jlbe

1997 F150, 4.2L, 5 speed, 88,500 miles. Have tried searching the forums but haven't been able to find a similar problem.
I have had the truck for 4 years with little problem (other than a leak where the line goes into the bell housing from the master cylinder). Two days ago when I went to start it in the morning, it kicked back like low voltage/bad ground but then started on the next try and also started fine a couple of times later during the day. Yesterday morning it started OK but had a slight miss and diminished power. I should add that where I work is only a 2 mile drive and it seemed to somewhat come out of it and run a little smoother. I hadn't changed the plugs in awhile (year +) so made a mental note to change them and to check the battery connections.
Noon that day I was going to go home for lunch and when it started (no hesitation), a LOUD clatter/rattle came from under the hood-my first reaction was that the fan was striking something so I shut down immediately and checked-nothing. I left the hood up, restarted it and got out to check-a very loud, fast, metallic and steady noise and seemingly from the passenger side. Shut it down and drove my boom truck home.
After dinner, a friend stopped by the yard (also an F150 owner) and I talked to him about the problem and also started it so he could hear the noise. His reaction (as was mine at the time) was a rod.
After thinking about it for awhile (it didn't seem likely that a rod would just "go out" at start up) I began putting the events of the last couple of days together and it occurred to me that possibly the timing belt (chain?) had "slipped" and that a piston and valve were trying to be in the same place at the same time.
So my questions are;
1
Does this sound plausible or is it something else?
2
If this is the problem, I am going to assume that at the very least the valve(s?) and piston(s) will need
replacing-I have some mechanical experience but it is definitely of the "old school" variety-classic Brit bikes & 1980 Dodge slant six-I have hand tools and a shop-is it plausible for me to attempt this myself or should I bite the bullet and let a professional do it?
3
Or, since the engine ran for 30-40 seconds in this condition, just get another engine (used, rebuilt or ??) and let a shop do it?

Any suggestions, comments much appreciated.

Kattumaram

...hard to diagnose the trouble with the description you have presented. The cause(s) won't be known until you take the engine down and assess the damage; subsequent damage will then determine whether you rebuild or replace. A rebuilt from Ford Engines is ~1800 bucks.
http://www.psengines.com/FORD6.htm

A rod cap can let go at any time, but the noise is generally a loud, solid knock that, once started, does not go away. A broken rod generally blows a hole in the block....can't miss it. A related failure would be a spun rod-bearing insert; that would rattle like hel* and possibly impact the valves.

A broken valve spring or spring retainer is a possibility. Maybe a rocker stud has let go or a push-rod has slipped its moorings. A remote possibility is a broken roller lifter. Any of those conditions would cause a missfire on that cylinder.

A timing chain expiring at only 88K+ miles is unusual, but not impossible, but the engine would not run at all and many of the valves would be bent.

kingbrian

other than the noise how is the truck running? is it smooth or missing? backfiring? a video might help.

TheJMC

The 4.2 head gasket tends to leak allowing coolant into the cylinder. What you experienced was hydro lock. Liquids do not compress very well. Something had to give. Usually the rod bends. Time for a rebuild.


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