Vacuum question

[Chris Dixon]

According to the service manual the reservac tank in the heater contol system is fed by vacuum from the inlet manifold, and as I can only find one takeoff which feeds the brake servo, and a pipe that goes from the reservac tank in the left inner wing to the other side of the engine compartment, where the servo lives, will I find a t-piece somewhere in the vicinity of the servo? As I don't recall the heating system having much of a reserve, the air flap tending to slowly close when the engine stops, there is likely a leak somewhere, but my attention is drawn to the check valve, would this prevent the reservac from holding a reserve supply, or is its function to stop it getting too much?

[vaultsman]

Hi Chris,

Yes, there is a T-piece....item #61 on Plate 88 (Page 506) in the Parts Book.

The air flap on my car will stay open for many hours when the engine stops, so it would seem you do indeed have a leak. The check valves are known to be a usual suspect, so I'd be starting there as it's accessible.

Some info here: http://www.britishcarforum.com/bcf/show ... c-Tank-MK2

New valves are still available from Barratts.

Good luck!
Stan

EDIT: A previous post from Jose on this....about 1/2 way down.
http://www.jagstyperegister.com/forum/v ... t=10&p=214

[Jose]

the T piece is to supply vacuum from the Reservac Tank to the Vent Scuttle Vacuum Tank located under the left wing, (driver's side in RHD cars). It is a smaller tank shaped like a bell. Its only purpose is to supply vacuum to the scuttle vent via the vacuum actuator located at the top center of the bulkhead, in front of the scuttle vent.

If your scuttle vent closes slowly when the engine is idling, but opens again if you rev the engine, the tank is leaking either at the valve or a bad hose. The tank itself could be rusted through. And the actuator's diaphragm could also be torn inside the actuator.

[Jose]

[quote=vaultsman post_id=28 time=1509440288 user_id

The air flap on my car will stay open for many hours when the engine stops, [/quote]

Hi,
you shouldn't leave the vent open for many hours as doing so stresses the diaphragm inside the actuator by keeping it in the compressed or "pulled" mode. These actuators are no longer available new. I press the OFF button, (the air/heat/off buttons under the radio), to close the vent flap when engine is off.