Although the final bits and pieces of the Test fit are covered in the Test fit — Final items post, I thought fitting an upgraded servo warranted a separate entry.
The Mk 2 braking system is servo-assisted with a separate vacuum reservoir, known as a reservac. The servo is mounted through the inner wing and the vacuum reservoir under the front wing, as can be seen here. A cover fits over the servo protecting it from road debris, and a stone guard protects the reservac. The original equipment servo is a Lockheed 6 7/8″ unit.
Rather than refurbish my existing brake servo and to (hopefully) improve braking performance, I decided to upgrade to the Lockheed LR18230 servo, purchased from SNG Barratt in the UK. The LR18230 has a 4.25:1 boost ratio, which is an improvement over the original servo, which I believe to be 3:1.
Of course, it would be too easy if the replacement servo fitted without modification, but we are dealing with classic Jaguars here! The original servo has three mounting studs around the perimeter. These attach the servo to its protective cover. The new servo has three mounting studs, which are located towards the centre of the unit. Therefore the mounting arrangement needs to be modified.
I decided to add this to the test fit list rather than tackle it later when the body was completed and painted. In their excellent Jaguar Mk2 restoration project, Kriss Motors cover the approach they took in fitting the LR18230 servo to the Mk2. This was broadly the approach that the team at the Surgery followed. The Jag-lovers forum also has several threads on this subject.
The first thing to check was the fit of the reservac and servo cover under the front wing to ensure that everything was snug. Apart from a broken mounting leg on the reservac, all was OK.
Modifications are required to mount the new servo (with its different mounting stud arrangement) to the existing cover mounting holes. Kriss Motors solved this by fabricating two braces connecting the new studs to the existing pattern. We followed a similar approach.
In my installation, the servo cover needed modification to allow space for the vacuum hose connection. This modification looks good (not that anyone will see it under the wing) and does the job perfectly.
The final few items were to replace the broken leg on the reservac cover and fabricate a bracket to provide additional support for the reservac. Jaguar fitted this from chassis number 127334 (mine is 111582). The bracket fits from the top of the reservac unit to the servo cover. Thanks to Eric Kriss for highlighting this in his blog (see link above)
Finally everything was cleaned, primed and painted, ready for the day when it all goes back in the car. Here are some images of the painted servo cover.
Nice job accommodating the updated servo. What did you use for your under seal? Keep plugging away.
Hi Lin,
It’s an oil based rubberised underseal, I don’t know the brand as it’s supplied direct to the Surgery. I must get myself a can of it. Yep, still plugging away. Very close to completing this phase of the project!
Really appreciate your blog, very informative. I have few questions.
In the engine bay there is a hose connection from the servo unit to a filter. How is that filter attached to the car body. Currently mine is loose and I am missing the hose, but I don’t seem to see mention of any bracket or how it is connected to the car in any of my research.
Also, my filter is black yet I notice in some of the pictures of various MK II engines some are metal/silver. What would the original have been?
Any comments would be appreciated.
Ray
Hi Ray,
Hmmm interesting question, I now suspect that my car never had that filter fitted during my ownership! Anyway, if you have a look at Lin Roses’s site (link here) he has an image of the bracket. Lin notes that it bolts to the radiator shroud. Regarding the colour, I’ve had a look through my copy of Nigel Thorley’s Original Jaguar Mk1/M11, and it looks to me like most were silver, but there is a black one shown as well.
Hope this helps, Phil
Phil,
Thank you for documenting your restoration. You, Lin Rose and Eric Kriss have done a real service for the Mark 2 community. I have the same replacement booster and am looking for tips on its install. In the picture captioned: “Insufficient clearance for vacuum hose connection”, it appears that the actual hose connection has been removed. Did you remove it as part of trial fitment? I’m hoping I can rotate it a bit for my install as I do not have welding tools/skills. I tried to rotate it, and it seemed to move, but I did not want to force it. Thank you.
Hi Eric, thanks for the feedback! Yes, the fitting was removed for the test fit, and it either screws or pulls off. The reason I’m not clear is that, thanks to your question, I’ve realised that the fitting hasn’t made it back with the rest of the parts from The Surgery following the test fit. Here’s a close up of the booster with the fitting removed.
I hope this helps, Phil
Phil,
Thank you for your reply. You indicated in your reply that you were providing a closeup of the booster with the fitting removed. I don’t see an image/link.
Thank you.
Phil,
Ignore my last comment. The link in “Here’s” was not apparent with my monitor settings. Thanks again. Eric
I have just purchased one of these, question, Does it need the vac tank as well, as the new servo unit has already got a non return valve, with the vac tank that makes two, or can it be fitted without the vac tank.
Hi Chris,
Thanks for reading … As I’m sure you know the vac tank provides additional capacity in the engine failure. Removal of the tank is hotly debated in forums and I’m not qualified to have an opinion. I’d check with a qualified engineer before deciding not to fit it. I’m not trying to duck the question its just that with brakes we have to get it right! I’m fitting mine.
Cheers, Phil