2004 3.4 no heat, overheat and sudden cool off

[waterkeeper03]

I was driving along the other night and the car overheated within the first 5 minutes of running but the heater was blowing only cold air. I pulled over shut off the engine but left the key on to watch the guages. after a minute or so the temp gauge rapidly dropped back to normal levels. as if the engine cooled off in 15 seconds. i started the car and the heater worked and drove home no issues.

this same scenario happened three times on different nights. cold nights. day after second occurence I opened the radiator to check to see if coolant was low and it actually started spilling out all over the ground.. car was level. I left it alone and have been driving on it ever since.

car temp remains normal most days, other than this random sudden over heating and sudden cooling off.

any ideas?

[aleekat]

Sounds like your thermostat is sticking shut. Really should replace it before you overheat your engine.

[Ed_Strong]

Did you check the coolant level while the engine was still hot? Or did you wait for it to cool before removing the cap on the degas bottle?

First paragraph leads me to think low coolant level!

Second paragraph leads me to think there a restriction or blockage on the coolant flow?

Seem the thermostat on your engine is calling it quits

[Tech II]

Should never open the radiator cap, when engine is warm or hot....the system is under pressure.......can get scalded.......

Best way to check is first thing in the morning.....look at the level in the reservoir(there is a cold level mark on the reservoir)......then remove the radiator cap to see if it is full.....

from the sound of it, I think you are low on coolant, causing an air pocket to form in the top of the engine.,.....this can prohibit flow through the heater core, causing cool/cold air, even though the temp gage is high.....

Could have a leak externally at the radiator, hoses, water pump, heater core, or there could be an internal leak at the head or head gasket or the lower intake gasket(which could also leak externally).....

My money is on the lower intake gasket......this is a $500-$800 jo, depending on where you live, and who does the work......the price is just a heads up....

Should have a pressure test done, to see if you have an external leak.....

The lower intake usually puddles under the throttle body on one side of the engine, and under the PS pump on the opposite side.....

You do not want to neglect this......overheating the car is not good for the head and gaskets, and if coolant gets into the oil, that is not good for bearings in the engine....

Have this checked out right away....

[waterkeeper03]

I opened the cap the morning after while the engine was still cold.
I never let the car over heat but it got hot really fast and I shut it off immediately. i know when I see it get to the 3/4 mark I kill it and roll to a stop.
what I don't get is the miracle action where it cools off after 1-2 minutes. how can it drop from 200+ that fast while shut off and the heater suddenly work when I turn it back on? i know the heater doesn't work when the coolant is low, but the coolant overflowed on me when I opened the cap..


the throttle body side of the engine is clean and dry.
the side behind the water pump is another story.

what says "new wet spots" i simply don't remember being like that before. could be wrong.
http://i.imgur.com/WiwWTJx.jpg
http://i.imgur.com/D9NkXY7.jpg
http://i.imgur.com/WUAdnST.jpg
http://i.imgur.com/fZXfNcw.jpg

looks like a nice chore to get to the thermostat on this thing too....

[j cAT]

I agree with others this is the thermostat sticking closed. with this I would do coolant flush and replace the thermostat with one that has a guarantee. if this continues I have seen the radiator plastic tank crack when the thermostat pops open .

could also be and I have seen this ,,,the coolant concentration is not sufficient this also will cause the thermostat to stick closed.