Practically Classics Forum

As threatened this is about LHM.

At first sight LHM a mineral oil is better than Dot brake fluid.
It doesn't damage paint appears to be the only advantage.
The disadvantages are.
1. LHM is hydrophobic any damp that gets in via micro pores in the system will pool at the lowest point. The damp will boil at 100c so the boiling point of the fluid is 100c.

However because the LHM system is engine pumped the pumps and hydraulic accumulators will simply pressurise the vapour and the driver won't even know.

But on manual system like late 2CVs LHM could cause hydraulic fade.

2. From experience with LHM Rolls Royces and LHM citroens LHM is very leak searching stuff.

On LHM Spirits the calipers are the same as Dot Shadows. The seals are different rubber. Leaking Dot Shadow calipers is rare not so with LHM Spirits. I have also noticed the LHM Citroens always leak somewhere.

So once again Dot Brake fluid proves to be best.

Also dot fluid is made to a std. There is no such std for LHM.

Note the water bit also applies to silicone Dot5. I recommend 12 mth changes for silicon and LHM.

Bob

Hydrophobic or Hygroscopic ?

Edit , I looked it up ! http://en.wikipedia.org/wiki/Brake_fluid Well , you live and learn ! Good post!

I thought DOT was also hygroscopic - which is why brake fluid should be changed every two years (certainly required on all my VWs over the last 20 years). I was under the impression that DOT5 wasn't affected by water.

The later David Browns (with Q-cabs and hydraulic brakes) use LHM instead of DOT. That causes problems for some owners - farmers don't know technical things and brake fluid is brake fluid...

LHM and Dot 5 are hydrophobic they dont absorb water. The water pools at the lowest point often the calipers. The water will then boil at 100 c. Thus lowering the boil point to 100c for the whole circuit.

Dot 3 4 and 5.1 are hydrospocpic and absorb water. This means that the higher than boiling point of water is maintained.
Max for dot is 3.7% water and at 8% the boil point is 100c. So change every 2 years for dot fluids and every year for silicon and LHM.

Of course this negates one of silicons advantages. However read my posting on GM and brake hoses.

The water absorption abilities of Dot brake fluid is an advantage and intentional. The only problem is paint work.
I have read much about dot brake fluid over the years and been on a Lockheed course. A lot of people also think dot is not a good lubricant, actually it is very good for this type of system. Dot 4 is for ABS systems which have to work once in a blue moon. So reassured Dot 4 is an excellent lubricant with anti rust inhibitors.

This is why modern cars favour dot brake fluid nothing had been found that is better.

Of course the silicon fans will no doubt disagree about water but the water is there causing rust in the system unless the silicon is changed.

I hope that explains what I mean

Bob

Forgot Kevin has complained about using the word dot. And someone just mentioned fluids a fluid.
A good few years ago a guy wanted to buy some brake fluid but he brought automatic gearbox fluid thinking that fluid was a specific product. Of course it ruined the master cylinder. This why I frequently use the word Dot, fluid covers a wide range of liquids and gases. I don't want anybody to make the same mistake. One must remember that a 16 year old could be reading this stuff trying to inderstand cars

Fluid can also be any number of bodily excretions hence why you prefix it with the word brake when referring to brake fluid.
The confusion comes in when a self declared "expert" decides to start preaching to the choir using non-standard terms.

bob please don't keep trying to teach your granny how to suck eggs..

Rich,
Although you may already know the tech stuff there will be others who do not.

I can tell from replies that some don't know. But they do now. Most of the stuff I post isn't too deep.

I found that people who learnt about cars from what they see when they repair there own car have gaps in their knowledge.

Professional grease monkeys like me have been to technical school and manufacturers courses. So my gaps in car technical knowledge are smaller. On every course I have been on I have found things I didn't know about.

Yesterday for instance I discovered about protection of magnetic reed switch contacts using a 10 ohm resistor. This is in connection with Dot Brake fluid level switches.
I didn't know anything about this but I do now.
A gap filled when I didn't know that there was a gap.

Others on this forum have said they enjoy my posts and the good choice of topics.

There is an infinite amount of room on this site.

Kind regards
Bob.

Bob

Why don't use some of your energy and obvious superior knowledge to start a thread on your car, show us its history and most of all some pictures of it?

Kev

Kev,
Thank you for the compliment. However I only know this stuff because a cleverer person than me explained it to me.
I had one lecturer who was a serious expert on automatic gearboxes. He really knew his subject very deep.He did a book on boxes for his masters degree. Ones learns a lot from people like that. My highest qualification Is an OND.



I am using a borrowed mobile for these postings. The spell check is hopeless and posting photos is not possible.

I am also in ill health with a disease that is not curable its
not fatal but makes working on cars differcult.
I am going into remission and hopefully will be able to work on cars. At the moment because of meds I dont even drive. The meds and concentration don't go together.

Plus I have a tablet turning up soon which may support photos.

Kind regards
Bob.