Page last updated 11 June, 2007

Technical Questions - Braking


Date asked

Question Answer

9th June 2007

By Martyn

Do you know what the rear brake hoses for the 2500M are from? They seem to be at least 16 inches long.

I'm pretty sure TVR made these themselves - I bought a pair of rear hoses a few years ago from unipart here in the UK - they did match some but from a list of sizes rather than from a specific car - I do know TR6 ones were too short. I have seen some for sale on ebay though (as for most things!) - links are here:

Also a store that does them:

22nd August 2006

By James Collier

I've had the brake system apart and when I've come to bleed the system through again the "BRAKE " warning light on the dash is always on. The peddle has some feel but is low. The brake warning light is controlled by the brake pressure differential warning actuator - see my Technical Manual in the brakes section for all the info. Sounds like you have a leak somewhere as the pedal is low.

6th February 2006

By Wim Boon

When I keep my foot on the brake pedal of my 3000M (1977), for example when
I am waiting for a traffic light, the pedal goes down very slowly. So I have
to let it come up after a few seconds and press it down again. There is no
leakage of oil or any other noticable failure.
I don't think this is the right way to perform for a braking system, so if
you can, please help me to solve this problem
It sounds like you may have a servo problem, or air in the hydraulic system of the brakes.

For Servo diagnosis: With the engine off, try pumping the brake pedal until you feel a solid pedal. Then with your foot pressed on the pedal, start the engine. If the brake pedal drops, the Servo should be ok, if it doesn't, there is a servo fault. Also check around the servo unit for signs of leakage. However this is sometimes hidden - the only way to see is if the fluid level in the reservoir has gone down a little.

For brake system diagnosis - you would normally see a leak, unless perhaps air is being drawn into the system. A leaking rear wheel brake cylinder can cause a pedal that loses pressure - it would be worth removing the brake drums and having a look.

29th December 2005

By Alan Nicholls

(The Brake Pressure Differential Warning Actuator) PDWA for the late model 3000m - I have found on the Web at a parts promotion where they are selling the unit [with switch!] not for the list price of £143.68 but for £18.92+ VAT and postage = £24.58!

Parts Promotion Lagonda December 2005 - part number 33 - 11489

On first / second and third glance it looks identical and check the price of a recon kit etc.

Many thanks - a bargain for anyone who needs one of these valves! Looks pretty likely the valve is the same.

18th June 2005

By Brad Barclay

I Have a 1970 TVR Vixen 1600. How do you replace the rear wheel studs? Are they from a TR6, or some other car?

Follow up 21st June:
After beating on them, and heating them, I came to find out that they are Screwed in then peened from behind. Just had to grind them off from the front then drill hole and use a left handed easyout. I've never seen such a thing.

I'm not 100% sure what the hubs are off. All I know is that normally studs are splined and are pressed out (or knocked out) using a suitably sized punch/press tool and tubular spacer behind the stud.

16th June 2005

By John Musacchio

I recently purchased a brake servo rebuild kit for my TR6, however I can't seem to find instructions anywhere, and I can't quite figure out how to take the servo apart. Can you either send me directions, or point me in the right direction? Thanks.










Follow up 17th June 2005:
Thanks for the quick response Mark. This looks like directions for rebuilding the Master Cylinder. I have some pretty good directions for that, and yours also seem very good, however my problem is that the Servo also needs to be rebuilt, and I can't seem to find directions to rebuild it. Note that I purchased a rebuild kit, but there were no directions for it. The manual I have tells how to remove and replace the Servo, but not how to rebuild it. Any further assistance would be appreciated. Thanks.










Follow up June 21st 2005:

Thanks a bunch Mark, I'll give it a try. I appreciate your assistance on this.

I have yet to complete the master cylinder part of the technical manual, but in short:

1 - Remove the cylinder from the servo by removing the 2 fixing nuts/split washers.
2 - Undo the bolts/split washers holding the reservoir to the cylinder.
3 - Undo the tipping valve securing nut (using an Allen key). This is at the rear of the cylinder in the larger reservoir connection. Remove the nut and also the tipping valve & seal (push in the pushrod slightly to allow the valve to come out).
4 - Remove the front seal on the cylinder's reservoir connection.
5 - Remove the pushrod's dust cover, then push in the pushrod enough to remove the internal circlip from the cylinder bore. Take out the pushrod.
6 - Use compressed air (low pressure) to blow down the reservoir holes to extract the internal pistons. Keep the internal parts in order on a clean worktop (cover with newspaper or similar).
7 - Clean all parts and check the pistons & cylinder bore for wear. Any noticeable wear on these parts - even slight - will mean the complete cylinder requires replacement.
8 - If all is serviceable - strip out the seals and fit the new ones using clean brake fluid to assist you. A hook or pick set is handy when doing this job. Do not use a screwdriver as any slight tear in the seals could compromise your safety. Note that in the centre of the unit there is a spring retainer which needs to be lifted to allow the internal sections to be seperated.
9 - Rebuilding is the reverse of dismantling, but make sure everything is 100% clean.

Sorry I have no photos yet! I hope it helps you.







Follow up June 20th 2005:

I'm not sure what is in your Servo repair kit, but there should be an air filter for the end under the rubber gaiter which is meant to be changed every major service.
The only other parts that can be replaced are the seal and end plate assembly which are on the other end of the pushrod (master cylinder end) - basically the seal/plate inside the recess.
To check the servo for problems you can measure the clearance between the servo's casing and the domed end of the pushrod (master cylinder end) using a straight edge across the servo casing over the recess containing the domed pushrod end. If the measurement is not between .011" to .016" then the instructions I have say the shole unit needs replacing.

Saying this, however, I do know of an old friend who had the facilities to replace the servo diaphragm - by bending open the servo casing and then tapping it back after. He did have a very well equipped workshop to do it though and due to the safety risk involved is only something that should be done as a last resort.

Hope that helps you a little more!

16th December 2004

by Tim
Re: Brakes
What do people do to uprate them sensibly?
I have been told twin pots off a toyota pick up fit is this true? If so which pick up?

Four pot calipers are the most common way to do that....Wilwood make a set that fits and I'm told they're very good. The standard ones as you know are only just about adequate for lower speed driving. Toyota pick up calipers do fit but only early ones - I had some emails from someone in the USA who has done it successfully using ones from a 1979-83 Toyota 4wd Petrol pick up truck. In the USA they cost only $43.00 each re-conditioned. I tried to see the website but it has been removed. However here is an interesting forum chat that I came across which should help you a great deal -

11th August 2004

by Simon

Do you know what sort or brake fluid should I use for a 1976 3000M please?

The manual is not much help in this area.

DOT 4 fluid is fine...most cars use this so it's probably the only one
you'll find in the shops.

I do know some people use Silicone Fluid but this cannot be mixed with DOT 4, and it's DOT 5 classification.

See here for more info. on DOT 5 fluid

14th May 2003

by Steve Bourne
Every interior photo I see of cars of the same age shows the handbrake lever mounted on top of the transmission tunnel whereas mine
is mounted on the side of the transmission tunnel. Is there any specific reason for this?
I'm almost certain this was done because the overdrive gearbox prevented the top mounting being used - they had to come up with an alternative.