Servo- removal and fitting a repair kit.

When I last did a job like this it was 1978, the vehicle was a viva HB; there was a Girling spares shop merely 1/4 mile down the road that stocked all the service kits you could possibly want... and I was much more flexible. Furthermore, the job was aided by the inevitable impression one gets on opening the bonnet of a Viva HB in that the question immediately arises... "Where the Hell is the motor?"! The tiny lump is surrounded by tennis courts worth of space with excellent access, and dealing with the servo mounts was a breeze... I sort of expected similar with the Lotus!!!


Well, if you ever think you might need to work on the Excel servo... my advice is to think very carefully about it. As I've never had my car running I don't know if the servo works or not... it may be fine but then I thought that of the master cylinder and the way that it had been full of gunk! I suppose, more for the experience and coloured in the rosy glow of a simple and successful service in the viva,  I decided to have a go at fitting a new seals kit while I have the MC off... after all it did look a bit rusty down by the push rod seal.

I rapidly wished I'd left it until later... getting at the servo mounting nuts requires  double jointed,  incredibly long arms and  fingers like ET!

I tried to test the servo in situ. I connected up the hand vac pump that was part of the  one man bleed kit, and tried to evacuate the thing through the non-return valve. It did pull a vacuum  at around 10-11 mm Hg but it rapidly fell back to atmospheric. Of course this may be normal behaviour, there was no obvious hissing sound so no really big leaks then. Also as the MC is off its possible that I have the pedal in the wrong position allowing air into the rear chamber- so not necessarily a sign of a problem. In any event I will fit a repair kit. The servo on my car is a Girling supervac 74049019 and the service kit it needs is a Girling SP2495. I couldn't find a kit listed under the car but searching this number turned up one easily enough. If necessary I will follow that with a new non-return valve... this is expensive but quite easy to replace so I can do it as a separate job if/when I ever get the car running and I can tell if I need a new one or not! The N/R valve is the push-in type as fitted to the triumph TR7 so easily obtainable from Rimmer Bros.

One unexpected bonus of this joyful task was that as the car has been standing for several years now, this turned out to be a wonderful opportunity to brush up on my entomology!

The MC was already off (see separate post) so all (!) I needed to do is unbolt the servo... hmmm. The servo is held on by 4 hidden and inacessible  13mm nuts positioned right up behind the pedal box. These are arranged in a square, there is a 5th nut that's in the general area but whatever its doing, it's not holding the servo on so doesn't need to come off. In addition the servo push rod is connected to a clevis pin about 2/3 of the way up the brake pedal. Access is really difficult- its hard to see what you are looking for and a lot has to be done on feel! Pictures are few and far between here because its so hard to see anything but I had a go.

This is the view looking up from the drivers foot well towards the pedal box... a maze of springs, struts and wires! The centre shaft here is the brake pedal.

 Sticking the camera up the back and you can just see the clevis fastening of the brake pedal to the servo push rod... in this pic I have already removed the pin and its retaining clip. Bellows of the servo rear dust seal visible bottom left

 This is one of the 4 nuts, a second is hiding under the cross strut  and the two on the other side are hidden by struts springs and pedals.

This was my eventual solution and I recommend it. You can manage with a crescent wrench and  a ring spanner (pref both ratcheting) but this got all 4 nuts. Its a 3/8 drive handle and 6in extn, connected via a 3/8 to 1/4 drive adapter to a 4 in 1/4 in extn that terminates in a 1/4 drive UJ and finally a 1/4 drive 13mm socket. Even a 3/8 drive socket is too big to fit in many cases. You will need to experiment to find the best route to feed the socket up and use a second hand to guide the socket onto the relevant nut. This was quite successful and got all the nuts off- but refitting will be a nightmare as I can't see how to offer the nuts up to the servo studs to start them on the threads! Ah well that's a problem for another day!

Servo front- on bench, corrosion round by seal in front seal  housing.

Servo rear, boot and push rod- more corrosion

This is the adjuster- the clevis fork can be screwed in and out along the push rod to adjust the effective length of the the rod. In my case it was corroded and rusted solid.

Removing the boot. Easier if you take the clevis off first but mine was rusted on. Its no big deal though and I wont be reusing the boot anyway.

Once the boot was off I could see the push rod- its rustier than I would like. Luckily there is an 8mm flat on the rod, so holding this and not the lock nut I could unscrew the clevis fork by passing a Phillips screwdriver through the holes.

The lock-nut wasn't disturbed so I shouldn't have changed the rod length but I did clean up the threads a little so that adjustment will be smoother. I will use some copper grease when refitting. I could also just lift out the sponge filter- which effectively fell apart on being touched. I think there maybe should be a retainer on top of this filter- later found it inside the old boot! The shaft of this rod looks like it needs more cleaning.

Close up of corrosion around the push rod seal on the front of the servo, its relatively soft stuff but I would like to remove it and de-rust this area later.  However I will wait and see whats in the seal kit and whether it comes with any instructions.

I masked off the vulnerable areas and rubbed down the servo prior to respraying. It wont make it work any better but at least it will look as if it works!

Servo repair kit arrived from Northwestclassics

This is a new version of SP2495, the original Girling kit would have contained a filter element and filter retainer but these are missing in new kits, and the filter has generally disintegrated in old ones! The new kit has a new dust boot, front vacuum seal and two ring seals (which are placed  between the M/C and servo in some applications- these are not needed in the Excel) and some vacuum grease. I will reuse the filter retainer from the old fittings and cut a new filter from some air filter foam.

The kit lacked instructions (also supplied with the original kit) but I got some copies and show these below.

I needed to clean up the servo before fitting the new parts. The rear push rod was also corroded. I can see what I assume is a valve at the bottom of the rod- looks like a retainer, spring and seal. I would like to take this apart and clean it properly, but there's no mention of how to do this and as new parts aren't available, I think this would do more harm that good. I decided I would just clean the rod as best I could- at least over the parts I can reach. I want to de-rust but not to let the stuff get everywhere so I used a gel formulation de-ruster.

Like the seal at the front, the rear pushrod was also corroded.

Solution- hammerite rust removing gel- this stuff is quicker than Deox-C

Gel applied over front and rear pushrods, and here- also around the front seal cavity

Rear push rod cleaned and rinsed to remove gel

Once the rust was clear at the front I removed the seal using snipe nosed pliers- it just pulls out

Seal out- Sadly this revealed more corrosion- so back into the gel

Clean at last!

 The second application of gel did the trick and I was pleased with the result. One good thing- there was no sign of loose rust or leaking brake fluid inside the servo so I am hopeful it is in good condition- and that I have't made it worse by cleaning and fitting the kit!

I examined the new seal, surprisingly it didn't have a metal side. There is no mention of swapping these in the servo instructions but I am assuming the metal cover needs to be there, so it was simple to fit it to the back of the new seal- note this pic shows the upper surface of the new seal and the lower of the old.

New and old seals- Note due to mental dysfunction these have been photographed in opposite ways up! The new seal (left) shows its upper surface, the old seal (right) shows the lower which bears the metal washer.

Metal plate swapped onto LOWER surface of the new seal

I greased the edges and centre hole of the new seal with rubber grease from the kit. I also put some of this onto the centre push-rod before fitting the new seal and pushing it home.

The instructions are adamant that the domed nut on the front push-rod should not be adjusted- so I left it in position and just fitted the new seal.

At the rear, the air filter I had removed was clearly no longer usable, there was no new filter in the kit so I made one using some air filter foam

Odd piece of air filter foam. You can get this on eBay for motorcyle air filters

I stamped out an appropriate size with a Neillsen punch kit (cheap and v useful for gaskets etc)

Change head and...

...stamp out centre. I later enlarged this and re-centralised.

The new filter slipped over the greased rear push rod and fitted well.

Nice fit!

 Next step was to refit the filter retainer (re-used from servo) and new boot

Filter retainer clips over end of rear tube

 Its very awkward to fit the new boot over the retaining lip at the base of the servo rear tube, so roll the bottom 2cms up and over before fitting the boot

New boot- the lower cm or so has been rolled back (inverted), you can see the retaining ridge at the bottom of the servo tube

 Then flip the rolled up portion down whilst hold the boot in position and it should clip easily over the retaining ridge.

Boot refitted, clipped over retaining ridge.

 The next problem was the dreaded refitting of the servo. In fact this went much better than I had feared. The trick is to use a long 1/4 drive extension with a wobble end, fitted with a 13mm 1/4 drive socket. Put the nut in the socket and fiddle around with the bar to find the best route to offer the nut to the servo studs. Rotating the bar then starts the nut. This worked fine for 3, although I had to use the UJ as before for the last. I used the UJ to tighten all of the nuts. Actually re-fitting the clevis was a dreadful job- took ages as there is no easy line of access or even sight! Also you cant get a finger up there to do it by feel (!) so it was a pig of a job. However- eventually it was in and the "R" clip reinserted.

I was then able to refit the rebuilt master cylinder (see other post)  and add some fluid. Pleased with the appearance- hope it works!