There are only a small handful of topics in life where I’m reasonably confident in my abilities and knowledge, and one of them is automotive. Whether it’s the mechanical bits, performance terminology, or just about anything else short of actual track time, I feel like I generally know my way around. I guess after a string of successful mechanical rescues you begin to believe you can really fix anything (and that fixing it is worth the investment in both parts and labor). Well, I’ve just been served a big, steaming helping of humble pie. And the flavor? 4.6L Ford.
My Diagnosis Was Incorrect
In the last post, I was convinced that the atrocious knock in this F-150’s 4.6L v8 was caused by a timing system failure of some sort. My wife and I bought all the parts (new chain guides, chains, tensioners, the whole shebang), then installed them whenever our newborn allowed us to.
After all that effort, we started it up and…the knock persisted. Damn.
So what else could it be?
Other Possibilities
I’m no expert, but from my extensive research into this engine I’ve found a few other potential causes.
- Failed wrist pin on one of the pistons
- Bad crankshaft bearing
- Engine demons
At least two of these things mean either:
- A ton of time and money to tear the engine down to the bare block, take it to a machine shop, then fit a new piston or bearing
- Grabbing a big ol’ cup of nope while reading number 1, get an engine from a junkyard and hope for the best after the swap
Neither of those options are particularly appealing, especially when you take into account that it could be something totally different that I didn’t think about.
What to do, what to do…
I Gave Up
I’m not a proud man.
We realized that, given our current pace of work, it’d likely take us until the end of the year to get this truck back on the road for our family member. And remember, this family member uses his trucks everyday for hard work and is currently down to only 1 vehicle for his job. The longer we have this truck, the longer it’s not on the road being used for work.
Also, this F-150 has almost 450,000 miles on it and has been through 3 engines and as many transmissions, so it’s not exactly a spring chicken.
So we decided to just put the truck back together, apologize to our family member, and have them pick the truck back up with our tails between our legs.
After Action Report
It turns out that, even with the best of intentions and an ample supply of tools and parts, at the end of the day some things are just not worth fixing yourself. This is the first time I’ve come to this conclusion and it’s a hard pill to swallow.
Luckily for us our family is awesome and he’s planning on just selling the truck instead of putting a ton more money into it for a replacement engine. Doesn’t seem too torn up about it and is now eyeing some gently used vans to take over some of the lighter-duty work.
We’re disappointed we couldn’t fix it for him but I guess at least we tried?
Out of My Element 