Coolant bled, still running warm

[JoshMcMadMac]

I have a 2005 V8 LS. I had noticed that the radiator fan was running at full speed when I would park it, even though the temperature gauge was in its normal location. Using my scanner I found that operating temperature was getting to 235-240°. The degas bottle was a little low, so I topped it off and that resolved the issue for a few days. Once the fan started running high again, I looked harder and found that the plastic portion of the upper radiator hose was weeping. I replaced it, and have bled the system verbatim to the shop manual more than once to no avail. I have bled the system before without incident. The heater is running nice and hot. I am not convinced it is an "overheating" issue, as the car seems to be stabilizing right at 235° no matter what...I can idle in the garage forever, or drive down the interstate at 60MPH in 30° ambient with the heat blasting and it makes no difference. Are there any tips or tricks that I am missing?

 

[joegr]

I would very strongly suspect that you have other plastic parts weeping. It's time to replace all the plastic parts at the front of the engine, the lower radiator hose, and the degas bottle. The system is probably not fully pressurizing.

 

[JoshMcMadMac]

I would very strongly suspect that you have other plastic parts weeping. It's time to replace all the plastic parts at the front of the engine, the lower radiator hose, and the degas bottle. The system is probably not fully pressurizing.

I was thinking that, but the coolant loss has stopped. Also if I run the system without the cap on the degas tank, it remains at a more reasonable operating temperature.

 

[joegr]

You may (or may not) find that the plastic holding the thermostat together has cracked inside and that could be altering how the thermostat works. I'm sure there are other possibilities too, but I'm just shooting at the common issues. I doubt that you are an exception to the "most of the plastic starting to fail at about the same time" rule.

 

[LS4me]

You may (or may not) find that the plastic holding the thermostat together has cracked inside and that could be altering how the thermostat works. I'm sure there are other possibilities too, but I'm just shooting at the common issues. I doubt that you are an exception to the "most of the plastic starting to fail at about the same time" rule.

Odd...... My upper radiator hose failed a couple of years and about 30K miles ago...... Nothing else has failed.... Yet....

 

[JoshMcMadMac]

Any idea what pressure the system runs at? 10-15psi like most? I have a spare degas cap from another Ford, I might throw a valve stem on it and see if I can pressurize the system to provoke any leaks. I still find it odd that they system runs normal without pressure.

Also, what is the setting for "too hot" coolant? I would have thought the gauge would be programmed to climb above horizontal by 235°. It is also strange to me that it stabilizes at that temperature.

 

[joegr]

15/16 PSI is the correct pressure according to the manual (it gives a range of 13 to 18 PSI as acceptable). When I tested mine, the cap vented at 15 PSI. I chased a leak for a couple of weeks a few months ago. I couldn't get it to leak on demand at any pressure (didn't go over 16 PSI) or temperature. Still, after driving I would sometimes find some coolant on top of the engine. Worked out to be one of the rubber seals between the crossover pipe and the engine.

Ford and most (all?) other car makers decided a while back that most people were too stupid to understand a real temperature gauge or oil pressure gauge. They found that customers were much happier with gauges that always read dead center. When the temperature gauge goes above the center position, the engine is really in trouble.

I'm not sure how hot is too hot. Coolant should start to boil at about 220 F, without the pressure cap on (265 F at 15 PSI). This assumes sea level pressures.

 

[JoshMcMadMac]

Before I bastardize a cap...how did you pressure test your system? Any suggestions?

I tend to run coolant at a 3:1 dilution, so I get pretty much the same values for boiling that you have. I do find it peculiar that they did not want the gauge to climb before 240°, as that does not leave much buffer before bad things can start happening way too fast.

 

[joegr]

I disconnected the engine air bleed hose from the crossover pipe. I connected a short hose that was plugged at the other end to the crossover pipe. I then connected the open end of the air bleed hose to a compressed air source with a pressure regulator in line. The degas bottle cap actually hummed when the pressure was just right for it to just barely vent. (I did have to put grease on the gasket of the degas cap to get that to seal completely to do this test. I think that normally it does seal all the way after a few days.)

 

[jrand]

good to know; just found a crack in my upper.