2008 Silverado 4.8 Overheating

Joshnyah · August 13, 2019

Hello all, My 2008 Silverado 4.8 has never given me any trouble. One morning I was driving to work and "Mind you its dark out and my instrument panel is not bright" But I got the ding on my dash saying that my engine was overheated and the engine was shutting down to half power or something, I immediately pulled over and popped the hood, the plastic Y that splits the HVAC heater hose and Overflow hose into the water pump was spitting water out it had a crack in it. A mile and a half from home I waited about 30 minutes and turned on the engine and my temp was just over 210. so I drove about a couple blocks till it started getting hot and sat for around a half hour till it cooled down again, I did this over and over till I got home. "It took me about two hours to go maybe 2 miles" A few days later I bought a new HVAC heater hose that is apart of the Y that cracked. put fluid in and waited, it started getting hot again. I changed the thermostat and it started getting hot again, I took the thermostat out and it got hot again

I took the hoses off and ran water thru the block and radiator and it seems to run thru clean and flows well. My fans seem to kick on ok. But it gets hot after like 5-10 minutes of sitting Like it wants to peg at the hottest. I pulled the heater hose off and when the engine is idling the water trickles out but when you rev the engine it comes out like a water hose.

I am stumped, I dont know if I need a new water pump.

I do not have any leaks

No water in my oil.

New thermostat or no thermostat it still gets hot.

I have never had an issue with my truck getting hot until that little crappy piece cracked, Could running my truck hot for those few minutes have messed something else up? I literally have never had an issue till this day, any help would be greatly greatly appreciated.

Thanks -Josh

silveradosid · August 14, 2019

could be an air lock. had the same thing with an envoy with the 5.3. keep the reservoir full, start it and let it heat up and then shut it off and let it cool down. you will see that it will suck the coolant down in the reservoir. i had to do this 5 times on the envoy before it finally worked the air out and didnt over heat antmore

Joshnyah · August 14, 2019

I will try this tonight. Thanks.

Joshnyah · August 17, 2019

On 8/14/2019 at 4:33 AM, Joshnyah said:

I will try this tonight. Thanks.

So I’ve been burping it for the last couple days. I am almost to 2 and a 1/2 bottles of coolant. And getting less bubbles in the coolant tank before my temp would max out at 260 but now it gets to 235 but I noticed my fans aren’t coming on at the right times. They used to come on around 210. Today they didint kick in for the longest time and when they did kick on they did not drop the temperature of the engine just kept it around 235 when I turned on the ac the temp started to climb so I shut her down. And I believe before when I shut the engine off the fans would still run for a little bit but now they shut off when I turn it off. Any help?

Also im in Arizona so I feel like they were always running before.