MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MG Y Type - DOT 5 or not?

A friend asks:
How can one tell if there is DOT 5 Silicon Brakefluid being used in an older Y Brake System?
Anton Piller
Anton Piller

Colour - always(?) purple AFAIK.
Nigel Atkins

i have dot in the system
total rebuild
it is purple
difficult to get the air out
i will tell you on wendsday if all ok
FT Franz

If your renewing ALL your brake rubbers (wheels and Master) it's a no brainer for me.
Its not meant to hold water which means if car is unused for long periods the cylinder wont pit. I have just had a failed master cylinder due to tired rubber seals and was pleased to find it only needed a kit, the wall of the cylinder was perfect.
This Y is the first car I've every purchased that had silicon fluid in it.
I know Franz is having trouble bleeding his car but I have bleed hundreds of cars and my recent experience is it bleeds up exactly the same as other fluid using the old method of an assistant in the car pumping the pedal as required. I've never tried those self bleeding kits perhaps they struggle with silicon.

Kevin
K Weeds


Gentlemen

Thank you for your feedbacks. I also assume that DOT 5 is "always" of the colour purple, but nobody could confirm this.

Maybe, I will have to place a tiny drop of the fluid on the paintwork and check if it damages the paint.
If it it does not do so, we can assume that it is DOT 5?!

cheers
Anton
Anton Piller

"Maybe, I will have to place a tiny drop of the fluid on the paintwork and check if it damages the paint." 🤣
Nigel Atkins

Anton it is important that the 2 types don't get mixed together as it will soften the rubbers (different reports on how quick this will happen). On my car there was a sign screwed to the cover flap explaining not to use ordinary fluid and not to top up with ordinary.
Are you saying you don't know if it's silicon or not in your car and your hoping the colour will tell you?

If so I guess it shows the importance of attaching sturdy signage when you change to silicon.
K Weeds

Anton,

Here in the USA, DOT5 fluid MUST contain a purple dye. The color will fade with time/use/heat to yellow. Color alone is NOT a reliable indicator of fluid type.

Being silicone OIL based, DOT5 is near totally immiscible in water. DOT 3, 4 and 5.1 are poly-glycol ether based and will mix with water.
Add a few drops of DOT5 to 100ml of water and they will float to the top. Do the same with DOT3,4,or 5.1 and they with completely mix into the water. Much better than damaging your paint!!!

MOSS sells adhesive labels warning of the presence of DOT5 in a car's brake system (p/n 215-005 $4.49US).

I have used DOT5 in all my M.G.'s for over 30 years and have never had to replace any of the master or wheel cylinders. I have had trouble with the flex lines, but since converting to modern Teflon based ones have had no problems.

DOT5 is slightly more compressible than glycol fluids. This may explain Frantz' comment about difficulty in bleeding the system. It may in fact be air free all the time!

Rocky
Rodney C "Rocky" von Dullen

find a yard or more of plastic pipe to fit snug over the brake nipple then open this, and hang the other end of the pipe over a chair back - pump the peddle until you get a column of clear fluid in the pipe - you can be sure there's not a bubble all the way back to the master cylinder.
Bryan

that was teh tip i got
and it works perfect

now i have to adjust the exenters, that was my problem
forgotten it
silly ;-)
FT Franz

I just use a 400mm length of plastic hose attached to nipple which I loop up and then down into a bottle/jar. I just pump pedal until the hose is full of brake fluid with no bubbles and sitting in fluid in the bottle/jar.
When the pedal is released, as fluid is sucked back into pipe, fluid from jar is sucked up as well. Then I just tighten bleed nipple.

cheers
Stuart
Stuart Duncan

We hear a lot about not mixing dot 5 and dot 3/4 (and presumably dot5.1 as well) but has anybody any unequivocal experience of brake failure through mixing them? Certainly it makes common sense (if indeed that exists) to not mix unsimilar materials but does it do any actual damage? Swelling of rubbers is an oft repeated claim with exhortations to change all rubber parts when changing fluid but without knowing the type of rubber used we would be hard put to know what the real cause was, especially in these days of poor rubber in general. In fact it is just possible that we may be replacing good quality old rubber with the poor excuse for rubber which is sold to us unsuspecting car enthusiasts nowadays. Of course a scientific analysis and experimentation could hold the answer but has this been done as without it we are left in the dark about the truth of the matter while repeating ad infinitum exhortations which owe more to the risk averse modern world than to the reality. Silicon fluid is certainly lass mischible with water, even I accept that, but as far as I am aware this has the advantage of needing fewer changes as it doesn't of itself degrade but the disadvantage of allowing any water to get into the system to pool in awkward places where it may be difficult to flush and where it "can" cause more localised rusting than more conventional fluids. Didn't the US military stop using it for this reason?

regards
Ian
ian thomson

I'm glad someone has put something about stories around silicon fluid and pointed out the piss poor rubbish rubber quality of modern made rubber parts and items, going back 15 years in my experience alone, and old rubber just being old and worn.

In the A or the T sections here a contributor put where he'd not flushed and cleaned from putting silicone in after glycol and another put that it was only when emptying out brake fluid he found he'd a mix of glycol and silicon in his system but had never known or noticed experiencing any differences or issues.

I know someone who has silicon in his two MGs and one of them has had the silicon in for 20 years without it being touched or issues.

I'm not suggesting deliberately mixing fluids or to leave any fluid in untouched for 20 years and I always put that brakes are the number one concern on a vehicle (which includes tyres) but perhaps some stories about silicon are unsubstantiated (as you may say my stores are too).

Like a lot of things, such as which oils can be used, there are beliefs around the use silicon fluid and beliefs are hard to change but it doesn't matter what they are if they cause no harm.
Nigel Atkins

Dear Nigel, Franz, Kevin, Stuart, Ian and Rocky

I am overwhelmed from all your replies and especially gratefull for Rockys method of water testing the DOT5 fluid. This was unknown to me and probably should be added to the "Technical Center" section.

I always buy and use Automec DOT5 fluid for my YT because a triangular DOT5 warning badge comes with the bottle. I placed one of them (hidden) to the steering collumn. Another one is glued to the tin lid that allows access to the master cylinder - see attachment.

My mate who asked the question in the first place is very appreciative :o)

cheers
Anton

P.S.: I am not referring to the poor quality of reproduction rubbers....


Anton Piller

I made up a DOT 5 only label and stuck it to the M/C cover on the floor. Just to let everyone know. No colour left in my DOT 5, just perfectly clear now.
..CR
CR Tyrell

CR,
It is my understanding that if you DOT5 becomes clear, it's likely time it was changed.

Despite it's non-hydroscopic properties, it does suffer deterioration from heat cycles and time.

Safety Fast

Tony
The Classic Workshop
A L SLATTERY

Tony - cutting to the chase: if (hypothetically) you had a rebuilt brake system from front to rear, with just a smear of standard assembly lube dot 4, would you fill your m/cylinder and lines with dot 4 or dot 5??
You know why I'm asking!
John.
J P Hall

Yes, If you are doing an all cylinders rebuild, flush out the lines with metho and use silicon fluid and forget about seized wheel cylinders forever.

You can buy Silicone Brake Fluid from you local Harley Davidson store.

Safety Fast

Tony
The Classic Workshop
A L SLATTERY

Good enough for me mate. No need to flush lines, as they've never had anything in them. Your point about non-siezing cylinders is a good one; it probably outweighs the oft-quoted risk of non-hygroscopic fluid leaving moisture/condensation to find somewhere to collect. Off to the motorbike shop tomorrow!
John.
J P Hall

Its probably very expensive at the motorbike shop. Over here it is $90 for a few hundred mls.
I got Penrite from a parts shop for under $40 and used less that half the bottle to do my yb.
The best deal I found is from Moss motors in California (not the UK), I think a quart was $35us.
K Weeds

Tony, Thanks for the info. I checked again. Actually sucked some fluid out to look at it. It is still purple.... just really clean and clear.
.. CR
CR Tyrell

Gentlemen, I can report that my mate chaged all rubber parts (cup seals and hoses) and fill the system up with DOT 5 Silicon Brake Fluid. He reckons that it might be a good idea to replace 70 year old brake components.

For fun, I add two photos of the cardboard boxes that come wit the Automec DOT 5. The second picture shows part of the text on the rear side. It says the two different kinds of fluid would work safely together - even though it is not recommended!

Not that I would recommend it, but.....

Anton

P.S.: It further says that DOT5 must never be mixed with Mineral Based Brakefluids. Could this be the reason for a lot of warnings stories?





Anton Piller

Well, so there it is in black and, er, yellow the two fluids will work safely together, pity no one has posted that before!

Nothing about any need to clean or flush out the system before refill with DOT5 (although a thorough flushing as a cleaning is always a good practice at any fluid change).

Anton and I have seen posts where others have told us this.

Another case of RtFM (or box in this case)!
Nigel Atkins

Anton,
I don't think the mixing with mineral would be the main cause of confusion I think it's more the mentality of sticking with old ways because that's what was done back in the day, lack of trust and understanding of improvements in following decades.

I think I'd be more worried about replacing seals with modern made piss-poor rubbish rubber seals I'd be very careful about the source of any modern made classic parts that include any rubber.
Nigel Atkins

Nigel,
What does RtFM stay for?
Well, we got the cup seals from our trusted supplier - the one with the three letters name.
Anton
Anton Piller

Hi Anton.
I didn't know either, so I googled it.

Try Wikipedia, and check out the variations.
Or if you wish a quick heads up, Read the F...ing Manual. Bit rude by my reckoning.

And there is an acronym for Just Google It.

Anton, thanks for your many posts. You are a gem.

cheers KGM


K G Mills

ETA: I typed all of below whilst Kevin unknown to me had posted, so it can be rude but also not necessarily, when Googling as with other research you do need more than one point of reference.

Anton,
RtFM is from "read the manual" or "read the field manual" but is also often used to mean "read the f***ing manual" as a telling off for arrogance of not doing so and often cocking something up to someone else's cost. Many men proudly say they don't read the manual thinking they are clever or being clever by learning for themselves often because they're arrogant or intimidated by peers or expectations.

Engineers and mechanics will refer to technical publications and tables but not operating instruction manuals as these are beneath them, these are invariably men. Sometimes we used to refer to such as "Billy-big-bollocks" for their alfa mindset.

It may not apply here as some may have read the box label and just disagree with it but I've used the term in it's wider context meaning read the label.

Reading another article I was pointed to, over here the rubber bits need to have "Made in England" on them to give more confidence.
Nigel Atkins

KGM & Nigel

Thank you for the flowers, regarding my posts.

And also for letting me know what RtFM means - I like the rude explaination best :o)

At present there seems to be a "worldwide" shortage of 3/4" cup seals, so one will have use what you get.

Anton

P.S.: the "Billy big b" statement helps me to refine my English :o)

cheers
Anton
Anton Piller

Anton,
I had another phrase or saying for you in my last post but it went out of my mind as I was typing.

The Billy-big-bollocks is probably a very local old expression as it came from a mate decades back and has been used as a technical term usually only within the confines of the workplace. other expressions might be brought in when conversing with other workers from different parts of the country.

When someone has cost you lots of time, hassle and money which can't be regained or compensated for then much more colourful and often inventive and funny terms have to be used to relive the tensions and emotions. Short or long-term nicknames would sometimes originate this way, such as Digit for an employee that was unable to fully work for a while due to "doing a PJ" (private job) of removing a rubber cambelt, as well as part of a finger.
Nigel Atkins

Nigel, I like old expressions! Especially shop floor related ones. In my South African days (11 years), I earned a living, doing construction work as a boiler maker - not my trade but tremendous fun, with all the rough necks!

stay tuned
Anton

P.S.: I did my appreticeship as a precission mechanic / toolmaker
Anton Piller

This thread was discussed between 15/08/2021 and 20/09/2021

MG MG Y Type index

This thread is from the archives. Join the live MG MG Y Type BBS now