schmendog

iTrader: (10)

This is on my friends equinox, not my GTO but if you can help please do.


What I tried:

New thermostat
New belt tensioner
New belt
New coolant temp sensor
Verified fans kick on at correct temps
No external coolant leaks
Correct mixture of coolant/ Distilled water
Bleed air from system multiple times (jacking up right side/ thermal cycling engine)
Engine oil looks fine (changed recently)

Symptomes:

Warms up to operating temp
thermostat opens fine at 195 (verified temp drop with scanner)
temp drops to 180-ish
goes back up fluctuating between 190 and 210 for about 10 minutes
It will do this fluctuating quite a bit, sometimes getting up to 220, then drastically drops 20 to 30 degrees within 10 seconds or less (air bubbles going by temp sensor??)

Test drive:

After bleeding out air in the system, I take off and car drives fine for about 20 minutes, then all the sudden starts slowly climbing.
heat turns cool after a little bit and temps climb to 240 or 250 (fluctuates up and down between 210 and 240 usually)
Sometimes the temp drops 40 or 50 degrees within 10 seconds while driving.

Car bellows white smoke even after warmed up (hard to determine if it smells sweet or not)
Getting Fuel lean code (Cyl 1), Cylinder 1 misfire code
During overheat engine studders and idles poorly
during overheat, resevoir tank spits coolant out the overflow tube slowly abd i can hear what sounds like air moving through the heater lines.

Summitracing

Your friend’s symptoms sound like a head gasket failure due to the poor performance. Take a prong style retrieval tool holding some clean paper towel and run it into the cylinder through the spark plug port. If you are getting a lot of fluid into the combustion chamber it will be evident on the paper towel. This is also a good time to check the plugs to see if they are getting “steam cleaned”.

joecar

A block test kit can be used to detect combustion gases in your coolant.

mezzyshreder

Thick white smoke is the engine burning the antifreeze that slipped info the cylander by sneaking past the head gasket. That would surely indicate a blown head gasket.