yet another LS over heat issue

[dwenz]

Ok everyone been reading on here for two days all the threads on overheating. Great site but Still cant find all my questions answers OK were talking about a 2000 v8 LS It just started temp guage goes hot upper radiater hose is hot,lower radiater hose cold.Tried the fill procedure 3 times. Temp guage starts normal,then goes to 9:00 heat comes out of duct work best at 2000 rpm then at idle cools down. Then after 5 min temp guage goes on up to hot. The motor is hot . Motor seems to push out boiling coolant out degass ..but radiater lower hose cold
Yes fans are working on high and low. Thermostat is not gunked up or blocked I checked,also is not sticking I can open it with a push
Also I saw a mist or steam come out of duct work a couple times when messing with heater control at first start up.
I'm thinking water pump due to the fact lower Rad. Hose has no temp in it.
Yes heater blead has steady flow at idle.
Yes filled engine fill to top when engine off..
Please help

 

[flash2010]

Is there any pressure in the lower hose? Sounds like youve got a clog somewhere in the radiator.
It wouldn't hurt to replace the thermostat if the car never had it replaced in its life time. Think of it as preventative maintenance.

Joe will comment shortly with a proper diagnosis

 

[dwenz]

radiater clog would most likely not just suddenly appear

 

[joegr]

The most likely problem is a crack in a plastic part somewhere letting air in and therefore preventing coolant circulation.

A good second possibility is a failed thermostat. Just because you can move it, doesn't mean it will open when hot. If you are unwilling to spend $10 for a new one, at least put your existing one in a pot of water and heat the pot. See if the thermostat opens before the water starts boiling.

A clogged radiator is rare, but possible. (Has stop-leak or similar ever been used?)
The impeller on the water pump is plastic, so it could have broken, but that is rare. (Fortunately, it is easy to remove and inspect the water pump before buying a new one.)

If you really have steam coming out of the vents (and not just fog from the AC), then your heater core is bad and that's where the air is coming from.

 

[dwenz]

there wasent any visable loss of coolant till I started to bleed it after it over heated.
don't think there stop leak in system
Some times vent hose trickles sometimes shoots a stream 6 to 8 feet
steam or mist only visable for 2seconds
What about aux. Water pump .....will it hold back circulation, is it needed for proper engine cooling.?
Why is heat hotter in regards to cabin heat when rpms are at 2k than idle? Seems like a aux pump or a circulation issue although still over heat?
Could I test pump circulation in some form of hose removal or clear hose

 

[joegr]

Aux pump failure would relate to climate control heating problems. It shouldn't be a factor in such rapid engine overheating as you are describing.

 

[dwenz]

Well you were right again the thermo stat was tested in hot water against a new one and it didn't open at all were the new did. Is the a metal or something inside the center that goes bad? I could easily push open but it didn't in boiling water. Thank you guys!!

 

[joegr]

Usually, there is some kind of wax inside that expands when heated. I'm not sure if that is the case here. If it is, it may have leaked out.