[GMCnet] Brakes and brake fluid

[David H. Jarvis]

I lifted this from a hot rod site..............

Brake fluid does wear out and become contaminated.
Some people are still rejecting the notion of changing transmission fluid on a regular basis. How are we going to convince them that they should now change brake fluid regularly?

For years, many considered brake fluid to be a brake-job-to-brake-job service item. Do a brake job, and rebuild the wheel cylinders. Then, bleeding the brakes will flush the system - sort of.

Well, brake fluid always was, and continues to be hygroscopic - meaning that it absorbs moisture like a sponge. Leave a container of brake fluid open for a few hot, humid summer days, and it will likely absorb enough moisture to render it un-useable according to DOT specifications.

From a brake engineering point of view, absorbing and dispersing moisture throughout the system is good. It keeps moisture from forming in puddles within the system. Of course, these water puddles would settle into the lowest areas - such as wheel cylinders and calipers - where they can easily be boiled into steam by the heat generated by hard braking conditions and cause a loss of braking known as brake fade.

The downside of brake fluid being so hygroscopic is that the moisture dispersed throughout the system lowers the brake fluid boiling point, increases its viscosity, and promotes rust and corrosion.

• BRAKE FLUID SPECIFICATIONS

The DOT 3 specification requires a minimum boiling point of 401° Fahrenheit for "dry" brake fluid - fluid that contains no moisture whatsoever. To meet DOT 3 specs., "wet" or fully saturated fluid should reach 284° before boiling.

DOT 4 specs calls for minimum boiling points of 446° dry and 311° wet.

Most DOT 3 and DOT 4 brake fluids sold today meet or exceed the above specifications, but it is important to know the numbers.

NAPA DOT 3 brake fluids, for example, actually exceed minimum DOT 4 standards with a dry boiling point of 450°, while many of the cheaper brake fluids barely meet the minimum requirements to call themselves a DOT 3.

As with most other things there really IS a difference between a cheap brake fluid and a quality brake fluid.

DOT 5 is silicone-based brake fluid with a wet boiling point of more than 500° F.

You may ask yourself why the manufacturers do not simply switch to DOT 5 spec fluid. After all if some is good, more is better, and too much is just right. Right?

Well the DOT 5, while better under heat conditions than DOT 3 or DOT 4, does NOT absorb any moisture, so any moisture that finds its way into the system WILL puddle up somewhere causing rust, corrosion and, possibly, brake fade. You don't want slugs of water floating around any brake system.

Also, DOT 5 silicone fluid contains more absorbed air than DOT 3 or DOT 4 glycol, and it will aerate much more easily when it is pumped through small orifices such as those on an ABS system. For that reason, most manufacturers warn against using a DOT 5 fluid in cars with ABS.

DOT 5 is recommended for vehicles that sit for long periods such as antiques and classics that are stored all winter, and, of course, for racing due to its high heat tolerance. But conditions within the hydraulic system MUST be monitored.

• THE REAL WORLD

Even in sealed automotive brake systems, brake fluid will absorb one percent or more moisture every year simply from opening the reservoir to check fluid level, opening the bleeders, and through microscopic pores in the rubber hoses.

According to one trade publication we read, many two-year-old vehicles have been found to contain two to three percent water in the brake fluid. Imagine how much water must be contained in some six, seven, eight year or older vehicles that have never had their brake fluid serviced.

One percent water content can push DOT 3 fluid down to a 369° boiling point while two percent can push it down to 320°. Three percent can get it down to 293° - dangerously close to minimum DOT 3 requirements.

The rate at which this occurs depends on a lot of things such as the age of the vehicle and the type of hoses used. Better quality hoses are lined to make them less permeable to moisture. Some manufacturers chose to skip the lining in order to sell their product a little cheaper. You get what you pay for.

DOT (Department of Transportation) 3 and DOT 4 specification brake fluids are made from glycol and additives. Glycol absorbs and disperses moisture. The additive package helps to keep the moisture from attacking the internal components of the brake hydraulic system.

Another area of concern on today's automobile that was not a factor years ago is Antilock Braking Systems or ABS. There are many close tolerance components within the ABS system, and moisture can wreak havoc with them. Replacing a single ABS component is often much more expensive than a simple brake fluid service would have been.

The average car on the road today is 10 years-old. According to Brake & Front End Magazine, only half of these cars have ever had their brake fluid changed.

For the average motorist, there might not be that much risk under normal driving conditions. But, prolonged braking such as mountain driving and trailer towing might tax old brake fluid beyond its capacity.

--
"I've always been crazy, but it kept me from going insane"
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist

[Gary Casey]

Thanks, Dave, for the most excellent information. On my way to town to get fresh DOT 4....
Gary

________________________________
From: David H. Jarvis <jarv...@shaw.ca>
To: gmc...@temp.gmcnet.org
Sent: Fri, November 13, 2009 2:16:53 PM
Subject: [GMCnet] Brakes and brake fluid

I lifted this from a hot rod site..............

Brake fluid does wear out and become contaminated.
Some people are still rejecting the notion of changing transmission fluid on a regular basis. How are we going to convince them that they should now change brake fluid regularly?

[Rob Mueller]

Gary,

I've sent you an off net message with an article about Dot 4 brake fluids.

It provides some good info and shows that ATE Super Blue Racing Fluid is the
best on all fronts.

Here's a link to their website:

http://www.ate-na.com/generator/www/us/en/ate/ate/themes/20_ate_brake_produc
ts/50_brake_fluid/bf_info_us.html

http://tinyurl.com/q2xtm

As you can see the article backs up the website claims.

Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426

-----Original Message-----
From: gmclist...@temp.gmcnet.org
[mailto:gmclist...@temp.gmcnet.org] On Behalf Of Gary Casey
Sent: Sunday, 15 November 2009 4:57 AM
To: gmc...@temp.gmcnet.org
Subject: Re: [GMCnet] Brakes and brake fluid

Thanks, Dave, for the most excellent information. On my way to town to get
fresh DOT 4....
Gary

_______________________________________________

[John R. Lebetski]

The other thing about silicone is in cold climates the water can freeze. And tired Dot 3 has a chemcal and PH change that really tears up rubber parts. (hence it often turns black and contains particulate rubber.) If you have a Powermaster, it also attacks the seal in the pressure vessel and causes loss of nitrogen charge. Motto, brake fluid is so relatively inexpensive, change it often. If you get it on paint, water is the anecdote.
--
John Lebetski
Chicago, IL
77 Eleganza II

[George Rudawsky]

When we redid the brake system on my Palm Beach last year, we used the silicone Grade 5 brake fluid as it does spend most of it's time sitting. I'm eager to see how well things hold up with time, or if we start seeing seal troubles, etc. Since the system was totally apart, it seemed like a good time to give it a try.

I've used plenty of Castrol LMA and Ate brake fluids in my other cars over the years, and they have also worked well. We also used Ford Heavy Duty truck brake fluid in race cars years ago as it had the highest dry boiling temperature rating at the time. We did change and bleed brakes on a regular basis, but I hope that the silicone experiment works OK on the motorhome. Time will tell, but I do think it's a good idea to change the fluid regularly on any vehicle you own.

Whatever you do, don't change over to silicone fluid unless the entire system is apart!
--
George Rudawsky
Chicago, IL
75 Palm Beach

[Les Burt]

I have been using Cartel DOT 5 silicone fluid for almost 20 years.

http://www.cartelproducts.com/performancebrakefluids/siliconebrakefluiddot5.
html

http://tinyurl.com/ygbgpta

I have a tandem axle trailer with hydraulic drum brakes that I converted to
DOT 5 over 15 years ago with no flushing or maintenance since the initial
conversion. I recently went through the system to inspect it and was
surprised to find it in perfect health with no water or rust damage
internally.

I also have used the DOT 5 in an Audi 4000 with disc/drums, an Audi 5000
Quattro (AWD) with 4 wheel discs & ABS, and a VW Passat with ABS. None of
the cars had any trouble with the stuff even though I did very minimal brake
system maintenance over the many years I ran these cars. The fluid
manufacturer warned me that I may experience problems with the ABS system,
but after 8 years in the Audi, and 7 in the Passat, I can say everything
worked very much to my satisfaction. Because of the road conditions we see
here in Montreal, the ABS systems got a good workout.

I noticed several major improvements in my vehicle braking systems since
running DOT 5.
First,
The cold weather brake pedal sensitivity appears to be improved as the fluid
does not appear to increase in viscosity like typical Brake fluid. The rear
brakes also respond quicker in extreme cold than with regular fluid.
Second,
The silicone fluid is a good lubricant, so the hydraulic parts suffer less
frictional losses. This also helps improve the pedal sensitivity.
Third,
Every car I've owned with rear disc brakes has had premature e-brake
mechanism failure do to the inevitable road salts we see here in Quebec.
Since using DOT 5, the calipers seam to be lasting several years longer
before seizing up. This may also be partly due to my meticulous caliper
rebuilding techniques.

I can honestly say that I believe the DOT 5 I use has saved me on brake
system repairs over the years. I always did a full system overhaul and flush
to be sure that all seals were in perfect shape, and that all traces of the
old fluid was removed prior to pouring in the DOT 5. Bleeding was always
done with a pressure bleeder and not by pumping the pedal. Any results I
obtained were not through any controlled testing, just a seat of the pants
feel.

I can assure you that my coach will be getting DOT 5 along with a rear disc
conversion. The main reason for doing so will be to help prolong the
hydraulic component lifespan. I do recommend that a system flush be done
every 2 years to ensure removal of any foreign substances even though I did
not follow that recommendation on my previous vehicles.

My second choice for fluid has always been the ATE Superblue and the yellow
equivalent. I have used this fluid in many cars as well. I alternate between
colours each system flush.

Les Burt
Montreal

-----Original Message-----
From: gmclist...@temp.gmcnet.org
[mailto:gmclist...@temp.gmcnet.org] On Behalf Of George Rudawsky
Sent: November 14, 2009 5:02 PM
To: gmc...@temp.gmcnet.org
Subject: Re: [GMCnet] Brakes and brake fluid

[Rob Mueller]

Les,

Wow that's an impressive service history!

Do you agree with Cartel's statement:

Simple changeover - just perform normal "brake bleeding job"

Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426

-----Original Message-----
From: gmclist...@temp.gmcnet.org
[mailto:gmclist...@temp.gmcnet.org] On Behalf Of Les Burt
Sent: Sunday, 15 November 2009 10:49 AM
To: gmc...@temp.gmcnet.org
Subject: Re: [GMCnet] Brakes and brake fluid

I have been using Cartel DOT 5 silicone fluid for almost 20 years.

http://www.cartelproducts.com/performancebrakefluids/siliconebrakefluiddot5.
html

http://tinyurl.com/ygbgpta

Les Burt
Montreal

[Shan Rose]

Natürlich es ist ein Deutsche kompanie , so nur höchste qualität akzeptabel ist! :) Deutschland ist wo das Auto wurde geboren... :)

Robert Mueller wrote on Sat, 14 November 2009 13&#58;57

[Les Burt]

Rob,
The very first car in my fleet to receive the DOT 5 was my father's Audi
5000. We did a 5 minute flush using the DOT 5 and the pedal pump bleeding
procedure, unaware of the fact that DOT 5 is bad for creating & holding air
bubbles. We got a mediocre pedal initially but it got better after a few
days. We eventually did a second bleeding procedure several weeks later with
a pressure bleeder and the car ran for many years like that without any
problems. The brake system was not dismantled and cleaned, The lines were
not flushed, and the hydraulic components had been in service since the car
was new. I certainly would not do that now with the knowledge I have gained,
but the car didn't suffer any from the way in which we did the conversion.
This was the car in which we noticed the improvement in rear brake
sensitivity during severe cold operation (-20 and colder) We had done the
conversion over Xmas so we had a good feel of the before and after with no
other changes to the braking system.

During a lengthy discussion with the engineer at Cartel many years ago, I
asked about what happens to the two fluids when mixed together. The engineer
said that the old fluid would just puddle in the lowest points of the system
and be somewhat harmless other than to hold moisture and potentially cause
corrosion at those points. The two fluids would not intermix. He said that
the best method was always to do a thorough cleaning and refurbish of the
hydraulic system prior to using DOT 5 silicone fluid.

If you wanted to just dump the old fluid and add DOT 5 without dis-assembly
& cleaning, the engineer recommended a thorough flush of the system first
using fresh, clean DOT 4. This ensured that whatever DOT 4 fluid remaining
in the system after a DOT 5 conversion would contain a very low moisture
content and be relatively harmless.

Les Burt
Montreal

[Les Burt]

I also forgot to mention that if not flushing the system prior to adding DOT
5, the fluid boiling point would only be as good as the lowest rated fluid
existing in the system. This is especially valid since the lowest point in
the system is almost always the calipers or wheel cylinders.

This also applies to regular Dot 3 & 4 fluids. If the system is not properly
flushed when switching fluid specs, moisture and boil protection will not be
at it's max ability.

[George Rudawsky]

Before I did my changeover, I also played with mixing DOT4 and DOT5 brake fluid, and they are definately like oil and water - they seperate and do not mix. When I shook the test tube containing the two of them, I managed to get lots of small bubbles, but the next day they were layered again.

I think that the idea of first flushing the system with clean DOT4 fluid would be a good idea if the system was not all apart before the conversion. I was told that one should have the system apart, and since we were replacing the master cylinder, combination valve, and wheel cylinders, it seemed like a good time to do the rest of the changeover. So far, the brake pedal and stopping has been good (but us flatlanders don't have to put quite the strain on the brakes as you mountain people!).

--
George Rudawsky
Chicago, IL
75 Palm Beach

[roy keen]

I have been using dot 5 in my street rods for 30 years. It keeps everything real nice inside. I don't worry about rusted wheel cylinders anymore like I did with dot 3. I converted the GMC to dot 5 just by flushing the old fluid out with new dot 5. It was OK for a few years but then I had problems on steep mountain grades (brake pedal went to the floor when the brakes got hot). If you are running dot 5 in the GMC I would change it just like dot3 as it will wind up with water pockets in the system and if that happens you will loose your brakes at the worst possible time. It is a lot less expensive to change dot 3 or 4 every couple of years. If you never get the dot 5 hot it will be OK like in my street rods.
Roy

[Rob Mueller]

Les,

Since you didn't disassemble brake system in the Audi and it worked OK then
the old adage of "you can't argue with success" is apropos.

I wonder if it would be a better to blow all the Dot 4 out; flush the system
with denatured alcohol, blow it out again, and then fill it with clean Dot
5.

HOWEVER, I think the "best practice" would be to take the whole thing to
bits and clean everything then change over to Dot 5!

Les Burt
Montreal

_______________________________________________

[David H. Jarvis]

Is it possible to blow out all the lines with air?

--
"I've always been crazy, but it kept me from going insane"

[George Rudawsky]

You could, but then you have to get all the air out of the hydraulic system. It's the main culprit in most of the brake problems! If you're not disassembling the entire system, I think that a fluid flush makes more sense (perhaps the alcohol step may be a good idea, but I'd check with other sources before doing it).

--
George Rudawsky
Chicago, IL
75 Palm Beach

[Les Burt]

I've always disconnected the lines and blown them out with air only. I've
had the belief that any solvent not designed specifically for brake system
flushing might potentially affect the boiling point of the new fluid should
any of the solvent remain in the system. Alcohol has a fairly low boiling
point, and in a closed system, would not be able to evaporate unless long
periods of air flow were provided through the system prior to adding brake
fluid. There is apparently a proper solvent made specifically for flushing
brake systems but I haven't looked for it.

Another point of interest:
All commercially rebuilt and new brake hydraulic components are lubricated
with a water soluble grease and/or brake fluid. Unless you are willing to
fully clean and appropriately re-lubricate these parts before using DOT 5,
you will always have a small qty of a hygroscopic product in the system.
Unless you are a purist to the Nth degree, this isn't really an issue.

I always recommend that any DOT 5 conversions begin with all the hydraulic
components being dis-assembled, cleaned with alcohol and dried, then
re-assembled with a light smear of Dow Corning #4 silicone die-electric
grease on the moving parts. The Cartel DOT 5 that I use dissolves & blends
with this grease over a short period of time, so it has no negative effect
on the system function. Doing this much work assures you of having the best
possible chances of not having trouble later.

Les Burt
Montreal

-----Original Message-----
From: gmclist...@temp.gmcnet.org
[mailto:gmclist...@temp.gmcnet.org] On Behalf Of Rob Mueller

[Gary Casey]

I'm trying to work up the ambition, so I thought I would ask the question: I've got a '73 with about 155,000 miles on the original timing chain, as best I can find out. Were there any plastic sprockets used in these models? Should I change my chain now? I've got the heads off, so now is as good a time to do it as any. I just need the ambition....:-). I assume I have to jack up the engine to remove the front engine mount.
Gary

[Gary Casey]

Just another anecdote: Way back when (my long term memory still functions :-) I remember that GM was planning to go to DOT5. Reason was the high cold viscosity of DOT3 degraded brake response in the north country. Then they found out that if they filled the system in the same building as they painted they couldn't get a good paint job. Subsequently, all silicone products were banned from the final assembly plants. No WD-40 allowed. In our plant we didn't paint, but we filled sensors with silicone fluid. To get rid of the water and air we conditioned the oil at a few millitorr (almost a perfect vacuum and one that took many thousands of dollars of vacuum pumps to accomplish) for 24 hours. I don't know if the story about the GM plants is true, but after a few years of using silicone all our floors were pretty slippery and we had to use special cleaning processes for safety reasons. Silicone gets everywhere.
Ron is right, if you get vapor in the system the brakes go to zero in a flash. As someone said, they "cease to function properly." I'm not going to be driving if the temperature is below 0F, so I think I'll go out and just bleed my brakes using DOT4. As I understand it, one of the benefits of the glycerine-based fluid is that it tends to distribute the water through the system, avoiding any water pockets in the wheel cylinders. The bad news is that it absorbs water - the good news is that it absorbs water.
Gary

________________________________
From: roy keen <royn...@charter.net>
To: gmc...@temp.gmcnet.org
Sent: Sat, November 14, 2009 5:55:07 PM

Subject: Re: [GMCnet] Brakes and brake fluid

I have been using dot 5 in my street rods for 30 years. It keeps everything real nice inside. I don't worry about rusted wheel cylinders anymore like I did with dot 3. I converted the GMC to dot 5 just by flushing the old fluid out with new dot 5. It was OK for a few years but then I had problems on steep mountain grades (brake pedal went to the floor when the brakes got hot). If you are running dot 5 in the GMC I would change it just like dot3 as it will wind up with water pockets in the system and if that happens you will loose your brakes at the worst possible time. It is a lot less expensive to change dot 3 or 4 every couple of years. If you never get the dot 5 hot it will be OK like in my street rods.

[Steven Ferguson]

Good info here:
http://gmcmotorhome.info/engine.html#chain

--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/

[Rob Mueller]

Gary,

Here's some info on Gene's website regarding changing the timing chain. Keep
scrolling down until you get to the bottom of the page.

http://gmcmotorhome.info/engine.html#Rebuild

Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426

[Terry Skinner]

75,000 would have been a better time to change that chain. I would be
willing to bet that you will find little pieces of plastic blocking
the oil pump pick-up screen.
Not enough?
If you pull one of the heads off you will find evadence that the
valves are just missing a colision with the piston as in marks in the
carbon.
Still not enough??
Your timming, as in camshaft to crankshaft is so bad that you have lost 50 HP.
Get busy. No need to pull the radiator, just the shroud (good time to
split it) and front end of the engine junk. (You wanted to powder coat
those brackets any way.)
Its winter, get to work!! <VBG>..............Terry

On Sun, Nov 15, 2009 at 3:57 AM, Gary Casey <casey...@yahoo.com> wrote:

--
Terry Skinner
Roy. Washington
'76 GMC

[Rob Mueller]

G'day,

Another anecdote; Harley Davidson used Dot 5 for years but changed back to
Dot 3 a couple of years ago. I think the fact that water could gather in
slugs was the reason. Now you've got to be careful not to get it on the tank
and front fender if you add brake fluid.

Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426

[Gary Casey]

Terry,
Okay, okay, okay! I sort of deliberately didn't mention that I have a heated hangar right behind my house in which to do the work. If I had said that to begin with I wouldn't have gotten any sympathy at all :-)
Gary

________________________________

Still not enough??
Your timming, as in camshaft to crankshaft is so bad that you have lost 50 HP.
Get busy. No need to pull the radiator, just the shroud (good time to
split it) and front end of the engine junk. (You wanted to powder coat
those brackets any way.)
Its winter, get to work!! <VBG>..............Terry

[Steve Southworth]

Robert Mueller wrote on Sun, 15 November 2009 07&#58;03

> G'day,
>
> Another anecdote; Harley Davidson used Dot 5 for years but changed back to
> Dot 3 a couple of years ago. I think the fact that water could gather in
> slugs was the reason. Now you've got to be careful not to get it on the tank
> and front fender if you add brake fluid.
>
> Regards,
> Rob Mueller

The reason I heard Harley switched from DOT 5 to DOT 4 was the cop bikes were getting ABS and the ABS unit mfr specified DOT 4, no DOT 5. Harley supposedly originally went with DOT 5 because of the paint damage issues with DOT 3/4.

The Vette has had DOT 5 since before 81 and I have overheated the brakes a number of times (high speed autocross on racetracks) and never lost pedal. The Harley brakes have also been overheated (track days at Road America and Blackhawk Farms) with no loss of brake pressure. In both vehicles I knew the brakes were hot as I had severe brake fade from hot pads, and from the smell. On the Harley if I did not flush the brake system annually I would loose pressure when I went over high Rocky Mountain passes, brakes were cold. I had that happen twice before I figured it out. DOT 5 absorbs air and the air came out under low pressure forming bubbles. Not fun but the Harley has a big engine and lots of manual gears so engine braking is very effective. The Vette has never been into the Rockies with DOT 5 in the system. But if I am going to take the Vette there it will get a flush before I go.

On the GMC, based on my experiences with DOT 5, I will be using DOT 4 in two colors.
--
Steve Southworth
1974 Glacier TZE064V100150
Palmyra WI

[Charles]

Gary,
When I did my chain, the net recommended I get a double roller set.
Charles

[Matt Colie]

Another Anecdote:

I have been using all 3 types of brake fluid for more than a few decades. (A friend looked and my shelf and asked if I had some problem making up my mind.)

DOT5 has always been my preferred for things that either get little use or extreme use - nice mix??

On a very few occasions, there have been component failures shortly after a change of fluid only from DOT3 to DOT5. For this reason only, I will not convert the GMC to DOT5 at the upcoming brake service.

I have never ever had any difficulty with a system changed to DOT5 when the entire brake system (like everything but the backing plates and maybe drums) is replaced.

When I change to all stainless lines and braid over flexible while converting to six wheel disk (hopefully with anti-lock), I will change the system to DOT5. That is only waiting for the results of the lottery to go my way.

Matt
--
Matt & Mary Colie
'73 Glacier 23 Chaumiere (say show-me-air)
SE Michigan