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brake and clutch cylinder cap corrosion


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A general enquiry to see what solutions others have for the problem of corrosion inside the brake and clutch master cylinder caps when using dot4 fluid. Apart from using silicone fluid that is.

Corrosion around the inside of the cap threads makes them difficult to remove. I have tried to make sure I clean up the threads and then use silicone grease sparingly on the threads (making sure it doesn't get into the fluid. Is there a rust inhibiting 'grease' that others have found to work?

Just for info I check the conductivity of the fluid regularly to make sure it is <1% between fluid changes. I use one of the pen type that you can get on the internet.

Keith

 

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11 minutes ago, keith1948 said:

 

Just for info I check the conductivity of the fluid regularly to make sure it is <1% between fluid changes. I use one of the pen type that you can get on the internet.

Keith

 

Hi Keith,

why do you check the conductivity of the fluid. Is it for water content?

 

Roger

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There's a plastic cover available for the master cylinder used on the TR4.  I believe it was used on Landrovers.  Works well as it seals better and doesn't tend to jam.

I've found them at autojumbles, but worth looking at Parts List for Landrover.

Ian Cornish

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1 hour ago, RogerH said:

Hi Keith,

why do you check the conductivity of the fluid. Is it for water content?

 

Roger

Hi Roger. Yes it's for water content. Old dot4 fluid absorbs water and reading goes up. Just a simple check but doesn't alter need to change brake and clutch fluid regularly. Old fluid is also darker in colour. I have found higher readings than 1% before for old fluid.

Plastic caps don't look as good as original metal ones but won't rust though. 

I have thought about copperslip but don't think it will stop the rust forming. Same for graphite. Maybe some way of passivating the rust somehow?

Keith

 

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1 minute ago, RogerH said:

Hi Keith,

Regarding the rust !!  Are the lids steel - I thought they were Aluminiinium!!!

If they are Ali then sure a quick clean with a wire brush would help

 

Roger

They are Ally, the problem being the cylinder is cast iron so galvanic reaction is the problem.

Stuart.

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master cylinders sit very close together - I have found that some are so close to one another that the plastic cap (which is a little more bulky) won't fit..... worth trying as a a remedy to the original problem - you may be lucky :)

...... Andy

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Hi Roger, Andy, Stuart,

Rust seems to be on the caps rather than the cylinders. They look like aluminium caps but something is iron somewhere. There is brown 'stuff' under the rubber seals inside the lids and it looks like rust. I think I might have seen ally ones on sale before. I have what might be original caps somewhere but I replaced them because of rust inside. The cylinders aren't rusting.

Andy's point about the size of the plastic caps is a good one. Not much of a gap between the cylinders.

On a different note just looked at mileage done this year in the TR - 5 miles! Just looking it over for MOT coming up. Everything seems to be working, clutch hasn't seized, brakes work etc. It passed last year so expecting the same again...........

Keith

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16 hours ago, ianc said:

There's a plastic cover available for the master cylinder used on the TR4.  I believe it was used on Landrovers.  Works well as it seals better and doesn't tend to jam.

I've found them at autojumbles, but worth looking at Parts List for Landrover.

Ian Cornish

+1 I had both clutch and brake masters with plastic cap and problem solved.

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Just found the original caps that were on the car when I got it 30 years ago. They are steel and very rusty inside which is why I replaced them. Problem seems to be the dot4 fluid in contact with the metal. Can't understand why during manufacture they didn't treat the inside of the caps as they do on the inside of tins of fruit or tomatoes to stop rusting. Mind you there is less oxygen inside a tin of fruit so less oxidation potential for the iron. 

Thanks Pete - that would maybe work on the threaded part but still leaves the corrosion between the rubber seal and the inside of the lid.

Ian I shall look in my parts book that lists parts that fit alternative vehicles. Don't you sometimes yearn for the return of the old days when parts would fit a variety of makes of car so you had more scope for 'alternatives'.

Keith

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16 hours ago, RogerH said:

Hi Keith

Where is the rust coming from - Ali lid, Ali body !!!!

Is it not dis-coloured Ali oxide

Roger

Hello Roger

The body of the master cylinder is Ali as you say but the caps are attracted to a magnet so must be steel/iron in there somewhere because aluminium isn't magnetic. The brown stuff looks like rust. Aluminium oxide is white and fluffy in appearance (as you will know) and looks completely different. Also dot4 is reported not to affect aluminium but is hygroscopic but it contains corrosion inhibitors. I might try cleaning up the inside of the caps and then using a rust passivator to neutralise any remaining rust. Can't paint it obviously since dot4 is quite good at stripping paint. I have some special brake grease (for rubber seals) that I could smear on the threaded part and between the rubber seal and cap and see if that reduces the problem. Otherwise new caps.

Keith

 

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I think the cap is zinc plated steel. The grease sold to go on rear and sides of brake pads is compatible and helps, plastic caps are the best solution although so far I have only managed to obtain one for the clutch which came with the new cyl. Ones on ebay are a different thread and not quite the right size. 

Chris 

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As mentioned above, I have a plastic cap on my TR4's master cylinder, but I had modified the cap to incorporate a float-type low level detector, linked to a small buzzer, hence I am unable to read any useful markings.

However, I did some research and found that Competition Supplies Ltd (competitionsupplies.com) sell replacement reservoir caps for both brake and clutch master cylinders, and these fit the TR4.

The Part Numbers in the catalogue are 6447602 and 74470144, respectively, and I purchased one of each to make sure of the fit.  And they do, so the tin lid from my clutch cylinder is now in the car's boot, along with a spare plastic cap for the brake and a container of fluid.

I put a tape across the outside top of each master cylinder, and measured 6.03cm and 4.2cm, so if the Girling master cylinders on other models of TRst have these dimensions, the caps should fit.

Each cap is made of strong plastic (feels like nylon), has ears to provide grip and a decent "rubber" sealing ring on the inside.  The master cylinder cap is not cheap, but probably worth it if your TR wets itself - especially if using paint-stripper brake fluid!

The Part Numbers moulded into the caps which I received this morning differed slightly from those in the catalogue, being 64474601 and 74471230, respectively, but, since each fitted, I put this down to production variations for different models of vehicle.  Both are marked Castrol Girling.

Ian Cornish

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18 minutes ago, ianc said:

As mentioned above, I have a plastic cap on my TR4's master cylinder, but I had modified the cap to incorporate a float-type low level detector, linked to a small buzzer, hence I am unable to read any useful markings.

However, I did some research and found that Competition Supplies Ltd (competitionsupplies.com) sell replacement reservoir caps for both brake and clutch master cylinders, and these fit the TR4.

The Part Numbers in the catalogue are 6447602 and 74470144, respectively, and I purchased one of each to make sure of the fit.  And they do, so the tin lid from my clutch cylinder is now in the car's boot, along with a spare plastic cap for the brake and a container of fluid.

I put a tape across the outside top of each master cylinder, and measured 6.03cm and 4.2cm, so if the Girling master cylinders on other models of TRst have these dimensions, the caps should fit.

Each cap is made of strong plastic (feels like nylon), has ears to provide grip and a decent "rubber" sealing ring on the inside.  The master cylinder cap is not cheap, but probably worth it if your TR wets itself - especially if using paint-stripper brake fluid!

The Part Numbers moulded into the caps which I received this morning differed slightly from those in the catalogue, being 64474601 and 74471230, respectively, but, since each fitted, I put this down to production variations for different models of vehicle.  Both are marked Castrol Girling.

Ian Cornish

Direct link https://www.competitionsupplies.com/girling-replacement-reservoir-caps

Stuart.

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Thanks for finding those Ian and Stuart. Just found similar from Demon Tweeks with same part numbers.

Anyway main thing is that they are readily available and we now have the part numbers.

Maybe treat the car after it passed it's MOT this morning.

Thanks

Keith

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  • 4 weeks later...

ChrisR-4A queried the dimension I had given for the diameter of the TR4 Master Cylinder, saying that on his TR4A it appeared to be nearer 6.1/6.2cm as opposed to the 6.03cm which I had stated.   He asked whether I had meant 6.3.  Understandably, he didn’t wish to spend over £20 on something which might not fit.

Competition Supplies states for the brake cap 64474602:

Large Girling reservoir cap used for most Girling remote type reservoirs and Girling master cylinders with large integral reservoirs, and suit a reservoir with a male thread of a diameter of approximately 2.54" (64.5mm).

My TR4 Triumph Parts Manual gives 510844 as the Part Number for the Brake Master Cylinder and the same for the TR4A.  So what fits my TR4 should fit the TR4A.

However, the description by Competition Supplies states "approximately", and as I had to go out to the garage, I took calipers with me.

Perhaps I did mean 6.3 when I posted on 17th November (senile dementia?), for I measured about 6.27 on my Brake Master Cylinder last night.  These castings are pretty rough on the outside and if one slides the calipers slightly further downwards, the reading increases. 

As the 7440144 from Competition Supplies fits my Master Cylinder, I don't think anyone need worry about it fitting their TR4 or TR4A.

For the Clutch, the Cap Part is 74470144, which fits my TR4 Clutch Master Cylinder 130887 - and the TR4A uses the same Master Cylinder.

Ian Cornish

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