C Type brake booster

My C Type replica has had the brake booster pump disconnected, I think because the brakes were too strong.
The photos show the two hoses from the pump that go to a bulkhead connection under the dash. One pipe ends there ( not plugged ) and the other goes to the top of the brake fluid reservoir/ pressure doodad. It’s the pipe which looks kinked ( it isn’t ).
How does this setup work ( if it was connected ) ?
I can’t find anywhere that the other pipe could be connected to.

Hi Garry…havent seen that set up before. …what make is the C type…lots of knowlegable guys on this facebook group just dealing with historic Jag replicas…post there if no answer here…Steve Jaguar Historic Replica and Specials Register (Jaguar Drivers' Club) | Facebook

Thanks Steve but I don’t do facebook. I wonder should I post in the XK section on here?

Hi Garry…i dont do anything on facebook apart from the jag group i linked to… its very easy to join and use and will give you acces to many who own C,s…dont think posting in the XK section will make a difference…genuine C,s didnt have brake boosters they are something added to replicas…Iv seen a lot of C replicas but never seen the canister unit or the 2 pipes going into the gearbox tunnel befor…what do they connect to…typical system is brake pedal, master cylinder with or without servo(vac operated from manifold)…more photos of what you have from pedal onwards to calipers may help…does your pedal go into the rear of that round canister?..Steve

A couple of questions:

1 can you post a photo of the master cylinder
2 you talk about a “pump”. Can you expand on this. Is it a vacuum, pressure or fluid pump
3 Can you post a photo of the brake pedal
4 does this car have dual brake circuits
5 how and where do you add fluid

The car is a copy of the ‘53 cars and I believe it’s a Plessey pump on the rear of the gearbox, hydraulic.
The front and rear brakes are on separate circuits.
Fluid goes in the cannister in the second photo, the plug on top screws out.
The brakes work fine, it has 6 pot calipers on the front and 4 pot rears. I just changed the brake fliud and it made me wonder how the boost system works.
I’ll post some more photos later.

Hi Garry…so more of a tool room copy than the ususl replicas…more info here on plessy pump systems although titled 150 just read through till you get to the C type…you will get good replies on the XK section with a heading like …Plessey pump brakes… XK150 Disc Brakes

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Thanks Steve, the calipers pictured near the end of that thread are the ones.

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Photos as promised

That’s the brake pedal pushrod in the upper left hand.

Thanks, as I said I’m really just curious as to how it works.

Might have to move it, the sound of crickets is becoming deafening…

Is that a Racing Green replica? Their brake setups were so killer / the six piston Dunlap repro calipers a complete work of art.

I would urge you to post on the Facebook replicas page as noted, you’ll get some very good (and quick) responses. I know just little enough about the Plessey system to most likely give absolutely wrong information.

With a dual master setup, the reality is no assist is needed. You are very over-braked on a car weighing in just at or under a tonne or ton :wink:.

My replica runs zero assist on a dual circuit, with stock MK2 calipers in the rear and fairly hefty 4-pot Willwoods up front.

Thanks Jeff,
I think the car may be from Coventry Classics (New Zealand) and assembled/painted/whatever by Concours Sportscar Restoration here in Aus. When I was looking at it to buy I did try to talk to CSR, but I must say they weren’t particularly helpful.
As I’ve said, brakes are fine, so I’m not about to bury my feelings about facebook.
I’m just curious about the disconnected hose and I did think the brains trust on here would know something about it.
Whatever, it is a lovely thing.
Gratuitous shot of the carbs - I’ve just finished plating most of the linkage, mixture screws etc.


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Hi Gary
That looks like a dummy reservoir and pipes. Probably no pump on end of gearbox. Original gear driven hydraulic boost sytem was to solve pad knock off causdd by axles bending giving unexpected long pedal. Kept 2 psi in the lines to keep pads near discs. When the brake oedal was pressed full pump pressure was applied to master cylinder. When pedal at rest ie not braking fluid circulated from pump to reservoir via back of master cylinder and back to pump. Your car has standard tandem later xk120 mater cylinder and no boost. Pipes are for show. Dunlop banana brakes fine unboosted. Long pedal avoided with stronger stub axles and tighter bearing clearances plus a couple of other mods. Nice looking C Type. Drive it often!


Well the reservoir holds brake fluid - I just changed it a few days ago.
And it has the pump on the back of the gearbox.
It’s just missing a hose from the bulkhead. Where that hose went to, I don’t know.

Hi Garry…if there is fluid in it then can’t be just for show…i havent noticed a post on the Jag historic facebook site i linked to above…thsts a place you will get answers. …Steve

Okay. Sorry. My mistake. Sounds like the master cylinder has been changed and the pump disconnected. Normally the fluid went from pump to m/ cyl to reservoir and then back to pump from reservoir. Pressing prdal opens valve in back of master cylinder giving boost. But if pump fails then no boost and not much braking just foot pressure. Adapted from a grand prix car of that era. Phenomenal system when working properly but scary when not. However with normal xk120 type master and no boost system they still work fine. Twice the piston area of an xj6 on a car half the weight. Original boosted c type system very similar to later D Type but different calipers.

Lovely looking recreation. If you need more assistance I can connect You with a friend in the UK who has been very helpful to me on my build.


Disc brake / watch!

Thanks for the offer Marshall, but everything is fine with the brakes. As I said I was just wondering where that hose was meant to go.
The brakes need a decent push on the pedal, but they certainly work!

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