Best way to test a radiator?
 

Whats the best way to check to see if my radiator is cooling properly? The lower hose is much cooler than the top. I'd call it luke warm. I know it is supposed to be somewhat cooler as the water has been cooled by the radiator, but while searching here it also seems like this may be an indication of a clogged radiator. Visually, I have no leaks and it is not boiling over. Any way to check flow or otherwise check to make sure it is working properly?

Take it to a radiator shop and have them clean and pressure test it

I would replace it if it's questionable. I'm sure that's not the answer you are looking for.

No need to replace it if the fins are solid to the touch and there are no leaks. The bottom acts as somewhat of a filter, and sediment builds up there causing poor flow and cooling.

you might just need a t stat

From my experience with the bottom hose being cooler always ment (for me) that the water pump needed to be changed out.

I should have mentioned, water pump and t stat are brand new. Everything seems to be working just fine, I was just concerned by the cooler lower hose. Should I be?

A very simple little flow test I do (with the radiator out) is put my palm over the lower outlet and fill the radiator with water, then remove my hand and see how fast the radiator drains out. It should empty very quickly and completely. If you have to turn it upside up to get it to drain completely you'd have some blocked tubes. If it drains slowly it has partly blocked tubes. I've never quantified any drain time rates, I just go with my gut feeling.

If in doubt throw it out sounds like a good way to go too. Radiators are pretty cheap and if you've put 10 years of use into it that's about $12-15/year.

Anyone else? Does having a cooler lower hose definitely mean I have a problem? Truck does not seem to run hot (other than occaisional overshooting) but I don't trust the stock gauge at all.

The bottom hose should be cooler since the radiator has done it's job cooling the hot coolant coming from the top hose. Mt. goat has the right idea. At least that way tou can check if it's signifigantly plugged (or all the way). We have an old ass radiator flow machine at work that isn't super-precise accurate,but gives you a good idea within a couple gallons per minute. A 2row copper-brass 4cyl radiator typically flows around 12-18 GPM on our machine. If you start getting around 8 or less is when customers say they were having an overheating,or "running warm" issue. You have to be careful with some of the newer radiators on newer cars,Because they are NOT meant to flow that much for higher efficaincy reasons. They up the fin count, lessen the rows of tubes and "dimple" the tubes to actually slow the flow down so the coolant is in the core longer, having more heat pulled from it. Those radiators are hard to get a good flow check on. Especially subarus.

How much cooler is acceptable? I don't want it cold do I? Seem to be getting conflicting opinions here.

If it was really constricted, wouldn't it be pretty ovbious that the truck is overheating?

Going by the lower radiator hose is a poor, and inaccurate way to tell how you're radiator is cooling. If the heater blows HOT, and the temp gauge reads NORMAL, you're fine. Quit over thinking this, if you're concerned about your radiator, replace it. Its not rocket science :chair: