BRAKE SERVO / MASTERCYLINDER; SORTED!
Discussion
If you were following the recent thread on this subject you will be aware that there was a great deal of interest in sorting out a viable alternative to the SAAB set up, and to get it documented. I was very anxious that this should be 'bottomed' and that the solution should be documented in a way which could, if necessary, be justified to insurers. I am sorry but this will be a long post!
I’ve set out the current position and what I hope will be a clear statement of the option to adopt if you wish to ‘updated’ from the SAAB set up.
I would propose to ask for a link from the Alternative Parts List to this information but, before I do, I would ask you to look at it critically and let me know if you have any concerns or any other information.
All the available parts information from TRW (Lucas/Girling) has now been studied. I have also received a good deal of info from other forum members which has helped establish exactly what TVR fitted and what the exact issues are in making a change.
I am now satisfied that I know exactly what TVR fitted: Most cars have a SAAB sourced system but later cars have a particular FORD Fiesta sourced system. There doesn’t appear to be a precise change over date. It was important to establish exactly what the later system was as this system would have had 'type approval' by TVR. Therefore a change by us from a SAAB to an original but later TVR set up would be an updating in specification rather than an alternative arrangement, and not therefore a ‘modification’.
(There has been some further confusion in that at least 2 references refer to TVR fitting a FORD Sierra servo, I am now satisfied that this is incorrect).
The original SAAB sourced system (SAAB 9000 2.0ltr ) uses an 8” diameter servo fitted to a 22.2mm master cylinder. The master cylinder is of the Lucas steel type and uses a remote reservoir.
TRW part number for the Servo is PSA314 and is now listed as unavailable.
TRW part number for the master cylinder is PMH237 and is now listed as to be discontinued.
The FORD Fiesta system is that fitted to certain Mk 3 Fiesta’s. Most Mk3 Fiestas use the same 8” servo, so that is easy to identify. However a note of caution is necessary re the master cylinders: At least 6 different ones were fitted, several were externally similar but differ in bore and swept volume. I would therefore advise that if you wish to purchase second hand you restrict that to the servo, and fit it with a new master cylinder using the part number below.
I have confirmed with TRW technical staff that the following specification appears to be what TVR used (there do not appear to be records at the supplier end) and would give the same performance.
SERVO:
TRW part number for the servo is PSA 328 and is readily available new. The servo was fitted to the majority of Fiesta Mk3 models (89-95) whether ABS or not and should be readily available second hand.
The servo is dimensionally identical to the SAAB in all major respects and will fit directly into the existing holes in the bulkhead.
There is however a small change necessary at the pedal connection. The SAAB servo uses an 8mm clevis pin while the Fiesta servo uses a 10mm pin. The brake pedal needs to be drilled accordingly and a larger pin fitted. (If you leave the 8mm pin you will get increased slack in the pedal and increased wear at the joint.)
There is also a small change in width of the clevis which requires slightly different packing washers to be inserted.
The only other change is that the vacuum pipe is now on the engine side of the servo rather than the outside, and the vac pipe needs to be shortened.
This is a link to a picture of this servo (I have pictures from other aspects if they are of use to you)
http://i199.photobucket.com/albums/aa102/greymrj/1...
MASTERCYLINDER
TRW part number for the master cylinder is PMH247 and is readily available new. The cylinder was only fitted to certain non ABS models, I am only able to confirm fitment to the non ABS Fiesta 1.4 89-95 and 1.8D 89-95.
This is a four port Lucas type steel master cylinder, 22.2mm bore, externally very similar to the SAAB part but using a top mounted reservoir.
When supplied new, or as fitted in the Fiesta, two ports are fitted with external pressure regulating valves. For the TVR application these need to be removed because the S type has a separate pressure regulator (on the bulkhead above the servo).
The positioning and thread sizes of the ports match the SAAB fitment.
This is a link to a picture of this master cylinder (I have pictures from other aspects if they are of use to you.)
http://i199.photobucket.com/albums/aa102/greymrj/1...
Again, please note that there are at least 6 Fiesta Mk3 master cylinders, of which at least one is outwardly identical but is not identical internally.
(It would also be possible to use the more common Fiesta master cylinder PMH138 which has identical bore and stroke but has only two ports and would require an external T piece, but there is no advantage in doing so and as it isn’t what TVR fitted it would be a ‘modification’
A couple of further notes;
The Fiesta servo PSA328 has a small adjuster screw on the piston rod that operates the master cylinder piston. There should be clearance between the rod and the piston when the brakes are off. This gap should be correct as set at the factory but occasionally it may be necessary to adjust the rod slightly to maintain clearance.
Do not be tempted to match the Fiesta servo to the SAAB master cylinder, it would be possible but the piston rods differ in length and the cylinder piston might not be able to return properly when the brakes are off.
I wouldn’t advise trying to fit a Fiesta top mounting reservoir to a SAAB cylinder with the remote reservoir. It may work but it isn’t an approved adaptation.
Phew!!! I sincerely hope that helps some owners. I now have a 28 page folder, CD and parts manuals on the subject!
I’ve set out the current position and what I hope will be a clear statement of the option to adopt if you wish to ‘updated’ from the SAAB set up.
I would propose to ask for a link from the Alternative Parts List to this information but, before I do, I would ask you to look at it critically and let me know if you have any concerns or any other information.
All the available parts information from TRW (Lucas/Girling) has now been studied. I have also received a good deal of info from other forum members which has helped establish exactly what TVR fitted and what the exact issues are in making a change.
I am now satisfied that I know exactly what TVR fitted: Most cars have a SAAB sourced system but later cars have a particular FORD Fiesta sourced system. There doesn’t appear to be a precise change over date. It was important to establish exactly what the later system was as this system would have had 'type approval' by TVR. Therefore a change by us from a SAAB to an original but later TVR set up would be an updating in specification rather than an alternative arrangement, and not therefore a ‘modification’.
(There has been some further confusion in that at least 2 references refer to TVR fitting a FORD Sierra servo, I am now satisfied that this is incorrect).
The original SAAB sourced system (SAAB 9000 2.0ltr ) uses an 8” diameter servo fitted to a 22.2mm master cylinder. The master cylinder is of the Lucas steel type and uses a remote reservoir.
TRW part number for the Servo is PSA314 and is now listed as unavailable.
TRW part number for the master cylinder is PMH237 and is now listed as to be discontinued.
The FORD Fiesta system is that fitted to certain Mk 3 Fiesta’s. Most Mk3 Fiestas use the same 8” servo, so that is easy to identify. However a note of caution is necessary re the master cylinders: At least 6 different ones were fitted, several were externally similar but differ in bore and swept volume. I would therefore advise that if you wish to purchase second hand you restrict that to the servo, and fit it with a new master cylinder using the part number below.
I have confirmed with TRW technical staff that the following specification appears to be what TVR used (there do not appear to be records at the supplier end) and would give the same performance.
SERVO:
TRW part number for the servo is PSA 328 and is readily available new. The servo was fitted to the majority of Fiesta Mk3 models (89-95) whether ABS or not and should be readily available second hand.
The servo is dimensionally identical to the SAAB in all major respects and will fit directly into the existing holes in the bulkhead.
There is however a small change necessary at the pedal connection. The SAAB servo uses an 8mm clevis pin while the Fiesta servo uses a 10mm pin. The brake pedal needs to be drilled accordingly and a larger pin fitted. (If you leave the 8mm pin you will get increased slack in the pedal and increased wear at the joint.)
There is also a small change in width of the clevis which requires slightly different packing washers to be inserted.
The only other change is that the vacuum pipe is now on the engine side of the servo rather than the outside, and the vac pipe needs to be shortened.
This is a link to a picture of this servo (I have pictures from other aspects if they are of use to you)
http://i199.photobucket.com/albums/aa102/greymrj/1...
MASTERCYLINDER
TRW part number for the master cylinder is PMH247 and is readily available new. The cylinder was only fitted to certain non ABS models, I am only able to confirm fitment to the non ABS Fiesta 1.4 89-95 and 1.8D 89-95.
This is a four port Lucas type steel master cylinder, 22.2mm bore, externally very similar to the SAAB part but using a top mounted reservoir.
When supplied new, or as fitted in the Fiesta, two ports are fitted with external pressure regulating valves. For the TVR application these need to be removed because the S type has a separate pressure regulator (on the bulkhead above the servo).
The positioning and thread sizes of the ports match the SAAB fitment.
This is a link to a picture of this master cylinder (I have pictures from other aspects if they are of use to you.)
http://i199.photobucket.com/albums/aa102/greymrj/1...
Again, please note that there are at least 6 Fiesta Mk3 master cylinders, of which at least one is outwardly identical but is not identical internally.
(It would also be possible to use the more common Fiesta master cylinder PMH138 which has identical bore and stroke but has only two ports and would require an external T piece, but there is no advantage in doing so and as it isn’t what TVR fitted it would be a ‘modification’
A couple of further notes;
The Fiesta servo PSA328 has a small adjuster screw on the piston rod that operates the master cylinder piston. There should be clearance between the rod and the piston when the brakes are off. This gap should be correct as set at the factory but occasionally it may be necessary to adjust the rod slightly to maintain clearance.
Do not be tempted to match the Fiesta servo to the SAAB master cylinder, it would be possible but the piston rods differ in length and the cylinder piston might not be able to return properly when the brakes are off.
I wouldn’t advise trying to fit a Fiesta top mounting reservoir to a SAAB cylinder with the remote reservoir. It may work but it isn’t an approved adaptation.
Phew!!! I sincerely hope that helps some owners. I now have a 28 page folder, CD and parts manuals on the subject!
whenever we meet!!!
Mine has 4 connections, not sure of the thread size.
The two at the far end from the servo go to the front brakes, one connection to each wheel (though its clearly supplied from the same cylinder chamber) and the rears are supplied from one of the connections nearer to the servo - the other is blanked off with what looks like a brake caliper bleed screw.
There is a 'T' for the rear pipes in the centre of the car just in front of the diff to the passenger side of centre.
It occured to me that the master cylinder maybe different in terms of swept volumes depending on whether you have rear discs or not (I do, V8S) but I have no evidence to back this up.
Chris
The two at the far end from the servo go to the front brakes, one connection to each wheel (though its clearly supplied from the same cylinder chamber) and the rears are supplied from one of the connections nearer to the servo - the other is blanked off with what looks like a brake caliper bleed screw.
There is a 'T' for the rear pipes in the centre of the car just in front of the diff to the passenger side of centre.
It occured to me that the master cylinder maybe different in terms of swept volumes depending on whether you have rear discs or not (I do, V8S) but I have no evidence to back this up.
Chris
Edited by Barkychoc on Wednesday 26th March 11:04
Hi Ken, I can chuck it in the bin now can I!!! Nice to know that it became the 'reference' for the dimension checks we did with TRW. It didn't die in vain!
I should have clarified that my objective was to sort out what to do for the cars which had the SAAB set up (which appears to be the majority). Very late cars, and particularly V8's, may or may not have the same Ford set up, I simply don't know. I assume owners of such cars can do a 'like for like' replacement.
Chris, regarding the pipe unions: you are correct. The master cylinder has in effect got two pistons in tandem and provides a separation of the front and rear brakes so if one end fails the other shouldn't! Each of the two front ports on the master cylinder (the two furthest away from the servo) connects to one of the front brakes.
The lower rear port connects to the pressure control valve which is then piped to a union at the back of the car where it is split to each of the rear brakes. The top rear port takes a bleed valve (although I am not sure that it has any real use in practice as the master cylinder slopes up from it!)
Sorry 'pies' I cant help you on that, I'm not sure what you have got (might be able to tell from pics?). The two pics I have linked are of the new components as supplied by TRW (Many thanks to Steve Ryder of Car and Commercial Components of Blackburn for the loan of components to photograph and measure, and of reference manuals and CD's)
Finally, I very much appreciate the comments above, thanks. The little moving icon looks temptingly like Guiness to me, at least I hope so!!!
I should have clarified that my objective was to sort out what to do for the cars which had the SAAB set up (which appears to be the majority). Very late cars, and particularly V8's, may or may not have the same Ford set up, I simply don't know. I assume owners of such cars can do a 'like for like' replacement.
Chris, regarding the pipe unions: you are correct. The master cylinder has in effect got two pistons in tandem and provides a separation of the front and rear brakes so if one end fails the other shouldn't! Each of the two front ports on the master cylinder (the two furthest away from the servo) connects to one of the front brakes.
The lower rear port connects to the pressure control valve which is then piped to a union at the back of the car where it is split to each of the rear brakes. The top rear port takes a bleed valve (although I am not sure that it has any real use in practice as the master cylinder slopes up from it!)
Sorry 'pies' I cant help you on that, I'm not sure what you have got (might be able to tell from pics?). The two pics I have linked are of the new components as supplied by TRW (Many thanks to Steve Ryder of Car and Commercial Components of Blackburn for the loan of components to photograph and measure, and of reference manuals and CD's)
Finally, I very much appreciate the comments above, thanks. The little moving icon looks temptingly like Guiness to me, at least I hope so!!!
Good work! I salute your persistence!
Just to clarify and cover all possible angles, to change from the Saab unit to the Ford unit, do you need to drill new holes in the bulkhead or not? When I looked at replacing my saab fittings I discovered that if you fitted the Ford unit directly into the pre drilled holes in the bulkhead they were in effect 90 degrees out meaning that the integral fluid reservoir was on the side of the master cylinder, not the top.
Cheers
Just to clarify and cover all possible angles, to change from the Saab unit to the Ford unit, do you need to drill new holes in the bulkhead or not? When I looked at replacing my saab fittings I discovered that if you fitted the Ford unit directly into the pre drilled holes in the bulkhead they were in effect 90 degrees out meaning that the integral fluid reservoir was on the side of the master cylinder, not the top.
Cheers
Hi Tom, provided you change to the particular Ford Fiesta Servo and master cylinder combination specified then the alignment is correct and will match the original holes. As the servo is fitted to the bulkhead by four bolts at equal spacings then it is of course theoretically possible to turn the servo to fit in one of four positions, the correct position will have the correct alignment for the Fiesta master cylinder (and the vac pipe will be on the top right looking from the front of the car.
Hi Richard
The holes on the Saab unit fitted to my S2 are not equidistant, they allow you to intstall the mastercylinder / servo arrangement the correct way or upside down. Their spacing did not allow the unit to be turned through 90 degrees, only 180 degrees. Likewise when I tried fitting a ford servo / mastercylinder assembly, the fluid reservoir pointed either to the left or to the right but not to the top or the bottom. i.e 90 degrees out from the Saab fittings if you see what I mean.
Have a look at the photos taken of the bulkhead from the footwell in the other posting. You will notice that they are not the same between the Saab unit and Ford units and whilst you can fit the Ford equipment in the Saab equipment holes it will mean that your integral fluid reservoir will be on the side of the fluid reservoir, not the top. Hence the requirement to elongate or drill new holes in the bulkhead.
If you don't have to redrill the bulkhead, thats brilliant (although it does mean that I spent far too much on Saab equipment when it was available) but I'm fairly sure you will have to - although I freely admit I didn't look into it in much detail as your good self! I got hold of a scrap unit off a fiesta and offered it up....
Hope this makes sense!?!
Cheers
Tom
The holes on the Saab unit fitted to my S2 are not equidistant, they allow you to intstall the mastercylinder / servo arrangement the correct way or upside down. Their spacing did not allow the unit to be turned through 90 degrees, only 180 degrees. Likewise when I tried fitting a ford servo / mastercylinder assembly, the fluid reservoir pointed either to the left or to the right but not to the top or the bottom. i.e 90 degrees out from the Saab fittings if you see what I mean.
Have a look at the photos taken of the bulkhead from the footwell in the other posting. You will notice that they are not the same between the Saab unit and Ford units and whilst you can fit the Ford equipment in the Saab equipment holes it will mean that your integral fluid reservoir will be on the side of the fluid reservoir, not the top. Hence the requirement to elongate or drill new holes in the bulkhead.
If you don't have to redrill the bulkhead, thats brilliant (although it does mean that I spent far too much on Saab equipment when it was available) but I'm fairly sure you will have to - although I freely admit I didn't look into it in much detail as your good self! I got hold of a scrap unit off a fiesta and offered it up....
Hope this makes sense!?!
Cheers
Tom
Hi Tom, that certainly does deserve checking. I think I can understand what you mean. According to the spec sheets they both have the same PCD for the mounting bolts but I still have Kens old SAAB servo in my garage, I'll get the new Fiesta one back from the factors and make up a template to check. I'll report back!
Richard browsing the burton power catalogue last night they do a servo 'clevis pin adaptor for master cylinder' as a seperate item - I think you said that replacing the saab unit with a ford unit needed a different size one??
I'll dig it out if you can't find it. Don't know if it is right but worth a look. Their part number is BRK007 £5.99
Chris
I'll dig it out if you can't find it. Don't know if it is right but worth a look. Their part number is BRK007 £5.99
Chris
Edited by Barkychoc on Thursday 27th March 18:40
Thanks Chris, I had a look, an interesting catalogue indeed. The part they are listing isn't the part we need to change, it is only the pin through the end of the clevis that needs to change. I presume it might be sensible for me to add a 'spec' for the pin as well so I will measure it exactly. I did however 'google' clevis pin and, amazingly, there is a specialist for that too! See; http://www.boneham.co.uk/clevis-pins.htm
You will see from their picture that the part is really very minor. Don't know how they would feel about selling just the odd one though.
You will see from their picture that the part is really very minor. Don't know how they would feel about selling just the odd one though.
Hi Richard
You are absolutely correct, both units do have the same PCD. The problem manifests itself at the master cylinder end. Its not until you attach the Ford master cylinder to the Ford servo bolted through the Saab holes that you discover it!
The Ford master cylinder flange connection (that attaches the unit to the servo) bolting position is different in relation to the fluid reservoir connections. This means that when you attach the master cylinder to the servo the reservoir connections are on the side and not the top.
I hope this explains a bit more clearly!
Cheers
Tom
You are absolutely correct, both units do have the same PCD. The problem manifests itself at the master cylinder end. Its not until you attach the Ford master cylinder to the Ford servo bolted through the Saab holes that you discover it!
The Ford master cylinder flange connection (that attaches the unit to the servo) bolting position is different in relation to the fluid reservoir connections. This means that when you attach the master cylinder to the servo the reservoir connections are on the side and not the top.
I hope this explains a bit more clearly!
Cheers
Tom
OK, thanks for the contributions, I am now satisfied this is sorted, properly this time! Went as far as making a 'mock' bulkhead and fitting first the SAAB then the Fiesta servo.
Although the PCD's of the 4 mounting holes are identical, each of the servos has two 8mm opposite mounting bolts on a 90mm PCD and two on a 102mm PCD, regrettably it is the opposite pair on the Fiesta servo!.
That means that the bulkhead does need to be redrilled. This is actually quite a simple job.
I've attached a drawing/template showing the position of the existing holes and the position or the required holes.
With the old servo off, working from the engine side, draw a line through the centre of the diagonally opposite pairs of holes. The top left and bottom right holes need to move IN by 6mm, the top right and bottom left need to move OUT by 6mm. As the old and new holes overlap, if you try to drill 8mm the drill is likely to 'drift'into the old hole so I suggest you drill about 4mm holes and file the holes out to 8mm.
The bulkhead is reasonably thick glass reinforced plastic with a steel plate on the inside. The steel plate provides the strength and is sufficiently strong for the extra holes not to be any problem. I would however recommend that you use wide thin washers, approx 20mm wide, under the nuts on the inside together with additional sealant around the holes just to ensure water cannot get in.
On the drawing I have also put in the dimensions for the new clevis pin required.
http://i199.photobucket.com/albums/aa102/greymrj/T...
Do you think the 'thread' should be left like this, and a link made from the alternative parts list? I suspect that it could be slightly confusing as it is and that it would be better for me to summarize in a 'new' thread, include the drawing as a picture in the thread, and link that 'new' thread to the parts list.
Although the PCD's of the 4 mounting holes are identical, each of the servos has two 8mm opposite mounting bolts on a 90mm PCD and two on a 102mm PCD, regrettably it is the opposite pair on the Fiesta servo!.
That means that the bulkhead does need to be redrilled. This is actually quite a simple job.
I've attached a drawing/template showing the position of the existing holes and the position or the required holes.
With the old servo off, working from the engine side, draw a line through the centre of the diagonally opposite pairs of holes. The top left and bottom right holes need to move IN by 6mm, the top right and bottom left need to move OUT by 6mm. As the old and new holes overlap, if you try to drill 8mm the drill is likely to 'drift'into the old hole so I suggest you drill about 4mm holes and file the holes out to 8mm.
The bulkhead is reasonably thick glass reinforced plastic with a steel plate on the inside. The steel plate provides the strength and is sufficiently strong for the extra holes not to be any problem. I would however recommend that you use wide thin washers, approx 20mm wide, under the nuts on the inside together with additional sealant around the holes just to ensure water cannot get in.
On the drawing I have also put in the dimensions for the new clevis pin required.
http://i199.photobucket.com/albums/aa102/greymrj/T...
Do you think the 'thread' should be left like this, and a link made from the alternative parts list? I suspect that it could be slightly confusing as it is and that it would be better for me to summarize in a 'new' thread, include the drawing as a picture in the thread, and link that 'new' thread to the parts list.
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