2001 gmc sierra overheating

SOURCE: 1996 buick roadmaster keeps overheating:

A shotgun approach to repairs can really rack up the bills.

If your symptoms are loss of water and you have replaced the thermostat, you more than likely have an issue with steam. And that steam more than often comes from a bad head gasket. Most head gasket gasket failures seem to be confined to the water side initially, but let it go on bigger damage will occur.
You can buy a litmus test strip to dunk in the coolant. It will indicate if there are exhaust residuals in the water and thus a gasket failure.

However it may just be something simple, given that you have just about replaced everything:

have you given the radiator a good hosing inside and out?
is the radiator fan running when it should be?

SOURCE: Changing a water pump on a 2005 GMC Pick-up

Open the hood of your truck. Look inside the engine bay. See the fan assembly and the pulley that the belt rides on. The water pump is behind the pulley. Changing water pumps can be somewhat of a task. Professional help will be needed for someone that can't find the waterpump. 


 The water pump is on the passenger side front of the engine; I had to drain the coolant, I kept the belt in place, then I removed the 3 bolts from the pulley to give me access to the bolts on the top (it will require a set of metric tools for it). Then I removed the passenger side front tire and the splash cover from under the car just above the tire, removed all bolts that holds the pump on the lower part of it, then removed the belt, scraped and clean very well the old gasket. The new water pump came with a new gasket, so I just got a gasket maker and applied to the gasket, so I did not have to do it again. Work backwords to reinstall everything, good time to replace the coolant and if you have not done yet, replace the thermostat valve along with any hose that may be cracked, rigid or enlarged (check the hoses to the heater core also). Please check your belts and hoses so you will not have to redo the process again. 

SOURCE: 2005 GMC Sierra Overheating

If your sure there is no trapped air in system after refill and air bleed off, is fan clutch pulling good air thru radiator? Even if it is, the heater should have coolant as hot as what temp gage is showing! Try backwards flushing heater core (dex cool is notorious for plugging these up). There is a TSB for cracked cylinder heads from GM for unexplained coolant loss.Remove drivers side valve cover, and look at center three head bolts for coolant around them, if coolant has been getting in thru this suspect area, there will be a milky/pudding like goo under valve cover and on head. GM had a company called Castec cast these and the areas near the head bolts were found to be too porous (NO recall YET!) Ya, you guessed it, replace heads! Unfortunately, if its gotten hot to many times, it has probably hurt the heads/gaskets. Hope this helps. PS: The castec logo is under the rearmost pair of rocker arms,may have to remove them to see.

SOURCE: 2001 GMC SIERRA . ABS LIGHT STAYS ON

Wheel speed sensors misadjusted, damaged , or metal shavings and other debree, since they are magnetic can give false readings from one of the wheel circuits. Over sized tires can give of false speed readings as well. there are many other causes including bad relay, control module, e.t.c. It is best to have the proper scan tool to diagnose an ABS problem

SOURCE: how to replace a water pump on a 5.3 liter sierra

I suggest that you visit the autozone.com website and register the vehicle. It doesn't cost anything and will give you access to an online repair manual. The steps for replacing the water pump should be available there. Hope this helped and best wishes.