N12Turbo.com lanyards are now available! Click here to visit the shop

Oil Pump Jackshaft Gear Split, Help Please!

General chat related to anything N12.
Post Reply
theS-man88
Posts: 10
Joined: Thu Sep 27, 2012 10:34 pm

Oil Pump Jackshaft Gear Split, Help Please!

Post by theS-man88 »

Hey guys,

I've just had the oil pump jackshaft drive gear (the one that's driven by the timing belt) shear apart, so that the oil pump wasn't spinning for approximately 3-4km. I'm just wondering whether this is a common problem, or maybe some thoughts as to what might have caused it? The gear didn't appear to have any damage when I fitted it.

Also, is there even the slimmest hope that my main/rod bearings, cam lobes, rings, etc. weren't severely damaged by not having an oil pump?

Cheers all.
User avatar
poeticjustice88
Posts: 281
Joined: Tue Jan 17, 2012 11:24 am
Location: gold coast, queensland

Post by poeticjustice88 »

i cant say that I have seen many cases of this happening on the forum.

you said you fitted it, How long ago?
could you have possibly over tightened it?
did anything get in there, like a stick or rock? I know it sounds weird, but I have seen it happen.

4 km with no oil pressure to the head would have me worried. pull the rocker cover off and see if you can notice any grind that weren't there before.

I would take the chance of driving it until you have a look.

Hope this somewhat helps bud.

Michael
theS-man88
Posts: 10
Joined: Thu Sep 27, 2012 10:34 pm

I think I see the problem now...

Post by theS-man88 »

It was fitted around last November, I'd say. It's possible it was overtightened, but it broke on the edge.

Here's a pic -

Image

I think your third suggestion might be bang on - I don't know how I missed those marks, but it looks like a bolt has come loose behind the timing cover and caused the damage. Will investigate some more this afternoon.

Many thanks for the reply, Michael!
User avatar
poeticjustice88
Posts: 281
Joined: Tue Jan 17, 2012 11:24 am
Location: gold coast, queensland

Post by poeticjustice88 »

A break like that makes me think of two things

1. It was poorly cast when it was made. If so, just the tension and force of the timing belt on it pushing against the bolts could have pushed it to breaking point
2. It has been rubbing on something for quite some time and has finally let go

Michael
theS-man88
Posts: 10
Joined: Thu Sep 27, 2012 10:34 pm

Post by theS-man88 »

I think you're definitely right there. The timing belt has corresponding marks on it too.

Just pulled the rocker cover off, cam lobes feel a bit dry, but no evidence of really bad wear. I think the top end might be ok in the short term if I drive very easy on it. A bit concerned that it's going to spin a bearing at some point, but that's life.

I'll probably build up a spare motor using a spare crank, rods, pistons, etc. It needed new valve stem seals anyway, probably time for a head service too. Ah well!
User avatar
tassuperkart
Administrator
Administrator
Posts: 5578
Joined: Wed Jul 05, 2006 8:39 pm
Location: Southern Tasmania
Contact:

Post by tassuperkart »

Unless there is some evil noise in the engine after you repair it, Id say there is little chance of any serious engine damage.

Engines will run a remarkable length of time with no oil at all and Id seriously doubt you lost complete oil pressure.

If the toothed section had completely let go, then the belt would have loosened completely off and there is no way in hell it would have NOT jumped teeth on the cam/crank sprocket and lunched a handful of valves.

Does the pulley show signs of rust on the inside? As in, say, sitting in a box somewhere upside down and gotten water in it?

I cant imagine the belt tension could be gotten so great as to flex the pulley to death where it has let go.............
Id have expected it to let go in that area right around the bolts.

NEVER seen a failure like that...... very strange indeed.

Oracle
Forcd4 wrote:Oh fuk no dude it's you a again, the oracle.
theS-man88
Posts: 10
Joined: Thu Sep 27, 2012 10:34 pm

Post by theS-man88 »

Ah, well this sounds promising! I'll find out next week when the jackshaft seal comes in (pierced it with a screwdriver trying to stop the centre of the pulley from spinning) whether there are any of these evil noises. But the fact that it might actually be ok makes me happy!

The pulley had no signs of rust on the inside that I could see. However, there are a lot of metal shavings inside the timing cover, a worn spot on the plastic on the timing cover just underneath the gear, and a matching mark on the gear on the inside.

Is it possible that a bolt has come loose, gotten jammed in the gear, and the jamming has caused the pulley to shear off?

Thanks, Oracle!
User avatar
panagiwtis N13
Posts: 99
Joined: Sat Feb 09, 2008 10:55 am
Location: Athens-Greece.

Post by panagiwtis N13 »

wow! never seen that on a e-series engine or ever heard of any kind of that failure.you were very unlucky! hope the engine is ok.
i don't care:
if you're black, white, straight, bisexual, gay, lesbian, short, tall, fat, skinny, rich or poor.
If you're nice to me, I'll be nice to you. Simple as that.
theS-man88
Posts: 10
Joined: Thu Sep 27, 2012 10:34 pm

Post by theS-man88 »

Well guys, after slapping it back together, everything appears to be back to normal. I think perhaps the motor has always been a bit tired, as I can hear an occasional and random knock coming from the sump. But that sound is no worse than it was before, and if anything the engine is slightly quieter. Haha!

Thanks for all your help everyone!
Post Reply