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MG MGA - Fitting a brake servo unit
|As I mentioned earlier I shall be fitting a new remote brake servo very shortly. Before doing so I have one question. Does a servo act on all four brake drums or just the front two?|
The servo will act on all your brakes operated by the master cylinder. Which servo unit will you use and where will you mount it?
|Frank, In Australia there are good supplies of PBR Brand Vacc. Boosters VH40 and VH44 models suit our cars. I have used the 44 model on TR3a's MG TC's And MG A Coupe.
The 2 leading shoe front drum brakes on an MG A work very well--provided that the linings are not too hard. These days, brake shops tend to bond on linings that are too hard. These hard bonded linings requiring a high pedal pressure ---so the booster multiplies the fluid pressure in all of the lines so providing better stopping.
My Coupe' has a factory heater-- so there is limited space under the bonnet for the booster. Some owners mount these behind the mudguard splash plate . My uniit is fixed up behind the dash board. It can be heard making faint squelsh sounds as it works The Vacc. pipe from the manifould is best made as short as possible. Using space down by the rear axle requires too long a tube.
Disc brakes certainly require a booster unit. The pedal pressure required to stop the car with discs, is much higher, since there is no mechanical servo assistance as there is, in the design of twin cylinder drums brakes.
English Fords and MG A 's of the era used the 2 leading shoe design on front brakes -- together with linings of a suitable hardness to suit normal driver's pedal pressure.
Make up a nice bracket---alter the brake tubes- fit the vacc. pipe from the manifold-bleed the system--the results are gratifying.
Its a good safety mod.
|Thanks Dave, I bought a POWERTUNE 1.9 : 1 unit.I only received it today so I am not sure yet where it will be fitted. Can you give me any suggestions where to put it. As an add on, can you explain which brake pipes go exactly where. There are two places on the servo where two brake pipes are screwed in. Which two brake pipes go on the unit. But I am not so sure which is which. Can you be so kind to illustrate exactly where and what pipes are connected.|
I bought a Powertune 1.9:1 too and fitted it behind the dash in the radio space. There are some notes on Barney's site under BT-201H.
The brake pipe from the master cylinder goes into the side connection on the servo and the pipe to the junction fitting near the starter motor is connected to the nose connection at the pointed end of the servo.
You should have got a book of fitting instructions in the box with a diagram showing connections on page 7.
I arranged it so the brake pipes and vacuum pipe pass through the redundant holes for the LHD brake and clutch bracket.
You will need to find a way to fit a vacuum tapping to the inlet manifold. I have an MGB manifold which already has a tapping. There was a recent thread on how to do this for the MGA manifold on Autoshrine.
|My thanks also go to IW Cowen from Australia for his input to my thread.
Dave I'm grateful to you for the information you have posted. I wasn't sure where the pipes actually go, and which goes where. Thank you so much. As for the book of fitting instructions, yes this also came with the unit. The problem was that the cardboard box in which the servo was shipped was made from thin material, and consequently when in transit the cardboard was damaged in three places,(rough handling). The instruction leaflet, which was lying loose inside was also torn, with small pieces of the paper missing. I have since emailed the seller and asked him to post me a copy of the leaflet. Hoping he treats as urgent as I wish to install the servo in the car as soon as possible. Lastly, I feel sure that there is a threaded outlet for the vacuum rubber pipe, I will have a look later on. Thanks again for you assistance.
|I mounted my servo under the front RHS wing during my restoration work. I took the air supply from the inlet manifold. I had a threaded bush (cut from an MGB manifold) welded onto the end of my manifold. It all works fine, and the only downside is that I'll need to take the wing off if the servo needs servicing.
|But if it is installed properly, it may be serviced by removing only the splash panel.|
This thread was discussed between 23/07/2017 and 30/07/2017
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