Well I think I pushed not repairing the lower intake gasket, as suggested by many of you, to the limit. I started it yesterday and had a loud THUNK followed by some serious tapping. A co-worker thinks the connector rod bent which is slapping the cylinder wall producing the noise. I had everything ready to do the gasket this weekend, b ut now I'm in limbo as far as what to do? Would a mechanic go through all teh trouble of tearing the engine apart to replace one rod? I was told the whole engine would have to be rebuilt and if so time for a new truck. Any inputs?

Dale

PS; The advice given by everyone here was not ignored, but I just didn't have the time (due to working 12hrs/6 days a week).

 

How many miles are on the truck? Is it in good shape? Maybe you can get away with installing a crank kit and replace any bent rods.At the most,you'll have to put out about $3-$4k for a new engine,or about $800-$1000 for a crank kit.All include labor............OR.............
you can buy a new truck and have a truck payment each month........

 

Sorry to hear of your bad luck.

A few year sback when I had my gaskets replaced, the shop who did my work said they had redone several just replacing the bent rod and addressing any other damage done.
Everything else was left as-is.
He said when they put them all back together, compression and leak-down tests were fine and the engines seemed to be OK and ran fine.
I believe the suspect rod can be change from the bottom end, so that the entire engine does not have to be disassembled.

If you like your truck, I'd look at having it repaired.
A few grand is waaayyy less than a new truck.

 

The shop I called about the gasket repair said they used to replace connecting rods but stopped (said a lot of shops had) for some reason. The only reason I asked him about the gasket was to see if he would try to bend me over but he quoted $400 which was what you guys said it should be (approx) so I trust the guy. He said he could put in a new Jasper with 3yrs/75K mile warrenty for $4000-$4500 total. Now to me this sounds like the route I may take because I do want to keep the truck and do not want a 5yr note to pay on a new one. Decisions, decisions...

 

How do you know that it has a bent rod? You have not really tested to know for sure. A bent rod would NOT likely hit the cylinder wall. It would have to be REAL bent to do that.
If you hydrolocked, then you tried to compress coolant in the compression chamber. It generally happens after you park, and the coolant leaks in and fills the cylinder, maybe just partway. You try to crank, and the starter cannot compress the coolant, so the crankshaft stops and the starter either gets hot from trying to turn over the engine, or you let go of the key.
Did you do a compression test? Is the tapping high or low on the engine? A bent rod could be silent or could be loud depending on how much it bent and in what direction. Some of the 4.6 engines bend rods and just have a lopey idle because the piston does not come up high enough for good compression. They run, but are slightly weird.
The price for a rebuilt of course depends on location, but it sound hi to me. I'd suggest looking in a boneyard for a used engine, but that depends what shape your truck is in now. I'd figure about 1 days work to swap, so 8 hours X the going labor rate. Or rent a crane and do it yourself...
tom

 

I kinda agree with tomw's theory. I'm not convinced you have a bent rod if the motor still runs. I think some more investigation is in order.

 

I have 2 friends that own Ford products with the 4.2;one is a 98 E-150,the other a 97 F-150.Both engines hydro-locked and both engines bent #4 rod.I heard each engine running after they hydro-locked and it sounded like 90lb jackhammers.When the oil pans were removed to re-install on the new engines I "SAW" the bent rod! And yes,they were bent bad!I've seen post' and pics on other websites where the rod actually broke and went thru the oil pan!

 

I guess that answers that, it'll run with a bent rod. And I thought there was some reason for optimism...

 

It still doesn't satisfy the question of whether it IS a bent rod. Deville needs more investigation if he wants to know for sure. They can bend has been determined. Did he bend one of his or not has yet to be determined. (without a little bit of doubt, anyway)
tom

 

I have seen and repaired a couple dozen of these 4.2 V6s with bent rods. The 4.2s have a long rod that is not verry strong. When they stroked the 3.8 to make the 4.2 the piston at bottom dead center is verry close to the fly weight on the crank maybe only .015 to .020 of an inch. When the cylinder hydrolocks the weak rod bends easy. It only has to bend a little and the piston will hit the fly weight on the crank when at the bottom of its stroke causeing a loud knock. It can be repaired but it is a labor intensive job. The oil pan and the head on the affected cylinder bank will need to be removed to change the rod and most likely the piston.
Good Luck!

 

Well I appreciate all teh posts, and I probably do need to know for sure if the rod is bent or not. The "jackhammer" sound is hitting what I hear right on the head, so I'm still leaning that way. However if a compression check will let me know for sure I'll do that first although I am running out of time since I am renting a car (weekly) until I get my truck fixed, and I DO WANT to keep my truck. I've said before in other posts that I am not a master mechanic and hev never done a compression check before but now seems like the right time to learn. Any suggestions/comments/do's-don't-s I should know about?

 

Pull all the plugs out, lock the throttle wide open and with the compression gauge screwed into a spark plug hole, crank the engine over till it hits on compression three times. You can hear the starter slow down as the cylinder comes up on compression. Read the gauge after the third compression stroke.

Good Luck