T1N timing chain replacement

lindenengineering

Well-known member
Well from my experiences, its the exhaust cam chain wheel spokes that fail, then the whole lot simply comes apart.
It can do some spectacular damage to the valve gear, but so far I have yet to see any rods or pistons badly damaged by valve contact and by everything doing the crunchies!
There was an earlier more reliable wheel available and used on earlier engines ( as mentioned by Andy B) but its not now available.

In any case its an isolated problem, but I confess the recent three I have dealt with have turned up in the last 9 months.
Dennis
 

NelsonSprinter

Former Nelson BC Sprinter
Has anyone ever heard of a timing chain breaking on the T1N? My uncle has a NCV3 and his timing chain just broke. And because that engine is an interference engine ( the valves come in contact with the top of the Pistons if the timing chain breaks) it destroyed his engine and he had to buy a new one... For $17,000. ouch.

Does anyone know if the t1n has an 'interference' engine? Is replacing the timing chain something that would be smart, or overkill?
Is your Uncle's a 4cylinder 2.1L Diesel?
 

jackbombay

2003 158" shc
There was an earlier more reliable wheel available and used on earlier engines ( as mentioned by Andy B) but its not now available.
Some time ago I had chatted with Andy, and I recalled that it was the OM647 that had the better exhaust cam sprocket on it, and the OM612 had a less stout sprocket on them. But that was 8 years ago and my memory could certainly be in error.

Or is it that the early OM612 sprockets different than the late OM612 sprockets?
 

wlauberds

New member
Getting additional info from the shop, who have been great to work with, it was the cam chain wheel spokes that failed. From what the mechanic can see, the chain is still in one piece, but he can see the worn out spokes on the cam wheel.

Still sorting out best route, but, every shop I have talked to advised against rebuilding and instead getting either a new engine, which is likely cost prohibitive or buying a remanufactured from a shop like sprinterengines.come or the like.

Bummer situation. No options have come in at under 8k unless I buy an engine off ebay for $3k with no idea on the history or warranty. No shop wants to rebuild and it seems like rolling the dice if the valve rods and cylinders are smashed up.

Thanks for the help and advice on the thread. Dennis (lindenengineering), your responses and initial posting were super helpful. Still need to figure next step, but your comments have been helpful.
 

Cheyenne

UK 2004 T1N 313CDi
How about getting the whole thing shipped to Dennis for a rebuild?

IIRC another forum member did it recently. Again IIRC the cost of shipping plus Dennis's bill came in less than a new engine local to where the van failed.

Keith.

Edit to add, From Dennis's recent post...

Well I did one similar recently at around $5000 but adding a lot of stuff that needed replacement other than just the engine repair , like water pump, accessory belt, tensioner etc that added another $1000 to the bill.
Still not a cheap job but better than 11 Grand.
Dennis
So if you could get it shipped for less than six grand then you're in the money!
 
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Midwestdrifter

Engineer In Residence
Diesels tend to have shorter valves, and turbodiesels have smaller valve diameters on average. The piston dish volume and low operating RPM means that chain slippage does not always result in major engine damage like it does on Gasoline powerplants. If only the exhuast cam slipped you may even have less damage than you think.

In general a boroscope inspection through the injector holes will tell you right away if the damage is major. It won't take long either.

If the scope comes back clean. The head is probably salvagable, and the bottom end surely is.

Pull the head and check it at this point. It probably just needs new valves, seats, and guides, and maybe a bit of cleanup on the chamber. If you are really lucky the seats will be good, and and new valves and guides will get you fixed.

At that point its just the labor for Head R&R, new timing chain, and ancillaries. Most skilled shops could do that in less than 15 hours labor. I would not throw away the engine without at least giving it a look! If the shop doesn't have a source or machine shop they trust to work on your head/engine, you probably should just have it moved somewhere else.
 

Lotus54

Member
I had a chain come loose (Lotus twincam) at 7000 rpm. Bent all the valves (expensive big valves too)
Didn't hut the pistons, rods, seats or even guides.

Since the valves are often at angles, what I've seen a lot is the valve just bends, and that's it.
(Obviously everything should be checked)
 

lindenengineering

Well-known member
For info just about all of them bust the valve guides when the valve bends.
MB does not supply guides --It a new head from them .
Uncle Dennis has guides !

In just about every case the bucket followers are crushed and the cams are broken into bits.
In any case I remove the pistons and check for land damage and rod bend.

The whole timing chain, sprockets and guides get tossed into the trash with the cam girdle cams and caps etc .
Take no prisoners !
Dennis
 

220629

Well-known member
Properly replacing a Sprinter any diesel engine won't be cheap no matter how you cut it.

How about getting the whole thing shipped to Dennis for a rebuild?

...

So if you could get it shipped for less than six grand then you're in the money!
+1
Shipping deals can be found if not on a tight schedule.

And Colorado is nice a nice area to tour when you go to pick up your properly repaired Sprinter. :thumbup:

:cheers: vic
 

wlauberds

New member
Looking at the numbers, shipping + rebuild is about the same as a remanufactured. Still an option on the table as I continue to weigh what we are going to do.

So far, no options under $8k seem to exist as no one locally (Portland OR) seems to be willing to rebuild the engine. Most only seem willing to put in a brand new engine from MB.

Thanks again for all your help.

@jackbombay, I don't know enough to call the situation to call this a fragile exhaust cam sprocket, but, my engine was the OM647.
 

lindenengineering

Well-known member

traT3gic

New member
To add my tiny .02 to the discussion, my 7.3L Ford has planetary gears for timing - basically for life. The T1N on the hand has the chain with apparently cams being the weak points. So my question is can the engine be rebuilt in situ or does it need to come out of the van ? If rebuilt for the cam damage I am guessing there will be metal slurry in the bottom end and bits of crap everywhere at the top end, the head will have to be pulled and I would be looking at a solid 10-20hrs of commitment ?
 

lindenengineering

Well-known member
To add my tiny .02 to the discussion, my 7.3L Ford has planetary gears for timing - basically for life. The T1N on the hand has the chain with apparently cams being the weak points. So my question is can the engine be rebuilt in situ or does it need to come out of the van ? If rebuilt for the cam damage I am guessing there will be metal slurry in the bottom end and bits of crap everywhere at the top end, the head will have to be pulled and I would be looking at a solid 10-20hrs of commitment ?
A clarification is needed here.
My apologies for being a bit pedantic but you would only find PLANETARY gears in the E4OD transmission (gearbox) attached to the back of that 7,3 engine !
An example :-
https://www.google.com/search?q=pla...o94MKHfajBwcQ9QEIiQEwDA#imgrc=EesKgbHCRz7slM:

In fact for clarification the engine you mentioned does have a SPUR gear timing set to drive the camshaft and HPOP pump etc etc . Helical tooth form is prefered in this application.
https://www.google.com/search?q=spu...hXD4IMKHRDvAwkQ9QEILjAB#imgrc=JfCJ0JMVosac8M:

For information on engine architecture/design MB (like many manufacturers) prefer a timing chain for the application, simply because the engine is used in passenger cars and engine quietness is a strong consideration.
Conversely the 7,3 International Navistar engine was principally designed as a truck engine for medium duty truck applications like the IH 404. --404 is of course 400 CU Inches or 7,3 litre!
Ford of course adapted this engie for light duty PU applications where noise was less of a consideration.

As for the camshafts you mention that are weak!
Essentially they are not, but rather being a cast induction/ case hardened item, they fracture when impacted by sudden arrest! (Such as in a valve hitting a piston when the timing chain arr' lets go!) in short they are not very ductile as in most applications.
The weak area is in fact the spokes on the exhaust camshaft chain wheel which fracture/shatter in some cases.
The issue is not a prevalent one but more a weakness created by mass production and induction hardening processes is the cause.

It is preferable to tear down the engine which in any case dictates removal!
Why you might ask?
Principally metal fragments and swarf are dumped into the engine oil pan/sump.
The oil pan can be removed from the engine in situ but its much quicker to pull the engine as a complete powerpack for a clean out.
In any case the head will have to be removed and the piston crowns inspected for valve impact damage. In some cases the impact can be severe and this will damage the top ring land rendering the piston as scrap.
For that very reason alone, it is preferable to pull out the pistons and carefully inspect them for impact damage. Equally the rods checked for alignment when repairing this engine after such a failure.
As with most repairs be thorough for the best results.
Dennis
 

Patrick of M

2005 T1N 2500 (NA spec)
Thanks for the clarification re spur gear/planetary and how the mb sprocket is getting broken. Does beg the question how is a sudden stoppage happening if the sprocket is not the cause? Chain tensioner? Chain breakage?
On a completely tangential issue, my B18 Volvo engine, which was used in passenger cars, marine engines ( and tractors by the sound of it), uses spur gears to drive the cam. The noise (and long term reliability) was reduced by having the larger gear made of fibre. They still last over 500,000 miles in most cases, and mine looks fine at aprox 300 k miles. These old engines don’t really care if the fiber gear fails, you can just pop on a new one . No interference back then.
 

Nautamaran

2004 140” HRC 2500 (Crewed)
In any mass-produced item there is the chance of production flaws, so likely the sprockets that break had flaws that were missed by MB quality control checks. A likely failure mechanism is metal fatigue on the spokes, as they flex slightly with each rotation. 3000 hrs @ 2000 rpm is 180 million cam cycles, and a minor flaw (such as weak spot around a casting inclusion) could grow into a crack and the spoke suddenly break. Sprocket wheel inspection is possibly preventative, but this is an uncommon failure and not worth pulling front covers off engines fleet wide, though you might get lucky and spot a cracking spoke by peering through the oil cap with a borescope?

-dave
 

lindenengineering

Well-known member
Thanks for the clarification re spur gear/planetary and how the mb sprocket is getting broken. Does beg the question how is a sudden stoppage happening if the sprocket is not the cause? Chain tensioner? Chain breakage?
On a completely tangential issue, my B18 Volvo engine, which was used in passenger cars, marine engines ( and tractors by the sound of it), uses spur gears to drive the cam. The noise (and long term reliability) was reduced by having the larger gear made of fibre. They still last over 500,000 miles in most cases, and mine looks fine at aprox 300 k miles. These old engines don’t really care if the fiber gear fails, you can just pop on a new one . No interference back then.
Yes !
To reduce the mesh noise, the fibre of the day was a material called phenolic resin.
Since some engines are designed for multi applications, fibre gear is used to reduce the noise in passenger car applications.
Back in the 70's the most famous one was the straight 6 Ford engine in E Series vans; notorious for tearing off the teeth on the half time idler pinion .
I suppose today the preferred material is delrin.
http://www.cncplastics.com/customgears.php
Dennis
 

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