Not a good run out today 
. Driven about 10 miles and doing about 60 when felt heavy resistance, no warning, no stange noises just like driving whilst pressing hard on the brakes. Definitely not engine related. Car has CV conversion otherwise standard. When I pulled over felt all the wheels none were hot, could be wrong but thought if brakes then wheels could be hot. After about 5 -10 minutes whatever had locked released and the car rolled slightly and was free. Had the car recovered in case it went again. But now where to look.
Any advice or experiences similar appreciated. Thanks Alan.
My master cylinder caused similar issues for reasons unexplained. Replacing the master cylinder fixed the issue but perhaps changing the length of the actuating rod would help.
Brake servo would be my first thought.
2 Likes
Hi Alan,
My Series 3 did the same thing. I was on the local motorway when the car started to slow down. A few rapid and hard kicks on the brake pedal released it. The rest of the trip was done without using the brakes. The callipers were new, so I went straight for the master cylinder. It had collected quite a lot of unknown crud causing the piston to stick.
I also discovered that it was actually the smaller clutch cylinder being used on the brakes.
A new cylinder and remembering to re-use the pushrod and all was well. Good luck.
Eric in Burnley
1967 S3SE DHC
Thanks for the replys. Well, I wouldnt have suspected the master cylinder. Was about 1/2 a mile since I used the brakes. Simple enough to change as a start.
Hi Alan,I had the same problem,if you have I believe a Lockheed type servo as a replacement for the original girling type,they can cause your problem,I was told it could be caused by the angle that the servo is mounted,i repositioned mine and has been fine since
Phil
1 Like
Hi
I had this on a Plus 2. It was the servo. I used to carry a spanner and release a calliper bleed nipple when they locked on.
Berni
1 Like
Not sure what type of servo i have but it was replaced about 14 years ago this is first time had a problem like this. @ phil how do you heve yours positioned now? Can you send a photo?
Thanks Alan
Hi Alan,I believe the piston end of the servo has got to be higher than the diaphragm side ,I read somewhere 30% slope,the laycock servo comes with a metal strap that surrounds the piston end and can be fitted in a simular position as the original only sloping,sorry never uploaded a photo yet
Phil
Sorry meant Lockheed.
I had the same issue on my S4. Tracked it down to a faulty Lockheed servo. To get me home I disconnected the servo vacuum hose and all was good. As a permanent fix I removed the servo altogether!
So several votes there for the servo, i will post a pic of the servo location at the wekend, see how it compares if you think its in the right position.
As above recommendations but I’d also check the rubber brake hoses that go to the calipers if they have any age to them - they can collapse internally with rubber degradation so they can temporarily act like a non-return valve. I had this experience on an E-Type that had me flummoxed for a while.
I have seen several cars that had the flexible brake hoses act like one-way valves. Pressure would go down, but not release, holding the brakes on. Nothing from outside showed an issue.
I would expect brakes to have gotten pretty warm, but if a rear- they are well inboard and you would not feel unless touching rotor.
Thinking about when it happened, after braking for a roundabout I had accelerated to about 60 and driven for another couple of hundered yards before I started to feel the resistance. Could this be the brakes holding on or something like the cv joint locking up.
I recently overhauled the brakes & clutch and was amazed at the amount of large ‘dust’ in the dirty fluid in both
Master cylinders . I had to suck the fluid out of master cylinder as the dust particles were too large for the bleed nipples. The car had only done 4,000 miles in 5 years since a garage overhauled! So a full drain is worth it for piece of mind. My brakes & clutch are fine & passed rigorous MOT last weekend
1 Like
One more post to check for old rubber brake hoses! I had an intermittent issue with what appeared to be calipers seizing, the pads got so hot that they were smoking.
I rebuilt the calipers, but I noticed when I went to bleed my brakes with a power bleeder I would have to press the brake pedal to get the brake fluid to push out the bleeders. The power bleeder would not push brake fluid through, even at 20psi! Changed the hoses for new ones & no issues bleeding or the calipers getting warm again. Fuel consumption has gone down noticeably as well.
I cut through the hoses after to inspect them, note the internal diameter is very small:
3 Likes
Had similar on a previous car, no oil in the diff!