dryhero

Searched topic before posting, sry if this is a duplicate. Son and I, purchased '08 4.6 L Shelby conv (w/K Bell SC) last summer. 102K on odo. Have tried to resolve this by scouring the internet, but I'm out of ideas.

ISSUE:
Since purchased, when driven from cold and brought up to operating temp, it usually will do fine. You can drive it for an hour, OBD reader engine temp stays in 190-194 degrees.
- However, rarely the temp gauge will instantly spike to into the red, and then just as quickly go back to normal.
- Most often the issue sporadically shows itself after your park the car for 10 - 20 minutes. When you start it up again, after 20 seconds - 2 minutes(ish), sometimes the cluster temp gauge and an OBD reader will very quickly jump to the red, sometimes putting car into limp mode.
If you shut car off and promptly restart, the temp usually is at "normal" again (190ish).
- On very rare occasions car will not heal itself and has to be left to cool down
- Temp can also peg into the red for a few seconds and return to normal with the car running the whole time.
- Sometimes the car will run without issue for weeks (approx. 50-100 miles/week)
- The other day the cluster temp gauge dipped to 0 for just a second, back to normal, into the red, and back to normal. Only observed this a couple times.
- The cluster gauge and OBD temp don't always agree, with cluster gauge lagging by a few second.
- Rarely the cluster gauge and OBD temp won't agree, one will show a spike 200-240, the other shows "normal"
- This is the only symptom we can most often (not always) reproduce. With a warm engine, after about 10 seconds under mild aggressive highway acceleration, OBD temp often will instantly spike. Cluster gauge usually isn't fast enough to react. Temp instantly returns to 190ish a few seconds after taking foot off accelerator.

OBSERVATIONS:
- It doesn't do this all the time. Just often enough for me to trust it again. It can go weeks without any issues, but then back to unreliable. I want my son or wife to be able to take it out, have fun and confidence, and not get stranded in traffic.
- We not loosing coolant
- Thermal camera confirms coolant leaving radiator is definitely cool, barely warm to touch. Coolant entering radiator is hot.
- Coolant appears clear, bright (orange in this case)
- Coolant passed our own combustion leak test, didn't detect combustion gasses in coolant (could try it again?)
- Oil filler cap is clean, clear. Oil on dipstick isn't milky
- Do not observe white smoke


ATTEMPTED SOLUTIONS: in order
- New thermostat, 170 degrees
- New GT 500 fan (fan wasn't running at high temp)
- During fan replacement we discovered the melted fuse block connection under fan relay. (Repaired connection, we thought YES! But no)
- Replaced water pump
- New coolant, with some water wetter
- Replaced upper, lower radiator hoses (Mishimoto)
- 2X,did our best to burp air from system as much as possible (hot engine, steep incline, alternating low to 3000 rpm cycles, aggressively squeezing hoses during process), Did liberate some air
- Brought in an old priest and a young priest

PISSING IN THE WIND
- Head gasket leak? Ugh
- Air bubble left in coolant system?
- Bad engine block temperature sensor?
- Bad ground? (all other gauges appear to work as intended)

Any feedback, wisdom appreciated. Thank you in advance!

05stangkc

Sounds Electrical Not Mechanical if Temp Can Change So Dramatically Either Way. Certainly Replace Sensors With Oem Parts To Eliminate That Posability.

https://www.fordpartsgiant.com/parts...&filter=(39430)

Punch in Vin To Be Sure on Part Number.

Shows Different Number By Engine Tag Number.

Cooling System Shop Manual PDF Below!

https://www.fordpartsgiant.com/parts...tml?pnc=12A648


KC

dryhero

Thank you!

05stangkc

You Are Welcome!

Just Posted Sensor Locations Pdf as Well!

KC