Fuel Filter Replacement (Banjo Bolts and Sanity)

About a week ago I decided innocently to change the fuel filter on my 1990 4L XJ40, and since then I’ve been battling with stopping the banjo bolt from leaking when the system is pressurised.

Cutting a long story short, I suspect that I’m using the wrong copper washer sizes.


  • What is the size/s of washer that should be used?
  • How many washers should be used, and where?
  • What material should the washers be (Copper seems highly likely and is what I used before, but see last paragraph below)?

Thank you.

More detail below, but I ramble a bit…

The first new filter came with four copper washers (now all crushed and distorted so I can’t measure them accurately. One that seemed to fit the bolt well, and others that were loose enough to allow a gap at the bottom when hanging out from the assembly. I tried in vein to push them in with fingernails while tightening, but it always leaked. Then I eventually stripped the hex head on that end of the filter trying to tighten it up because it keeps slipping back into its cage as I’m tightening.

I decided that I’d broken the end of the filter, as it looked like fuel was coming from there (I’ve since become suspicious of this, but it doen’t matter now). So I bought a new filter locally (unfortunately the same cheap Wesfill WZ400, but at three times the price). This came with only two copper washers, one wide one that fit the bolt tightly, and an narrow one that didn’t.

Now holding the filter with a spanner on the inlet side while tightening the banjo bolt - so that it doesn’t slip off (but tends to distort the filter a bit).

I tried various combinations of those washers, and reusing the old ones. Four washers, two washers, tight, really tight, really really tight. Always met by a fine spray of fuel either from the flter side of the “collar” (bit between the bolt and the filter), or the bolt head side. My take-away observation is that a new, wide, tight fitting copper washer, and a new, narrow, tight fitting copper washer, both on either side of the “collar”, may be the ticket. But I never got any “narrow, tight fitting” ones, and only one “wide, tight fitting” one with each filter.

So I drove (another vehicle - no trails of fire behind me :slight_smile: ) in to the nearest town where you can buy a copper washer assortment pack. The 12mm ones match the description of “wide, tight fitting”, but again the next size the fits is narrow, but too wide and hangs too far out (though it would possibly work if you got it exactly centered, which I’ve already failed to achieve).

I tried again anyway, this time also finding someone to push on the other end of the filter while tightening, so that I could hold the filter on the outlet side and prevent distorting it. Result: the grip on the filter’s hex end still slipped, the pipe going in to the “collar” was pushed against the bottom of the car and bent, so that’s ruined. Got the part from my parts car. Tried again, back to using the spanner holding filter on the inlet side. Leaking again, from the bolt-head end. Final copper washer arrangement was: 1x 11mm wide on bolt-head side of “collar”, 1x 11mm wide and 1x 14mm narrow on filter side (there is by now a round indentation on the end of the filter that I figured might centre the loose washer).

Narrow = ~2mm copper width (outside diameter = inside + 4mm)
wide = ~3mm copper width (outside diameter = inside + 6mm)

The washers on the fitting on my parts car were 12mm ID, narrow (~2mm width), and Aluminium. One per side of the “collar”, Just to confuse things more. It also wasn’t done up all that tight.

Have you tried using the Ali washers from the parts car?

No, and thanks, that might be worth a try. Though one problem is that I lost one of them in the dirt/grass (the shed where my parts car lives is in a bit of a state), but I’m sure I can have a better look for it.

Doing a bit more research online I found the official Jaguar Part:

Pictured here:

Although they also appear to provide four copper washers with the filters that they sell/sold:

So I’m not sure what to make of it all. The aluminium washers from the parts car certainly don’t look like those Jaguar parts.

Have you tried using original OEM Jaguar fuel filter seals CAC89682 (or their supercessions KSR605002 or XR829166)?


Item 25 in the above illustration are certain to fit on the pipe union connectors irrespective of any aftermarket filter you use. They are the same seals as used on just about every Jaguar from XJs to XJSs up to XJ8s and are still available quite cheaply from JDHT and probably most Jag dealers.

Thanks, no I haven’t tried them. I’ve got the early larger style fuel filter which the JDHT site shows with the CBC6461 “seal”, so I’m guessing that might be the one to go with.

Just to confirm: you don’t need any copper washers when you use these, correct?

Sorry, my mistake - I picked the wrong year.

I believe you should use the ‘Dowty’ style ‘bonded’ seal with the rubber insert, not copper washers as your illustration of CBC6461 shows.

Right, I’ve ordered a few of the CBC6461 seals from an Australian stockist. Hopefully I’ll have them by the end of the week.


The bonded seals arrived, installed as per the Jaguar diagram, and no more leaks!

So I’m a convert to using the seals. One question for the next filter change though: Are they reusable? I assumed not and ordered six, but I notice that they’re steel so I imagine they could be reused as long as the rubber part is alright.

While heating with a blowtorch, I also managed to bend back the pipe that I bent where it goes into the “collar” (on part that I replaced with the one from my parts car), though there’s still a kink there. I guess I’ll keep it aside and find out whether that kink restricts the flow too much if ever I need another one of those parts.