meesh1902

Ok, bought a 1999 chevy Silverado 1500 LS 5.3...
It overheats almost immediately within a mile of home!!!
This week had the heads done, new head gaskets, new thermostat, new radiator.
Runs better and doesn't get hot now for about a mile and a half.. then there it goes!!
Don't want to blow another set of gaskets..
Local parts store says there is only one water pump to go on this model (LS)
but after running the web, seems to be a choice of clockwise or counterclockwise..
Top hose gets hot, nothing else does..both sides of tanks on radiator get hot, but everything else stays cool..
Does anyone know a way to tell which way the water flow is supposed to go?? Been at this every night for a week now and am ready to sell the damn thing..

tech2

usually the flow is out the thermostat to the top rad hose out the bottom rad hose and back to the engine



what kind of shop does all this work and gives it back not working??

justimagination

Previous post is correct on water flow. I would first check fan clutch listening for ROAR prior to running HOT, as well as turning the HEATER on to circulate and check both heater hoses(they should both upper and lower) be hot. I suspect an AIR LOCK in the heater as well as the CLUTCH FAN being bad. If you replace it, there is a two letter code stamped on the center of the clutch, I suggest only AC DELCO. Good luck,
David g.

tech2

if coolant is circulating correctly, there should be a temperature drop of at least 12*C from the upper rad hose to the lower rad hose. Measure the temp of the rad hoses with a infrared temp gun.


When the thermostat opens, you should be able to squeeze the upper rad hose and feel coolant flow as you restrict the flow.

if there is no temp drop across the rad and you feel no flow...the thermostat may be stuck closed for the new rad is blocked.

remove the thermostat for a brief test drive or test it.

another possibility is a cracked head. put a pressure tester on the system and watch for pressure pulses after the thermostat opens.

at highway speeds the fan clutch does nothing to add to air flow through the rad.

meesh1902

It DOES matter whether you have a clockwise or counter clockwise rotation on your water pump and where your belt is located. And do your own homework!! DO NOT listen when the idiot at the parts store tells you, "there is only one direction of waterpump for this vehicle"..Problem solved by looking at a few sites, trying 3 different pumps, and having a LOT of determination..
Thank you to those that responded, and I DID change the clutch fan while I was at it!

Rednucleus

Very interesting (and frustrating no doubt) Great troubleshoot on your part.

tech2

pump rotation is important...as an apprentice I routed a belt wrong and it spun the wp backwards...the car got hot and the ecm went into a failsafe mode to limit heat production. Smart engineering saved the day for my mistake.


what vehicle was the pump meant for an old body 99? That's all I can think of for that kind of mix up. That is the danger of aftermarket part information systems. To many options.