Brakes!!!

[iannima]

I remember that the day I first saw my vehicle, I had just sat down on the passenger's side for a drive out, when the seller told me: "the weak point of the Gaz 69 is the brakes"... From then on, I have seen -thankfully third hand- the truth of his statement. Many are the horror stories I have read on the German forum . On the basis of these warnings, until now, I have therefore taken this approach:
IF
a) they don't leak;
b) the vehicle brakes, when required;
c) it passes the MOT
THEN
LEAVE WELL ALONE!

However... maintenance and checks need to be carried out any way, and I thought it would be useful to start a single thread on which we can all share our collective "braking knowledge" so that we might have a reference point (in English) when we do need one. This is all the more necessary because the axles and the brakes mounted on the Gaz 69s are not all identical, and therefore comparing notes is a good idea.

My VERY basic understanding is this:
Earlier vehicles have Duplex brake cylinders on BOTH front and rear axle, like these:

supplied by Trapper
This means that there is one Leading shoe and a Trailing one pushed out by a single cylinder with two pistons.
Later vehicles probably have the Uaz 469 arrangement whereby the rear axle is the same as before, but the front one now has two cylinders per wheel station with one piston each pushing out two leading shoes. Samter has some for sale:
http://www.ebay.co.uk/itm/GAZ-69-Radbre ... 500wt_1093

Now on the shoe-front... there are two options: riveted and glued.

I obtained the riveted ones from Todor and the glued ones from Samter
The riveted ones are all identical. Samter seems to imply that these are for the later arrangement but that they work on both axles.
The glued ones are instead intended for the earlier arrangement and are different: the leading one is lined all over whereas the trailing one has the topmost section of its arc unlined:

Notice the original boxes with different part number
When "assembled" this is how they compare:


Are the riveted and glued ones really going to be equivalent? What have people got on their vehicles? I know I have the glued ones all over with Duplex cylinders both front and rear.

[Geronimo]

Brakes, indeed, are a life-saving attribute when roaring at incredible speed through the landscape . I can subscibe to everything Matteo listed above.

On my Gaz, I also have 4 times these duplex cilinders but had to exchange them into new. It seems that there are, however, two sizes (diameters) of these cilinders since the new ones I bought are only 25mm. The original ones were well over 30mm and now I have no idea about the implications this could have.

Concerning the partly lined shoes I can confirm that this is also the case on my Gaz with the rivetted ones and also there I have no idea of the purpose because for the rest all (8) brake shoes are identical and one could argue that the more friction, the better the car brakes. The difference between rivetting or glueing lies in my opinion in the trust you have in the glue. Glued shoes have a longer life because you can use the lining until the end, while rivetted shoes are gone once you reach the rivets (+- halfway the lining). I chose the rivetted ones.

I would like to add to this subject two other, very important issues concerning the brake system: first, it has to be absolutely air free. So it is really wiser to pump out the air one time to much than to less. And second, always check that there is enough brake fluid (level until max 2cm under the rim) in the brake pump.

cheers.

[iannima]

For the sake of completeness here is the diagram of the Simplex system at the front axle:

I had to take this from the Uaz 469 manual but one of the Gaz 69 manuals I have displays the very same diagram.
The Duplex system I found instead on the 1950s Russian language manual for the Gaz 69

Notice how it is visible that the trailing shoe is not lined on its full arc

[Onbevreesd]

Hello Matteo, (I think you have got the duplex and simplex mixed up in the post above) very clever of you to start this thread. I consider myself an expert in the GAZ braking system ;) as I think I encountered every single problem related to this issue when replacing my brake system.

When I got my GAZ 2 years ago it has stood for about 3 years so the brakes were all seized up. Since parts from Todor are cheap I decided to replace the lot (around 300 euros for all brake cylinders, shoes and hoses). Then the nightmare started!

Getting all the old stuff off was not a problem. Because the steel lines looked ok I decided not to replace them.
I changed all the parts, bled the system and pressed the brake pedal firmly for the first time ... a hissing noise came from under the body: the steel line burst open ... so the next step was to replace all the steel brake line with copper line.

I have got the UAZ front axle so the two opposing brake cylinders per wheel. Because this system uses a small line that connects the two cyilinders it has a banj bolt, a few copper rings, adapter pieces and other bits and bobs.

It takes a bit of practice to make a nice trumpet shape end on the lines but I got it in the end. After installing all the new tubing the system was filled up with silicone brake fluid (DOT 5, as was advised on the German GAZ forum) and bled. First the fluid came out of the back (!) of one of the front cylinders. It turned out that the thread in the hole where the banjo bolt comes in wasn't deep enough. Because it kept leaking I tightened it a bit more ... until the cast iron snapped and formed a crack in the brake cylinder.
Tip #1: check and test fit connections



To get all those described connections leak free took a lot of time. Once I thought I had solved a leaking joint another leak occured. Here you can see where the line goes from the top cylinder to the bottom cylinder:



Also the copper washers gave a lot of trouble, they needed overtightening to get them closed. I think a next time I would choose those aluminium washers with a rubber lining (the industrial name is Usit-rings).
That's tip #2.

The pistons on the front brake cylinders are made of aluminium and carry two regular rubber o-rings as a seal. The rubber rings were of very poor quality. Again I found this out after installing the parts on the car and discovering them leaking from inside. Inspecting the rubber o-rings, they had flat spots on them and weren't even deburred; the excess rubber casting material wasn't removed so made it possible to leak fluid along the seals. I got a few replacement o-rings of western quality at the local hydraulics workshop and got that problem sorted. Sorry, no picture of this.
Tip #3: check rubber o-ring seals and replace if necessary. 'new part from Russia' doesn't mean 'better then the old part'

Another part that I messed up was one of the front brake hoses. As they have a fine thread it is absolutely necessary to test fit them by hand and only proceed using tools when you have made sure the connection is screwed in straight for a fair number of turns.
That's #4 for you there.

I already mentioned that forming the lines end requires some practices. This resulted in having to redo some of the lines ends or complete lines in order to get them leak free.
Tip #5: take the old brake lines to a motor shop and have them copied. Or practice first before replacing them yourself.

All these leaks meant that brand new brake shoes were covered in silicone brake fluid. Since I did not want to start with any contaminated brake shoes I had to order some new ones. As a result of all these mess ups and leaks I had to extra order: 5 brake shoes, 2 brake cylinders and one brake hose. I had to open up all 4 front wheel brake cylinders to replace the rubber rings so also covered the inside with ATE brake cylinder paste. Since I always learned that you are never to take a new brake cylinder apart, because then you are likely to damage the seals, I have not taken apart the new rear brake cylinders. I have not had any trouble with them. Also the new master brake cylinder is functioning without any trouble. It has been mainly the front ones, trumpet shaped line ends, copper washers and connections in general that gave the trouble.

After all the trouble the front brakes looked like this:



In general: replacing the brake lines can be done on the car as it is. But it is a hell of a lot easier when the steel metal panels are removed for better access. It's extra work but it pays, especially when brake hoses and lines on the front of the car have to be replaced.

Bleeding silicone brake fluid filled systems seem to take more time then bleeding regular brake fluid filled systems. After bleeding it for the first time, I found out that a second time was necessary after the vehicle had stood for 24 hours. Brakes are now rock solid.

Also take your time to adjust the brake shoes according to the manual. It pays off.

Since the brake system is overhauled I have driven approx. 3000 km with the GAZ without any brake issues. It brakes very well for a drum brake type car. However considering the nature of the system I do plan to replace the seals of all cylinders every 2 years. It's only a few euros but can save a lot of trouble.

I think that's all the brake issues on my GAZ covered ...

Regards,

Marc
Holland

[Eastblock]

If you can't get copper washers to seal then they may need to be annealed. Heat them until they are red hot and let them cool down. They will now be much softer (copper work hardens).

[iannima]

Hello Matteo, (I think you have got the duplex and simplex mixed up in the post above) very clever of you to start this thread. I consider myself an expert in the GAZ braking system ;) as I think I encountered every single problem related to this issue when replacing my brake system.
Marc
Holland

Thank you for sharing your braking expertise That's exactly what I thought we should have!

[Turk_Gaz69]

remember that the day I first saw my vehicle, I had just sat down on the passenger's side for a drive out, when the seller told me: "the weak point of the Gaz 69 is the brakes"...

I think this seller never drive a Willys Jeep. If he drived a willys Jeep, when he drive a Gaz 69, he has to feel like adriving a Mercedes.

Gaz69 brakes are much much better than a willys maybe also Land Rover series. You can stop the car with first press to brake pedal on Gaz69 but on the willys this is impossible also on LR.

Osman
Turkey

[Geronimo]

Since I plan to exchange the complete brake system on my Gaz, I came to the issue of the brake fluid. I have some experience with the red stuff (DOT3 or DOT4) and I know this fluid is first, extremely agressive (and not only to paint) and second, has to be exchanged every second year or so.

Lately I followed a discussion on the German forum and they recommend a silicone based fluid which seems to be maintenance free. They also mentioned that the bleeding has to be executed in two steps with an interval of 24h because of the slower migration of air in this fluid. It seems that one can buy it at every Harley-Davidson shop and that the future availability will be for sure better than the original Russian fluid.

Does anybody here has (good or bad) experience with this silicone based fluid? Is it less or not agressive?

Thanks for any tips or recommendations.

[haymish]

silicon based brake fluid way less aggressive.but got to have the right seals for it.can be a pain to bleed and pedal feels different.travels further and feels softer in most vehicles.maintenance free just a bad joke!it still needs changing but just not as often.danger with it is that it doesn't change colour as it deteriorates so no warning of decay.also no lubricity in it so more jammed pistons possible-finally water-doesn't absorb it like ordinary fluid which seems good-but if water gets in the system it then pools at lowest points resulting corrosion worse than you would get with ordinary fluid.also if pools in wrong place then can turn to steam destroying your pedal pressure.

[Onbevreesd]

As I wrote in my post I use it in my GAZ. Bleeding takes a bit more patience but the brake systems feels rock solid. I have driven around 3000 happy kilometers with it, without any issues.

Please not that silicone fluid and regular fluid don't mix. Before you change the fluid make sure to flush the old systems with white spirit and clean or renew all rubber seals. If you don't, they'll swell and go kaputt.

I changed the whole brake system so changing to silicone was easy. One point of warning: silicone fluid is coded DOT5. Don't get that mixed up with DOT5.1, which is an uprated regular brake fluid.

Regards,

Marc

[haymish]

not saying dont use it-just dont believe the fill and forget as suggested on the german forum.i use it in some vehicles.one point-flushing with white spirit not normally advized cos can react with some seals and very hard to remove all traces.normally denatured alcohol is the recommended flushing agent-followed by compressor air line to eject/evaporate any residual alcohol.alcohol prefered cos it will dissolve any sludgy residues and compatible with any grade of brake fluid.
one serious failing of silicon fluid-beware if you have a servo.if it is leaking internally the silicon brake fluid ends up in the engine-no problem if ordinary brake fluid cos just burns.silicon brake fluid burns to produce silica sand!wears out the engine in double time.
quite a few classic car owners swear by it cos it suits being left in cars that are not used often-cos unlike ordinary fluid is not busily absorbing water vapour but in many instances it is more lobour intensive than ordinary fluid.-also note some vehicles can get hold over on the brakes using it-because it is thicker than ordinary fluid it can take longer for the brakes to release when foot comes off the pedal.dont think i'd put it in a gaz 66 cos the pedal moves so slowly anyway-dont want to slow it down more with thicker fluid.
p.s. if silicon brake fluid really was the best-how come the vast majority of vehicle manufacturers dont use it,infact recommend not using it.

[Onbevreesd]

Thanks for your information Haymish. I have read that manufacturers don't advise it to use in modern cars, where speeds are higher and pressure in the brake lines are higher. The evaporation point (hope that's the correct English term) of the silicone fluid is lower so hard and/or often braking at high speeds leads to vapour in the fluid which then leads to a decrease in braking power.

So the tip of the day should be: if you use the GAZ on a regular basis and drive it like your cornering the hammerhead, use regular fluid.
If you take it out of the garage only occasionally to drive your granny to her monthly bingo evening, use DOT5.

Marc

[haymish]

yup -about sums it up.-biggest concern with modern cars is abs doesn't like it[cos slower reaction time and lack of lubricant qualities].i put it in a ducati mille-in the clutch cos it was awful sharp and harsh and it transformed the clutch.just slowed it down a touch and smoothed it out.horses for courses.

[portamurda1]

and one other problem...its a bitch to get off if your spray painting!!!

[haymish]

yes -met that problem

[Umvoti]

Hello Matteo, (I think you have got the duplex and simplex mixed up in the post above) very clever of you to start this thread. I consider myself an expert in the GAZ braking system ;) as I think I encountered every single problem related to this issue when replacing my brake system.
Marc
Holland

Thank you for sharing your braking expertise That's exactly what I thought we should have!

if its of any help here is what my front brakes look like, I'm using the riveted versions

Bill

[explore4x4]

Hi there to all!

I have the older GAZ 69 model!

The front brakes of my gaz have the single twin piston slave cylinder!

Unfortunately I sent the brakes in to a brake part supplier to see if there are any standard equivalent shoes and brake drums! They had these pieces for a while. In my absence the shop was bought by a new owner, so in the chaos of the ownership change they lost my stuff!

The new owner is blaming the old owner, so I have to make a plan for the front brakes!

I am not sure if the rear brakes are the same as the front brakes (size of drums and diameter of the slave cylinders)

Or alternatively, any other parts that may fit! I have seen some disk brakes on the internet, but not sure it's the most sensible solution!

I live in a mountainous region of southern africa! I NEED good brakes!

Any help will be appreciated!

Jacques

[iannima]

I resurrect this old thread to keep the brakes story in one place.

Some of you may know that since last summer I have had an intermittent problem with the brakes. Every now and then they seized completely solid. It happened a few times with all four wheels getting very hot and the brake light permanently on. The odd thing was that releasing the pressure at a brake nipple would enable me to get going again, and then months would pass with no problem At one stage Gordon had a good look at all four wheel cylinders; re-honed the back ones but pronounced the front ones OK. Matters did improve but the problem would occasionally come back again.

Last Sunday I got fed up with it I was coming back from a show, and because of a road closure I was re-directed on to the motorway, which is something I normally avoid. I knew that something was not right, because before getting on the A1M I had noticed that the normal free-play on the brake pedal was absent. The vehicle seemed to "perform" normally, so I saw no reason to stop and investigate. But as soon as I got to "cruising speed" = 75 Kmh I knew something was up. The temperature gauge started going uncomfortably up. It was a hot day, so I was expecting it to run hot and had the heater flap on to help it cool down, but this was more than envisaged. Of course overheating could be due to any number of things, but my money was on the brakes being sufficiently on to make the engine work overtime. I managed to get off the motorway onto an A road and stopped. All four wheels were hot. Not red hot as I had known them to get, but then the brakes were not fully on, and the brake lights were off. I cracked open a brake nipple, and set off again. Engine temperature came down to normal (hot) levels which was consistent with conditions and past experience.

But I had had enough... It should be said that the brake fluid is the full silicone one and that I had done nothing to the system for practically eight years. Indeed the substitution of the fluid had been done by the seller before I bought the GAZ in 2009. Because it all worked I had elected to leave it well alone. Now things had changed and it probably was to be expected.

[iannima]

So today Derek came over and we decided to tackle the problem head-on. My suspicions concentrated on what had not been touched by Gordon last October: the master cylinder and the silicone fluid itself.

So we disconnected the pipe at the back of the master cylinder and started pumping. At first very little would come out, then more, but in such uneven squirts ... whereas Derek said that it should have come out smoothly . So we immediately knew we had found something untoward. Which is good from a certain point of view.

We took the master cylinder off and proceeded to take it apart. The circlip came off easily but the entire piston arrangement seemed pretty stuck With more brute force it all came apart. The fluid was very dirty and then we noticed various solid particles here and there. Like little stones which are likely to explain the cylinder getting occasionally frozen solid when we were pumping the fluid out.

We then proceeded to clean the entire system blowing air into the pipes at the brake nipples on al four wheels. The purpose of this was not only to drain the system, but to check whether there were any blockages in the pipes downstream from the master cylinder.

Luckily I have acquired spares over the years. So I had a brand new master cylinder which we decided to use, instead of the old one which we cleaned and put back together for future reference. I had also bought a full litre bottle of silicone fluid, which is expensive (£27 I think) but worth the investment given what the brake system is like on the GAZ.

Then it was all a matter of putting everything back together; filling it up and bleeding the system. First (limited) test drive seemed pretty good. No signs of leaks Will check again in a couple of days...

Any way, thanks to Derek this work should change something...

Total time from start to finish: two hours which is pretty good going I would say