2000 chevy silverado 5.3 replaced the thermostat and water pump and flushed the radiator still overheating

SOUNDS TO ME LIKE YOUR HEAD GASKET HAS FAILED

Sounds like the water pump fins aren't doing their job. I suggest changing the water pump. Been there, done that. Bad pump.

250 TOO HOT FOR ENGINE AND TRANSMISSION. SOUND LIKE COOLING FAN CLUTCH BAD ITS FREEWHEELING NOT LOCKING UP TO DIRECT DRIVE TOO COOL ENGINE OFF BECAUSE THE FAN CLUTCH THERMOSTAT NOT WORKING THE HOT SILICONE OIL CAUSE IT TO EXPAND TO PUT RESISTANCE ON CLUTCH TO PUT DRAG ON FAN CLUTCH CAUSING IT TO LOCK IN GIVE IT DIRECT DRIVE.I WOULD STILL REPLACE THERMOSTAT AND RADIATOR PRESSURE CAP IF TEMPERATURE STILL 250 DEGREES YOUR RADIATOR AND COOLANT SYSTEM NEED FLUSHING.

possible blown head gasket, have a leak down test done to see if there is bubbles present in the radiator when looking in through the radiator cap hole. you can also remove spark plugs and see if there is any water or moisture present on plugs.
even though you may have flushed your radiator ( I presume that "you" have done that) there may still be a few bars blocked with dirt etc, you may have to have the top and bottom tank removed and have the individual bars cleaned to make sure there are no blocked bars.
Hope this helps

If it overheats very quickly, it likely has a bad thermostat. If the radiator does not fill easily when re-filling, likely the radiator is internally blocked and requires either a flush, boil out or replacement. Make sure any electric fans are properly operating. If you have any white smoke or coolant in engine oil, you may have a blown head gasket. A shop can identify this condition by checking for hydrocarbons in the cooling system, or by doing a compression or leakdown test.Do the easy stuff first...change the thermostat. If problem continues, go further with your diagnostics.

Flushing the radiator, replacing the radiator cap, adding new coolant, replacing the sensors and a new thermostat solved the problem. Probably didn't need to do all of these things - but since we just purchased the truck, and given the fact that is probably hadn't been done in a while, we chose to do all of these things (which really didn't cost a whole lot), it's running like a charm now.

The rust is probably in the engine. There are many little pockets, water ways, water jackets (around the cylinders), etc, so getting all the rust out without dunking the block and heads in a cleaning tank is about imposible. I would recommend giving it really good flush every 4 to 6 months. I would try flushing the radiator before replacing it because it is probably not rusted, even though it is full of gunk.

try checking the hoses for blockage,and if not that make sure the fan is working right as it might be the fan cluch,or your water pump may have went out,best of luck

Hi,

Based on your description "hard line from thermastat area has a heat wraparound it goes towards firewall", that would appear to be part of the heater system for the inside of the vehicle and would not affect the overheating of the engine.

Most engine overheating could be caused by:

• insufficient coolant in the radiator or reservoir;
• defective (stuck) thermostat;
• too soft radiator hoses (upper/lower);
• water pump, belt, tensioner;
• clogged radiator;
• radiator fan motor, clutch (if has got one), relay.

Additionally, in a large number of vehicles, the radiator fan motor would only work the A/C or heater is ON.

Corrective action would require determining which is the culprit, pls try:

• remove the thermostat completely out and test drive, see if the overheating comes back, if yes, then it is not the thermostat, if no then the thermostat most likely is stuck closed and would need replacement;
• on start from a cold engine, remove the radiator cap and pls check if the water flows when the engine is revved. If yes, water pump is working, if not, water pump is defective;
• in a closed loop cooling system such as in your car, there is a possibility that the radiator hoses might have thinned down or gotten softer. This could be checked by revving the engine while looking over the hoses, there should be apparent sagging or reduction in diameter when the engine is revved. If any, then they are too soft and would need replacement;
• clogged radiators could be flushed/cleaned by removing the drain plug at the bottom.
  

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards. Thank you for using FixYa.

Overheating can be casued by a few things.

1)Thermostat
2)Water pump
3)Dirty coolant clogging the pump

A thermostat is the cheapest part to replace, a thermostat opens and closes allowing coolant into the motor as needed to keep it cool, if it gets stuck closed then it doesn't allow any coolant into the motor thus overheating.

A water pump is what pumps your coolant around the system, and if this goes no coolant moves thus overheating. Usually when these go bad they leak coolant and are also noisy when bad.

Lastly could be bad or dirty coolant, a coolant flush can take care of this.

If I were you I would start with the thermostat followed by the coolant flush, both of these can be done in your driveway.

Hope this helps