Re: [MBZ] '85 123 vacuum system
> RA wrote: > > I finally reached the point where the engine will not shut > off when removing the key last week. I must use the stop > button under the hood each time. The door locks also > stopped working. Classic symptoms of a failing vacuum control system. It could be lines or hoses - but I rarely see anything but the "vacuum element" fail. (I don't really like the word "vacuum element", but that's the word Mercedes uses in the manual for the vacuum actuators.) > Dan wrote: > This is all of maybe 10-15 minutes worth of diagnostics with a MityVac > Rick wrote: > > Buy a Mity Vac. Do it yourself. > Rich wrote: > > First is to put your mity-vac (HF sells a version for cheap > but a "real" one is not that much anyway) > Curt wrote: > > Buy a MityVac and do it yourself I contend that a MityVac is unnecessary. It is just a vacuum source - but so is the pump on the front of the engine. A vacuum gauge is handy, but even just a finger over the end of a hose can be enough to the difference between strong vacuum and weak-because-there-is-a-leak. Unlike a MityVac, the engine vacuum is only available with the engine running and it's harder to move from door to door. To troubleshoot, first make sure the source vacuum is strong. If the power brakes actually have power assist, then the vacuum pump is probably okay. Next check at the "T" near the booster. By "check" I mean "put a finger over the end and feel the pull". Then start "following" the vacuum forward 'till you figure out where it's getting lost. Twigs or golf tees are pretty much required to plug various lines to isolate. With a MityVac you can check each branch - arguably the easier way to do it, but I have identified and isolated many vacuum problems while I was many miles away from my MityVac ___ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] '85 123 vacuum system
he is not getting the 20 psi to restore all functionality. Atmospheric pressure is less than 15psi. Vacuum is customarily measured in inches or mm of mercury, not (negative) PSI. Your guy's being pretty sloppy with his terminology. Perhaps that's not all that is sloppy? -- Jim ___ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] '85 123 vacuum system
Hi there, do you have a first name? Your first bet that he's incompetent is he says 20psi. PSI is a pressure measurement, vacuum is measured in inches of mercury. The steps are dead simple, find the first T after the pump (on the front of the engine) and cap it. Pull a vacuum on the engine side and see if it holds, if not theres a problem in the pump or the line, fix that. If that holds move to the next junction. Cover everything under the hood first, then move to the driver's footwell and track throughout the car. Buy a MityVac and do it yourself, very rewarding. -Curt From: RA via Mercedes To: Mercedes Discussion List Cc: r...@rhonald.me Sent: Tuesday, September 1, 2015 12:01 PM Subject: [MBZ] '85 123 vacuum system I finally reached the point where the engine will not shut off when removing the key last week. I must use the stop button under the hood each time. The door locks also stopped working. A mechanic has found one source in the drivers door and something else under the hood. He says there is a still a leak somewhere, he is not getting the 20 psi to restore all functionality. He says he is not getting any air to the tailgate area. I received an MBZ parts catalog and am reviewing the Vacuum System 1977-85 on page 15. I am losing confidence in his ability to properly troubleshoot and repair the system. Any thoughts on where else to look? Thanks R 1985 300TD 241,000 miles ___ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] '85 123 vacuum system
Yeah what they said. First is to put your mity-vac (HF sells a version for cheap but a "real" one is not that much anyway) on a hose near the brake booster where some branch off, and see if you are actually getting vacuum from the vac pump. The diaphragms tear in them over time and vacuum gradually decreases. Or it could be bad/cracked lines or tees up there under the hood, I ended up bodging some brass barbs and tees into the system by the brake booster because the plastic things were all brittle. Lines crack and leak too. From that set of branches you can start testing what is leaking if the pump is sucking right, could be the brake booster diaphragm or anything in the door lock system. You can stick a pencil or a golf tee in those lines at the main tee there by the brake booster and see if that restores your brakes and shutoff, in which case you can leave the line going to the doors disconnected and at least have brakes and shutoff until you resolve the issue further downstream. If you don't want to fool with it for now, get about 6 ft of vac line and run it to the shutoff then the other end into the cabin where you can get it, suck on it to shut off the car. You still won't have brakes but that will alleviate the shutoff process. I have a writeup with pics on changing the vac pump diaphragm, it is not particularly hard just a bit fiddly. --R On 9/1/15 12:20 PM, Rick Knoble via Mercedes wrote: RA writes: I am losing confidence in his >ability to properly troubleshoot and repair the >system. Any thoughts on where else to >look? Buy a Mity Vac. Do it yourself. It isn't too terribly difficult to T/S vacuum problems, but it is time consuming, and much like electrical troubleshooting, you must possess the ability to think logically, and in a straight line. Isolate one system at a time, vacuum it down, etc. I have a comprehensive vacuum troubleshooting guide I received from Craig several years ago. I can post it online, with a link if you wish. Rick Sent from my BlackBerry Z10 ___ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] '85 123 vacuum system
RA writes: > I am losing confidence in his >ability to properly >troubleshoot and repair the >system. >Any thoughts on where else to >look? Buy a Mity Vac. Do it yourself. It isn't too terribly difficult to T/S vacuum problems, but it is time consuming, and much like electrical troubleshooting, you must possess the ability to think logically, and in a straight line. Isolate one system at a time, vacuum it down, etc. I have a comprehensive vacuum troubleshooting guide I received from Craig several years ago. I can post it online, with a link if you wish. Rick Sent from my BlackBerry Z10 ___ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] '85 123 vacuum system
This is all of maybe 10-15 minutes worth of diagnostics with a MityVac. It's vacuum, not pressure, so I'm confused why they would reference a positive pressure. If you have access to a MityVac and some time, let me know and I can outline the steps. It's stupidly simple once you know how. Dan Sent from my iPad > On Sep 1, 2015, at 12:01 PM, RA via Mercedes wrote: > > I finally reached the point where the engine will not shut off when > removing the key last week. I must use the stop button under the hood > each time. The door locks also stopped working. A mechanic has found > one source in the drivers door and something else under the hood. He > says there is a still a leak somewhere, he is not getting the 20 psi to > restore all functionality. He says he is not getting any air to the > tailgate area. > > I received an MBZ parts catalog and am reviewing the Vacuum System > 1977-85 on page 15. I am losing confidence in his ability to properly > troubleshoot and repair the system. > > Any thoughts on where else to look? > > Thanks > > R > > 1985 300TD 241,000 miles > > > > > ___ > http://www.okiebenz.com > > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > ___ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
[MBZ] '85 123 vacuum system
I finally reached the point where the engine will not shut off when removing the key last week. I must use the stop button under the hood each time. The door locks also stopped working. A mechanic has found one source in the drivers door and something else under the hood. He says there is a still a leak somewhere, he is not getting the 20 psi to restore all functionality. He says he is not getting any air to the tailgate area. I received an MBZ parts catalog and am reviewing the Vacuum System 1977-85 on page 15. I am losing confidence in his ability to properly troubleshoot and repair the system. Any thoughts on where else to look? Thanks R 1985 300TD 241,000 miles ___ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com