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Hi,

 

Now this isn't a problem as such but just bit odd to get used to ....

 

My TR4A came with a replacement servo assist brake unit on it. And it does stop very well. However ..... Once i start breaking, it just continues to break until it's stopped.

 

I'm not sure of that makes sense but basically, if I'm slowing down for a junction or tight bend, I will apply the break and then lift off the pedal and expect to then roll on. However, with my car, when i lift off the pedal, it's like i haven't taken my foot off at all and the car continues to brake until it's stopped.

 

If i accelerate away it's fine, so I'm currently just learning a new way of driving .... So, not really an issue as I'll get used to it but i do wonder why it does this and if it's normal.

 

I have the paperwork for the servo ( Powertune RLE72696) but there does not appear to be any kind of adjustment on it.

 

Any thoughts welcome - thanks

 

Andy

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Hi Andy,

something seriously wrong there.

 

Haven't got an answer But be very careful when using it.

 

I'm sure somebody has the answer.

 

Roger

 

just found this in the search facility http://www.tr-register.co.uk/forums/index.php?/topic/31109-brake-problem-holding-on/?hl=%2Bbrake+%2Bservo+%2Bsticking

Edited by RogerH
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Hi Andy,

something seriously wrong there.

 

Haven't got an answer But be very careful when using it.

 

I'm sure somebody has the answer.

 

Roger

 

Perhaps I haven't described it well, as it's easily manageable. It's only really noticable when at low speeds, like coming up to a junction where i plan to stop anyway. it's just that I'd normally break up to the junction and then roll the last few meters so i can continue if it's clear without stopping. However, the car won't roll that last bit as the breaks feel like they're still applied.

 

So, if i'm on an A road doing 60 MPH, it doesn't scream / skid to a halt if i apply breaks ! Normal driving doesn't feel any different, just at very low speeds

Edited by TR4 AJJ
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Hi Andy,

the brake should not interfere with normal driving. If you have removed your foot then the brakes should come off.

 

After using the car have you felt all four brake drums/wheels - are they hot/too warm.

Some thing could be stopping the pads/shoes from returning.

 

Roger

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Hi Andy,

the brake should not interfere with normal driving. If you have removed your foot then the brakes should come off.

 

After using the car have you felt all four brake drums/wheels - are they hot/too warm.

Some thing could be stopping the pads/shoes from returning.

 

Roger

 

No, I haven't but i will.

 

I haven't really driven it enough yet. In had a long journey collecting it (150 miles) but being that was mainly clear motorways, i don't suppose i breaked that much. I do like to think i can get round a motorway without breaking every ten minutes like some folk.

 

However, the few short journeys I've done since home have been mainly on country lanes where the breaks are required. After these trips i haven't smelt anything odd or seen any smoke. I have a feeling it may stop after a bit of use. I think the car had stood still for some time.

Edited by TR4 AJJ
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In order of investigation: first I would first inspect the brake pedal linkage to see if anything is sticking there - not sure if this occurs on TRs but it can do on some cars. Then I would try the car with the servo disconnected. I have heard of servo defects causing this type of problem, could be as simple as a defective return spring.

 

I will let a TR grown-up decide whether to ask the brake fluid question!!

 

Nigel

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Hello Andy,

 

You said:

 

"....Now this isn't a problem as such but just bit odd to get used to ...."

 

You also said:

 

"....it's easily manageable...."

 

As Roger said:

 

" something seriously wrong there. "

 

My personal view is:

 

SOMETHING IS SERIOUSLY WRONG THERE.

 

Take the car to a garage that knows about these things .

 

This sort of thing IS NOT "... easily manageable..."

 

Charlie D

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Andy

 

I would be interested to hear how you get on.

 

I have a similar problem where the brake sticks on and the brake pedal goes really hard. A quick press of the brake pedal sets everything back to normal. I started a thread some time ago and it was suggested that this is most probably a servo issue. Roger's suggestion was to disconnect the servo and see if this made a difference - I haven't tried yet as I have been distracted by other issues and have not driven the car for some time.

 

Thanks

 

Bob

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Andy

 

I would be interested to hear how you get on.

 

I have a similar problem where the brake sticks on and the brake pedal goes really hard. A quick press of the brake pedal sets everything back to normal. I started a thread some time ago and it was suggested that this is most probably a servo issue. Roger's suggestion was to disconnect the servo and see if this made a difference - I haven't tried yet as I have been distracted by other issues and have not driven the car for some time.

 

Thanks

 

Bob

 

Hi Bob,

 

I'm not sure mine is the same as that. The pedal lifts off OK but the breaks don't. When I'm next out, I'll see if a 'quick press of the brake pedal' makes any difference.

 

Andy

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Andy

 

I would be interested to hear how you get on.

 

I have a similar problem where the brake sticks on and the brake pedal goes really hard. A quick press of the brake pedal sets everything back to normal. I started a thread some time ago and it was suggested that this is most probably a servo issue. Roger's suggestion was to disconnect the servo and see if this made a difference - I haven't tried yet as I have been distracted by other issues and have not driven the car for some time.

 

Thanks

 

Bob

 

I just took the Tr out for a drive ....well the suns out ! Anyway, i can confirm now, that my pedal is pretty well rock solid after breaking like yours Bob. It pretty much acts the same as yours by the looks of it.

 

 

DO NOT DRIVE THE CAR.

 

GET IT TOWED/TRAILERED TO A COMPETENT GARAGE.

 

Cheers

 

Alec

 

I respect your concern but i do feel that the issue is not anywhere near a problem as some think. My description must have been inaccurate. The car is easily driven safely and the brakes are not over heating. It is literally only felt on the last 3m of breaking. I did 200 miles before I even noticed it and even then i just assumed it was part of the servo assist. I'm sure Bob above will concur with me on this, as he seems to be living with the same issue.

 

My 68 Spitfire doesn't have a servo (i just wear a size 14 steel toe boot) and my daily driver is of course equipped with modern breaking systems. So, the TR4A breaks with the added servo are a new 'experience' for me.

 

All said, it's booked into a garage that have done some great work on my Spitfire on Tuesday and the forecast for Easter weekend is terrible ..... so it's unlikely to move before then.

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Andy

 

My problem is not constant and only happens occasionally. As I said, it hasn't been driven for a while and I await the results of your investigation with interest.

 

I agree that it is not unsafe - the brakes work fine and never actually let me down by refusing to slow/stop.

 

Good luck - lets hope it's a cheap solution.

 

Regards

 

Bob

 

PS Hope you are not restricted to only driving the Ferrari

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Servo problem by the sound of it, the cheap repro ones arent that clever.

Stuart.

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My gut feeling is that its servo related too. Its all very new, as are quite a bit of the engine bay stuff. Hopefully, just an install or set up issue but Im confident the chap I use will diagnose ok.

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Andy ...

 

Regards

 

Bob

 

PS Hope you are not restricted to only driving the Ferrari

Good God - so do I !!!

 

Ill be knackered ....I sold it two months ago !

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What fluid are you using?

 

If you're on Silicone, it doesn't lubricate the seals and they stick. You can rebuild with Molycote Silicone grease and this cures the problem.

 

But, as everyone else has said - Get it checked, don't drive it!!!

 

Ade

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What fluid are you using?

 

If you're on Silicone, it doesn't lubricate the seals and they stick. You can rebuild with Molycote Silicone grease and this cures the problem.

 

But, as everyone else has said - Get it checked, don't drive it!!!

 

Ade

 

Thanks Ade,

 

It certainly looks like it has Silicon in there. There's a label fixed to the master cylinder that states to only use silicon.

 

Thank you for your post - this is something I can tell the mechanic on Tuesday that may help diagnose the issue.

 

post-15231-0-26599400-1522331785_thumb.jpg

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Hi Andy,

 

Plenty of good advice on the earlier posts but I thought I’d just mention that I had a problem last year which sounds very similar to yours, albeit mine was somewhat intermittent.

 

After a lot of investigation and research, I eventually decided that it must be related to the servo air valve piston sticking slightly. Disconnecting the servo solved the problem and confirmed the diagnosis.

 

However, be warned if you think of disconnecting the servo ………. not long after I did so, the seal failed in the master cylinder, resulting in a sudden and total loss of braking. Fortunately, and somewhat ironically, the car was actually on the rollers for its MOT brake test at the time! The conclusion was that removal of the servo had changed the master cylinder operating range slightly, causing the seal to wear rapidly and fail.

 

With the master cylinder seal being a single point of failure, it's an inherent risk with all single-line systems. It’s clearly not a great idea to run to failure, so my view now is that the master cylinder should be properly rebuilt or replaced at intervals on a preventative maintenance basis. There’s a similar single point of failure in a remote servo, namely the air piston valve seal, and the same applies.

 

Hope you get the problem sorted ok

 

Regards

Mike

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Had a similar problem a few years ago. Good advice from somewhere on the Forum came my aid with advice to change the air valve. These are readily available from the usual suppliers. Problem solved immediately. Best of luck.

Hi,

 

I think Ive found that old thread (2013). The majority of the posts are discussing the actual need (or not) of a Servo.

 

However, the original posts certainly describe exactly whats happening to my TR and its even the same make / model servo. This is all good stuff for me to show the mechanic. Hopefully either a silicon lubricant of parts or total replacement of air valve will sort this issue.

 

Thanks.

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