clive
Rover Rookie
Posts: 44
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Post by clive on Sept 28, 2020 20:26:52 GMT
I've noticed this large drum like tank under the front wing on my 3 Litre and always wondered what it's for. Whatever it does, does it require any maintenance? I thought I knew my car really well but I've never looked into what this all about!
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Post by p5andrew on Sept 28, 2020 20:46:32 GMT
The tank you mention is the air reservoir for the brake servo. It is important to make sure it remains free of corrosion, especially given its exposed position up in the wheel arch.
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Post by enigmas on Sept 29, 2020 3:41:01 GMT
The single circuit brakes on a P5 are power assisted. The power assistance utilizes engine manifold vacuum to operate the brake booster. The 'vacuum' tank under the wing/guard/fender stores a reserve of vacuum. If the engine were to cutout at speed or descending a steep incline you would have a few more 'reserve' brake pedal applications before all power assistance to the brakes would be lost!
So ensure the vacuum tank is externally in good condition. Any corrosion causing a venting hole will render it non functional.
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Post by Phil Nottingham on Sept 29, 2020 4:52:37 GMT
It can pinhole from corrosion and cause erratic running as it causes an intake air leak as can perished vacuum tubes. It has a drain plug to drain out moisture which is worth removing periodically. It is not required with Lockheed servo conversion.
To test its operation start the engine with your foot hard on the brake - the pedal must move down an inch or so
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clive
Rover Rookie
Posts: 44
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Post by clive on Oct 1, 2020 9:45:24 GMT
Thanks for the reply's, next time I get the car out I'll give it a once over I seem to remember it's losing it's underseal. Are they easy to remove to recoat it again!
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Post by Phil Nottingham on Oct 1, 2020 11:18:04 GMT
As easy as anything that has been under front wing for 60 years! Best to renew the flexible vac pipe at the same time
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Post by Eric R on Oct 2, 2020 10:00:30 GMT
I replaced the Girling unit with a Lockheed on my early Mk1 and I'm sure it already had the reservoir tank 501531. My P5B had Lockheed from the start with the tank. On both cars, starting and running was a nightmare until it was realised that these tanks can fill with brake fluid so although I don't see any reference to maintaining them, they should be drained and cleaned out from time to time. Was it ever a requirement in service manuals?
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Post by Phil Nottingham on Oct 2, 2020 11:47:32 GMT
Yes
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