The 'E' Type Forum

Good evening all

Is the vacuum tank used just for the brakes or is there any other component that also need the vacuum?

Just brakes although the Trico Reservac was originally designed to operate a vacuum windscreen washer system. Jaguar re-purposed it for use as a brake vacuum reservoir.

Is this tank really useful unless you want to brake while applying throttle?
Need the space for an oil breeder tank so thinking about ditching it.

The vacuum tank provides emergency braking when the engine cannot run and you must stop faster than the mechanical only braking will allow. Perhaps there is a different tank from another car or industry that can be used. It could go inside the passenger compartment. Or changing the brake system to allow better mechanical only braking would work. The shape of the tank is rounded to prevent collapse.

Also a possibility to have a vacuum pump fitted.
But even if the engine died, you can still generate vacuum.
So to conclude it can work without the tank and there is some scenarios where it can be useful like if the engine died and at the same time propshaft broke so that the wheels cannot turn engine around and generate vacuum

Cars of the same era as the S2 such as MG and Lotus have no vacuum reserve tank but a similar sized brake servo and they work fine. Indeed I can't think of a car of that era that did have an associated vacuum reservoir but the additional length of pipe between the servo and brake reaction valve would add a little to the vacuum requirement.

However, depending on the inlet manifold design and the carb types fitted on an E type there may be only one or two cylinders out of the 6 that are actually being used for their vacuum and so without a reservoir tank it may have been considered to take too long to recharge the vacuum in the brake servo without a reservoir to help.

If you need the space, I'd suggest relocating a (smaller) vacuum reservoir under the battery tray.