Fredness
Elite Explorer
- Joined
- June 2, 2000
- Messages
- 722
- Reaction score
- 75
- City, State
- Tejas!
- Year, Model & Trim Level
- '05 Sport Trac Adrenalin
So, the Sport Trac is 5 years old, but we've had it for a year. After a failed left front hub, and the trans going south, I've decided to start from scratch with the maintenance/routine.
So, fluids were first.
The oil, trans, transfer case were recent, now the coolant.
While testing, I noticed that the reservoir was full of "gold" (Motorcraft Premium Gold-ish), but the radiator appeared to be clear. It felt like coolant (viscous/slippery), but the color seemed off. When drained, the radiator was VERY light green, like cheap old school coolant.
This frightened me, knowing that the "Gold" isn't supposed to be mixed; I decided to flush the system and change the coolant. I used a multimeter to test for stray AC voltage between the coolant and the block. On the Focus, it was .172v after 5 years. Good, but I decided to flush the system to change coolant. Now, the Sport Trac was .3v - indicative of electrolysis. This can eat a heater core or radiator in as little as 7 days (.5v or higher).
Since I found some research that suggests it could be a ground issue, I thought I'd check. The Focus (as a control) was ~2 Ohms from Battery to Chassis and ~3 Ohms Battery to Block - acceptable.
The Sport Trac? How about 5 Ohms to the Chassis and 25 Ohms to the Block? WTF?
O.K., something's up, let’s check some other points, like the shield for the PCM harness, that should be 2-3 Ohms, right? How about over 40? The PCM to Chassis Ground? 63 Ohms!!! Wow...
So, now we know something’s wrong for certain!
I decide to do some research on grounds. I wanted to clean all the connectors, bolts, washers, scrape the paint to the ground points and reassemble with Dielectric Grease. I chose to connect all the grounds to a single "Daisy-Chained" path using the Ford Service Manual to locate all the major grounds. With 8 and 4 ga high Silicone Copper stereo power cables, I crimped, soldered and heat shrinked the ends as needed. I started at the PCM ground (near the PCM), then to the PCM Harness shield (at the wiper motor) and wanted to go to the main ground on the block, but couldn't find it. Ford shows it near the engine harness connector, but no luck. For ease of routing/mounting, I chose to go to an open bolt hole on the AC/PS bracket - all with 8 ga. From that same spot, I took 4 ga to the Battery and from the Battery to the Chassis. From there it is 8 ga to the ABS/Horn/Lighting ground behind the Battery.
What about the Ohms to ground now? How about 2 Ohms to all points? Yeah, that's better!
...and the stray AC voltage from the coolant in the radiator to the engine block? <.001 volts. It doesn't get any better...
PCM starting point...
PCM starting point during...
PCM shield was next...
PCM shield finished, with PCM Gnd to the left (dotted lines show path)...
All the ground wires were corroded, rusted or worse...
Radiator Brace and behind Battery...
All finished, one ground path start to finish.
Here's the layout.
So, fluids were first.
The oil, trans, transfer case were recent, now the coolant.
While testing, I noticed that the reservoir was full of "gold" (Motorcraft Premium Gold-ish), but the radiator appeared to be clear. It felt like coolant (viscous/slippery), but the color seemed off. When drained, the radiator was VERY light green, like cheap old school coolant.
This frightened me, knowing that the "Gold" isn't supposed to be mixed; I decided to flush the system and change the coolant. I used a multimeter to test for stray AC voltage between the coolant and the block. On the Focus, it was .172v after 5 years. Good, but I decided to flush the system to change coolant. Now, the Sport Trac was .3v - indicative of electrolysis. This can eat a heater core or radiator in as little as 7 days (.5v or higher).
Since I found some research that suggests it could be a ground issue, I thought I'd check. The Focus (as a control) was ~2 Ohms from Battery to Chassis and ~3 Ohms Battery to Block - acceptable.
The Sport Trac? How about 5 Ohms to the Chassis and 25 Ohms to the Block? WTF?
O.K., something's up, let’s check some other points, like the shield for the PCM harness, that should be 2-3 Ohms, right? How about over 40? The PCM to Chassis Ground? 63 Ohms!!! Wow...
So, now we know something’s wrong for certain!
I decide to do some research on grounds. I wanted to clean all the connectors, bolts, washers, scrape the paint to the ground points and reassemble with Dielectric Grease. I chose to connect all the grounds to a single "Daisy-Chained" path using the Ford Service Manual to locate all the major grounds. With 8 and 4 ga high Silicone Copper stereo power cables, I crimped, soldered and heat shrinked the ends as needed. I started at the PCM ground (near the PCM), then to the PCM Harness shield (at the wiper motor) and wanted to go to the main ground on the block, but couldn't find it. Ford shows it near the engine harness connector, but no luck. For ease of routing/mounting, I chose to go to an open bolt hole on the AC/PS bracket - all with 8 ga. From that same spot, I took 4 ga to the Battery and from the Battery to the Chassis. From there it is 8 ga to the ABS/Horn/Lighting ground behind the Battery.
What about the Ohms to ground now? How about 2 Ohms to all points? Yeah, that's better!
...and the stray AC voltage from the coolant in the radiator to the engine block? <.001 volts. It doesn't get any better...
PCM starting point...
PCM starting point during...
PCM shield was next...
PCM shield finished, with PCM Gnd to the left (dotted lines show path)...
All the ground wires were corroded, rusted or worse...
Radiator Brace and behind Battery...
All finished, one ground path start to finish.
Here's the layout.