idle increase when pushing the brake pedal

[Jkalplus1]

The car is idling. In neutral. I push the brake pedal, RPM increases by 200-300RPM. Is this normal? If not, what do you think is the cause? My car is a 64 without power brakes.
J

[garymand]

You sure you don't have a brake booster in there somewhare?  Without a booster, I can't think of anyway the A/F mixture could be effected by the brake pedal.

[kampala]

Thought "power brakes" were standard on all w113 models and not an option --- but I may be wrong. 

Typically, as Garymand wrote, when rpm rises when applying brakes, it usually means your brake booster may be leaking or the gasket between the master cylinder and booster has a leak.

[66andBlue]

Correct. I don't think it was an option to eliminate the brake booster. 
Perhaps he means "without power steering"? 

[Jkalplus1]

I see. I did not know PB was standard (I do not know mechanics). Yes my car has PS. The brake booster, I assume is the large black cylinder in the rear left of the engine bay (when sitting in the driver's seat. Is this an easy DIY job? Does anyone have an idea how much fixing the booster typically costs? It never bothered me since I can easily lock the wheels if needed and no one but me drives the car.  I just want to make sure this is not the kind of thing that gets more expensive the longer I wait.
Jerome

[rico_vancouver]

I had this symptom too. It's the brake booster, which was not a DIY thing for me. A replacement one is costly, so I went for a used one for $600. Should have replaced the master cylinder at the same time (got a new one online ~$110), as you need to bleed the brakes, so might as well have done both at the same time.

[66andBlue]

... Is this an easy DIY job? Does anyone have an idea how much fixing the booster typically costs? ...

Easy DIY job? For the technically savvy: yes; for others it can be more damage during the process.
Costs for repair are about US$250 plus shipping. See: http://www.sl113.org/forums/index.php?topic=17598

[MikeL43]

I called Power Brake Exchange about a month ago and they quoted me $190 plus shipping.  They said they would powder coat it for free.  I haven't sent mine in yet but it sounds like a very good deal considering the cost of a rebuilt or new PB booster.

[Cees Klumper]

This seems to be about the going rate, under $200 for a rebuild. According to banter at another classic car enthusiast site, the necessary seals, gaskets etc are around $20 but to open the booster requires a special purpose tool that compresses + turns at the same time. So not really DIY and a rebuild place should be able to handle it for under $200 generally. This is all in the US, not sure about ROW.

[glenn]

Does the the increase in rpm mean it is idling rich?

[Ulrik]

If anybody in Europe can renovate I would be interested to get some contact details.

I'm in Denmark but don't mind shipping to Germany for example

Kind regards
Ulrik

[Jkalplus1]

This seems to be about the going rate, under $200 for a rebuild. According to banter at another classic car enthusiast site, the necessary seals, gaskets etc are around $20 but to open the booster requires a special purpose tool that compresses + turns at the same time. So not really DIY and a rebuild place should be able to handle it for under $200 generally. This is all in the US, not sure about ROW.

Please pardon my ignorance: I have very little knowledge of car mechanics.  I am thinking, since my car is driven very little (less than 2000 miles per year), and I lived without booster for years, can I not just keep on driving safely like this? I know my car, braking power required, etc.  I am thinking "could this not be something I fix only when (if!) I want to sell the car?"  No one but me drives it.  Or is it something that needs to be fixed in order to prevent further damage in the braking system?

Like many owners, I have a budget for the car and I do the regular flushing of all fluids, greasing, maintaining impeccable cleanliness, plus the occasional cosmetic upgrade.  This booster thing seems like something that can wait indefinitely, like Hardtop reassembly. Thoughts?

[Benzo]

Rock Auto will also re-manufacture your brake booster for a reasonable price.

[ejboyd5]

I am thinking, since my car is driven very little (less than 2000 miles per year), and I lived without booster for years, can I not just keep on driving safely like this? I know my car, braking power required, etc.  I am thinking "could this not be something I fix only when (if!) I want to sell the car?"  No one but me drives it.  Or is it something that needs to be fixed in order to prevent further damage in the braking system?

Of course you can keep driving it  - the brake system is designed to  operate even without the power assist.  However, considering the minimal costs involved you may recoup your investment very quickly through the increased driving pleasure you will enjoy in operating a car that performs as it was intended to perform.