Brakes

Post any Tech Tips or any matters and questions relating to upkeep
pruyter
Posts: 84
Joined: Thu Jul 28, 2011 11:31 am
Location: The Netherlands

Brakes

Post by pruyter » Mon Aug 05, 2013 11:09 am

Hi,
I have the following problem: when using the brake pedal I have sometimes to pump it up two times before it sits as high as before. There seems to disappear some brakefluid (silicone brake fluid). I have checked the master cylinder and I see no brake fluid near the pedal. I have checked both wheel cylinders and the calipers but I see no loss of brake fluid. I see no white smoke in the exhaust which could indicate a leak in the servo. So where is brake fluid going to and why I have to pump up the pedal twice (not always!) before it sits as high as before?
I should appreciate some advice. Thanks a lot in advance!
Regards,
Peter

meadowhog
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Location: South Bucks

Post by meadowhog » Mon Aug 05, 2013 9:38 pm

Air in fluid but I guess youve checked that. Rear wheel cylinder not set right if using non self adjusting mechanism.

Do you loose fluid and have to keep topping up or does the fluid level come back?

pruyter
Posts: 84
Joined: Thu Jul 28, 2011 11:31 am
Location: The Netherlands

Post by pruyter » Tue Aug 06, 2013 7:31 am

Hi,
Up til now I did not have to fill up brake fluid, but the level in the reservoir is a little bit lower than usual. The problem just began a few days ago. So it seems that I am losing brake fluid, but it goes very slowly. I have checked the adjustment of the rear brakes and everything seemed okay.
Is it possible that the brake fluid disappears in the servo and because of the low quantity of brake fluid in the servo there is no white smoke to bee seen at the exhaust?
What puzzles me too is that sometimes the brake pedal feels okay and sometimes I have to pump it up twice before everything is normal again.
What could cause that?
Thanks for your reaction, I appreciate it very much!
Best regards,
Peter

Mal
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Location: NZ

Post by Mal » Tue Aug 06, 2013 9:42 am

Sounds as though you have air in there.
Have you tried bleeding the brake system. Start with the furtherest away from the MC and work your way to the closest to the MC. You should end up with a firm pedal. If not you could be sucking air into the system.
It could be the seal in MC starting to leak or it could be the servo doing the same.
The MC is easy to replace the seal and if your brakes have not been overhauled it could be a good time to do it.
Is your servo the original, if so Brad 1380 found someone to rebuild it.
Mine had been replaced with a lockhead, It was starting to leak fluid into the diaphragm and it was nearly as cheap to replace it with a new unit than have it rebuilt.
With single circuit brakes you want them to be right.

Good luck , I hope this is of help.

Cheers Mal
Image

pruyter
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Joined: Thu Jul 28, 2011 11:31 am
Location: The Netherlands

Post by pruyter » Tue Aug 06, 2013 2:24 pm

Hi Mal,
thanks for your reaction. I have a Lockheed servo which is installed about 20 years ago. I also do use silicone brake fluid.
I have been thinking too about air in the system, but how is it possible that air has entered the brake system?
I have checked the whole system on leakage of brake fluid and did not see any leakage. If the master cylinder should be leaking one should expect to see some brake fluid either near the brake pedal or in the engine bay. The only way that brake fluid can disappear without being spotted is when it goes to the servo. That is why I started to suspect the servo. I also don't understand why I have sometimes to pump up the pedal but not always. If air is the culprit than I should expect to pump up the pedal every time I use the brakes or am I mistaken in this one?
I don't want to take of the servo for nothing, so if the servo is the culprit I first want to rule out the master cylinder. The questin is: how do I do this?
Is there a theory which explaines air in the brake system and at the same time losing brake fluid which can't be spotted?
Thanks for your help Mal!
Best regards,
Peter

meadowhog
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Joined: Fri Dec 16, 2011 1:50 pm
Location: South Bucks

Post by meadowhog » Tue Aug 06, 2013 9:00 pm

Assuming you have checked for leakage by removing drums etc on brakes and found nothing, have you checked behind the rubber boot on the rear cylinder. If the piston seal is bad it could allow air to be sucked in and fluid to be held in the rubber boot.

Another area for air to get in is through the MC running low and the brake being applied. If too low, air can be sucked in but when you stop and look in the reservoir it wont look empty.

Im no expert on how a servo works but you would need a considerable amount of fluid to leak into it before you get the white smoke. This would fit with you thoughts.

I cant say definitively why you have spongyness 'sometimes', but it really does look like air in the system. If you do as Mal says and you find air in a certain leg of the pipes it will show you where the leak is. Also consider how much fluid you bleed-if its hardly any before bubbles appear then the problem is very close to the bleed off point. If you bleed alot it could be from the MC. Bear in mind if you have air at the MC you may not bleed this out and it could get trapped in the pipe after the T and before cylinder.

You may not cure the problem (or for a time) but it could point you to where the issue is. It doesnt take that long (with a helping hand or a kit) if the bleed nipples come undone!!

Try not to do it with your Mum. Up, Open, Down, Closed, is sometimes too difficult to follow!

alpine5gt
Posts: 109
Joined: Thu Jul 28, 2011 10:08 pm

Post by alpine5gt » Wed Aug 07, 2013 5:16 am

You metioned you are using silicon fluid. It is very hydroscopic, it will absorb mosture where mineral fluid will not. There is quite a deal of discussion on air absorbed into silicon brake fluid. Not saying this is your problem but worth checking. Some users boil the fluid under pressure so the air boils out of the fluid.

pruyter
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Joined: Thu Jul 28, 2011 11:31 am
Location: The Netherlands

Post by pruyter » Wed Aug 07, 2013 9:15 am

Hi meadowhog,
Thanks again for the information! I had checked the rear brakes by taking of the drums, but I did not lift the rubber boots on the rear cylinders. I will do that now. For the record: the brake pedal did not feel spongy but was lower than normal and by puming the pedal one more time it feels again like it should be.
The master cylinder has never been low in brake fluid, because up til now only about 2 cm from the top of the reservoir has disappeared. The level of the brake fluid is still above the maximum indication. So according to your explication air can not been enterd the system via the master cylinder.
So resuming: I will first check if there is any brake fluid tracable when I remove the rubber boots from both rear wheel cylinders. Next I will bleed the system and see what information I get out of this.
And yes I will not ask my mum to help me (is not possible either because she passed away for a little more than a year ago) and I will defenitely not ask my wife. I will ask a fellow Tiger owner whom is always very helpfull.
Best regards,
Peter

pruyter
Posts: 84
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Location: The Netherlands

Post by pruyter » Wed Aug 07, 2013 9:31 am

Hi alpine5gt,
Thanks for your reaction! I am a little amazed about what you wrote about silicone brake fluid. I have it now for 18 years in the Tiger and it is in this car for 21 years. I never had any problem with it and the reason of using silicone brake fluid is that it doesn't attract moisture which on the contrary mineral brake fluid does!
New for me is the item that there is a discussion bout air absorbed into silicone brake fluid. I never heard that one before, but that doesn't mean that it can't be thrue. But......for a period of 18 years I have had a brake system with no problems at all, so why now when silicone brake fluid should be the culprit?
Anyhow, I appreciate it very much that people on this forum take an interest in my brake problem and spend their valuable time in trying to help me, so to you also: thanks a lot!
Best regards,
Peter

alpine5gt
Posts: 109
Joined: Thu Jul 28, 2011 10:08 pm

Post by alpine5gt » Wed Aug 07, 2013 9:33 am

alpine5gt wrote:You metioned you are using silicon fluid. It is very hydroscopic, it will absorb mosture where mineral fluid will not. There is quite a deal of discussion on air absorbed into silicon brake fluid. Not saying this is your problem but worth checking. Some users boil the fluid under pressure so the air boils out of the fluid.
As I have already said, you may have nothing leaking and all the brake system good. The spongy pedal can be because you have air in your silicon fluid from when ever it was used and possibly when the top of the master cylinder was opened. I see my comment was ignored, so be it.

pruyter
Posts: 84
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Location: The Netherlands

Post by pruyter » Wed Aug 07, 2013 12:18 pm

Hi alpine5gt,
Why are you reacting the way you do? That I don't understand immediately what you are trying to explain doesn't mean automatically that I ignore your comment. I do really appreciate that you are trying to help me. I am not a technician, but I want to understand the logics of what is being said.
I have been reading a lot about silicone brake fluid and the most pregnant thing that is said is: silicone brake fluid does not attract moisture and about attracting air I have never heard or red it before. I explained already before that I will bleed the system after I have checked if there is any brake fluid visable under the dust rubbers which are on the wheel cylinders. I have also stated that the brake pedal does not feel spongy but needs sometimes two times pumping before the pedal is at its normal position. So there are two problems to solve: one is the missing brake fluid and number two is sometimes the need of pumping up the brake pedal twice. Again: thanks a lot of spending your time at my brake problem.
Best regards,
Peter

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redbaron
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Location: Essex

Brakes

Post by redbaron » Wed Aug 07, 2013 6:59 pm

Peter,
the problem that you have may be that the brake master cyl rubbers are not holding pressure and allow a small amount of fluid to creep back past when you apply the bake pedal pressure,this can sometimes give the problem of needing several pumps to bring pedal pressure up.
How old are the seals in the cyl?
You will also experience this sensation with silicone,far better to use a good normal fluid.
Whilst silicone will not absorb moisture it will still enter system via caliper and cyl rubber parts,and hoses if so fitted and will be in the system.

tigermany
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Location: Germany
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Post by tigermany » Wed Aug 07, 2013 9:13 pm

Hello Peter,

I think your problem is the small seal from your brake master cylinder.
It is going bad.
I had a similar problem in the past.
When I pushed the brake padel - the feeling was soft like "air in the system" but no bubbles found, also no leaks - I checked all seals from the BMZ and found the worn small seal - replaced it and the problem was fixed.

Good Luck

Thomas

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redbaron
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Location: Essex

Brakes

Post by redbaron » Wed Aug 07, 2013 9:29 pm

Peter,
as Thomas,has posted,the small seal can be the culprit and will not seal off the cyl,it will let a small amount of fluid back into the cyl reservoir,as you apply the brake this would mean that you need a couple of pumps to get a hard pedal.

Try a Master cyl rebuild kit if the cyl is not too badly scored.
Regards David

pruyter
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Location: The Netherlands

Post by pruyter » Thu Aug 08, 2013 9:54 am

Hi redbaron and tigermany,
many thanks for your reactions! The master cylinder is installed new in oktober 1995 so it is nearly 18 years old. I bought the car from Brian Postle and he used for the brake sytem silicone brake fluid and for the clutch system normal mineral fluid. I haven't changed that and regarding the brakes I never have had any problem with it. With the cluthc I had several times to renew seals in both the master cylinder and the slave cylinder. So that gave me the impression that silicone brake fluid wasn't a bad idea at all.
To be precise: the brake pedal never feels soft like air in the system, it just needs two times to pump up before it sits as high as before.
I understand your explination about the seal in the master cylinder, but what about the sinking level of the brake fluid in the reservoir? If the small seal is the culprit how can then be explained that the fluid level is (very slowly indeed) going down?
If you have any idea how this is related to the small seal in the master cylinder I should appreciate it very much to hear it from you
However thank you very much for helping!
Best regards,
Peter

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