Cooling System Bleed Screws

CapitalTruck · July 17, 2006

The GM shop manual advises that when draining and refilling the cooling system, while refilling, "open the cooling system bleeder screws" Does anybody know where on an '04 4.8 liter these "bleeder screws" would be located? I would believe this to be a crucial part of the draining and filling procedure (I don't want to have air in the system after changing coolant).

m3gumby · July 17, 2006

hey when you drain your coolant...there's a plug at the bottom of the radiator to drain it. run some radiator system cleaner through it and drain it again. once you've done that fill it back up with the proper amount of 50/50. keep the cap off of the overflow tank and keep the truck on, idling. wait till there are no more bubbles comming up and screw it back on.

chris_kucia · July 18, 2006

I believe (and could be wrong) that the bleed screws are the plugs that are screwed into the sides of the block.

From what I remember, they were so difficult to find and get to that I didn't bother. I figured I'd change the coolant more frequently to allow for the extra old stuff that I couldn't get out.

obbop · July 25, 2006

Seems that some do not realize the importance of removing every last bit of air from the coolant system... especially important with Dex-Cool.

From what I read in thine query your reference to bleed screws refers NOT to removing liquid but to assisting in allowing air to escape the closed system while you fill it.

Can't get to the Helm manual right now to find the reference to bleed screws there.

A call to the Chevy service department may get you the needed info.

It can be tough with some components to find then via the eyeball method.

When it is time to drain and flush and refill my coolant system (doing it at 30,000 miles) I am pondering adding my own "extra" bleed screw (air removal point) by splicing into one of the heater hoses. I don't think it would be too difficult to use pre-existing components and add an air removal point to assist in ensuring ALL the air is removed.

I think I may use a new slightly longer heater hose so I could elevate it so as to get the bleeder as elevated as possible. Between the overflow tank and that added bleeder at the heater hose I hope that every last bit of air could be removed.

Also, by having easy access to the extra bleeder I could go back once in awhile and elevate that hose then run the engine a bit so those last pesky air bubbles can reach that bleeder so they can be removed.

If anybody has any other ideas to assist in removing every las bit of air from the coolant system I'd sure appreciate hearing about them!!!

C & A s Dad · July 25, 2006

I could be completly wrong here, but I know of no bleeder screws on the 4.8/5.3. From what I know, air in the system is typically a problem with a vehicle whose radiator is lower than the engine, which is not the case with a GM truck.

I flushed my Yukon XL a few months back and have no issues with air in the system. I had experienced this with a Dodge Intrepid and the temp gauge would move up and down every 1 to 2 minutes as the steam pocket traveled through the system.

I would recommend that if you use a flush, us a mild one and not one of the heavy duty ones. Pesonally, I refilled my system with clean water and drove it at least 10 minutes and repeated this 3 times before refilling it with Dex Cool. I wanted to be sure all of the flush and old coolant was gone. I also believe in and use a product from Lubegard, called Kool It. It is one of those "watter wetter" products but it is recommended by Modine Radiator Co and will help eliminate electrolysis, which is a huge enemy to modern colling systems.