XJ6 Series 1 early brake fluid reservoir

Afternoon, chaps.

The brake reservoir I have on my '6 is the early version, still serviceable, but evidently starting to leak. Leak as in ‘distribute copious amounts of brake fluid around inaccessible areas under the bonnet’. The source appears to be a loose edge around the cap, but I’ve not removed the reservoir body for inspection yet (it’s summer…) and there may be a more challenging failure hidden from the eye.

I know the easy(ish) option would be to swap to the later version, but it feels as if this would be an admission of guilt and the hen would have lost another tooth from its beak. So, do any of you have recommendations for how to go about repairing 54 year-old plastic?

I’m working on the basis that (i) it might just fall to pieces as I remove it and the die will have been cast in any case, (ii) ordinary plastic solvent will not adhere to the unknown plastic type and be susceptible to aggressive attack by the brake fluid and (iii) a heat welding solution will only hasten the demise of the beast.

Not of the usual rogues have early reservoirs even listed, let alone on back order. I have thought about 3d printing, but I’ve not identified a plastic that will be suitable yet…

This is s sort of open ‘I haven’t a clue’ question, so any thoughts or suggestions welcome, before I lose all of the paint on the left side of the engine bay :slight_smile:


step 1) positively identify source of leak by clean and dust suspect area with talc adhered to vaseline

step 2) examine area of leak under bright light and magnification

It may reveal a crack, or something simple

Step 3) If it is a crack, or damage, identify type of plastic is important, then select appropriate number Loctite superglue

I keep one that is designed to repair “O-rings in the field” in my fridge it lasts several years, I think it is Loctite 302, anyway it works on almost anything, but some plastics need a special formula

I ordered it off ebay

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Thanks, Tony. I suspect that identifying the type of plastic non-destructively will be a challenge, but further research suggests that is no such thing as ‘brake fluid resistant glue’.

And my son (a mechanical engineer) gave me the necessary slapping for even thinking about 3d printing a new reservoir…

It appears I will have to bite the bullet and buy a new reservoir.

I have had the later type on my S1 fail at the cap thread, in the “trough” of the thread. If it’s not failed here and there isn’t a “vertical” crack (coming down from the top edge) it’s not an intuive failure that I can imagine, at least in the body. What condition is the gasket in?

I have seen some glued up from the outside, but also seen that sort of brake bottle that has reached “end of life”, and they go a deep yellow and the plastic is brittle as anything and crumbles into bits when handled

Only you can judge were its at, but you would need remove & inspect, clean and look for damage at very least

Unfortunately the replacement items have a bad reputation for poor quality, and (apparently) consistently leak at the nipple

Removing the old hoses may prove difficult, you (could) get OEM style replacements with yellow stripe from Barrats some years ago anyway

The risk is that it has indeed reached the end of life. I initially thought that the feeder pipe was at fault and bought a replacement (without the yellow stripe, but purportedly a direct replacement), which proved to have a slightly larger internal diameter (metric instead of imperial, of course) and served mainly to introduce another source of fluid leakage.

The main benefit to this exercise was to prove that the plastic around the outlet nipples at the bottom of the reservoir is still resilient enough to tolerate manipulation.

I’m tempted to carefully remove the original reservoir, clean, repair and preserve it as best I can, and install an off-the-shelf remote tandem reservoir as a working solution. Needless to say, until I’ve got it out of the car, I can’t be certain where the failure is.


I’d leave the original reservoir in place and hunt for an original replacement part. Even if used it may be better than yours and even if slightly damaged it gives you the chance of trying out repairs and see what works.

Once you know you have a good replacement part you can dive into swapping parts and be confident that by end of the day you’ll have a driving and braking car.

Good luck


75 XJ6L 4.2 auto (UK spec)

Switch to the series 3 master/reservoir and lose all the leaky hoses and bottle. Diligent searching will find a better price.

I realise that this is the sensible thing to do, but then it wouldn’t be an early Series 1…

Daft rationale, I know.

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Series 3 is different mounting along with metric brake fittings.

So nothing else in the car hasn’t been changed or updated either?

Jerry, almost everything else is period correct. Only the steering rack has been updated to Series 3.

Paul, then maybe start off by doing what Jochen said, but finish it differently.

I.e., leave your original (failing) one, leave hoses connected to it (but they are capped when out of sight), then install a new brake fluid reservoir which actually feeds the master cylinder.

There must be some where to put a new one, and disguise it or hide it.

It has to be higher than the master cylinder for gravity feed. Other than that …

It seems that you are willing to make updates for safety, as long as the updates are not readily ‘in your face’ visible.

Thanks, Jerry - interesting idea.

Sorry, Paul - I missed your reply.

I’ll know more about the overall condition when I dismantle the reservoir. I’m collecting my newly-graduated son from the other side of Europe over the next four or five days, so I won’t get to it until mid-July.

‘Clean’ is the key word here, Paul. The old plastic has been drenched/penetrated with brake fluid - which is bad for any adherent…:slight_smile:

By the way; with thermoplastics’ one mode of repair is with a soldering iron - but not always practicable…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

I am pretty sure I have a S1XJ6 reservoir from a RHD '71,

So yours must be early

I have a quite a few S1 spares left from when I owned a '71, and a '70 wreck

However the reservoir is not like that, it is a cylinder, much larger diameter than the early round MKX, I think it is the same as S2, as I had S2 XJ12 as well

The parts book would probably show the different configurations

I have seen enough wrecks to know if the plastic has become brittle, its all over, from an engineering & safety perspective

I presume the later XJ6 have a spare readily available form major suppliers

Do not throw the old part away, maybe you can get one or more laser printed in the near future, that is the only way certain plastic parts are available

Yes, the brake reservoir shifted during SI run. This is the early reservoir

and the next one is the same type as used in SII and readily available.

In this case I’d probably sacrifice originality - at least for the moment. You can save the original parts and keep searching for a good replacement part, while driving a safe car:-)



75 XJ6L 4.2 auto (UK spec)


good for going original. Here you go for a used original for 26€:

If you need help getting it in Germany, and forwarding it to you, let me know.

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That is the very early XJ6 Series 1 reservoir, C29190.

I have a good used one in inventory. It is one of three received into inventory before we updated computers and didn’t save purchase history before 1989 so has been in inventory for at least 35 years so should be relatively young when saved as used. However, I can’t put my hands on it quickly to sell as we are moving a lot of that inventory around. I have seen it last year. If you can’t find another, let me know and I’ll contact you when it surfaces.