Coyote Crank Timing Sprocket Failure

BootsyCollins

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Hi All,

I haven't seen a lot of information anywhere about the stock coyote timing sprocket, other than MMR's posts about their billet sprocket and how they recommend it for any boosted application.


For a bit of background, I have a 2011 Mustang GT with the 5.0 V8 and the MT82 6 speed manual and 77,000 miles. The only modifications that I've made are welded in Flowmaster 40 mufflers and an MGW short throw shifter. I've also replaced the stock transmission fluid with Royal Purple Synchromesh. They really cleaned up the sloppy shifting of the MT82!

Anyway, once the weather turned cold in NC I started getting a CEL, and after pulling the codes saw that the downstream O2 sensors in both banks were throwing catalyst efficiency codes. I ordered new O2 sensors and replaced all 4, but now had another code. There was a P0017 stored in the ECU, and a P0018 pending. Also, at idle the car began making a pretty nasty tick from bank 1. I couldn't wrap my head around what could cause this issue, but I bought the entire timing kit from Ford Performance, including tensions and cam phasers.

I started out by pulling out the factory airbox and the associated plumbing.


Then I removed the coolant reservoir tank, the radiator, the water pump, and the alternator.

Finally I tried pulling off the harmonic balancer. I had a hell of a time getting the thing to come off. I finally broke down and ordered the Harmonic Balancer Removal Tool from American Muscle. It took the harmonic balancer off without any issues. I found that my seal on the balancer had developed a leak at this point.

After taking off the valve covers, I was finally able to remove the front timing cover. As soon as I took it off it was pretty clear what the issue was.

The keyway had torn out of the timing sprocket. It was honestly the last thing that I'd expected to see when I opened up the timing cover. Once I had all the chains removed, I was able to inspect the damage to the key and to the crankshaft.

At this point I didn't have a replacement key, because I'd never considered that it could possibly be damaged. So I replaced the secondary chains, tensioners, and cam phasers, but had to stop before putting on the new crank sprocket and primary chains.

Having access to a metallurgist at work, I took the sprocket and the key in to have him hardness test both components. The key came in at 45 HRC through hardened, and the sprocket was 51 HRC "partially case hardened". I'll ask him for clarification tomorrow on what he means by "partially case hardened".

My biggest questions are:

What caused this? I know that this is a cheap, powdered metal part, but I'm running a low mileage, stock application. It seems pretty unacceptable that I'm seeing this kind of failure this early.

Can I even reuse this crankshaft? I really don't like seeing that kind of fretting across the diameter of it. I ordered some Loctite 660 to try and take up the slop, but I really don't feel very comfortable putting Loctite on a crankshaft. I'm about .002" smaller in diameter versus the undamaged portion.

Thanks for your inputs!
 

MG0h3

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I wouldn't be surprised if you have .002" margin of error between your two factory sprockets, let alone your aftermarket one.

I'd see how the billet gears feel sliding them on. Is the keyway in the crank damaged at all?
 

BootsyCollins

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I didn't word that very well. I don't have .002" of slip between the new sprocket and the crank. The damaged portion of the crank is .002" smaller than the undamaged portion.

The Ford Performance timing kit actually just includes another powdered metal sprocket. I just have the stock sprocket. There's a noticeable increase in the amount of side to side play versus the undamaged portion of the crank, but nothing obscene.
 

MG0h3

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Nah I understood what you meant; inboard portion of the crank is 2 thou smaller than outboard.

Thats a tough one man. I figured you would order the billet gears since this happened already. Maybe you get lucky and it's a little tighter.
 

BootsyCollins

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Honestly, I would have ordered the billet replacement the minute that I saw that the stock part failed had the crankshaft not been damaged. Now I'm wondering if doing so would just be throwing good money after bad and it'll fail either way unless I replace the crankshaft, if that makes sense.
 

MG0h3

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Honestly, I would have ordered the billet replacement the minute that I saw that the stock part failed had the crankshaft not been damaged. Now I'm wondering if doing so would just be throwing good money after bad and it'll fail either way unless I replace the crankshaft, if that makes sense.

Hear what you're saying. Someone else has to have had the same happen and could offer some insight.
 

BootsyCollins

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I feel like I can say pretty confidently that it wasn't. I bought it in 2015 with 26,000 miles, and from everything that I can tell I've been the first to really break into it at all. The only evidence I've found of anything being touched on it prior to buying it is the spray painted red intake manifold cover. Beyond that, everything appears to have been untouched.
 

Stangra

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I feel like I can say pretty confidently that it wasn't. I bought it in 2015 with 26,000 miles, and from everything that I can tell I've been the first to really break into it at all. The only evidence I've found of anything being touched on it prior to buying it is the spray painted red intake manifold cover. Beyond that, everything appears to have been untouched.
I see the sprockets have chain wear too. Could it be that this engine has bounced off the rev limiter a few too many times?
 

BootsyCollins

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I see the sprockets have chain wear too. Could it be that this engine has bounced off the rev limiter a few too many times?

I'd guess that I've probably done between 15-20 launches with the car over its lifetime, with probably half of those coming from a roll. I can't speak for the previous owner. That does make the most sense of anything as to what could've been the cause though.

As of now I think that my plan is to put Loctite 660 on the inside of the sprocket and put the drivers side chain on without the tensioner to get it into position before it sets up. I'll leave the tensioner off for 24 hours so that it fills the diameter evenly and doesn't pull off center.

If it doesn't work, I guess I'll be in the market for a forged crank and connecting rods!
 

MG0h3

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Geez man is that sleeve locker? You'll never get it off.

Plus Id be concerned if you don't have it on it just the right position the sprocket and chain will tear each other up.

I say keep researching. There's no way someone else hasn't opened it up and found that.
 

BootsyCollins

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I've found sprockets that have exploded and caused the engine to need a total rebuild, but I haven't had much luck finding any where there's a damaged crank but the rest of the drivetrain is still intact.

It's a pretty legitimate concern that I might not get the position quite right. I'd guess that not allowing the sprocket to float would result in shorter chain life regardless. Maybe I'll reach out to the guys at MMR and see if they've had any experiences like this and/or what their recommended repair would be.
 

assasinator

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well i have 105,000 miles on mine, and it's been launch hundreds and hundreds of times. been off the limiter thousands of times. powershift and driven like i stole it from day one. hell i hit the limter nearly every time i drive it. 7800-8000. its hard no to with it revving so quickly. i got mine new and ordered it when the 2011 bank opened. ive never driven a car so hard as this one.

OP, it just happened thats all.
 

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