Sweating Brake Fluid Hose

[1954Etype]

I've used the stuff Hutson supply for years - not cheap but doesn't sweat!

I thought you used silicone fluid?

I do on my cars but have also used non silicone for customers.

[Heuer]

I cleaned the hoses of sweating fluid 6 days ago and this is what they look like today:


Hose came from SNGB - avoid! I bought some Cohline 2337 hose from Hutson's which they say will not sweat. However it does not seem to be the same stuff as I used on my OTS. That came from Stevson's and had the blue braid and blue inner and was Cohline 2322:



Further research says Cohline 2337 EPDM was manufactured specifically for VAG so it is not in the general catalogue: "Low pressure hose for connecting fluid reservoirs to master cylinders. Resistant to all types of brake & clutch fluid. 7mm ID. Will easily push on 8mm hosetail. Supplied with IVA declaration."

You can also buy it from these suppliers at ?7/metre:
http://www.cbsonline.co.uk/product/Brak ... ose_BFHOSE
https://www.merlinmotorsport.co.uk/p/7m ... m-m-sph8-4

[Patrick NICOLAS]

David, thank you for this very comprehensive work.

Since this subject is brought to the surface, I looked on my 1965 s1. The three hoses are healthy. I think I'm lucky because they are certainly not original. One is smooth, the other is dressed in linen, the third is plastic made. But no sweat.
So, I'll leave them alone for the moment.

[wol916]

I used www.advancedfluidsolutions.co.uk for the fuel pipe I chose to use fuel injection pipe inside the boot to stop the sweating problem as more and more ethanol is added to fuel these days.
They stock SAE J30 R9 fuel hose and the range of CHOLINE hoses for dot 3&4 brake fluid.
Fuel hose ?3.99 per meter
Brake hose ?6.89 per meter
Deliver to UK starts at ?1:15

Warren

[jag68]

I haven't read all pages of this thread so this might be reptitious. XK's Unlimited in now selling yellow stripe hose - Part No CO-18717

[Heuer]

Just swapped over the sweating hoses for the new Cohline hose (on the 3.8 you only need half a metre) and it looks as though the old hoses have started to disintegrate from the inside given the colour of the brake fluid I extracted - it was grey/black. I have been corresponding with Julian Barratt over this and he assures me they have had a test hose filled with brake fluid for the last three years without problem so they are somewhat puzzled. He is however investigating the supply of Cohline and in the meantime I am sending my old hoses back to them for Peter Stant, the SNGB technical guru and QA manager, to investigate further.

Angus assured me I could simply empty the bottles, remove the hoses, refill and wait for the air bubbles to plop out - no need to bleed the system - and sure enough they did. However as I wanted to change the hydrostatic clutch slave to a conventional one I bled that circuit and found the black fluid.


I then bled the brakes but interestingly, whilst some grey fluid came out, it was nowhere near as bad as the clutch fluid for some reason. If you look at the above picture you can see the two brake fluid bottles are darker than the clutch bottle so it seems dirty fluid gets mixed there but not in the clutch bottle because it stays in the cylinders. I wonder if it is regular movement of the fluid in the hose that exacerbates the problem and why a static test does not shoe up a problem?

For the time being, and until Julian can give us a definitive answer (bad batch, wrong type of hose etc), I suggest you simply visually check your hoses once a week to see if you are effected. Keep a particularly watchful eye on the one closest to the frame.

As for the XK's 'yellow stripe' hose you need to ask for details of what rubber it is made from. Quote "Low Pressure Brake Flex Hose With Yellow Stripe. Sold Per Foot. (Note: This is an attempt to replicate the original hose but it is of much larger cross section. It is a step in the right direction but IS NOT absolutely original.)" Looks like the yellow stripe has been painted on to me.


Best way to check is to ask for a SVA letter of compliance - this is what kit car builders have to include with all their documentation when submitting their construction for its first test - and proves the hose has been tested as safe for brake fluid. The kit car constructors/suppliers have been immensely helpful in my research on this subject and it was they who pointed me in the direction of Cohline as being the only acceptable SVA compliant vendor of low pressure brake hose.

Last yellow stripe hose I had fitted (admittedly 1999) sweated after 5 years. So this is the third batch of hoses I have had with this problem - maybe it is just me

[jag68]

You can also try this hose from AP Racing. I've used their hose over the years without issue. http://www.apracing.com/product_details ... p6614.aspx

[Heuer]

Thanks but I will now only buy filler hose that has a SVA brake fluid compliance certificate or at least hose that is marked with the manufacturers name, part number and the type of rubber used as in "Cohline 2337 EPDM". The AP Racing hose has none of these.

[MarekH]

Dear David,

There are four potential sources of why the brake fluid may be discoloured black:-
1/ the sweating hose you are replacing;
2/ the master cylinder seal;
3/ the flexi hose between the two metal pipes; and
4/ the slave seal.

Whilst Angus's approach will work, it'd be interesting to see whether bleeding the brakes conventionally would yield a bit of grey fluid, clearer fluid, more grey fluid and finally black fluid, before the new brake fluid comes through. It'd also flush out any particles trapped in the line. What is more, if there is a chance of packing some red grease into the slave or master before reassembling any disturbed or replaced seals, then all the better.

kind regards
Marek

[Heuer]

Marek

Bled the clutch conventionally today and even more black fluid came out. Also bled the brakes the same way and we had some grey fluid in the jar. I am going to replace the clutch high pressure hose as a precaution (it has a white stripe) and see what comes out. The master cylinder appears to be new, or at least overhauled, so I suspect the hoses. I have lots of red grease but as I did not rebuild the units on the FHC I don't know if it was used. Just had the original Dunlop callipers rebuilt (courtesy of Angus's brother in law - great service, contact Angus for details) with s/s liners and I used red grease liberally when putting them together.

[MarekH]

Dear David,

With the prospect of mostly only poor rubber parts available these days, perhaps the thing to do is drop them all into separate jam jars of brake fluid and leave them for a month before looking to fitting them to the car.

It'd be a good candidate for a long term test and writeup.

kind regards
Marek

[Heuer]

Marek

My theory is the degradation has to do with regular movement through the hose - not sure if this is due to some abrasive effect but on my OTS the problem appeared after regular use and on the FHC started under my ownership where the car ceased to be a trailer queen and found the open road. SNGB have had a length of the same hose as mine steeped in brake fluid for three years without problem. The only difference seems to be fluid moving back and forth through the hose. I am open to other theories though. Also how do you measure the sweating of the hose if it is totally immersed in brake fluid?

[MarekH]

Dear David,

1/ re the jam jars:- I was thinking about the seals - if they are "bad", I'd expect to see a greyish haze around them after a while;
2/ I guess one could hook up a s3 windscreen washer pumps (?5 item) to a 12v battery and let the fluid circulate round for ever to check the movement theory.

Bear in mind that both the low and high pressure hoses have almost no fluid movement through them - the volume of liquid moving is only the gap between a piston and piston wall x 4 x about 1mm piston movement. There is plenty of friction and heat at the caliper end though.

kind regards
Marek

[vee12eman]

Hi,
Any possibility that certain types of brake fluid are more susceptible to sweating through than others? I know it's supposed to be the same stuff, whatever source you buy, but it clearly isn't as witnessed by the several different colours it comes in. Also temperature must play a part, the warmer it is the thinner the fluid will be. This also may explain why a trailer queen turned frequent use car is suddenly having problems as the under bonnet temperatures will be high (during usage) more often than if not used.

I have hose from SNG, live in warm temperatures with a V12 (very hot under bonnet temperatures so the fluid will be as warm/thin as it is likely to get), use the car fairly frequently (although not as much as I would like) but my hose shows no sign of sweating after nearly 4 years. I am not absoloutely sure which fluid I use, but I think it is Nulon DOT 4 (a local brand).

Regards,

[Heuer]

It does seem to be a lottery which is why I am championing the idea to only buy hose that is clearly marked with the manufacturers name, code and material. As far as I can recall my OTS (which twice suffered from sweating hoses) used DOT4 but no idea what was in the FHC. It seems Cohline offer two products which are immune from sweating and given the cost is minimal (compared to having to repaint your frames!) at 70p/100mm - 500mm required for a 3.8 - experimentation on different brands is probably pointless. Thing is Simon, both your hoses and mine were sourced from SNG and look identical but who is to know if the wholesaler ran out of the 'approved' stuff and supplied an alternative identical looking product to meet demand?

Simply buy Cohline 2337 or 2322 and make sure it is marked as such!

[gmunro]

Hi guys - fascinating subject and I really appreciate all the input to date. The final question after all the debate is ...... which Cohline product to go for ..... the 2337 or the 2322?

Brilliant research and thanks so much.

Kindest regards,

George

[Heuer]

Either will be OK. Suggest you order from Hutson as they have the correct type. Speak to Andy Raynes and mention the Forum.

[gmunro]

Many thanks David, I'll contact Andy as you suggest.

[Ropariva]

Hi
I just experienced this issue myself with supposedly correct reproduction "yellow stripe" hoses from a reputable supplier. This was after only 4 months and with virtually no use at all as the car is still under restoration.

My paint has suffered some discolouration as a result.
The brake fluid was Nulon DOT4.
A club member friend has reccomended I use silicon fluid once I replace my hoses, but that question is probably dealt with already in another forum topic.
Interestingly, it appears the car was still fitted with its original fluid hoses prior to the strip down, and they weren't showing any signs of sweating.

[42south]

Hi Guys

I've also had this problem down here in NZ. Finally after some searching I came upon this site in the USA: http://tiny.cc/bsmpxx He sells DOT approved 5/16th EPDM hose that is made by BF Goodrich in the states. The material is called 64A Santoprene. I checked on the Shurflo compatibility chart on the web and Santoprene and EPDM both have the same A grade rating for brake fluid. He states that he has never had a comeback in 7 years. Might be useful for our American mates

http://tiny.cc/bsmpxx