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I was adjusting the idle after a long, fast ride on a hot day (round the Strathbogie Ranges - beaut roads, unknown territory for me) and was surprised to find a very fine spray of oil coming from the oil filter cover. I found that the gasket had a break in it:



and the shim hadn't sealed against the cannister where it had a slight kink in it:



I couldn't find any problems with the o-ring.

I've always used genuine filters and, never having given it any thought, have always fitted the new shim, o-ring and gasket that came with the filter. This has been going on for 100,000km and I've never had any problems.

Of course now that I've read up on it (http://www.largiader.com/tech/filters/canister.html) I find that the gasket is not only unnecessary but can cause the o-ring to not compress enough to do its job.

I'm still not sure exactly what happened but I'm guessing that because of the gasket there wasn't enough pressure on the shim to overcome the kink (they often arrive slightly bent), I don't know how the oil got around the o-ring, and I don't know why the gasket broke (I put grease on them before installing) but this one looks as if it was seated oddly. The right hand bit seems to have moved outwards. I guess hot, thin oil found the weak spots.

This filter etc has been there for about 5000km and I don't know how long it has been leaking. I've been blaming pushrod tube rubbers for the oil on the engine. I guess I should have looked more closely.

No damage done this time, but a possible trap for those who take a simple filter change too lightly.

hzbloke wrote: No damage done this time, but a possible trap for those who take a simple filter change too lightly.

So I'm not paranoid. Could you please change your avatar?

hzbloke wrote:Of course now that I've read up on it (http://www.largiader.com/tech/filters/canister.html) I find that the gasket is not only unnecessary but can cause the o-ring to not compress enough to do its job.

That's not quite true, at least in the way that you've written it. It depends. In my case, I need the gasket. My /7 canister is 2.8mm deep. If I didn't use a gasket to move the cover away from the block, my o-ring would be very crushed and possibly split, resulting in disaster. It's important to measure the canister depth as Anton's site discusses. Then decide if you need a gasket or not, or even mulitple shims. It just depends on your configuration.

Kurt in S.A.

You're correct, Kurt. I would even go as far as saying that in order not to damage the O-ring you NEED at least to install one shim (regardless) and then compensate with gasket(s) even if your depth is less than 3mm to begin with. The shim provides a uniform interface for the O-ring to sit on and seal against whereas otherwise it would rely on the (rim of the) canister to be perfectly centered. I also believe the rim of the canister (even if centered) is to small for the O-ring to sit on squarely, it'll be crushed.

Stephen

hzbloke wrote:
I'm still not sure exactly what happened but I'm guessing that because of the gasket there wasn't enough pressure on the shim to overcome the kink (they often arrive slightly bent), I don't know how the oil got around the o-ring, and I don't know why the gasket broke (I put grease on them before installing) but this one looks as if it was seated oddly. The right hand bit seems to have moved outwards. I guess hot, thin oil found the weak spots.

It seems to me that the slight kink in the shim is only say 1/32 of the entire circumference, so in first approximation, you could have lost 1/32 of your oil pressure ... not enough to causing any damage, me thinks. I think it is important to note that the O-ring will not be able to "straighten" or compensate kinks in the shim, it is way too stiff (from memory).

Go ride.

Stephen

A timely reminder to us all.

I recall one opinion that suggested it's better to go entirely without a gasket, if possible, because that way at least you'll get an early warning that oil is being blown past the "O" ring.

Edit - here's the quote from Anton himself:

If you don't have a cover gasket in place, oil may leak out of the cover which is a great warning sign. Cover gaskets can mask this, which is why I try to do without them.

It is my understanding that the gasket is nothing more than a spacer. Since the o-ring should be doing the oil seaing, there should be no oil to make it to the gasket. Proper spacing will let the o-ring do its job. One can only determine the right stack-up by doing the measurements.

Or one could do it two other ways to gage results. The external bolts for the cover need to compress the o-ring somewhat. If the bolts go right down with no squeeze...you probably need another shim or remove the gasket. If the bolts require quite a few turns and/or force to draw the cover down to the case, then you need a gasket or reduce the number of shims (a minimum of one is needed). Another way is to look at the o-ring that comes out after a service interval. It should be nicely squared and not horribly distorted. Of course, by that point, if the o-ring comes out perfectly round, damage might have been done.

Kurt in S.A.

The parts microfiche for my '87 RS shows no gasket and no shim.

First, don't trust completely the parts fiche. Second, didn't the '85-on models come with rolled edges on the canister? If so, one could probably get by without a shim. Still, belt-and-suspendors suggests using shims/gaskets as dictated by the canister depth. This is one of the "critical safety items" or CSIs that are popping up in the military aircraft structural integrity programs...a failure in this area is well, costly.

Why did they move away from the /6 system???

Kurt in S.A.