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  #1  
Old 02-02-2008, 11:59 AM
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86' 300SDL Vacuum troubles...Whaddya got!?

My idiot brother used my 86 300sdl for 2 days...now I have a vacuum leak somewhere. Im wondering where it came from cause I thought maybe on the gravel roads he took, a chunk of gravel knocked off a tranny line or something. Heres the symptoms...

- The power brakes work perfectly, so can I assume the vacuum pump is operating correctly?

- The engine stops but seems like it takes a little while...probably the sign of poor vacuum pressure to the stop valve?

- The climate controls take extra long to switch settings...like 15 seconds...could there possibly be a leak in the dash somewhere that affects the whole system?

- Does anyone have vacuum diagrams for the OM603 1986 300SDL...the ones on here are for 617's.

- Also, I have a general idea of how the vacuum system works...but it would be a real blessing if someone could go into detail of the system for my model Benz

Thank you so much...Im almost positive theres a leak somewhere but dont know where or really how to look...its driving me nuts cause everything works but works slowly and poorly.

Putty

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  #2  
Old 02-02-2008, 01:18 PM
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I don't know much about the vacuum system on your model but I do know where you need to start. Get a MityVac and measure the amount of vacuum in the system. You should be able to isolate the various systems at vacuum junctions under the hood and determine where there leak is, if you have one. It does sound like you have a leak.
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1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
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  #3  
Old 02-02-2008, 01:59 PM
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No, no mity vac...is it just a gauge to read vacuum? If it is, Im an HVAC man and I have vacuum gauges. I just wonder how it could happen so suddenly.


When the vacuum lines go into the dash from the engine compartment...what do they do behind the dash?
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  #4  
Old 02-02-2008, 02:20 PM
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Measures vacuum and pumps vacuum. An essential tool for an MB. Most auto parts stores sell them as do Harbor Freight etc.
Three basic vacuum systems under the hood in your car I think. One system for shutting off the car, one for the climate control and one for the brakes. I think your door locks are on a separate system.
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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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  #5  
Old 02-02-2008, 03:05 PM
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I got a great engine compartment diagram for my 603 but it doesnt tell you what vacuum systems are behind the dash...I highlighted the vacuum circuits on my diagram cause I wanted to see where in the systems (ventilation and ignition cutoff) could share a common leak but according to the diagram, they are seperate circuits. One circuit (cutoff) gets its vacuum from the master brake line vacuum hose and the other (ventilation) gets its from the 4 way splitter vacuum hose directly off the pump...so, how could my ventilation AND my engine cutoff have such weak vacuum together but have such good braking power?
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  #6  
Old 02-02-2008, 07:45 PM
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hi Putty, there is not too much to the vac system on the SDL. Your mos likely place to start would be the check valve in-line with the break booster. then check connections just forward of the driver, in the engine compartment. there are several posts concerning this topic. try a search on 603 vac, or sdl vac. there are some really great topics and suggestions in here
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  #7  
Old 02-03-2008, 12:52 PM
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Yes, I agree...in comparison to the 617's the 603's are not as heavily dependant on vacuum. What are common places for leaks? The check valve on this car prohibits vacuum from returning out the brake booster doesnt it? If it were bad...would I have lousy or no brakes? The car turns off...just slowly. Is there any tests I can perform to help isolate the problem circuit...I mean, how long should it take to switch settings on your interior controls? At any rate, any help would be ggrrrreeeaaatttt!
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  #8  
Old 02-03-2008, 12:53 PM
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And perhaps some help explaining the functions (how they work) of the various vacuum components in the engine compartment...that would probably help me understand WHY instead of just HOW...
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  #9  
Old 02-03-2008, 02:08 PM
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Quote:
Originally Posted by Putty View Post
And perhaps some help explaining the functions (how they work) of the various vacuum components in the engine compartment...that would probably help me understand WHY instead of just HOW...
Find the smaller line that is the output from the vacuum pump. It will go to a five way connector. One supply and four consumers. Two of the consumers go to the right side of the engine. Cut these two lines and plug the hoses (right at the five way connector).

Drive it and see if the problem disappears.
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  #10  
Old 02-05-2008, 10:00 PM
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Nope, didnt do it Brian...the problem is getting worse...the car wont stop now at all...I looked at the stop bar on the injector pump...its alllllmost down to stopping but not quite...when I pull off the vacuum hose, it returns to normal position...then I plug the tube back in and it goes allllmost all the way down but wont stop the engine...maybe this will help you diagnose easier. Plugging the vacuum source to the EGR valves didnt change anything...what should be my bars of vacuum at the shut off valve...maybe I can isolate the shut off valve as a possible problem
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  #11  
Old 02-05-2008, 10:36 PM
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Originally Posted by Putty View Post
Nope, didnt do it Brian...the problem is getting worse...the car wont stop now at all...I looked at the stop bar on the injector pump...its alllllmost down to stopping but not quite...when I pull off the vacuum hose, it returns to normal position...then I plug the tube back in and it goes allllmost all the way down but wont stop the engine...maybe this will help you diagnose easier. Plugging the vacuum source to the EGR valves didnt change anything...what should be my bars of vacuum at the shut off valve...maybe I can isolate the shut off valve as a possible problem
Then, you've got a leak on the left side of the engine somewhere. If you have a Mityvac, spend some time and find it. The engine won't shutdown because of this leak. If the hoses are all original and the connectors are cracked.........the leak could be anywhere.
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  #12  
Old 02-06-2008, 01:23 PM
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86' 300SDL Vacuum engine stop...how to test.

I have posted a few things on here about my 300SDL's vacuum problems...I think I may have found the culprit...however, before I do any condemning...I need to know what to REALLY look for! The engine started taking a longer time to stop...now it wont at all...tells me that something is in the process of failing. Today, I pulled the line off the stop valve and switched it with the vacuum coming straight off the pump...it pulls the lever down but wont stop it. So, I pulled the line off and I sucked a vacuum on it myself...lever comes down but wont stop! Im thinking of condemning the stop valve...what do you think? If you agree...how do you replace/repair one of these?
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  #13  
Old 02-06-2008, 01:29 PM
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Hook your miti-vac (or equivalent) up to the line coming from ignition to stop valve. Check and see if you are getting a draw of 7+ in. If you are not before declaring the shut off valve dead look for vacuum leaks in the system. From the vacuum pump small line block off the "T" on the passenger side. If shut off is normal be suspect of the EGR valve. You should do some diagnostics before throwing $$'s at it. I have seen it both ways - a line that fell off and a dieing vacuum pump.
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  #14  
Old 02-06-2008, 01:55 PM
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This is a valid point...Brian has suggested I do the same...however, I tied off the EGR and it wouldnt stop. My method of testing without a mighty vac was to use the idling engine as a tester. Remember...the ignition is off but it still wont stop. I have brought in lines from other known working vacuum sources...I even hooked up a line directly to the shut off valve from the brake booster main...(bypassing the igition curcuit) still, wouldnt shut off. As a last resort, I sucked on it myself...I gave it everything I had...SURELY that would have shut it off!? I dont know if I have 7'' of vacuum...but I have heard that you should be able to shut off a diesel mercedes with your mouth. Could I really be looking down the wrong direction? Could it be a dying vacuum pump? Am I crazy?


A side note...when I am sucking on the line, (directly connected to the valve)it doesnt hold vacuum.
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  #15  
Old 02-06-2008, 02:00 PM
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No your not crazy however these SDL will make you crazy if you let them. I guess a person can produce 7 in of vacuum (and I am sure someone will chime in with a comment about that) Just didn't want you to throw parts at something that might not be dead. If you had a vacuum device simply attaching to shut off valve would give you some value to make a descision with.

Bottom line - If you are going to own a SDL you might as well bite the bullet and buy a miti vac. It is a must have tool.

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BENZ THERE DONE THAThttp://www.peachparts.com/shopforum/...c/progress.gif
15 VW Passat TDI
00 E420
98 E300 DT
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97 S500
97 E300D
86 Holden Jackaroo Turbo D
86 300SDL
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