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  #1  
Old 07-30-2004, 08:26 AM
cmichalik
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Question Vacuum pump - how many inches?

I'm still fighting the vacuum system on my wife's 82 300TD Turbo. I think I'm going to end up rebuilding the vacuum pump. I think it's working, but I don't think it vacuuming down the system enough for everything to work properly. How much vacuum is the pump supposed to put on the system? I bought a mityvac hand pump last night & will be testing everything tomorrow before I make a plan of action. So if I connect the mityvac directly to the vacuum pump, what kind of reading should I get?

Thanks a lot.
cmichalik


Last edited by whunter; 12-04-2011 at 02:37 PM. Reason: spelling
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  #2  
Old 07-30-2004, 10:27 AM
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Join Date: Jul 2004
Location: Annapolis, MD
Posts: 650
On my 300SD, I get around 22-24 inches. It's enough to run everything. Lots of places for leaks though.
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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer
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Old 07-30-2004, 01:07 PM
cmichalik
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Thanks for the quick responce. I'm going to measure how much vacuum the pump is making & go from there. If it's not making the correct amount I'll go ahead and rebuild it. If it is I'll start testing the other various systems & sealing up all the little connections as required. I'm thinking that if the pump is working properly that's it all the little conections leaking just a little. Creating a big problem.

Does anyone have any tips on problem leak areas. I've already bypassed the central locking system, but would like to reconnect it again.

Thanks
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  #4  
Old 07-30-2004, 01:38 PM
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smoke gets in your eyes
 
Join Date: Jun 2000
Location: Eastern TN
Posts: 20,832
Take a vacuum reading at one of the ports that branches off the brake booster line. Pull off both branches, hook up the vacuum gauge to one, cap the other. You should get ~20" and a steady reading after a few seconds from start-up. If you pass that test, the problem is a leak in one of the branches (enging shut-off or door locks/ACC).

Sixto
95 S420
87 300SDL
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Old 08-02-2004, 08:43 AM
cmichalik
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I did as suggested & this is what I found. First off I put the vacuum gauge directly on the pump to rule that out. Got a constant 25"Hg from it. I moved to the valve on the brake booster line next. Put the gauge on the first branch (closest to the pump) & plugged the other. Again I got 24-25". I switched the gauge to the rear branch & plugged the front one. Nothing! No matter how hard I tried I couldn't pull a vacuum on it. Does the port assembly on the brake booster line have a valve or diaphragm in it that can go bad? I looked into replacing it & all I can find is the whole line from the pump to the brake booster. Do I have to replace the entire line or can I just replace the valve in the middle.

Consequently, the port on the rear that I don't get any reading from is the same line that goes to the injector pump shut-off. One of the simptomes all along, beside rock hard brakes, is the engine does not turn off w/ the key anymore. You have to manually shut it off under the hood almost every time. What a pain.

Thanks for everyones help.
Cmichalik
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Old 08-02-2004, 11:34 AM
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smoke gets in your eyes
 
Join Date: Jun 2000
Location: Eastern TN
Posts: 20,832
Sounds like the check valve case is leaking. I can look up the part number later but I think 1982 is a split year so a VIN is necessary.

The fittings are something of a precise fit along the hose so it's sold as an assembly. About $35 through the FastLane link at the top of the page.

Sixto
95 S420
87 300SDL
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  #7  
Old 08-02-2004, 01:26 PM
cmichalik
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So I should be able to pull a vacuum at both ports?

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