I finally switched my fuel pressure gauge to the coolant reservoir (degas bottle). The objective is to see what typical pressure is in the reservoir and what effect, if any, a series of WOT events has on the pressure.

Here is my data:

Since the system was opened for the installation, the pressure after installing the gauge was 0 psig (calibration check).

Began drivingwith ambient temps around 34*F. Coolant temperature rose to 120*F before I saw 1 psig on the gauge.

As the temperature rose to 190*F, the pressure steadily increased to 6 psig.

After oil temps stabilized, the pressure stayed at 7 psig.

First WOT run - the pressure rose to 9 psig.

Within 10-15 seconds after the WOT run, the pressure dropped back to 7 psig.

I did a series of 4 back-to-back WOT runs and each time the pressure rose to 9 psig except for the last one and it "flickered" like it was almost at 10 psig.

Just as before, the pressure dropped quickly back to 7 psig every time.

The initial pressure rise was "as expected" as the coolant heated up and expended. The extra pressure during the WOT events was slight and also not un-expeced. It seems to me that there was no generation of any appreciable non-condensible gas since the pressure readily returned to the base state of 7 psig.

 

Did you happen to notice your ECT at the end of the WOT runs?

 

Didn't move much. It was cold enough that my ECT's were stable at 185-187 before the WOT's. Maybe hit 190 during the WOT runs and then dropped back down the 3-4 degrees.

 

After a week of operating w/ the degas bottle pressure gauge, I am moving it back to the fuel pressure service.

The data in the last week has been essentially identical every day of driving. I will say that my baseline measurements did shift up by one psig (the only change I saw). The initial 7-8 psig at operating temps shifted to 8-9 psig. I assume because my degas bottle is not dropping back completely to zero when it cools. The way it behaved on every WOT was identical to what was previously described (except shifted up 1 psig). I verified that the system is holding pressure by watching the pressure reading every 15 minutes or so while it sat cooling off. The pressure profile looked the same (in reverse) during the cool-down as it did in the heat-up. The pressure dropped only in response to the temperature change.

 

vey cool data , I would like to see the results from a truck with known hg issues

 

Are there any pictures of this setup?

 

I just checked mine 12.5 psi

I disconnected my coolant filter on the degas side. Popped a mechanical fuel pressure gauge (0-15) into the coolant hose.

Ambient temp 30F, After a solid "drive" into town (10 miles), no boost over 20 psi, gauge read 12.5psi. Let idle for a few minutes, slight drop in PSI. Did a few WOT tests on the way home and tested 12.5Psi back in the garage.

2 questions,

1st
i did not actually get to watch a "spike" during WOT or heavy boost, but does this seem normal?

2nd
I just finished resoldering my FICM (worked perfectly BTW), so i lost some coolant during RR, i guestimated how much i lost and replaced it. Is the amount of fluid going to affect my PSI significantly? If so can i run more or less and get a more accurate idea on my possible HG situation. Thanks

BTW ect/eot 190/191 during testing (less than 100 miles on fresh oil cooler and sinister EGR delete)

 

Sorry - no pics.

 

I posted this on another thread (https://www.ford-trucks.com/forums/1...eadings-2.html), but thought it may be of interest:I'm not sure if this is "normal" or a bad sign.

 

Just had headgaskets replaced. Here are my plots for pre & post headgasket work.

Post results are similar to what Mark was describing.

Ford Truck Enthusiasts Forums - Scott6.0PSD's Album: Pre-Post Headgasket Readings

 

preheadgaskets I have seen upwords of 30 psi.
just for fun https://www.ford-trucks.com/forums/1...9-08-03-a.html