Cracked Crank Pulley

I wondered whether any engine builders could shed some light on this.

I changed the front crank pulley on our truck which is an 2004 2.5TD Ford Ranger.
It had a new engine before my ownership in Jan 06 (big bill), but on seeing the run out on the pulley just assumed someone had caught the pulley taking the engine out. It was a special order part so took an age to appear I also changed the front seal. Nothing unusual when putting it back, pulley felt right on the crank even gave it a rock no play on the keyway. But on firing it up I have about 2mm run out back and forth, 1mm across the diameter thats better than the original pulley, which had 5mm back and forth, 3mm across the diameter. But it still looks odd.

Anyone ever come across anything like this before:confused:


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When you say 'new' engine Joe, do you mean new or a replacement. I would suggest checking the crank snout for run out in case the motor has been in a head on in a previous life or been dropped/damaged in shipping. For the Damper/Pulley to split along the Keyway area like that it has either come to a sudden stop or been forced over a high /bent spot on the snout. A loose retainer bolt would have left it with a lot more damage apparent.
Jac Mac
Good question, I was told by the company that supplied the engine that it was remanufactured, but with new parts. This can mean anything I understand. But I did persist and they told me new short engine and heads, the bill came to £4k. Apparantly the Turbo let go destroying the previous engine. This was carried out by a Ford service agent?

It would be quite hard to determine te run out with the crank installed as the diesel pump is gear driven by a gear situated behind the crank pulley, so one long key facilitates both. Try to run it or turn it over too much risks the key sliding out of the gear or the gear moving to far forwards.

On inspecting the pulley I would have expected some damage to the outer area if the lump had been dropped on the pulley but it looks fine. Do I think its the old original pulley, yes as its quite corroded on the front and has a quite a wear mark where the seal is located.

The pulley slid on fine, needed a wiggle to get it passed the new crank seal, but felt good. Its hard to see the nose of the crank as the front cover hides a lot of it, but what I saw of it looked ok.

Can a crank nose bend like this? without cracking and falling apart? I would have thought if it was bent the gear drive behind it for the pump would have mashed itself by now, its done 13,000 miles since the "new " engine

I checked round on the web to see what sort of tolerance there is on pulley run out most state under 1mm. Again I have not experienced engines with this sort of run out but a colleague reckons some is allowable, I am not so sure.

The retaining bolt was well tight enough, I wonder whether the crack opened up as it was loosened as there is quite a lip/step on the top edge.

Howard Jones

How about off roading contact with big rock. Stopped engine dead and cracked damper. The only other thing I can think of is one of the accessories seized up and the damper cracked at the same time the belt broke. This one is a long shot. Or bad part from the start.
Yes a crank snout will bend quite easily if its dropped or recieves a knock. The area that the gear fits may only have a small amount of runout compared to the area the pulley/damper fits on. I can understand your reluctance to turn the engine over without the retainer bolt etc fitted as I have had key's/dowels shear in that situation when degreeing cams etc with the valvetrain in place. If the key for the pulley could be removed and hyou have a local fitter/turner make up a sleeve with ID to suit the crank snout and concentric with the OD of that sleeve, you could place that on the crank snout with attachment bolt and safely turn the engine over on starter while observing dial indicator on the sleeve OD. Any more than 0.005" TIR would indicate a problem especially if a reading taken closer to the engine block was less.
jac Mac
I have one of these. On a tip years ago a friend told me about a 289HP engine was in a junk yard in Front Royal, Virginia for $100. Needless to say I was in place the following Saturday morning. The car was a 68 1/2 Cobra Jet Mustang fastback with a complete 271. The car was in a front end accident whereby the the motor mounts broke and the crank pulley & balancer smacked into the front cross member & fractured the unit so bad the junk yard guy said the engine had a broken crank (did I care?). Got the engine home and the pulled the abused balancer off and the crank looked fine. A dial indicater showed no runout on the nose.

Rock contact I would have thought would have showed damage at the contact point, but the outside of the pulley looks fine, no marks or dings, the pulley runs 3 belts, 2 for the alternator, one for the air con, the units all look like originals. I cant really see any signs of how the crack was caused.

Jac Mac
I am surprised a crank can bend, just thought it would crack and snap, specially with a large bolt going up the centre of it to hold the pulley on. Heres something else, I would have expected oil to leak really bad from the old pulley as you can see the crack ran right across the seal contact area, but to be honest it just has a small damp patch, says something about the seal, or did the crack only open up once the bolts undone.
As I often have to remind Fran, getting anything technical done like that over here, only makes you want ot emigrate.

Like you have have salvaged parts from scrap yards and I often get surprised at how bad something looks but on strip down has no or little damage, I suppose like you have said you would expect the crank puley to fall apart long before any damage is transmitted to the crankshaft. Its has a wasted out centre section with spokes etc, if it got impacted surely it would break there.

Could it be a duff new pulley? long shot
Could it have been a duff replacement crank and the runout on the nose caused the crack?

So what do we reckon strip it again, or leave it to see if it degrades over time, and live with a bit of run out. I can't here any noises but then its a diesel and sounds like a bag of spanners anyway.
If there is any damage to the crank nose it will mean replacement or complete engine overhaul anyway.
Even if its just worn the likelyhood of being able to get it loctited or teflon taped in the right place while you swing 230Nm on the bolt is very unlikey.

Thanks for your help

Russ Noble

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The thing I find strange about that crack is that it doesn't go straight down the keyway. For my money some external force has caused that crack. It has started at the keyway, the weak point, but some external force has caused it to crack through the thicker part of the pulley boss.

Since we're talking about a truck motor and not a race motor I wouldn't worry about a bit of runout so long as there are no oil leak issues. If the new pulley develops the same problem, then I'd worry. In the meantime just keep a watching brief.