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Old 11-11-2013, 11:04 AM
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Vacuum pump check valve confusion

Hi all, 1980 300cd with the older style vac pump. My check valve is just a hollow fitting. Pelican parts don't sell this valve but other part stores say valve is same for 1980-on models. I have no vac leaks, holding 22hg, but drops to 0 when brakes depressed. Booster passes all test I know of. Is missing check valve the prob? Should the booster drop vac to zero? Thx for any help

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Old 11-11-2013, 11:24 AM
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The check valve keeps the vacuum from leaking/bleeding off.
The pump pulls the vacuum, the reservoir 'stores' the vacuum
and the check valve keeps the vacuum from bleeding off.

Very often available at your local PNP locations.
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Old 11-11-2013, 11:30 AM
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FYI

Quote:
Originally Posted by Darmok View Post
Hi all, 1980 300cd with the older style vac pump. My check valve is just a hollow fitting. Pelican parts don't sell this valve but other part stores say valve is same for 1980-on models. I have no vac leaks, holding 22hg, but drops to 0 when brakes depressed. Booster passes all test I know of. Is missing check valve the prob? Should the booster drop vac to zero? Thx for any help
A picture or three would make this answer easier.

Are you speaking of the valve in the middle of the thumb size plastic line, going from the vacuum pump to the brake vacuum power booster ???


.
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Old 11-11-2013, 11:39 AM
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I'll take some pics. I'm referring to brass valve screwed into vac pump. Plastic inline valve near booster is good.
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Old 11-11-2013, 05:34 PM
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I replaced check valve on vacuum pump, brakes maybe a little better. Vacuum still drops to zero when fully depressed then vacuum builds back up in few seconds. Is this a faulty booster or a vac pump that can't keep up? Any help is greatly appreciated.
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Old 11-11-2013, 05:53 PM
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Answer

Quote:
Originally Posted by Darmok View Post
I replaced check valve on vacuum pump, brakes maybe a little better. Vacuum still drops to zero when fully depressed then vacuum builds back up in few seconds. Is this a faulty booster or a vac pump that can't keep up? Any help is greatly appreciated.
Knee jerk diagnosis:

The brake vacuum power booster is damaged = look for a good used unit..

************************

If you are lucky, the alternative is a weak/damaged vacuum pump.

.
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Heat exchanger durability.
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  #7  
Old 11-12-2013, 06:26 PM
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Thanks, replaced booster. Old one had a litlle brake fluid spray in it. Replaced master too. $49 at jy. Vacuum drops only slightly when braking. No more hard brakes. Beer time
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Old 11-12-2013, 06:29 PM
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Grin

Quote:
Originally Posted by Darmok View Post
Thanks, replaced booster. Old one had a litlle brake fluid spray in it. Replaced master too. $49 at jy. Vacuum drops only slightly when braking. No more hard brakes. Beer time
That is good news.

.

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Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
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1983 300D
1984 190D
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2002 Honda Civic

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