

The radiator is in the truck and it's filled with new coolant, I just need to top it off with more distilled water tomorrow and make sure it's completely burped. I'm leaving it alone, lest I break the gypsy spell that keeps this truck running so good.

If the radiator starts to leak or it starts overheating, I'm just gonna give it a new radiator. I'll probably end up doing that anyways by this time next year, when I get the truck ready for the move to Arizona. I don't need it exploding on me while I've got a trailer with me.

 

I've seen them where the passages are all but choked off, far far worse then what you have there.

Someone listened! I put mine there, it works well.