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  #1  
Old 01-23-2010, 05:51 PM
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81 300D Vacuum Questions Brake Servo Vacuum Hose

Getting some new Michelin tires on the Silver Fox today and decided to walk to harbor freight to kill some time. Walked out with a Mity-vac and an assortment of other must haves.

Got home and un-hooked the the brake servo vacuum hose (19mm connection to the break booster). Got a reading of between 15-17 hg, very bouncy. I then realized that I should unhook the 2 smaller connections (off of the Ts) and in the process snapped both Ts. I was even "trying" to be careful. So I guess I will be ordering a new brake servo vacuum hose . anyway I got a reading from the closest point to the vacuum pump, it was where the first T broke. I got a solid 17hg reading.

Questions is, since I will be ordering a new hose, should I also order a rebuild kit for the vacuum pump? From what I have found reading on here, it should be 23-25hg.

2nd question (and I guess this also might answer the first is this). Since I have owned her, about 3 months, she has always taken a few seconds to shut down. I can turn off the key, get out and start to lock the door before it turns off. I always assumed this was the shut-off valve. In my attempt to temporally fix the brake servo hose (super glue, random hose, etc...) I have been unable to hook back up one of the smaller hoses that I presume leads to the shutoff valve. At present when I turn the key off, she just not shut off. However, If I hook the mity-vac to the small vacuum line I was unable to hook back up to the break servo hose and give the mity-vac a few pumps she shuts right down. So I would presume that given the proper amount of vacuum pressure the shut off valve is working just fine. Anyway this kind of leads me back to my original question in that the vacuum pump is not giving strong enough vacuum to shut the car right off.

Thanks for any help on this.

Last edited by whunter; 08-09-2011 at 03:37 PM. Reason: spelling
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  #2  
Old 01-24-2010, 09:14 PM
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I decided just to go with the brake vacuum hose and hope for the best. I did something to the linkage when I did a valve adjustment so the STOP lever does not work. So I just pop the hood and give the vacuum hose that leads into the firewall a good suck and the engine stops.

Going to wait and see how the new hose works. Perhaps 17hg will be enough. If not, I will do the rebuild.
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  #3  
Old 01-24-2010, 11:05 PM
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Well, you've proved your vacuum shutoff valve is good at least. I'll bet those Y's, F's and T's were already leaky to begin with. Replacing them is pretty easy with the right parts.

You can order them from peachparts here. They got pretty much all the little parts, gadgets and gizmos that you'll need and they're real quick about getting it to ya. I ordered a whole slew of of little things that added up to more than $100 and saved the shipping.

I'll be working on my vacuum system over the next few days as well. If you don't get the vacuum stuff hooked up right, you'll have trouble with automatic shutoff, auto tranny shifting, door locks, and vacuum elements for climate control not to mention your brake booster.
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  #4  
Old 01-24-2010, 11:49 PM
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Quote:
Originally Posted by Koobos View Post
should I also order a rebuild kit for the vacuum pump? From what I have found reading on here, it should be 23-25hg.

.
Depends on your elevation. Those numbers are at sea level.
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1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
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  #5  
Old 01-25-2010, 01:29 AM
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Quote:
Originally Posted by kerry View Post
Depends on your elevation. Those numbers are at sea level.
That's what I wanted to hear! I didn't think about that being from CA, but now living about 5k up. I read somewhere that it is about 1hg per 1000 feet increase so that should put me in the low 20s. Thank you!
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  #6  
Old 01-25-2010, 01:30 AM
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Thanks! Good luck to you this week with your project. I hope to have my parts this week sometime.

Quote:
Originally Posted by Codifex Maximus View Post

I'll be working on my vacuum system over the next few days as well. If you don't get the vacuum stuff hooked up right, you'll have trouble with automatic shutoff, auto tranny shifting, door locks, and vacuum elements for climate control not to mention your brake booster.
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  #7  
Old 01-25-2010, 10:05 AM
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Quote:
Originally Posted by Koobos View Post
That's what I wanted to hear! I didn't think about that being from CA, but now living about 5k up. I read somewhere that it is about 1hg per 1000 feet increase so that should put me in the low 20s. Thank you!
I get about 18 at a mile high.
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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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  #8  
Old 01-29-2010, 05:37 PM
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Installed the new vacuum line to the brake booster (brake servo vacuum line) and hey my car turns off now! First time since I have owned her that she shuts right off. This is great! Now my transmission is sifting very smooth, but at very odd times. Before the sifts were very obvious, but now it kind of hard to catch them. It seems to shift right into 4th almost off of the line and acceleration is painful slow. I would imagine that replacing the vacuum line improved vacuum pressure to the transmission, but not sure why it is sifting that way. Any ideas?
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  #9  
Old 01-29-2010, 06:30 PM
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Shift points are controlled by the bowden cable that goes from the top of the valve cover down to the right side of the transmission. Did you mess with it by any chance?
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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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  #10  
Old 01-29-2010, 06:44 PM
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Quote:
Originally Posted by kerry View Post
Shift points are controlled by the bowden cable that goes from the top of the valve cover down to the right side of the transmission. Did you mess with it by any chance?
Not that I know of This is my first 300D so I am not sure how should should shift normally. However, since I have had her she has shifted a little hard. Right after I changed the line is when I noticed the shifting. It's now smooth as butter. I will have to look for the bowden cable and see if I bumped it, but I doubt that I did. Thanks for your reply!
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  #11  
Old 01-29-2010, 08:16 PM
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'81.

Sedan, right, so normally aspirated? No bowden cable. Just that bloody all-vacuum engine/trans interface. Poor design....

Jay.
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  #12  
Old 01-29-2010, 08:59 PM
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Quote:
Originally Posted by babyjames View Post
Sedan, right, so normally aspirated? No bowden cable. Just that bloody all-vacuum engine/trans interface. Poor design....

Jay.
Yes, Sedan. Would too much HG cause the quick shift. There was a small adapter from the vacuum booster house to the transmission setup that was much small and would appear to restrict flow. Not to mention all the gunk that was in there. I would be surprised if much hg was pulled prior to the replacement.
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  #13  
Old 01-29-2010, 09:27 PM
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Quote:
Originally Posted by babyjames View Post
Sedan, right, so normally aspirated? No bowden cable. Just that bloody all-vacuum engine/trans interface. Poor design....

Jay.
OOOps.

I'd pull the vacuum line from the transmission and see if the shifts return to their previous pattern. Then you'll have an answer.
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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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  #14  
Old 01-29-2010, 11:39 PM
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Quote:
Originally Posted by kerry View Post
OOOps.

I'd pull the vacuum line from the transmission and see if the shifts return to their previous pattern. Then you'll have an answer.
Thanks Kerry. I just gave that a go and it stayed in 1st the whole time. Interesting. May have to try and reduce the flow and see what happens?
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  #15  
Old 01-30-2010, 02:19 PM
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Thread follow-up...

This was my problem (quoted from: http://www.continentalimports.com/ser_ic20242.html)

Another common problem occurs after someone breaks the plastic source tee. During most of the ingenious repairs I have worked behind, the orifice was omitted. This leaves either a constant high vacuum or a variable vacuum that is skewed high. Either condition causes slipping or flaring conditions. This occurs when the vacuum supply is so great that the proportioned leak is small by comparison, resulting in vacuum thatís too high.

Attached is a picture of the little fitting. It's blurry I know, but hopefully you get the idea. Once I put that inline with the hose coming off of the main brake booster it is shifting just fine.

Thanks to everyone for your help and input.
Attached Thumbnails
81 300D Vacuum Questions Brake Servo Vacuum Hose-part.jpg  
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