Hi Guys, n Gals. I have an intermittent issue with my RHD 2003 2.5 S type. On some cold mornings, the car stumbles at idle, and along with that, i get loss of brake boost from the servo. it seems to cure itself after 30 seconds to a couple of minutes. once warm, it never happens. On one occasion, it put out a few DTC codes for cylinder misfires..
I can't figure out what could be causing it....all pipes and connections seem secure.
Vacuum pipes don't have a leak and then fix themselves!. Diaphragms don't get a split and then fix themselves Surely??. I don't want to splash out on a servo, unnecessarily, as they are very expensive. I cant hear any vacuum leaks or hissing when it happens.
Any Ideas Guys?? ('n Gals)!
Cheers Andy

 

1. Delayed vacuum to diaphram? There is a check valve between the intake manifold and the booster. Is it congested with old crankcase oil (from PCV system)?
2. Filter media congested at poppet valve inlet on pedal side?
3. Poppet valve congested?

If vacuum is present and atmospheric air is allowed, brake boost is present.

4. When was the brake fluid changed. If it is other than clear or amber, completely flush the brake fluid.
Brake fluid is hydroscopic. It absorbs moisture from the air. If your brake fluid is very old, it could become thick at reduced temperature.
See the video:



Let us know what you find.