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  #1  
Old 03-03-2012, 05:27 PM
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What should a vacuum pump check valve look like

ok maybe a stupid question, but i've tracked down a vacuum problem to either the pump or check valve.
i have an 81 300D with the newer style, single outlet pump. i pulled the valve and hose off today, the hose is fine. the valve though, i'm guessing it should have some kind of internal structure? mine is right now, basically just an empty fitting.

my symptoms are 5-10" of vac at cold idle, once the motor has been running for about 20 minutes, full 24" vac. it's causing the trans to shift like garbage for the first 20 minutes of driving. would a bad valve cause this or should i just look into getting a pump.

also since this is the newer style pump i'm also assuming i dont need to worry about it self destructing into the timing chain right?
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  #2  
Old 03-03-2012, 05:31 PM
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Trace your Main Vacuum Line to the Vacuum Pump, The Check Valve is the Fitting the screws into the Vacuum Pump Body and the metal Tubing of the Main Vacuum Line screws onto the Check Valve.

If you want to see a pic check one of the internet part Sellers.
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  #3  
Old 03-03-2012, 05:33 PM
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Quote:
Originally Posted by Diesel911 View Post
Trace your Main Vacuum Line to the Vacuum Pump, The Check Valve is the Fitting the screws into the Vacuum Pump Body and the metal Tubing of the Main Vacuum Line screws onto the Check Valve.

If you want to see a pic check one of the internet part Sellers.
yup, i pulled that valve off along with the hose. the hose held vac fine. but the check valve doesnt really look like a valve. it's completely empty inside. it's just a hollow brass fitting at the moment.
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  #4  
Old 03-03-2012, 06:22 PM
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Originally Posted by sleepstar View Post
but the check valve doesnt really look like a valve. it's completely empty inside. it's just a hollow brass fitting at the moment.
That would be because the retainer plate rusted/failed and dumped the check valves components into the pump inlet. Time to go fishing. You want to find a spring, a plunger, and a retainer plate.
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Old 03-03-2012, 06:42 PM
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Originally Posted by tangofox007 View Post
That would be because the retainer plate rusted/failed and dumped the check valves components into the pump inlet. Time to go fishing. You want to find a spring, a plunger, and a retainer plate.
wow that suckkkkks. do you think i can do this with the pump still attached to the motor? any chance these parts have been shredded inside of their already?
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Old 03-03-2012, 07:36 PM
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ok with some more focused searches on here i've learned the valve pieces are too large to actually fall completely into the pump, so im not worried about that. but i wonder if this failed valve is still the cause for low vac when cold, but full vac when warm. gotta replace it anyway i guess.
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  #7  
Old 03-03-2012, 07:40 PM
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Originally Posted by sleepstar View Post
...i wonder if this failed valve is still the cause for low vac when cold, but full vac when warm.
Intermittent vacuum is the typical symptom. My guess is that the valve components rattle around in the pump inlet and intermittently block air flow into the pump.
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Old 03-04-2012, 02:00 AM
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You need a Good Check Valve to hold the proper Vacuum. I had a Vacuum Issue and removed my Check Valve and sprayed it out with WD-40 and put it back on and it worked fine after that. And, yes my check valve was not hollow.

The Check Valve is slightly expensive. I do not see why one from a Junk Yard would not work if you take a look and see if the parts are inside and still good.
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Old 03-04-2012, 10:32 AM
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I have a pdf laying around, this page should be of help.
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What should a vacuum pump check valve look like-screen-shot-2012-03-04-10.30.46-am.jpg  
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Old 03-04-2012, 11:19 AM
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Originally Posted by toomany MBZ View Post
I have a pdf laying around, this page should be of help.
Wrong check valve.
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  #11  
Old 03-04-2012, 11:28 AM
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yeah, bad title at this point. should have said "what should the inside of a vacuum pump check valve look like"
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  #12  
Old 03-04-2012, 11:42 AM
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Originally Posted by sleepstar View Post
yeah, bad title at this point. should have said "what should the inside of a vacuum pump check valve look like"
There are three more check valves inside the pump.
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Old 03-04-2012, 12:29 PM
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The pdf is a generic diagnosis, yet the instructions should tell you if the valve is operating.
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What should a vacuum pump check valve look like-screen-shot-2012-03-04-12.26.39-pm.png  
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Old 03-04-2012, 01:44 PM
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Originally Posted by toomany MBZ View Post
The pdf is a generic diagnosis, yet the instructions should tell you if the valve is operating.
1. That check valve has nothing to do with the brake booster.
2. If the "guts" of the check valve are missing, no further diagnosis is required. The check valve cannot possibly operate.
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  #15  
Old 03-04-2012, 01:47 PM
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Originally Posted by sleepstar View Post
wow that suckkkkks. do you think i can do this with the pump still attached to the motor?
Try a vacuum cleaner at the pump inlet port. The plate and spring are magnetic, so a magnet might be somewhat effective.
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