Car was over heating and spilled out the overflow tank.'

1. Did block test and no exhaust or gasoline fume present in coolant system meaning head gasket is good.

2. Took t-stat out and boiled it and it opened.

3. Coolant hoses. Top is hot. Bottom is cool. Both are firm at normal temp.

4. Flush coolant system and refilled with head of car on jack.

5. coolant still spill out overflow tank and car eventually over heats. Fans do not engaged AND coolant from overflow DOES NOT get sucked back in when engine cooled down.

6. replaced cap with one from Advanced Auto.

7. No more spilling from overflow tank, BUT hoses are hot. (Top is hotter) Fans engaged! Coolant in overflow tank gets sucked back in when engined cooled down.


This puzzled me. with the new radiator cap, both radiator hoses are soft and easily squeezed with 2 fingers when engine is running at operating temp. (temp gage in middle).
Also with CAP off, i constantly see bubbles bubbling out like every few seconds when car is warmed up @ idle. Watched it for about 10 mins. Revved engine and coolant spills out. Bad head gasket?

???? normal ??? No over heating..

 

Sounds like a bad head gasket. Get radiator completely full, then start engine cold with the cap off and rev it. If bubbles / coolant coming out, head gasket is bad. There should be no action in the radiator with the engine cold.

 

It looks like everything is now normal except for the bubbles - no overheating, no coolant burping out of overflow.

mk378,

Could that indicate some residual air pockets that were never fully purged?
If the head gasket is blown, wouldn't the engine overheat or blow white smoke out the exhaust?