5.3 cooling issue

[sweet_87_iroc]

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I just started up my rebuilt 5.3. The only problem I am having is its not cooling. I am running a new ls1 water pump with a straight thermostat housing and a 2000 corvette ls1 thermostat. I have tried to burp it numerous times. I have coolant coming out of my steam vent hose connection when it gets hot. I am not sure if it's the different thermostat that is the problem but I can't seem to figure it out. Any help would be great.

[hoogiesngrinderz]

Where is the steam line running to?

Are the heater core lines hooked up?

[WMCCjames]

You most likely have air in the system. Sometimes it can be difficult to get it out. Have you ran it with the rad cap off until the thermostat opens? That usually does the trick for me.

[DanDalessandro]

What I do with my LT1 is open the bleeders, fill the radiator. Then close the bleeders, cap back on, and run the car until the thermostat opens. I then shut it off, and open the water pump housing bleeder to let the air out. Then just let it cool for a couple hours, refill the radiator and it has been smooth sailing ever since I started doing it like that. I don't know if the 5.3 has it like that too.

[hoogiesngrinderz]

^^ No bleeders on LS

The reason I ask about the heater hoses is because I've seen a lot of people pull the hose ends and tap/plug the holes. This can cause air to get trapped in the pump.

[sweet_87_iroc]

The heater hoses are hooked up. The steam vent goes to the top of the water pump where I installed a fitting. I am leaning towards changing this and running it back to the radiator. I have the cap off every time I run it. I also lifted up the front end.

[hoogiesngrinderz]

GenIII+ engines are usually not very finicky about trapped air.

I'd cap the fitting on the water pump and tun a temporary hose from the crossover and let it flow into a burping funnel. Keep an eye on the hose for air bubbles. If you get a solid stream of coolant with the engine at operating temp you should be good to go, just hook up the old line into the water pump.

[sweet_87_iroc]

That's a good idea. I am still nervous the thermostat is wrong. I think I may need to run a gto ls1 water pump.

[formula218]

i'll second hooking a burping funnel up to it and let it do it's thing, that's what worked for me after having problems with trapped air.

[sweet_87_iroc]

Where do you get a burping funnel?

[formula218]

any auto parts store should have them, i grabbed mine from NAPA, i think it was only $18 when i got it.

http://www.napaonline.com/Catalog/Ca...000_0405868358

[sweet_87_iroc]

the one on the left is the corvette style with the aftermarket housing. The one on the right is the one I removed when I bought the pump. Let me know what you think.

[1BADAIR]

Make sure the vent faces up on the tstat

[Lucky SOB]

We had this problem on Liz's LS1. We were finally able to get the air out when Kyle brought over some fancy pressurizing bleeder system.

[1BADAIR]

No pressure. Vacuum