Servo's

[new to this]

Hi
are there any differences in the servo,from a single brake master cylinder to a tandem brake master cylinder ?

thanks Dave

[Carledo]

Only the studs at both ends are different, roughly speaking, single circuit cars have imperial studs, 5/16" UNF at the body end and 3/8" UNF at the master cylinder joint, whereas dual circuit cars have metric studs at 8mm and 10mm respectively.
But you can use either servo or either master cylinder in any combination on any year or model of car, just make sure you have the correct nuts for whichever servo you fit!
The Carledo is a 73 model Toledo with a 76 1850 imperial servo and a late dual circuit Sprint master cylinder ( but has also had a late Sprint metric servo fitted) So it's not hearsay, I've actually done it!

Steve

PS, if you've been offered a Sprint servo for sensible money, grab it, even if you don't need it, they are getting rather hard to come by. Which is why my car only has an 1850 one ATM! Not that there is any noticeable difference in performance between the 2!

[new to this]

Only the studs at both ends are different, roughly speaking, single circuit cars have imperial studs, 5/16" UNF at the body end and 3/8" UNF at the master cylinder joint, whereas dual circuit cars have metric studs at 8mm and 10mm respectively.
But you can use either servo or either master cylinder in any combination on any year or model of car, just make sure you have the correct nuts for whichever servo you fit!
The Carledo is a 73 model Toledo with a 76 1850 imperial servo and a late dual circuit Sprint master cylinder ( but has also had a late Sprint metric servo fitted) So it's not hearsay, I've actually done it!

Steve

PS, if you've been offered a Sprint servo for sensible money, grab it, even if you don't need it, they are getting rather hard to come by. Which is why my car only has an 1850 one ATM! Not that there is any noticeable difference in performance between the 2!

Steve

Thanks thats good to know,i have a sprint servo,but was going to measure a stag servo to see if its bigger[/

One other question,the PWDA valve one of the thread sizes is different from the rest,do you know what size it is

Thanks Davecolor]

[Carledo]

I don't think you'll have any joy with a Stag servo, for one thing, the Dolomite master won't fit it (wrong mounting hole centres) and IF it is bigger, it will probably interfere with the clutch m/cyl. Not to mention potential problems at the pedal end!
Yes the PDWA has 2 odd sized unions fitted and no, I don't know what size they are, I suspect they are a BSP thread, they are not the standard UNF OR metric size! What I do know, is that I sent one to my local factors as a pattern and they were unable to match it!
ON the PDWA itself, I initially fitted one to the Carledo, along with the late Sprint servo and dual circuit master (well it was part of the system) It turned out to be a total PITA, making brake bleeding an exhausting process followed by more careful bleeding to "set up" the PDWA itself. Then the valve itself turned out to be rather temperamental sometimes putting the light on and off for no discernible reason. In the end, I ditched the PDWA entirely, replacing the unit with a 3 way union for the front brakes and a line connector for the rears and using a scrappy sourced cap mounted fluid level sensor (from some sort of Ford IIRC) to operate the warning light. No more problems and brake bleeding is now easy peasy!

Steve

[SprintMWU773V]

There is a Land Rover servo which can be made to fit with very little effort. Not original but a much better design with no crappy plastic to go brittle and break rendering the unit scrap. Looks pretty convincing when fitted and has the benefit of being widely available and reasonably priced.

[sprint95m]

I don't think you'll have any joy with a Stag servo

There is a Land Rover servo which can be made to fit with very little effort.

There is a fair degree of interchangeability here…..
in 2003 I looked for a Stag servo/MC for upgrading a T2000 to 7/8" bore M/C (which is necessary if you fit XJ12 calipers),
to this end I borrowed a Lockheed catalogue.
From said catalogue I discovered that a lot of different servos use the same overhaul kit,
which led me to use a Sherpa/LDV servo and master cylinder.

Some years ago Mike Barker posted on here photos of a servo that seemingly will fit a Sprint, which looked to be the LDV one?


For a car with dual circuit brakes I would seriously consider using one of these LDV servo/MC combos because you get a 7/8" bore master cylinder
and a more durable servo.
If I was keeping the Dolomite servo I would use a Saab 99 or 900 master cylinder (again these are 7/8" (22.2 mm) bore.



Ian.

[AlanH]

ON the PDWA itself, I initially fitted one to the Carledo, along with the late Sprint servo and dual circuit master (well it was part of the system) It turned out to be a total PITA,

I've fixed my PDWA, put a thick plastic washer on the switch. Great fix (I think I saw it on here.)

[Carledo]

ON the PDWA itself, I initially fitted one to the Carledo, along with the late Sprint servo and dual circuit master (well it was part of the system) It turned out to be a total PITA,

I've fixed my PDWA, put a thick plastic washer on the switch. Great fix (I think I saw it on here.)

Does this mean the light never comes on at all? The whole point of the thing is that it puts the light on to warn you if it detects a pressure difference between the 2 brake circuits. It's an unnecessarily complicated Heath Robinson device to do a simple job, but it DOES have a purpose.
However, since a pressure loss in a brake circuit is 99.9% accompanied (or caused) by fluid loss, the reservoir cap mounted fluid level sensor is a cheap, simple and fairly foolproof alternative - which is why all modern cars have one of these rather than the expensive, complicated and unreliable PDWA. Though it grieves me to say it, sometimes the accountants get it right! But the cap sensor idea also conforms to the KISS principal of good engineering practice - and i'm a big fan of that!

Steve

[sprint95m]

http://www.ebay.co.uk/itm/LDV-Convoy-40 ... Sw4CFY4Vn9

I think it is this one?




Ian.

[Carledo]

It certainly looks VERY similar at the bulkhead end (which is the important bit) Only a tape measure comparison will confirm it! The 3 pipe master will need some bespoke pipes making, but do-able, just use the m/cyl rear circuit for the front brakes and the front circuit for the rears. It even has a level sensor in the cap so you can junk the PDWA!
Now, who would like to buy me this one so I can try it? (if it fits, i'll pay you back )

Steve

[sprint95m]

The Sherpa/LDV has a diagonal split dual circuit, so the two hole half of the MC does the back brakes and one front.
The master cylinder is 7/8" (22.2 mm) bore.
Earlier ones have the PDWA within the master cylinder and only two outlet holes (so one of the brake pipes goes to a t-piece….),
said PDWA is balanced during the process of bleeding the brakes.
The servo's fixing studs are M8 and I think are on a slighter bigger PDC than a Dolomite, therefore some alteration to the pedal box is necessary
but that is nothing to phase me, even though the pedal box will probably have to be removed from the car.

I should be able to get a hold of one of these servos, given that one of my friends has broken probably in excess of two dozen Sherpas/LDVs.
Something for me to look at next winter…
but if you want to try one sooner than that Steve, I'll put the money up.





Ian.

[Carledo]

The Sherpa/LDV has a diagonal split dual circuit, so the two hole half of the MC does the back brakes and one front.
The master cylinder is 7/8" (22.2 mm) bore.
Earlier ones have the PDWA within the master cylinder and only two outlet holes (so one of the brake pipes goes to a t-piece….),
said PDWA is balanced during the process of bleeding the brakes.
The servo's fixing studs are M8 and I think are on a slighter bigger PDC than a Dolomite, therefore some alteration to the pedal box is necessary
but that is nothing to phase me, even though the pedal box will probably have to be removed from the car.

I should be able to get a hold of one of these servos, given that one of my friends has broken probably in excess of two dozen Sherpas/LDVs.
Something for me to look at next winter…
but if you want to try one sooner than that Steve, I'll put the money up.

Ian.

I rather thought the LDV 3 hole master would work that way, on a Dolomite that would give 3 wheel brakes on 1 circuit and 1 on the other. Given that a rear wheel cylinder failure is the MOST likely thing to go wrong, it would be the 3 wheel circuit that became inoperable in this scenario. So I'd prefer to plumb it a-la Dolomite with the front brakes on one circuit and the rears on the other. But that is mere R&D!

I'm not in a dreadful rush to do this, but I DO have the Dolomega project shell handy, which currently has no viable master cylinder and a rather dubious Sprint servo - plus a big hole where these would normally be! The car is also getting my uprated Trackerjack kit with 256mm Passat discs and Puma calipers and carriers, a little more oomph at the top end will help pedal travel and I can use the full fat Sprint wheel cylinders that i've already bought without compromising the pedal. So the car will make a good test bed.

It would certainly be handy to have a modern and easily available alternative to the fast-drying-up Sprint OE bits

Steve

[sprint95m]

It is the 1976-1995 servo I had in mind, but it seems the non ABS type (part number LBU7168)
used from 1996-2005 is interchangeable.

Anyhow, here is something from a TR7 forum….
http://tr7triumph.com/forum/viewtopic.php?t=23559




Ian.