Broken crankshaft key leads to tear down and timing service

I’ve had wobbling in my crankshaft pulley recently and took it off to take a look at it. This is what I found. Am I f***ed? Looks like the key that the pulley locks onto is broken not to mention my pulley took some damage as well

 

Motor needs replaced now or what
Holy shit

I wonder why this happened
And if a FluidAmpr upgrade or earlier OE pulley replacement would’ve prevented this

the fact the rubber was already torn makes it look like it wasn’t dampening anymore and being harsher on the metal

could suggest the need to replace crank pulley as periodic maintenance

what mileage is the truck?

 

yeah man this feels terrible lol. It’s 230k. I don’t even know what I’m gonna do. There’s no way to replace a crankshaft without taking apart the entire engine right?

 

I mean that’s a big job and assumes everything else is good.

replace crank is probably:
-find good crank
-disconnect trans
-take apart front drive belt system
-drop lower oil pan
-drop upper oil pan
-drop crank out
-replace certain bearings or inspect tolerances using plastigauge against FSM specs

I’ve heard these motors can eventually need lifter adjustment or at least check within spec at high miles too (top end/cyl head)

probably not possible to weld on a keyway repair given the fine tolerance spec fit of it

question is,
1. Does the fitment use two keys
2. It looks like one of the keys on the crank broke off. Where did it go? Sent through inside the engine messing other things up?

you could throw a new pulley at it to see what happens. Low cost. Just doesn’t 100% garuntee success.

not sure if the high torque spec of the front crank bolt is enough to hold it on without moving forever and how much it relies on the key(s) to stay in place.

I think there’s two versions of pulley available, not sure why. If one is better or what.

FluidAmprs work better than stock, have good warranty, are strong, and last a long time. They (viscous dampers) are now used on newer vehicles from factory for that reason. But that would require 100 people interested to justify R&D (FluidAmpr told me this), which there is not.

 

yeah I’m not getting a good feeling about this at all. Engine has been running fine other than the wobble and a chirping sound coming from that area. Makes me wonder if it was all being held together by the pulley and taking it off just made everything crumble. I have a new pulley otw via Amazon but don’t know if that’s gonna help me at this point. I suppose I could try to put it on and see what happens. Throw on some thread lock and hope for the best. Anyone have a picture of that area that shows how the key should look? I’ve been looking but haven’t seen anything.

 

Got a welder?

 

I've read a lotttttt of TW forums posts, esp. on 2nd gen 4.0s, over the years.. I think this is the first instance of a broken crankshaft pulley I've seen. (Not that it hasn't ever happened, just that it doesn't seem at all common.)

Any additional detail on how this may have come about? How is the truck used, generally? Heavy off-roading?

 

Nope. Haven’t found any pieces of metal yet either.

 

the truck is mainly used on the street. Sometimes has some weight in it cause I do construction but other than that it hasn’t had too rough of a time since I’ve owned it

 

@Torspd is probably the best one to ask about this…

 

It's pretty clear the broken keyway was caused by the breakdown of the rubber damper in the pulley. Wonder what could've caused the rubber to break down that badly with only 230K miles on it.

I don't know what the stock crankshaft pulley looks like -- is that the original OEM pulley? Could it have been replaced previously and that broken one is an after-market pulley?

The only other thing I can think of is that at some point somebody dripped a lot of aggressive solvent (maybe brake cleaner or brake fluid) down onto the pulley, causing the rubber to start breaking down.

 

Pull that seal to get a better look. It looks damaged anyways, you’ll have to replace it

Looks like only the key is damaged, should be able to replace it. I doubt crank has to come out to do so, but I don’t know for sure

 

The seal is fucked so pull it and then get a better shot of the keyway.

 

This spring came out when I took the seal out…

 

Maybe there’s still enough of a key to put a new pulley on there and forget about it?

 

The picture shows a front crank seal gone. I take it you took that out.

the spring is probably from that. Crank seals have small long springs like that inside of the seal. Hidden on the backside of it. Some seals at least. To help hold and retain pressure in its shape on the seal inner lip.

I don’t see what else that spring would come from.
Prying out an old seal due for replacement tears it apart to the point where if it has a spring built into it, it can then fall out.


Welding is stronger than glue. But I wonder if a tiny square of metal matching a pulley keyway hole could be glued on.
Such as clean prep, then JB weld it on.

otherwise if you weld one on, then that would take some precise tool bits to grind the weld off on the outside so it’s a square shape. Like dremel type of tool bits.

you might even be able to get away with using a cheap low power flux core welder that’s good to have around for things like broken hardware removal on other jobs.
Cheaper and less labor than crank replace.

it may be possible but tricky
To get or make a square. Put it in the pulley. Have glue on the backside of the square. Place the pulley on the crank to set the square to right position. Let it cure.
Then take the pulley back off and weld the square.

unless there’s someone nearby down to bring over their mig setup or something. While the truck is down and taken apart.
With plenty of time to clean and dry the area and drained of oil. So there’s no oil interfering or anything flammable in the area.

if you take off the front timing cover
That would let you refresh it and give you more room to work in that area. More ability to clean and dry. Less oil to worry about slowly dripping.

 

Yes I’m just realizing that. And yes I took it out

 

I question the reliability of jb weld especially for something such as this. I also question my ability to weld something so tiny and in such a shitty spot. Im wondering if there’s enough key to fit a new pulley on there and drive it. And if it were to give eventually would it damage the engine more than it already is?

 

Obviously I will have to call around but does anyone know approximately how much replacing the crankshaft should cost? I’d like to have a tacomaworld point of reference ha ha

 

Looks like you were lucky to catch this issue when you did. If it was left to get worse, it might've failed catastrophically, possibly even tearing the front main seal out under load w/ total loss of oil pressure and tons of oil on the road.

JB Weld absolutely not.

Need additional photos of the key on the crankshaft -- mayyyybe it's in OK-enough condition to use as-is, it looks like the pulley itself took more of the damage.

If the key on the crankshaft is badly damaged, the only possible repair method I can imagine would be be careful welding followed by then attempting to re-shape the keyway carefully with very small dremel bits and/or hand filing.