Started Engine Swap, now Not so Sure

[FordNut]

One of the Marauders developed a knocking sound, so I figured it was a rod. Set out to swap the engine with the spare long block I have on standby. Just got the "bad" engine out and found that the flex plate has a crack all the way around the bolt circle where it connects to the crank. So now, what to do? Assume the problem was the flex plate all along, put a new flex plate on it and re-install, or go ahead and swap engines. It' a low mileage engine, didn't use oil or miss and actually ran better than any of the other stock ones in my stable, so I've had a hard time thinking the engine was toast this soon.

[Black Terror]

I would replace Flex Plate on original engine and reinstall, chances are pretty good that Engine was not the knocking sound. Hope this works out for the best, which car was giving the problem?

[blazen71]

New flex plate and put original engine back it. A cracked flex plate will absolutely make a knocking sound.

[Joe Walsh]

Yep,
Towards the end of my 5.0 DOHC's life, it was making a light knocking noise towards the back of the engine.
I thought "UH Oh! a rod is going bad."
When I pulled the engine due to its ultimate demise (the block had cracked between cylinder #1 & #2 because of sleeved 3.700" big bore....with low compression in both cylinders!) and started disassembling it, I found that ALL of the flex plate bolts were loose!
The flex plate could move just enough to make that knocking noise.

[offroadkarter]

New flex plate and put original engine back it. A cracked flex plate will absolutely make a knocking sound.


^^^^ 100% agree with this, I swear I remember a few people on this forum having this happen in the past

[FordNut]

I would replace Flex Plate on original engine and reinstall, chances are pretty good that Engine was not the knocking sound. Hope this works out for the best, which car was giving the problem?

The newest one, the '04. After a little internet searching, it sounds like it's not uncommon. New flexplate and re-install is my new plan.

[FordNut]

Got it back together with a new flexplate, noise is gone!

[blazen71]

I love it when a plan comes together!

[burt ragio]

Interesting, any idea why the flexplate cracks or the bolts come loose ? Constant stress Flexplate Deflection ? No Loctite ? Not balanced ?

[FordNut]

No reason I can tell. Some of the bolt heads on the torque converter and exhaust system showed signs of prior removal so it's not as I was told when I bought it. You know the story, never been apart, all original, never been wrecked, etc. And one of the alignment dowels between the block and transmission was missing, so that could have contributed.

[blazen71]

My guess would be a random flaw in the material. The mills producing the sheet that the flexplate is stamped from do test the material but its more of a "generic" Ultrasonic test that may not catch every flaw. But it really could have been a plethora of reasons which are moot at this point. Problem is solved and Brian's back on the road!

[Joe Walsh]

Got it back together with a new flexplate, noise is gone!

Nice!
Glad it worked out.

[Peace2Peep]

That's awesome! Great troubleshooting!!!!