I believe it is time for a new servo on my 67 420. Most current listings show it as being the same as the V12 E type, others list some servos by diameter. My suspicion is the V12 is larger that the 6 cylinder E type, does anyone have any experience with servos on 420's and what works best for them? Originally, Jaguar showed a specific servo for the 420's; are the E types one of those "close enough" interchanges? Of course, the costs are all over he place and this is a nice driver, not a show car, so 100% originality is not an issue for me.

Thanks for any input!

Submitted by mam.haggis@hot… on Fri, 06/27/2014 - 12:32

Edited on 2014-06-27 12:40:01
These are the two major suppliers as I am sure you know.

http://xks.com/i-7084300-gr-4258-510-brake-booster-v-12-e-type-420-new.html

http://www.jagspares.co.uk/Manners/PartView.asp?partno=4258&perpage=10&i...

I am rebuilding the whole brake system on my 340 and in my case I decided to rebuild my servo rather then fit the aftermarket one in. With the 340, (Mark II) the mounts are different and it requires an adapter plate.

I had the bores on mine sleeved, but the main culprit was the seal on the end of the bore where the shaft comes out that attaches the main vacuum piston.
That seal leaks after years of service and allows brake fluid to enter the vacuum cylinder _ in extreme cases it fills so full of fluid that the engine sucks it up and the car drives around with clouds of white smoke.

If you think the servo needs rebuilding, I'm betting that the master cylinder needs attention too.

Sleeving is the least expensive, but requires the most skill.