I have 2000 5.3 l silverado Z71 and having bit of overheating problem.
How do you test radiator for blockage with infrared temperature gun when A/C condenser is in front of the radiator.

 

Hi yanker,

Welcome to the Chevy Forums.

A leak at the water pump gaskets is very common in the Vortec V8s.

Do a thread search in this section, fortunately it's easy to fix.

 

thanks Rivereye.. I'll check it out...
just to fill you in on my probelm, whole thing started with towing of my boat. When outside temperature was 95-100 degrees and had AC on, temperature started to go up. Turn the AC off, then temperature will go back to normal. I had cooling system service done at the dealer and had thermostat replaced couple days later, cuz temperature was still going up. Had fan clutch replaced bit later. Thermostat was replaced again. Dealer and another auto repair place don't really know what is causing the over heating problem. Right now, only time temperature start going up is when I'm backing my boat on the drive way. I bought infrared temperature gun to see if I can locate if there are any blockage in the radiator, but since AC condenser is sitting in front of the radiator, I didn't know how to take the readings. I figured there are only two thing left, radiator and water pump. Since heater works, that must mean water pump is working.

 

Try the low-tech approach. Remove the top half of the fan shroud, and hose off the radiator fins from the back side of the radiator.

You will probably be able to do your thermal scan from there, too.

While the shroud's off, see if you can notice a small leak at the base of the water pump.

 

Yanker, rivereye was right - those water pump gaskets are prone to leak on the 5.3L. However, I've sold enough of those radiators to know they do go bad.

I would recommend you take your radiator to a radiator shop and have them flow test the radiator. If it doesn't pass the flow test, get a new radiator.