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  #1  
Old 11-02-2014, 02:44 PM
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A leaking brake caliper ,then no shut off ,could it be related?

In my 300cd daily driver I recently had the brakes soften up ,soon after the car wouldnt shut off .The caliper leaking was lowering the brake fluid reservior but would this affect the vacuum needed somehow for the vacuum shut off box ?.Ive checked the main vac line for any leaks and the shut off box for vacuum hold with good results. Monday Im in for a caliper replacement but as far as other parts has anyone had a similiar issue?

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  #2  
Old 11-02-2014, 03:09 PM
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The soft brakes and no shutdown could be related, but the leaking caliper is a completely different issue.
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  #3  
Old 11-02-2014, 04:33 PM
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The leaking caliper and the soft brakes can go together...as to leak fluid air must replace the brake fluid... leaving you compressible air in the line..
If the vacuum was less than it should be...which might affect the shut off actuator... the only thing it affects is the power assist... which would make pressing on the brake pedal harder to accomplish the same braking as with assist.
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  #4  
Old 11-03-2014, 07:33 AM
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Agree with posts #2 & #3.

Vacuum is not responsible for a leaking caliper.

You may have vacuum leaking from "other consumers", this would result in a slow to no engine shut off condition. Plug off the lock system, does the engine shut off?
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  #5  
Old 11-03-2014, 12:14 PM
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The power assist was not working also ,Im leaning to a weak Vac Pump right now,it will pull pressure but is their away to record a value of vac from the pump? This will get expensive in a hurry if the master cylinder gets a no pass.
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  #6  
Old 11-03-2014, 12:19 PM
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If you have a vacuum pump w/ a gauge, tap that in to your main vacuum line and run the engine. It will show you the vacuum being drawn by the pump. It should be close to 18Hg for everything to operate properly.

If you are seeing low vacuum, isolate the pump and test again (i.e. block off all other vacuum systems including the booster). If you then see around 18Hg you know the pump is fine, but other systems are leaking.

Do not jump to the conclusion that your pump is bad. Just in the last few years I've put my hands on a half dozen of these cars (some mine, some belonging to friends) with similar symptoms (hard brakes, no engine shut off) and none of them had bad vacuum pumps. All had vacuum leaks, usually in the door locks. Once the leaks were fixed the brakes and engine shut off returned to normal.
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  #7  
Old 11-03-2014, 02:29 PM
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Thanks for the info guys,its now evident the vac pump has gotten weaker over the past few days ,I checked my other 617 cars and the vac is much stronger by the olde thumb on the pipe test.It turns out the brake caliper was just due to give out at the same time.The older they get the more the hood goes up.Ill remove the radiator this time to get to the allen bolts on the VP ,seems it will be a much smoother job if you can see the bolt your taking out and aligning the new one on as well.
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  #8  
Old 11-03-2014, 08:20 PM
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There is a check valve located between the pump and main vac line, inspect that before you throw money at a new/rebuilt VP.
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  #9  
Old 11-04-2014, 09:47 AM
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The vacuum ,once I checked it with the mity vac gauge ,pulls to a 23 reading but takes 3 seonds to get their,on the 300cd parker I checked and it reaches the mark at less than a second.The pump is working but at a failing number to be considered at the required performance.This would be the only way to measure a failing pump is to calculate and take a time it reachs required vac which gives you the amount of revolutions the plunger on the pump gets to required vacuum.I pulled the vacuum line between the brake master cylinder and the connection pipe before the pump.The one last check before pulling and switching vac pumps is to check it directly at the pump itself eliminating the line for leaks.I hope to rebuild this failed unit giving that an already rebuilt one cost $450ish ,to get a rebuild kit is still $195ish but a saver for the next parts haul sure to come.

Last edited by chasinthesun; 11-05-2014 at 11:18 AM.
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  #10  
Old 11-05-2014, 11:31 AM
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Important note about this Vacuum pump issue,if you tend to have this same problem remember that the pump will work fine one moment then fail a short time after, then work fine once again .Trust the readings you have taken of the pump ,the pump will keep giving you the impression that other parts along the system are at fault ,their not . Throwing parts at the issue could double or triple an otherwise simple DIY.Im glad I kepT reworking the issue ,Im use to parts just not working at all ,then replacing them ,the pumps tend to die slowly.
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  #11  
Old 11-05-2014, 11:40 AM
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Quote:
Originally Posted by chasinthesun View Post
...... that the pump will work fine one moment then fail a short time after, then work fine once again ....
Can you describe the physics of the situation which might allow that to happen?
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  #12  
Old 11-05-2014, 11:45 AM
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Quote:
Originally Posted by chasinthesun View Post
Important note about this Vacuum pump issue,if you tend to have this same problem remember that the pump will work fine one moment then fail a short time after, then work fine once again .Trust the readings you have taken of the pump ,the pump will keep giving you the impression that other parts along the system are at fault ,their not . Throwing parts at the issue could double or triple an otherwise simple DIY.Im glad I kepT reworking the issue ,Im use to parts just not working at all ,then replacing them ,the pumps tend to die slowly.
It's pretty easy to identify if other parts are the problem or not, so yes if you get down to it and the pump isn't pumping properly it needs attention. However, 100% of the time for me the pump has not been the issue. It's definitely the least common vacuum issue on these cars. Please understand, I'm not saying pumps don't go bad - obviously they do. However it should be clearly stated in any thread about vacuum pumps that the vast majority of the time the problem stems from leaks, bad diaphragms, etc. Until you have eliminated EVERY one of these other issues the pump is the least of your worries
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1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino

http://i.imgur.com/LslW733.jpg

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  #13  
Old 11-05-2014, 12:09 PM
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Originally Posted by uberwasser View Post
..... However, 100% of the time for me the pump has not been the issue......vast majority of the time the problem stems from leaks, bad diaphragms, etc.
' Bad diaphragms ' ..... seems like that should not have been included in that sentence... it being the heart of the actual pump....
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  #14  
Old 11-05-2014, 12:29 PM
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Quote:
Originally Posted by leathermang View Post
' Bad diaphragms ' ..... seems like that should not have been included in that sentence... it being the heart of the actual pump....
I should have been more clear I was referring to the many diaphragms in the door lock system, the climate control, shut off valve, etc. which I was classifying as a separate problem form leaks at rubber connectors or from cracked/broken plastic lines.

And anyway the later style vacuum pumps didn't have diaphragms, the diaphragm pumps were earlier than 1980 only I believe?
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1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino

http://i.imgur.com/LslW733.jpg

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  #15  
Old 11-05-2014, 01:15 PM
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My '1980' s diaphragm gave way 20 miles from home ... almost rolled through several stop signs getting home... pushing on the brake pedal as hard as I could...
I put the year in quotation marks because changes are by VIN and not ' year ' ....

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