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Vacuum leaks narowed down to 3 items, 1982 300D (Pictures)
Hi, everyone.
Well I've tested every darn thing I can for vacuum leaks on my 1982 300D. I found two things that couldn't hold vacuum, and possibly a third item. 1. The Transmission Vacuum Shift Valve has a slow leak. I take it that it should be holding vacuum? 2. The transmission vacuum lever assembly will not hold vacuum and has a slow leak. The hoses you see in the picture below are hard, and extremely loose. I don't believe they are forming tight seals with the hard plastic. Is this assembly supposed to hold vacuum? (BTW, I replaced the little levers at the left of the assembly...that made a HUGE difference in the transmission shifting). 3. What looks like a green check valve will let you suck and blow air through it. Isn't it only supposed to allow air to be drawn out of it, but not let air into it? Do I have a faulty green check valve? Thoughts? Thanks, Pete. P.S. All the doors, the trunk, the reservoire, the vacuum pump, the shut-off, the brake booster, etc., hold vacuum. |
#2
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1. The vacuum valve on the injection pump is supposed to leak.
2. The valves on the valve cover operate the EGR, not the transmission. But when they leak, the loss a vacuum affects the transmission. 3. The green fitting is a damper, not a check valve. It should pass air both ways. As I told you in your earlier thread, the valves on the valve cover are the most likely source of your problem. You can confirm this by disconnecting the vacuum supply line to those valves (usually a white line) and plugging the supply line. Then drive the car and see how the transmission shifts. |
#3
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Thanks, tangofox007.
I take it then that I'm narrowed down to replacing the valves (or at least the hoses) on the valve cover? Thanks, Pete. |
#4
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The 3/2 way valves tend to leak when the get old. If you replace them, I would suggest that you spend the extra money for the OE valves. Other members of the forum have reported problems with the cheaper (MTC) version.
But to confirm that the valves/hoses are indeed the cause of your problem, I would recommend that you disconnect the vacuum to the valves and take the car for a test drive and see how your transmission shifts with the valves out of the picture. |
#5
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Quote:
Much appreciated, Pete. P.S. BTW, when I replaced those two levers (which were completely worn down and useless) on the 3/2 way valve assembly on the valve cover, I noticed a really big improvement in my transmission shifting....but you're saying that they don't have anything to do with the transmission... |
#6
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When you go to buy new vacuum valves, take your Mityvac with you and test them before you pay for them. I have seen brand new ones that leaked. Those valves are like single pole double throw switches. One port should hold vacuum in rest position, the other port should hold vacuum when actuated. A good one will have little or no leakage. If it leaks down in 5 or 10 seconds, it is NFG.
__________________
Palangi 2004 C240 Wagon 203.261 Baby Benz 2008 ML320 CDI Highway Cruiser 2006 Toyota Prius, Saving the Planet @ 48 mpg 2000 F-150, Destroying the Planet @ 20 mpg TRUMP .......... WHITEHOUSE HILLARY .........JAILHOUSE BERNIE .......... NUTHOUSE 0BAMA .......... OUTHOUSE |
#7
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The valves take vac from the transmission line to operate the EGR. When they leak or have worn levers, it messes up the available vacuum to the transmission therefore modifying the shift characteristics. Under normal working conditions the valves do not have any affect on the transmission.
__________________
Adam Lumsden (83) 300D Vice-President of the MBCA International Stars Section |
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