New thermostate and water pump, and coolant temp sensor. engine overheating

[moraljor000]

all coolant was drained before installing any parts, filled after.
Hot AC running. (blows room temp)
both heater hoses are hot and hard to the touch.
both top and bottom radiator hoses are cool untill the engine reaches 240+ then they swell and feel hot to the touch.
checked radiator flow by filling coolant from the top hose and watching it come out the bottom hose.
coolant ressiviour is bubbling almost like its purging air.
over flows when it gets past 240 F.
thermostat is rated at 187f


not sure whats keeping the coolant from making a full cycle here. please help super confused this is a 2006 chevy tahoe 2wd ff 5.3

 

[strutaeng]

Tell us about the history... Was the engine overheated at some point prior to this?

 

[moraljor000]

Tell us about the history... Was the engine overheated at some point prior to this?

first time i notice this became an issue i was driving down my normal commute, just had it start reaching high 240+ i stopped and let it cool till i finaly got it home. tried not to let it get past 250.

not to my knowledge.only owned by my family for 10 years no issues. done lots of changes ourselves.

 

[rockola1971]

Cooling fan(s) electric or mechanical? Once temp gets to around 190 deg, squeeze upper radiator hose with thumb and index finger. Can you feel pressure pushing outward on your fingers? You may also have a blown head gasket which would cause coolant to bubble like crazy. Could also be a trapped air pocket in your cooling system that is keeping coolant from flowing.

 

[moraljor000]

Cooling fan(s) electric or mechanical? Once temp gets to around 190 deg, squeeze upper radiator hose with thumb and index finger. Can you feel pressure pushing outward on your fingers?

electric fans
i will check back on what temp the lines really start to swell and get hot.

 

[rockola1971]

electric fans
i will check back on what temp the lines really start to swell and get hot.

Are cooling fans coming on at all? The upper radiator hose should be pushing outward on your fingers as you squeeze once the thermostat opens up. This shows you that it is opening up and coolant is flowing. Also on a cold engine, start it up and see if you immediately have a large amount of bubbles in the radiator while looking down the neck with radiator cap off. You could also notice exhaust gases rising out of the radiator which both mean you have a blown head gasket.

The engine temp should take a fair amount of time to raise enough to open the thermostat. If it rockets to 200deg and more really fast then you likely are superheating the coolant via a blown head gasket and those exhaust gases will raise your temp fast.

 

[Marky Dissod]

Did you burp the air out of the coolant?
If you fill the coolant too quickly, air pockets get trapped in the system.

Try to raise the nose of the vehicle slightly, then burp the air out of the coolant.

 

[S33k3r]

Do you have cheap, easy access to a replacement thermostat? You could have a blown head gasket like everyone else is suggesting, but it also sounds like your new thermostat is not performing correctly.

 

[strutaeng]

I've never had issues on these engines trapping air when replacing parts on them. They seem to self-bleed out the air by themselves.

The thermostat you can dunk in an old pot with boiling water and watch it open. It's a slow action, but you should see it.

Maybe you got a faulty water pump and it's not circulation the coolant? Not sure how you would test that?

I once had a heater core quick connect break on me and my truck almost got to the last red mark. Luckily, no blown head gaskets.

You can either get that kit that tests for combustion gases in the coolant or try that coolant pressure test kit to see if the system holds pressure, as further tests if nothing else works

 

[afpj]

I may have missed something here, but are you on the original radiator? How many miles? If replacement, what brand?