Brake Failure: A 5 minute job which could save your life!

[johnben]

Sorry about the tabloid headline but after my ?scare? I feel duty bound to inform as many E Type owners as I can. I had a fortunate escape following the ?dual? braking system on my Series 1 failing. It would appear that hydraulic brake fluid had entered into the vacuum system because of a seal failure in the servo master cylinder.
The 5 min job: - You will note that at the end of the master brake cylinder is a diaphragm housing from which there are 2 rubber tubes connected, one from the rim of the housing and one from the bottom rear pointing back towards the bulkhead. This is the one to disconnect for inspection, any hydraulic fluid found in this tube indicates a failure of the seal within the master cylinder and in my view any further use of the car would be foolhardy until the fault has been rectified. Incidentally there was about 100 ml of brake fluid in the vacuum reservoir (situated below the master cylinder) and I really should have picked up on this earlier when I started to have to top up the reservoir.
I understand that white smoke on starting is a clue to this problem, however hydraulic fluid would have already past the inspection point indicated above and on a frosty January morning when I had my incident I just thought it was the result of cold starting. I would be interested to know if anyone finds fluid in the tube, I have looked back through other Jaguar forums and found about 5 reports of similar incidents.
In response to my item above I received some replies, two of which I think, are of interest:

?An easier test for this condition, and one that should have been noticed earlier, is to listen to your engine. When you stop your car or when press on the brake while the engine is idling, it will speed up on application of the brake pedal.
Usually, LONG BEFORE you have any need to add brake fluid to the reservoir, this symptom will manifest itself. It is caused by the vapours from the brake fluid being drawn into the intake manifold when the booster refills and enriching the mixture.
Listen to your engine all the time; it will talk to you if you listen.?

?One more note on this, The exhaust smoke will smell odd because of the extra fluid burning.?

John
http://i112.photobucket.com/albums/n184 ... acopy.jpg http://i112.photobucket.com/albums/n184 ... lure2a.jpg

[Heuer]

John

Thanks for the very useful information and clear description. Your photos did not appear within your post. I guess you clicked on the URL or Img button in the editor. No need, just paste the Photobucket IMG code (last box down) into your post. Anyway, here are your pictures:

[e-bygum]

John
I find your post somewhat confusing. Are you suggesting that if fluid is found at the metal pipe hose connecter of the reaction vavle this will indicate both brake circuits are inoperative?
Surely for both circuits to fail there must be two faults. One in the master cylinder preventing foot pressure operating the brakes directly and a fault in the servo system preventing servo operation of the brakes.
Fluid in the reaction valve capsule will only indicate a failure in the master cylinder not in the servo cylinder.
I cannot see how fluid can get into the reaction valve from anywhere else other than a failure of the seal on the master cylinder intermediate piston which operates the reaction valve. That seal failure would have to be so bad as to prevent any pressure in the master cylinder being felt at the servo slave cylinder, hence no direct braking from the foot pedal.
In that circumstance the pedal would go to the floor and the push rod would activate the reaction valve by pushing directly on the intermediate piston. This would operate both brake circuits by the servo alone. If the servo did not operate the brakes there must also be a fault in the servo/slave cylinder assembly as well as in the master cylinder assy.

In my opinion fluid at the point you suggest will only indicate a faulty master cylinder and give no indication at all about the servo or the slave cylinder. Fluid in the vacuum tank could be from either cylinder.

It is unlikely that two faults of this nature would happen simultaneously. Either fault would/should give an indication by reduced braking efficiency and/or loss of fluid from a reservoir and should be noticed pretty quickly.

[johnben]

Hi David
Thanks for the advise on the images and displaying them.

Hi Pete
Thanks for your observations, I have stated what happened, I have since replaced the master cylinder and associated reaction valve assembly and all is well, so if there were two faults they must have been within this unit. My aim is to prevent another incident similar to mine, put it this way if I was able to read this post a month go I would have saved myself a nasty scare. You may be interested in a post I received from the Jag Lovers Forum, which I have reproduced below, and raises the same points. I think my advice holds good if you inspect this pipe and it contains fluid then do something about it.

John

?John, I hope you realize that the fact you had a complete brake failure indicates that half of your hydraulic system had *already* failed at some point in the (possibly) past. Had you taken note of that earlier failure, and corrected that problem, you would not have experienced a total failure now. Fluid in the vacuum system indicates a failure of the seal at the back end of the servo cylinder, or, more rarely, the seal on the RV actuating piston on the nose of the master cylinder. This *had* to result in loss of fluid from one of the reservoirs. The other common failure mode is a failure of one, or both, of the seals on the floating piston in the servo cylinder, which will result in transfer of fluid from one reservoir to the other (one goes down, while the other goes up). Either of these is a tip to the wise that something is wrong that needs to be addressed immediately.
--
Ray Livingston - '64 OTS Santa Cruz, CA?
_________________

[Heuer]

John

A number of people have wondered what was happening to their brake fluid when there was no apparent leak - now they know why! I particularly like the 'brake on/idle speed test' which I have never heard of before and something I will be cognisant of in the future.

[e-bygum]

John
In your first post you said that fluid had apparently entered the vacuum system because of seal failure in the 'servo' master cylinder.
You say that after replacing the master cylinder and associated reaction valve all is well. What about the failed seals in the servo cylinder - surely that fault is still there and would not be indicated by fluid in the reaction valve.
Are you sure you have full braking effort?

[Moeregaard]

This is a common problem on E-Types and late, servo-equipped Austin-Healey 3000s. Since the servo sits well below the master cylinder and its reservoirs, any leakage will allow fluid to drain into the servo's vacuum chamber. Many times, the process will take months before the fluid level reaches the port connected to the intake manifold, with the resulting white smoke often accompanied by a lot of pre-ignition. I think Castrol GTLMA has an octane number of about 40...

I once had this occur in heavy traffic, and did experience almost total brake failure. Because of this, any time I see fluid levels dropping with no apparent leaks, I will always overhaul both the servo and master cylinder. The kits are relatively expensive, but nothing like the cost of a new bonnet.

[johnben]

Peter

Thanks for the interest and perseverance, I fear I have been misleading you, it is the master cylinder not the servo cylinder where the problem occurred as indicated in the images. The servo cylinder has not been touched, but will be later this year, I regret the error. In my hast to warn other users of this problem I became careless with the detail. The original post should read:
?It would appear that hydraulic brake fluid had entered into the vacuum system because of a seal failure in the master cylinder.
The 5 min job: - You will note that at the end of the master brake cylinder is a diaphragm housing from which there are 2 rubber tubes connected, one from the rim of the housing and one from the bottom rear pointing back towards the bulkhead. This is the one to disconnect for inspection, any hydraulic fluid found in this tube indicates a failure of the seal within the master cylinder and in my view any further use of the car would be foolhardy until the fault has been rectified. Incidentally there was about 100 ml of brake fluid in the vacuum reservoir (situated below the master cylinder) and I really should have picked up on this earlier when I started to have to top up the reservoir?
I would be interested in your views following this amendment.

Regards
John

[e-bygum]

John
Thanks for the clarification. Please forgive me if I gave the impression of disputing what you were saying, I could not get my head around why you were concentrating on the master cylinder when you had said (in error) that the servo cylinder was faulty.
You are wise to consider checking out the servo cylinder as I would guess it is of the same age as the failed master. When one seal goes it can be expected that others are not far behind.
Did you strip the old reaction valve? I would be very interested to know what was wrong with it to prevent it applying atmosphere to the rear of the servo. The most commonly reported failure mode of this valve is for it to stick open so that the servo remains open to atmos. after the brake pedal is released. This causes the brakes to stay on. This is the opposite of your problem. The concensus of opinion is that this is caused by the small piston in the nose of the master cylinder sticking in the 'operated' position preventing the reaction valve diaphragm returning to a balanced position with equal vacuum on both sides.

[johnben]

Pete

Thanks for the comments, I to am curious about the reaction valve and what exactly the problem was. I intend to strip the unit down within the next 7 days and will post the results with pic's.

John