Simon's new Xantia V6 and Leaf blog

[Stickyfinger]

They would be my choice, I use that type for engine sump plugs and anything I can replace them with....they are used as standard on Volvo Truck gearboxes (hence I have a good selection via a mate).

[Gibbo2286]

If you want to try sealer Hylomar Blue is the stuff you need, invented by Rolls Royce and claimed to take up 10 thou of wear/distortion, Now made under licence and available from most motor factors and maybe Halfords and the like.

[Mandrake]

I have a tube of hylomar blue however I’d be concerned about any residue (which goes stringy and rubbery like mozzarella cheese) finding its way into the oil flow and lodging in a control valve. I think the dowty washer idea is a lot safer and easier.

[Mandrake]

Just discovered that nitrile rubber is limited to a maximum of 108 degrees C - normal operating temperature of the gearbox oil is 100C and can in theory get as high as 115C in exceptional circumstances. Hmm...

Viton can take 205 degrees C. Even though I’ve already ordered some nitrile ones I think I should find some dowty washers using Viton to be on the safe side.

[white exec]

Simon, have a look at polymax.co.uk website.
Hit O-rings, and under that are Dowty seals ("bonded washers", listed as nitrile) and various other high-temp items.
They're a helpful lot, so might be worth ringing them to see whether they can either supply or recommend.

[Mandrake]

Had a quick look at polymax.co.uk - their bonded seals only seem to be available in NBR (Nitrile) so no improvement unfortunately. While I was browsing on my phone last night I think I found someone that sells them in stainless steel body with viton rubber, will see if I can find it again on the laptop.

Edit: Stainless steel may not be a good choice as aluminium (the gearbox) is sacrificial anode for electrolytic corrosion with stainless steel:

https://www.bssa.org.uk/topics.php?article=89

From that list it seems the metal should be either aluminium (like the original washers) to be neutral, or if it was zinc plated steel (which is available in dowty seals) the zinc has very little potential compared to aluminium and would be sacrificial for any electrolytic corrosion that occurs so that you could just replace the washers instead of the faces on the gearbox joint eroding.

Finding seals with aluminum and FKM (viton) rubber in a metric size is proving to be a challenge. Not helped by most companies that sell these sort of seals having a "contact us for further information" policy rather than just letting you order what you want online. Zinc plated mild steel + FKM is a little bit easier to find.

Who knew selecting and buying a specalist washer was so complicated.

[white exec]

Would a fibre washer, or maybe copper, do the job?
Washer needs to be M14 hole, but how about the OD (or width)?

[Mandrake]

A copper washer works at a pinch - I used copper washers on the old V6 when one of the original washers split and I needed a replacement the same day, and I think I kept them on for nearly a year without a leak. However copper would cause electrolytic corrosion over the long term with the aluminium as the sacrificial anode... also copper would only seal if the faces on the gearbox part of the joint were still in good condition.

Unfortunately the face on the gearbox side of the joint is slightly pitted and eroded leading to it to leak slightly even with brand new original aluminium washers - pretty sure I've replaced the washers twice in the last 4 years and the joint always starts weeping again. Hence now taking the extra step of using a dowty seal with a bonded o-ring to try to get it 100% leak free despite the less than ideal mating surfaces. I want this leak stopped once and for all.

[Gibbo2286]

Can you not clean up the faces and remove the pitting?

[white exec]

Try these folk, Simon. Seem to offer Dowty's (bonded seals) in all sorts of materials...
https://www.easternseals.co.uk/products/bonded-seals/

[Mandrake]

Can you not clean up the faces and remove the pitting?

Nope. Faces are aluminium alloy so quite soft. They have to be perfect to seal only with a metal washer.

[Mandrake]

Try these folk, Simon. Seem to offer Dowty's (bonded seals) in all sorts of materials...
https://www.easternseals.co.uk/products/bonded-seals/

Yes I'd come across that one previously. Looks like I can't order exactly what I'm after off the shelf from anybody so I've sent an email enquiry to them and also these two others:

https://www.fairwayseals.co.uk/

https://www.ashtonseals.co.uk/

The latter in particular has a very impressive catalogue of bonded seals:

https://www.ashtonseals.co.uk/files/myd ... ochure.pdf

I'm asking for self centering, M14 bonded seals in Aluminium Alloy with Viton rubber. Lets see if anyone can supply them!

One thing that puzzles me is that many suppliers list "German metric bonded seals" and "French metric bonded seals" separately. What's the difference ? Metric is metric isn't it ?

And which would I need since the car is French but the gearbox is German.

[Mandrake]

Thought I'd follow up on the seal saga.

The original cheap dowty washers arrived however as well as being only nitrile rubber that's not really up to the temperature demands, the manufacturing quality of them, the rubber in particular is pretty poor - there are several in the bag that I'd say were not up to standard to fit to the car due to defects in the rubber, so I definitely won't be using those ones, at least not for the gearbox!

Eastern seals did get back to me however Aluminium with Viton rubber in M14 is not an off the shelf type so it would have to be made to order...

For the princely sum of £11.50+vat each with a 3-4 week lead time...

So scrap that.... It looks like Aluminium is too rare and non standard in this application. (strange, because it seems ideal for gearboxes...) So the next best thing for compatibility with aluminium is Zinc plated steel which is readily available.

From the reading I've done, although Zinc and Aluminium are slightly reactive with each other it's very minor compared to say aluminium and un-plated mild steel in direct contact (bad) or aluminium and copper in direct contact (really bad) and also rather than the aluminium being the sacrificial anode with steel or copper, the zinc is the sacrificial anode for any electrolytic corrosion that did happen rather than the aluminium, in which case the aluminium won't erode and you could just replace the washers...

So I've ended up ordering some zinc plated steel ones with viton rubber from here, which funnily enough is a company here in Glasgow:

https://www.ebay.com/itm/Dowty-Washers- ... 2749.l2649

Going from nitrile to viton really does bump up the price - it makes them about 5x more expensive, but I think it's warranted in the application with the constant high temperatures, and hopefully the quality of the rubber moulding is better than the cheap ones I first bought. £17 for 10 of them is still a lot cheaper than £11.50 each, and I should hopefully have them by Friday so I can get the banjo seals swapped over and the oil change done this weekend!

[Mandrake]

The zinc plated viton seals arrived, so I'm all set to do the oil change and replace the seals tomorrow.

The manufacturing quality of the second set is far better than the first set which I really wasn't happy with even besides the marginal temperature rating of the nitrile rubber. Not sure how well it will show on a picture but here is the comparison - the £3.50 (for 10) nitrile seals on the left, and the £17.50 (for 10) viton seals on the right:

As can hopefully be seen the quality and finish of the ones on the left is quite patchy - many of the 10 seals have misshapen/misaligned rubbers, chunks missing, poor bonding to the washer etc and the surface finish/plating of the washer is poor and variable from one seal to the next too. (Also I can't find out from the seller what the plating is - no reply! Can anyone guess what the plating is on the ones on the left from the colour ?)

The quality of all 10 of the new ones on the right is perfect and uniform, both the finish of the washer and the bonding and condition of the rubber. I confirmed with the seller that they are zinc plated, which is the 2nd best compatibility with an aluminium housing vs a (difficult and expensive to find) all aluminium washer and the zinc coating looks to be uniform and thick.

I guess you get what you pay for! If it was for something less critical I wouldn't fuss over the details of a washer so much, but sealing a pressurised external oil pathway on an auto gearbox that is exposed to road salt and which could destroy the gearbox if it sprung a significant leak without being noticed makes their compatibility and fit fairly critical.

The only thing I'm slightly worried about is the outer diameter of the new ones is about 20mm (I only have a worn plastic ruler at work so can't measure it accurately ) while the original washers are 17.9mm OD, so hopefully there is clearance around the flange on the side of the housing for the larger OD. From memory the original washers are actually recessed slightly and are a smaller diameter than the bolt head or flange so I think I'll be OK, as long as the sealing lip of the rubber is at the correct diameter and the outer part of the bolt and housing can bite onto the washer to torque up correctly.

[white exec]

We need to treat our Simon to a vernier caliper. Xmas (and maybe a birthday) approaches...
You're right about those LH seals - they do look scruffy.