I am a little confused right now with this overheating issue. I am still working all the little things out with this new engine and I can't figure out why it is running hot while the gauge shows 200-210. If I drive it around town a little with the air on it will stay below the 210 mark usually hovering around 190-200. Fans are working and the radiator is full. When I shut the car off is when it just starts boiling. I have a LS6 with 5.3 TEA stg. 2 heads, VRx5 cam that runs great except for this problem. What could it be?

 

oh btw....it really overheats the most when I have been running the a/c.

 

check for obstructions in front of your condenser. it made my car run hot with my AC on. a plastic bag got lodged in front of mine.

 

It may be because the system is de-pressurizing when the engine/water pump is off. How old is your radiator pressure cap? Replacing that may do the trick.

 

Boiling over of coolant means you have air in the cooling system.......period. Its getting in there somehow.
Blown head gasket
Tiny little leak somewhere
Water pump is leaking
Bad radiator cap

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I have the original radiator and it worked great before so I believe it is ok. Head gaskets are good and I am not loosing coolant anywhere SO I guess I still have air in the system. Whats the best way to bleed the air out?

 

Go to the bottom BLEED part...........


Best/easiest way to flush and get every drop of old coolant out.

-Cold engine.
-Remove radiator fill cap.
-Remove the t-stat from the housing. Leave the housing attached to the rubber radiator hose, just remove the 2 housing bolts and pull it away from the water to pump to get to the t-stat. (2-3 minute job).
-Put t-stat housing back on. (1 minute) Just put one bolt in, no need to put them both in, there’s no pressure in the system during the flush.
-Take the entire radiator drain valve (petcock) "off" and let it drain, don't just open the valve itself. It'll drain faster with it off and that’s what you want. ((Buy a new petcock valve before starting this flush process, sometimes they break when you remove them all the way just because they're cheap plastic and they get briddle over time, they're like $2.00))
-Take a hose and stick it in the radiator fill cap, running medium to high.
-Start the engine.
-Turn heat on full blast
-Let it run for about 15-20 minutes or until the water is running out the drain CLEAR.
-((If you want to, you can wait till it runs clear, "close" the drain valve, add some degreaser (I use ½ gallon of Formula 88 to clean mine) and let it run for 15 minutes, then let it sit for 15 minutes, then run it for 5 minutes, then drain it all again. Then open the drain and put the hose in for about 5 minutes run it all out till its CLEAR. The degreaser will help break up the crap thats stuck DEEP in the BLOCK that sits and swirls and doesn't like to come out.)) ***NO…degreaser will not hurt anything.***
-When it runs clear your entire system is clean.
-Remove the overflow reservoir from the car and clean it out real good. (I had to use gasoline to clean mine out because the sludge and grime was so thick inside. The gas broke it all down and then it flushed right out. I filled it about 1/3 up with gasoline and shook the hell out of it real vigorously, the black stuff kept coming out. I did that like 4 separate times with gasoline till no more chunks of black crap came out. Make sure the lines that go to the reservoir are also cleaned out. Or just buy a new piece of 3/8” heater hose and replace that line, 3 feet will do, then cut to fit. My sludge came from my power steering fluid leaking into my coolant system.)
-Put the t-stat back in.
-Put the overflow reservoir back in.
-Put the drain valve back in. Use the new one, what the hell.
-Put half a jug of Dexcool in the radiator. (Or if you live in very cold places, 1 to 1 ½ jugs of Dexcool)
-Fill the rest with water.
you do not need to use distilled water, clean hose water is just fine, just make sure your city water is clean and not total crap quality.

**Bleeding the system of air:
Take the radiator cap off when its COLD, start it up and let it idle, and let it warm up till the t-stat opens. I rapidly squeeze the upper and lower radiator hose like 20 times while its warming up to help move any air bubbles through the system and by the t-stat on the engine side. When the t-stat opens you’ll see the level drop as you squeeze it, its sucking the coolant through the system. You will also see the coolant start to flow in the radiator fill neck, once it starts to flow the level should drop down a lot, immediately top it off with coolant/water. Then the flow will stop when the t-stat closes. Wait one more time for the t-stat to open again and start to flow, if it drops down again top it off again. Do it a 3rd time if you want to make sure. When the level does NOT drop down when the t-stat opens and coolant is flowing....you're system is free of air bubbles. I always massage the upper hose during the whole process to keep any air bubbles moving through. Always works like a charm. Just keep checking your temp gauge until the t-stat opens for the first time to make sure it’s not sitting there overheating from a trapped bubble. May take 10-15 minutes for the t-stat to open the first time.
If you do start to get hot while sitting there and the t-stat will not open…..you have an air bubble on the engine side of the t-stat. Shut the engine off and rapidly squeeze the upper and lower radiator hoses again. Then start the engine again and see if the t-stat will open. Sometimes you just have to work those hoses to move the air through. Even after it seems topped off after a couple cycles…check it the next time you have a cold engine…top off if needed.

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i would remove rad......blow out/wash out accumulated crap.......in a/c fins too.....check hoses.......replace all maybe.......check t stat

 

LS6427....thanks man! Worked like a freakin charm! Turns out it still needed a good bit more fluid because I added a good bit as it was cycling through. I squeezed all the hoses, bubbles did arise here and there and after about 10 minutes it was idling with a/c on high with the fluid hovering around 178 ( I have the 160 t stat for now). On my scanner I watched the temp rise after I shut it off and it rose to about 196 then did not rise anymore. Feel a little better now...so thanks everyone for your input.

 

Sweet......glad it did the trick for ya.

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Did you do a full flush or just bleed the system?

 

just a good bleed of the remaining air, full flush was not needed