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Topic: Brake pedal causes engine to bog (Read 625 times) previous topic - next topic

Brake pedal causes engine to bog

Hey guys

As the title suggest I have a weird issue where if I press the brake on my carb auto 1.8 during the Dow press it directly causes the idle to drop a bit. Once fully depressed idle rises again.

I’m thinking two things - electrical draw on alternator ?? Or vacuum leak on brake servo being exposed during the down press.

I’m guessing it’s not normal and it only drops by 100rpm but thought you lot might know!

Re: Brake pedal causes engine to bog

Reply #1
It does sound very much like a vacuum issue.
Try (carefully) spraying a little clutch/brake cleaner over the vacuum lines while running and see if the idle picks up.
Mk2 Driver
Mk2 Silver 8v
Corrado G60 Turbo
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Mk2 BBM ABF
Bora 20vt
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Mk2 BBM 20vt
3.2 TT Roadster
Mk2 Red 16v
225 TT Coup
3.2 TT Coup
Mk4 Anniversary
Mk7 Red GTI Performance
Mk2 Red GTI Restoration

Mk2 BBM R32
911 Carrera 4S

Re: Brake pedal causes engine to bog

Reply #2
It does sound very much like a vacuum issue.
Try (carefully) spraying a little clutch/brake cleaner over the vacuum lines while running and see if the idle picks up.

Will give this a try! Any main ones to look for?

Re: Brake pedal causes engine to bog

Reply #3
Yeah, trace the main vacuum hose from the brake servo back to the engine, chances are, it'll be along that one.
Mk2 Driver
Mk2 Silver 8v
Corrado G60 Turbo
Mk2 Red 8v
Mk2 Grey 16v
Mk2 BBM ABF
Bora 20vt
Mk2 Green VR6
Mk2 Green ABF
Mk2 BBM 20vt
3.2 TT Roadster
Mk2 Red 16v
225 TT Coup
3.2 TT Coup
Mk4 Anniversary
Mk7 Red GTI Performance
Mk2 Red GTI Restoration

Mk2 BBM R32
911 Carrera 4S