Blocking / sticky brakes at 63 3.8 FHC with bellow-type

wagstefan · Post by **wagstefan** » Wed Jan 04, 2012 9:30 am

Hi there,

I would need you wise advise on a problem occurred during my first drive with my thoroughly maintained 63 FHC with the bellow type brake servo. I have checked the forum already but could not find a specific topic on the bellow type servo and blocking brakes.

Just as a side note: During the thorough maintenance everything regarding the brakes were redone beside the brake servo (lines, brake master cylinder, brake calipers, etc.)

What happened: I drove around 15 miles, applying the brakes a few times, when they started blocking. I stopped and identified that despite the brake pedal being there where it is supposed to be at unused condition, it could not be pushed down at all (it was hard as stone). And as I said, the brakes were blocked.

I had to wait for about 90 minutes and during that time I removed the vacuum pipe as well as the screw at the front of the bellow servo and all of a sudden the brakes were unblocked again. However I cannot say if the reason for unblocking was the working on the servo or just the cooling down of the brakes, which could refer to any kind of issues with the brake seals. While I was waiting and trying to organize some tools, I phoned up a garage specialized on Jaguar E-Types and they were telling me, that it could be the brake servo and that they experienced this already more often.

However rethinking what happened (the bellow was not compressed at least not visibly, which means that a "non releasing valve" should not be the problem), I am not sure, if the bellow servo really could have been the reason for the blocking. IF so, this would have meant, that despite the servo was not compressed it caused the brakes to block, which does not make sense to me?!

On my way home I drove with a non connected vacuum pipe and I rarely applied the brakes. It worked fine but maybe the brakes were starting to block again when I parked the car. But I am not 100% sure?!

Did anyone of you experienced similar issues with your 3.8 E-Types and what was the reason? Did anyone of you had similar troubles, which were caused by the bellow servo and what was the route cause?

Thank you very much for a short reply. I got already the bellow out and fully disassembled but I am not sure how to continue. There are no overhaul kits available hereover in Germany at least not from my preferred supplier. Therefore any kind of help is very much appreciated, which could narrow down the issue!

Thanks again in advance!

Best regards

Stefan

Ian Howe · Post by **Ian Howe** » Wed Jan 04, 2012 6:38 pm

Hi Stefan

As usual it is difficult to identify the problem without seeing the car. However, hard pedal/brakes locking on is usually caused by blocked/leaking lines, vacuum leaks in the bellows unit or the bellows is not adjusted properly. The service manual page L29 has all the info you need.

From my perspective the problem I had was the eccentric out of adjustment so once the brakes were applied they failed to come off. With the engine running in the garage you should be able to push the arm operating the servo against the valve and the brakes should apply - the eccentric bush adjusts the clearance and how far the valve is depressed. Too close a clearance and brakes could be sticking on - you need a little freedom but not too much. As an aside the valve assembly (parts manual plate 24 part 6 is not available but I have had some made up as mine broke) - anybody wants one I have a couple.

Ian
PS if you need a copy of the page from the service manual email me.

62 FHC
61 OTS

38E · Post by **38E** » Thu Jan 05, 2012 4:14 pm

This problem can also be caused by poor quality replacement master cylinder seals. I had it myself after totally rebuilding the brake system (and using supposedly correct boxed new seals).

In my case, I identified the problem as being isolated to the front brake master cylinder and a sticking seal. I cured it by changing the new seal for a good used one, put it all back together and I've had no further problem in years. ( I had already had the master cylinder sleeved and wondered if this might have added to the problem by causing the seal to be a tighter fit.)

There was a big discussion about these faulty seals on jaglovers a while ago.

daverawle · Post by **daverawle** » Thu Jan 05, 2012 7:53 pm

Didn't see the JL thread but am interested to know the seal make. I had a lot of grief with DSL seals, supplied by one of the usuals. DSL = Dowty Seals Ltd.
Dave

PeterCrespin · Post by **PeterCrespin** » Thu Jan 05, 2012 9:31 pm

Wasn't that with silicone though Dave, that they weren't specced for? Goodness only knows what might have happened since the good old days but Dowty was certainly a top class brand once and I'd be sad if they were truly junk nowadays in their intended usage.

These days brands get sold and resold for a fast buck all over the place, trading on a previous reputation for quality.

daverawle · Post by **daverawle** » Thu Jan 05, 2012 10:42 pm

True Pete, I am using silicone but both brake masters jammed from the off so couldn't even bleed them. My feeling is that it was too soon for any swelling additive in the fluid to have any effect so I distrust this brand.
Dave

38E · Post by **38E** » Thu Jan 05, 2012 11:25 pm

I used DOT5 silicone at first but got rid of it after a while. IIRC, it seeped through the walls of the reservoir hoses for one thing.

But that wasn't the problem when I had the brakes locking on. I had already changed to DOT4, the best alternative I can get here. The seals I used were either Lockheed or Girling and were supposed to be proper Jaguar replacements. It was a long time ago and I bought them in England.

There are also different length seals. See my JL photo album entry:

http://www.jag-lovers.org/snaps/snap_vi ... 1055094026

The shorter one was the used one that eventually worked.

And this for the whole front cylinder set-up. But be advised that photo #3 is wrong. It should show the shorter seal, shown in the other album. I can't edit my JL albums unfortunately.

http://www.jag-lovers.org/snaps/snap_vi ... 1055030626

BTW, I've never had another problem with the brakes since then.

wagstefan · Post by **wagstefan** » Sat Jan 07, 2012 12:29 am

Hi all,

Thank you very much for your posts!

As said, I have disassembled the brake servo and cannot think of any reason why this should have caused the brakes to block. I am even wondering whether the bellow was compressed (brakes applied) or not. I would assume the servo was not applied, the bellow not compressed, so definitely not the source for the blocking brakes.

However as there are no overhaul kits available for the bellow servo beside the bellow itself and the replacement is priced at somewhere above 600,- GBP, I will put the bellow servo back as it is and check again more thoroughly when the brakes will block again.

Thanks again and @Ian, when your brakes were blocked, the bellow must have been compressed, right?
@ 38E - nice colour. Is it opalescent maroon? My troublemaker is of the same colour! Very nice and in my case with an old red interior colour in colour very very nice. But it needed a bit of time to get familiar with the outside colour.

Best regards

Stefan

38E · Post by **38E** » Sat Jan 07, 2012 3:11 pm

Hard to do if you have the servo off already but you ought to try to check if it is actually the servo, or one of the two independent brake circuits.

Mine was just the front and I was able to discern that because releasing the pressure from a front bleeder(when the brakes became locked) temporarily cured the problem. So I new it was just the front, and worked on that.

andrewh · Post by **andrewh** » Tue Feb 17, 2015 9:52 pm

wagstefan wrote:Hi all,

Thank you very much for your posts!

As said, I have disassembled the brake servo and cannot think of any reason why this should have caused the brakes to block. I am even wondering whether the bellow was compressed (brakes applied) or not. I would assume the servo was not applied, the bellow not compressed, so definitely not the source for the blocking brakes.

However as there are no overhaul kits available for the bellow servo beside the bellow itself and the replacement is priced at somewhere above 600,- GBP, I will put the bellow servo back as it is and check again more thoroughly when the brakes will block again.

Sorry to bounce this old thread but I wondered whether you discovered what your problem was in the end ? I tried my first road test today and after three or four miles the rear brakes set fire! Well got rather hot let's say. I have been told some Green stuff pads are coming up a bit tight in the caliber and this could be my problem, but I am wondering whether there is anything else known to be a bit of a problem on brake blocking when hot on 3.8s.

Thanks again and @Ian, when your brakes were blocked, the bellow must have been compressed, right?
@ 38E - nice colour. Is it opalescent maroon? My troublemaker is of the same colour! Very nice and in my case with an old red interior colour in colour very very nice. But it needed a bit of time to get familiar with the outside colour.

Best regards

Stefan

Sorry to bounce this old thread but I wondered whether you discovered what your problem was in the end ? I tried my first road test today and after three or four miles the rear brakes set fire! Well got rather hot let's say. I have been told some Green stuff pads are coming up a bit tight in the caliber and this could be my problem, but I am wondering whether there is anything else known to be a bit of a problem on brake blocking when hot on 3.8

Ian Howe · Post by **Ian Howe** » Thu Feb 19, 2015 12:31 pm

Hi Andrew

I had a similar problem. Brakes working fine for years then one day had to brake VERY hard to avoid an accident. After that, the rear brakes locked on and would not come off - I had to eventually release the hydraulic pressure to the rear brakes to get home. The master cylinder seal (s) were responsible - I changed them although there was no apparent damage and brakes then AOK. If all the brakes stick on then it's the servo.

Ian

andrewh · Post by **andrewh** » Thu Feb 19, 2015 1:33 pm

thank you Ian. I have removed and replaced the rear pads which are the green stuff brand and filed these up a bit on the sides to make them less tight in the caliper. I understand they are known for being a bit on the tight side. I am also going to readjust me operating rod on the master cylinder as this could be a bit tight . I cracked the two bleed nipples on the rear and did not get much out but a little dribble which makes me think I have a little bit of hydraulic pressure still in the system when the pedal is off, hence the adjustment to the rod.

abowie · Post by **abowie** » Thu Feb 19, 2015 9:31 pm

Check that the air valve on the Kelsey Hayes is actually open again after you take your foot off the pedal. Also check that the air inlet filter isn't clogged.

andrewh · Post by **andrewh** » Wed Mar 18, 2015 5:11 pm

I still have an issue with the brakes on the 3.8 sticking on a bit. Well, I don't think its anything to do with the calipers or pads now. What happens is the pedal goes hard, or to be more accurate, the free play on the pedal disappears every now and again for no apparent reason. You then get a little smell of pads and the car slows if you dip the clutch but not a lot. Then it reverts to normal just as quickly as it did the other thing. I have put a return spring on the operating arm as we discussed earlier, although it may not have enough strength to make a big difference. The air filter is not clogged but what do you mean by the air valve? Are you referring to the small white pin in the middle of the servo behind the operating arm? If this is not always being cleared would this be applying brake pressure on its own? It may still be that I don't have enough clearance on the main operating rod, but why would it be ok some of the time and not the rest I wonder? Proving a little hard to track this one down

Springer · Post by **Springer** » Tue May 10, 2016 9:18 am

HI,
I am taking up again this old subject. I have now started to use my car after a complete restauration and experienced that the right front brake caliper blocks. What happens is that it seems to block when the brake is used so it gets warm. It isn't after just pushing the pedal hard but when I have used the brakes e.g. down a long hill so they gets warm. Then this caliper blocks and stay blocked until it is cooled in which it releases by itself. I have taken it off ones and it is a bit hard si I worked it a few times in and out but it might not be enough.
I am wondering if it is the center pin that need to be sanded a little?
The calipers are new.
Anyone experienced similar problems?

Mich7920 · Post by **Mich7920** » Tue May 10, 2016 4:35 pm

Hi Springer,
If you have a problem with only one caliper, it's only a factory problem and your seller will change it.
Really I will not touch the center pin, brakes are your security.
You have nobody around you who could lend you an old but working caliper ?
If no I can send you one. I change my original for coopercraft so I have a lot of, I can choose the better.
Mich

Springer · Post by **Springer** » Wed May 11, 2016 10:59 am

Thank you for your reply. I bought them from SNG so I will contact them and discuss.
Svein

Quattrofrank · Post by **Quattrofrank** » Wed May 11, 2016 11:01 am

Is it possible to use s2 brakes? If so I have a set of calipers taken of my car that you can try.

Mich7920 · Post by **Mich7920** » Wed May 11, 2016 11:53 am

No problem Svein, it's the better solution to come back to SNG.
Regards
Mich

trondvo · Post by **trondvo** » Wed May 11, 2016 8:07 pm

Not that it seem to be related but still, quite a few years ago I had a 65 FHC which would lock front calipers after spirited driving.

Tried all kind of approaches but was stuck until I changed the rubber brake hoses. The car had decent looking brake hoses but they were collapsed inside and worked like one way valves. Some years later I had a MGB with the same problem, a little wiser I did approach the rubber hoses before touching anything else and new hoses did the job.

I cannot rememeber the brand of the hoses but both cars had pleated pattern hoses and not straight lines if that tell you something.

Brake hoses are the least hassle and a cheap repair, unless you have good ones you may change them just for peace of mind.

https://newhillgarage.com/2011/09/13/wo ... he-brakes/
http://www.jag-lovers.org/xk-lovers/lib ... nding.html
https://themotorphile.com/2010/07/12/ja ... rs-part-3/

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Blocking / sticky brakes at 63 3.8 FHC with bellow-type

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