Seized brakes ( ? to remove the servo)

[661]

Took the car for it's first post hibernation run today. We got about 500m. The said distance had involved a few stops at junctions and all appeared well. After the last junction before the seizure I thought something wasn't quite right so applied the brakes on a straight bit of road and despite having released the brake pedal we continued to come to a stop. We sat there like a chicane for other road users until after a minute or two the brakes released and the car rolled again. I drove home using the handbrake.
The pedal was exceptionally hard and at the top when seized. It continued to behave like this after my return.
Most of the S4 system is newish. Certainly the master cylinder is fairly new (2y??) and the calipers are refurbed a couple of years ago. The servo however was last serviced 20+ years ago.
Once home all 4 wheels were locked.
Servo sticking is top of my list but I suppose the newish master cylinder could be a culprit.
I have plus 2 front calipers and discs and have been contemplating getting rid of the servo anyway.
Advice please? What's the likely first port of call and if the servo would you dump it? ( I have a good right leg)



Graeme

[elanman999]

Hi 661,
The servo is the first place I'd look with the problem you have.
To remove the servo or not? I have +2 brakes on my Elan and I found the brakes just too heavy without the servo. I had to fit a 5/8in master cylinder and now they are OK. Obviously non-servoed brakes have a different feel to them but you soon get used to that.
That's just my take on things.
Cheers
John

[NIGELAN]

Hi, don't panic! I had this problem on my +2 on its first trip to Goodwood Revival and had to keep stopping every few miles to release the brakes by slightly undoing the brake line to the servo.

The problem, I suspect, is with the new master cylinder. I had a new one and the 'fault' is that when releasing the pedal the piston does not move back far enough to open the return valve to release the pressure. Hence, each time you apply the brakes you pressure the system more and more until you have totally locked brakes.

My solution was to remount the master cylinder with a packing washer between the unit and the mounting plate to allow the piston to return a little further, approx. 2mm if I recall, which allows the valve in the master cylinder to open and release the pressure on releasing the pedal.

I hope this is not too confusing and although mine was a +2 I assume that a similar solution must be available on an S4.

[661]

Thanks Nigel,
Although I'm aware the master cylinders are fussy about the length of the push rods, presumably for the reason you cite, it's worked perfectly well for 18 months or so. Therefore, I would doubt it would suddenly find the return length wrong??? At the time I did try hooking my foot under the brake and pulling the pedal up but it was already fully up.

[types26/36]

Happen to me several years ago, detailed in this thread.
lotus-suspension-f42/brakes-girling-t1587.html

[661]

Happen to me several years ago, detailed in this thread.
lotus-suspension-f42/brakes-girling-t1587.html

Thanks Brian. That is pretty much it in a nutshell. The question now remains; to keep the servo or not?

[dgym]

I had my brakes lock on me not long after I got the car. My problem appears to have been an incorrectly mounted servo. The air control valve was at the top which is contrary to the fitting instructions.
I haven't had a problem since I re fitted it following the instructions.
http://tr4a.weebly.com/uploads/2/1/9/8/ ... lation.pdf


might not be your issue but might be worth looking at.

[worzel]

Hi Graeme

From what you report I'd guess the culprit is the servo air valve- girling ones don't seem to suffer but the problem is well known on the Lockheed models. Easily fixed (I speak from experience) but I still removed the servo anyway to simplify the system.

Only my experience so I'm not making any recommendations on such a safety area but when I first fitted the plus 2 calipers the brakes were not exactly brilliant and required a pretty hefty push. Tried the usual pad alternatives but no diiscenible improvement.

however when I managed to track down genuine (I emphasise genuine) old stock pads for the early unservoed Triumph Vitesse the effort at the pedal dropped noticeably. Now I wouldn't refit the servo as stopping power is just as good as a std served system- and the feel is better. This is using the 0.7 master cylinder incidentally.
stepping in from a modern car the brakes obviously feel different (the pedal obviously feels harder) but one soon gets used to them.

As I said- only my experience. As an aside, over 40 years ago I owned a S4 that didn't use a servo as std and I never noticed the brakes- they were just very good- but the pads were probably a lot softer then.

Regards

John

[661]

Thanks for your replies.
I really need to have a good look at the mounting and the type of servo. I've seen original drawings from the Lotus Cortina suggesting the servo be mounted at a specific angle and I can't recall ever checking mine. Time to get dirty.
I must say, I too was disappointed after fitting my newly refurbed calipers, bigger plus 2 discs and green stuff pads. The stopping power was really no better. I'm just not impressed by these pads. That said, I need to sort out the seizure. I'm kind of edging towards refurbishing the servo and keeping it, but please keep your experiences flooding in!

[Galwaylotus]

Although myS3 SE has the original type calipers, I had the same issue with locking brakes and I traced it to the servo. A few disconnections and removed fasteners and presto - added lightness! Seriously, I wouldn't go back to a servo as I love the feel of the brakes without it. I did replace the front pads with GreenStuff ones and the initial effort is slightly increased but I don't have a weak leg so I'm quite happy with the result.

[661]

Although myS3 SE has the original type calipers, I had the same issue with locking brakes and I traced it to the servo. A few disconnections and removed fasteners and presto - added lightness! Seriously, I wouldn't go back to a servo as I love the feel of the brakes without it. I did replace the front pads with GreenStuff ones and the initial effort is slightly increased but I don't have a weak leg so I'm quite happy with the result.

Thanks. This is the way I'm going to go.

[englishmaninwales]

I went through this with my Lockheed servo, with locked on brakes. Removed it, replaced the brake fluid and fitted Mintex 1144 pads to the front. This transformed the braking performance compared to the (pre failure) servo assisted performance.

[661]

Happy ending.
Servo removed, the brakes are fantastic ( +2 front calipers , green stuff, braided hoses, Motul 600) .

[Galwaylotus]

Happy ending.
Servo removed, the brakes are fantastic ( +2 front calipers , green stuff, braided hoses, Motul 600) .