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Transmission vacuum leak found !

 
Old 08-29-2011, 04:11 PM
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dwc928s4
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Default Transmission vacuum leak found !

Hello all, Found the reason for my 84 euro a/t to have hard shifting.
At the transmission there is about an 12 inch vaccum hose that goes up above the torque tube into a real small metal line. This metal lines stops just about up at the firewall and about a 6 inch rubber line goes from there up to another metal line that terminates plugged right in front of the spider.
My little 6 inch line by the firewall was leaking. I put a piece of standard vacuum hose in its place for now. The auto parts store gave me 3/16 and the package says its also used for 4 mm.
It still seems to leak out of the end a little like its not tight enough. Also the line is high heat so the old one was wrapped in cloth. I cant find this high heat 4 mm line anywhere. What do you guys use ? i want to replace the 12 in piece down by the tranny at the same time .

I'm really learning alot about this old car as i tear it apart. Having fun actually. Even went and bought me one of those vaccum testers to start checking everything.
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Old 08-29-2011, 04:26 PM
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JHowell37
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If you think it's leaking, get a vacuum line that is smaller in I.D. As for the high heat aspect, it should last for a few years and the line itself is cheap, so if the replacement isn't too difficult, who cares if you have to replace it every few years?
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Old 08-29-2011, 04:52 PM
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dwc928s4
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cause you have ot drop the exhaust to get to it...
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Old 08-30-2011, 12:38 AM
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Glenn M
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Reroute a new line around the exhaust to the vacuum modulator.
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Old 09-03-2011, 04:29 PM
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Was your hard shifting in all gears or just 1-->2 or 2--->3 ?
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Old 09-04-2011, 12:40 AM
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Dwayne
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dwc928S4,
I had the same problem with my '84 - same vacuum line needed to be replaced. I went to a local imported (German) auto repair shop and asked if they had any of the cloth covered vacuum line in stock. It turned out it's the same vacuum hose material commonly used on VWs. They sold me a segment and it worked perfectly. Might be worth a try.
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Old 09-04-2011, 12:58 AM
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borland
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3.5 mm cloth braded vacuum hose, eBay..

http://cgi.ebay.com/ebaymotors/VW-BU...item43a3614c2c

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Old 09-04-2011, 01:42 AM
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blown 87
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Originally Posted by Dwayne View Post
dwc928S4,
I had the same problem with my '84 - same vacuum line needed to be replaced. I went to a local imported (German) auto repair shop and asked if they had any of the cloth covered vacuum line in stock. It turned out it's the same vacuum hose material commonly used on VWs. They sold me a segment and it worked perfectly. Might be worth a try.
Most any place that stocks any Wurth stuff will have it.
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Old 09-04-2011, 12:06 PM
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dwc928s4
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thanks Dwayne,
called the VW near my home, and the had it. I changed the little piece up near the firewall, now im going to change the piece back at the tranny that is about a foot long.
I vacuum check the modulator, it held 12 for 10 minutes. I have a question. If i want to vacuum check plugging into the hose at the modulator forward. How do you plug the line in the engine compartment. My line does not go to a 6 way splitter, rather a solid steel line with a knucle plugged right into the spider.
am i on the right track to say to check the entire line from back at the tranny, i have to put some kind of rubber over the maf, and test the entire thing ?
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Old 09-04-2011, 06:30 PM
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Imo000
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On an '89, you can reach the line without dropping the exhaust. The small heat shield, by the downpipe (driver side), has to come off. After that you can fairly easily reach it. I would imagine this woudl be true on an '84 too.
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Old 09-04-2011, 08:39 PM
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Originally Posted by borland View Post
3.5 mm cloth braded vacuum hose, eBay..

http://cgi.ebay.com/ebaymotors/VW-BU...item43a3614c2c


Just bought a length...

-Allen
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Old 09-05-2011, 12:12 AM
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Dwayne
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Originally Posted by dwc928s4 View Post
thanks Dwayne,
called the VW near my home, and the had it. I changed the little piece up near the firewall, now im going to change the piece back at the tranny that is about a foot long.
I vacuum check the modulator, it held 12 for 10 minutes. I have a question. If i want to vacuum check plugging into the hose at the modulator forward. How do you plug the line in the engine compartment. My line does not go to a 6 way splitter, rather a solid steel line with a knucle plugged right into the spider.
am i on the right track to say to check the entire line from back at the tranny, i have to put some kind of rubber over the maf, and test the entire thing ?
I know what you mean - it's difficult to plug the end of that hard line that connects to the front of the spider because of the knuckle fitting. When testing for vacuum leaks, I connected my vacuum pump to the rubber hose at the firewall that leads to the hard line that goes to the transmission modulator. When everything checked out, I simply assumed the hard line from the rubber hose forward to the spider was sealed (i.e., no leaks).

To check the whole system for leaks, it is possible to manufacture a "plug" for the opening of the throttle body. I used a Fuel filter. I removed the Air Flow Meter (AFM) and measured the opening of the AFM that fits into the throttle body with the large o-ring. The AFM opening measures 80mm (see below)
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If you can get your hands on a used fuel filter, it's very close to the same size as the AFM fitting for the throttle body o-ring fit. The fuel filter also has a fitting on it that will allow you to charge the system and check for leaks. Here's the fuel filter...
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The fuel filter measures 74mm so it needs to "fatten up" in order to seal against the o-ring.
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I used duct tape. I began wrapping one end in the duct tape and on each successive revolution, I measured the overall diameter of the filter with tape until it reached just a little over 80mm to ensure a tight fit.
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I used lubricant on the outside of the duct tape and the throttle body o-ring (silicone lubricant) then fitted the filter with tape into the throttle body o-ring. With the filter firmly seated, I used the compressor with rubber fitting to press against the filter fitting as pictured below. This allowed me to pressurize the system and listen for leaks.
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I used a mixture of dishwashing soap and water and put it in a spray bottle and sprayed all the connections that could be sources of leaks. Wherever I saw significant bubbles, I would focus on sealing up that area and continued testing again.
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One improvement to the device I would have liked to made is to add a pressure gauge on the fuel filter fitting so I could tell how much I pressurized the system and could watch how long it took to depressurize. Hope this helps...
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Old 09-06-2011, 11:17 AM
  #13  
dwc928s4
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Helped alot Dwayne. thanks. I agree a pressure gauge would be nice because i would be worried not nowing how much pressure i was adding. I dont think 80 lbs. of shop air would be good.
I was able to test the entire run from the modulator to the knuckle attached to the front of the spider.
I plugged into the hose at the modulator with about an 8 ft hose. Then plugged my mityvac into this. This allowed me to hold the knucle with my fingers and pump up the mityac. Vaccum held fine.

I really like your testing trick though.
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Old 09-06-2011, 11:25 AM
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Very cool technique there, Dwayne.
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Old 07-02-2016, 10:46 PM
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Geo55
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Silly Question...could you use Hi temp silicone vacuum line as a replacement?
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