2.3L ('02-'11) Degas Bottle Keeps Overflowing

[toddro]

Hello All,

Hoping I can get some insight as to why I keep jetting coolant back into my Degas Bottle and seeing it spill over after I shut off my engine. Here is the detail on a 2002 XLT 2.3L 2WD with about 223,000 miles

• Noticed this after a flush/fill, so I replaced thermostat (Stant) and top/bot rad hoses (AC Delco). Bled system as best I could with new 50/50 green coolant.
• New degas bottle, new cap (Motorcraft 15psi)
• Checked radiator with laser thermo shows it even temp across its surface, no hot or cold spots
• Fire up engine and read ECT on scanner. Temp will rise to about 220-221 while driving (AC on and it is very hot outside). After about 15-20 minues of driving ECT will drop to 195-200 and stay there for rest of my drive. If I turn off engine at this point everything is fine.
• If I drive the truck for less than 15 minutes and turn off the engine while ECT is still in that 220 range, I get a bunch of coolant jetting back into the Degas bottle and it will overflow a little bit.
• Block test kit ordered and on the way, coolant and oil both very clean...

temp gaugh never goes high, ECT on scanner never goes above 221, heat works well on cold start and idle up, ac blows ice cold, heat blows nice and hot, system is not overfilled (just below "MIN" line on cold start), truck runs great...

Any ideas? Thanks in advance - great forum here!

 

[rubydist]

220 is higher than I would want, it seems like the new thermostat doesn't like to open and takes a long time to do so. I would change the thermostat again...

 

[Uncle Gump]

I'm gonna agree with the above... thermostat takes it sweet time getting open.

I think I would also test the "new" radiator cap. It shouldn't blow coolant to the tank if it will hold 15psi.

Maybe try putting the cap you replaced back on.

 

[pjtoledo]

long shot: look at the exhaust manifold runners with the IR thermometer, see if one is running
much hotter than the others.
what is the cylinder head temperature?

ditto on the cap not holding pressure. the degas bottle/cap also holds pressure.

 

[toddro]

Thank you for taking a look here. Update - I put in a thermostat for a 2004 (no electric control) and plugged the plug with a resistor. Temp holds nice and steady now at 205ish on a really hot day with AC running. No CEL with the resistor plugged in.

I also checked the engine with a Reld block tester kit - ran the engine alternating revving it and idling it for 10 minutes and then let it sit for 5. Fluid was as blue as when I started…

The tank still fills up with coolant when I shut off the car but I’m just gonna run with the coolant down about 2-3 inches below min (cold engine) and keep an eye on the ECT reading to make sure it doesn’t climb high.

not sure what else to do at this point…

 

[toddro]

I wanted to come back with an update in hopes this may help someone with the similar issue. I got a lot of scary advice - get a new water pump, a new radiator, or replace your head gasket. This turned out to be stubborn air trapped in the system. I used a pressure tester to pump up to 16psi, released pressure, started car, revved to 2,500rpm, shut truck off, and repeated 3 times. Problem solved with no reoccurrence. I tried everything to bleed system and this is what worked. Next time I will fill it under a vacuum - cheers.

 

[SenorNoob]

How do you pull a vacuum on the cooling system?