What I've been trying to find out, and couldn't figure out from the RAVE, is what the capacity of the radiator itself is; not the entire cooling system. This would be useful is determining how much blockage a used radiator, from a junkyard for example, may or may not have.

 

After I had mine cleaned it took damn near 3gal.

If you found one buy it, new cost 500+, used 100-150. To clean can cost 50-75. Cost me 75 to have it cleaned.

 

Thanks! I was going to get one from the pull-a-part but both of the ones I found had visible leaks & looked like crap. When I find a decent one I'll probably just get it rodded out. Summer's coming, time to deal with it.

 

Trying to figure on % of blockage not easy. The tubes get coated inside with calcium which varies in thickness, jagged edges, etc. Check temp top to bottom on fins, if more than 10F difference blockage has started. One shop I used took a rad out of a Chevy diesel, said it had so much calcium it weighed almost 150 pounds and took two mechanics.

 

If the radiator holds, for example, 10 quarts when new, and currently holds 7 1/2 quarts then in theory it's about 25% blocked. Of course there's no way of knowing if 1/4 of the tubes are completely sealed up or if there's just crud in every tube that you just might be able to flush out of there.
I let mine run for about 15 min, got up to about 150-160 in the driveway. I used the low-budget "touch and swear" method, and the fins started getting noticeably cooler halfway down. For whatever reason, it never got above 205 when the outside temps were in the 50s & 60s.
The problem seems to be finding a replacement in halfway-decent shape locally. Used ones off ebay are almost $300 with shipping. (I'd rather not go with the aluminum & plastic version.) I'm not ready to spend $600 on a new brass one. The search continues...

 

Actually, you would be better to go by performance. The interior coating won't be uniform, and it may not be 100% blocked in each row, but it will drop performance.

And it may not be a dry crusty inert substance, it may be Dexmud (Dexcool), which soaks up fluid, like a sponge, but does not allow full flow.

If you flushed on a schedule, OK. If it has been 10 years, the crud won't flush, I tried commercial flush; then white vinegar, the removed rad and tried muriatic acid. The rad shop rod out and hot citric acid flush brought it back from the grave.

 

Ahh yes, Dexcrap. Didn't know it was porous.
I got a boneyard radiator, but it looks like it's in worse shape than mine. (No visible leaks on the tubes, but a bunch of the copper fins are missing from the bottom.) I'll try it, and at the very least I may leave it in just long enough to get the original one rodded. Maybe I'll get lucky and it'll be fine after all.

 

I have a OEM radiator in the 94 I'm parting. No leaks. Not sure on blockage but the truck has bad head gaskets (exhaust gas in coolant) but it doesn't overheat. Supposedly replaced by the original owner but who knows. PM me f your interested