2004 Sprinter crank bolt snapped while on 101 fwy.

stoney500

New member
My 2004 Sprinter is down again. This time the bolt that holds the crank pulley and harmonic balancer on the crankshaft has snapped at the bolt head. I wasn't sure what the problem was but I knew something wasn't right. I didn't hear exactly when it happened but the engine wasn't as smooth running as usual and a sounded a little more noisy which was barely noticeable. I pulled off the freeway and into a Shell station and shut off the engine. I popped the hood and looked for the obvious problems that I could visually see. Nothing noticeably was wrong that I could tell. I checked the engine oil and it was fine. I got my trans fluid dipstick out and was going to measure the trans fluid level and when I started the engine I heard something curculating in my fan blades and then heard it drop to the ground. It was the beveled washer behind the head of the bolt that holds the balancer and crank pulley on to the crankshaft. Immediately I knew that this is not good as the head of the crank bolt has either unscrewed itself or has broken off. With an inspection mirror and a flashlight I determined it has broken off. The balancer was still on the crankshaft and the pulley appeared in proper alignment as if the balancer had not moved. After having the van towed (on a flatbed) it sits in front of my house and I have done nothing yet to start the repair. I realize that the grill bumper, radiator a/c condenser etc... has to come off to access the broken off bolt in the crank. My first question is: Why and how did this happen? I'm leaning toward that the bolt was damaged from over torquing or maybe something else might have caused this to happen? I'm not looking forward to this repair and will take any useful input from someone that has been through this repair before and can help make this repair a little less of a pain in the ass. I realize that the crank bolt is hardened steel and VERY difficult to drill into. I also realize that 240 lbs of torque is the torque that these bolts are supposed to be set at. With the bolt head gone is the torque relieved from 240 lbs? I imagine it would be relieved and the shank of the bolt could be removed without much drilling and using an ez-out to unscrew it.
Thanks for reading as my van is constantly down for one reason or another and this time I will be working on it in the sun at 90+ deg. temp. and want to do this as quickly as possible.
 

220629

Well-known member
First. As another 2004 owner let me offer my heartfelt sympathy. The good news is that it sounds as though the crank end should be ok.

I can't offer much.

The torque is used to set compression on the assembly so in theory once the fastener head snapped off there should be less resistance in extracting the remains.

There are some members who mentioned being willing to rent out the tools needed for the Harmonic Balancer replacement. It may be worth a search to find those comments. All Sprinter replacement HB units are not created equal. Word here is to go with OEM parts or at least the OEM manufacturer.

Keep us informed.

Good luck. vic
 

stoney500

New member
First. As another 2004 owner let me offer my heartfelt sympathy. The good news is that it sounds as though the crank end should be ok.

I can't offer much.

The torque is used to set compression on the assembly so in theory once the fastener head snapped off there should be less resistance in extracting the remains.

There are some members who mentioned being willing to rent out the tools needed for the Harmonic Balancer replacement. It may be worth a search to find those comments. All Sprinter replacement HB units are not created equal. Word here is to go with OEM parts or at least the OEM manufacturer.

Keep us informed.

Good luck. vic
Just got back from talking to Anatoliy (aka Sprinter Expert) who has a shop in Sun Valley Ca. All he works on is Sprinters and has a busy shop and when I told him the problem that I have with the crankshaft bolt head snapping off he told me that this was very unusual. He had never seen it before. I thought maybe over torquing the bolt was the reason for the failure and he said more than likely that's not it. I got the new crank bolt today from him and will be installing tomorrow after removing the old broken off one. Hoping the old bolt extracts easily but am ready for the worst. I have a few balancer pullers in my collection and one installer. If Sprinters require a puller specifically for Sprinters I'll soon find out. If the rubber hasn't seperated I am not pulling and replacing the HB . I will keep you posted.
 

abittenbinder

Doktor A (864-623-9110)
I have seen more than a few harmonic balancer bolt failures in Sprinters over the years.

The bolt in your '04 is the 10.9 grade version bolt. In most of those failures the pulley bolt had been improperly torqued or reused during a repair or rear A/C crank pulley retrofit.

The correct torque procedure is a 2 stage operation using a NEW bolt. First the 240 ft/lbs, then an additional 90 degrees of rotation.

This brings the new bolt to it's yield point and theoretically results in an infinite fatigue life.

Ignoring the second stage during tightening could cause a short fatigue life, reusing a old bolt could result in a shorter life as well.

You should be able to grind a small slit in the remaining bolt shank face using a Dremel tool and back out the shank with a screw driver.

Doktor A
 

mad max

2005 3500 158" SHC Cargo
:professor: I would have to agree with Doktor A on this. These bolts are called torque-to-yield. The key difference that separates these bolts from something like a wheel bolt is that they are designed to be used only once. The act of properly tightening the bolt causes permanent plastic deformation in the shank of the bolt. It stretches out as it is brought into full tightness. This technique is used in applications which are very sensitive to clamp load. Using a value of torque alone to tighten a bolt will give something like +/- 25% clamp load for a given torque, but by using a medium torque to seat the clamped assembly and then a specific angle value which is the deformation part, the bolt can deliver a consistently high clamp load.

Trying to reuse these fasteners in the same way usually leads to an excessive clamp load initially and higher bolt stress. The bolt work-hardens during the first use and trying to get the same torque+angle out of it in successive tightenings leads to higher and higher finishing torque until necking starts to significantly reduce the cross-sectional area. Meanwhile stress in the bolt (force/cross-sectional area) continues to climb with each reuse until it fractures completely. I would guess that someone re-used the bolt and to hit that required angle they had to exert a lot of torque on the bolt which would have caused very high stress.

Depending on where the bolt broke you may be able to get good access by removing the damper pulley (aka harmonic balancer) and possibly just putting some pliers around the shank of the bolt. You'll want to inspect the keyway of the damper pulley to make sure that it's not chewed up too badly. You'll also want to inspect the key-sprocket interface which may be a little tricky to see. Once that bolt stopped clamping, all of the torque to the pulley and the sprocket was being transmitted through the key which is really just an alignment device. It sounds like you shut it down quickly so it's unlikely to be damaged but it's worth inspecting while you're in there.

It's worth noting that once you remove the damper pulley there is a pathway to the crankcase. Your engine bearing buddies will thank you for stuffing a rag around the crankshaft before pulling out a dremel :2cents:
 

stoney500

New member
I feel privileged that the infamous Dr. A. posted a response to this thread. I thank you for your thoughts and input to my latest Sprinter dilemma. I also must thank all the members for their time also with the input that I'm sure will aid me in this repair. I have not torn in to the repair as of yet due to some loose ends I had to take care of. I'm about to start on it now.
Thanks for the dremel tool advice Dr. A. as I think I will go that route to remove the remains of the bolt. I don't see any other way to access the area but removing the front end of the van. Very little room to get to the bolt shank and work to remove it as a inspection mirror is needed just to see it. Before I purchased it my van was used to deliver fresh flowers from Calif. to Arizona and has an aftermarket refrigeration unit in back to keep the High temperatures of Ca. and Ariz. from damaging the flowers. That's probably the last time the crank bolt was installed is at the retro fitter company that added the refrigeration system with the added pulley attached to the crankshaft.
Bumper,grill,radiator,charge air cooler,a\c condenser is what I am most likely going to have to pull but I will look it over closely before I start. I have removed the front end as far as the radiator a while back and remember it being fairly simple.
 

stoney500

New member
I just finished up on pulling the front end off my van. Here's the damage as far as I can see: Crank bolt broken flush with balancer face. Balancer is not tight on the crankshaft as I can wobble it back and forth and side to side with ease. I can see the woodruff key and the key moves and rocks on the crank with the balancer and is not a tight fit as a balancer is usually snug and tight before torquing down not loose and wobbly. When I try to spin the balancer as if to rotate and spin the crank it turns about 5 degrees but the crank does not turn. I haven't removed the balancer yet but I know that it is junk. I just hope the crank will survive. I will find out tomorrow am when I pull the HB.
 

PATECO

Member
Do you guys now the part number for the Bolt. I am replacing the Balancer in my 2004 Freightliner 2500, and did not realize how important it was to replace the bolt.
 

stoney500

New member
just got the balancer off of the crankshaft. key slot on crank is rounded out and won/t hold a key.

My best guess is game over.
 

autostaretx

Erratic Member
The 2004 bolt was originally listed as (dodge) 05073696AA
The washer under the head is (dodge) 05080005AA

--dick
 

220629

Well-known member
...
My best guess is game over.
First. I haven't seen the damage.

How much do like to roll the dice?

The key is an index. Once the assembly is properly torqued into submission the key really shouldn't see much stress. when the assembly remains properly tight there is no movement against the key assembly or else the metal will fret... like your's did.

JB Weld and some other repair epoxies have done some amazing things. Some are very machinable in that parts can be reshaped by patiently using a hand file.

Of course there is some risk, but at what I pay myself per hour I have made some successful repairs which I would never do as a professional.

Good luck.

vic
 

danrduc

New member
I just happened to see this thread. I am not familiar yet with the sprinter balancer and crankshaft, I have used the metal mending products to repair other crank keyways with success. Even keyways that drive the camshaft belts.
Get a new key, clean the crank and balancer as much as possible. One side of the slot is usually still in good condition, use that as your alignment. Fill the other side with your choice of repair compound and assemble the parts.
Probably should lube the threads and underside of the bolt head. have the crank locked up at the flexplate end and torgue to spec. Doesn't sound like you should use any Loctite type compounds for this torque procedure.
Let it set for 24hrs, or as recommended for compounds used. I think it is Dexron that I like myself. Something like that.
 

mad max

2005 3500 158" SHC Cargo
This is not a game-over. 5 degrees is really not that bad and as others have pointed out it is possible to repair it. If you have been able to remove the key then I imagine that there are actually two keys used in this engine. One for the cam-drive sprocket and one for the damper pulley. Can you tell whether or not the key also engages with the sprocket?

The damper pulley is rarely a 'timed' assembly so if it it off by a few degrees it will be unlikely to have any negative repercussions. The sprocket on the other hand is of-course sensitive to timing, but 5 degrees is definitely not enough to cause valve interference and the effect it could have on performance is probably negligible. With a new key and a new damper pulley you may find that the amount of slop decreases, since some of that is coming from the deformed key and keyway in the pulley.

If it were me, I'd goop up the keyway in the crank with some 2-part epoxy, drop the key in and then slide the pulley on. Feel the slack in the joint and try to find the middle of that. Let the epoxy cure briefly and then remove the pulley without moving the key, clean up any excess and then let it cure fully before throwing the pulley back on and cranking it in. Turn the crankshaft until the keyway is facing up before doing any of this so that the epoxy doesn't run out and so that the key isn't being pulled in one direction or another.

You can apply some grease or vaseline to the keyway on the pulley to keep the epoxy from joining with it. You should also reserve some of the mixed epoxy so that you can test that to determine when it's cured enough to be able to remove the damper without moving the key.
 

stoney500

New member
Ordered new front seal,new crank bolt, new balancer alignment key and now looking for crankshaft lock tool to buy or borrow or rent. Parts should be in Tuesday a.m.
 

sailquik

Well-known member
stoney500,
You're not going to replace the harmonic balancer?
I'd be darned sure the inside bore of the HB was "perfect".
Right on size, no scars, smooth ground finish, perfect keyway.
Or did you miss a comma above and mean a new HB and new HB alignment key?
The more "on size and to spec the bore in the HB is the more reliable (in the long
term) your repair will be.
Roger
 

PATECO

Member
The 2004 bolt was originally listed as (dodge) 05073696AA
The washer under the head is (dodge) 05080005AA

--dick
Thanks Dick,

Ordered one from Local dodge dealer this morning. should be here tomorrow. Freightliner dealer said 3 days.
 

stoney500

New member
Ok, I spent 400.00 more and bought a new oem HB. I have the extra a/c so I had to get the HB with the added v-belt pulley. Now I need to lock the crankshaft and need to torque Crank bolt to 240 ft lbs + 90 deg. Anyone in the san fernando valley/ Simi valley area want to rent their om647 crankshaft locking tool? I'm happy to leave a deposit.
 

PATECO

Member
Ok, I spent 400.00 more and bought a new oem HB. I have the extra a/c so I had to get the HB with the added v-belt pulley. Now I need to lock the crankshaft and need to torque Crank bolt to 240 ft lbs + 90 deg. Anyone in the san fernando valley/ Simi valley area want to rent their om647 crankshaft locking tool? I'm happy to leave a deposit.
Why don't you just buy one Mercedes Benz Flywheel Locking Tool $19.99 +Freight



Or this kit off of Amazon Supercrazy Mercedes Benz Chrysler Jeep Engine Camshaft Alignment Locking Timing Tool Kit SF0102 $63.99 & FREE Shipping

 
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PATECO

Member
Got my Bolt yesterday looking to do the replacement tomorrow afternoon
 

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