I am pretty sure I have at least two, possibly more vacuum leaks (transmission is flaring between 1st and 2nd gear; and the power locks don't work at all). I am not sure if the vacuum tubes have ever been replaced so rather than just finding the leaks and replacing only those hoses (and connectors), I think I would rather replace them all. *************** has alot of different color options for vacuum tubing. I would prefer to keep different colors for each hose so I can keep track of which tube is which, but I don't know how long each needs to be. Does anyone know how the length each color vacuum tube I need?

I have an '85 300D (US - not Cali) and I want to replace both the engine vacuum tubes and the ones under the floor for the locks. Is this unnecessary? Do most of you just replace leaking vacuum tubes (and connectors) when you have multiple leaks? Or do you advise replacing everything?

My 300D is my only car so I don't want to pull all the hoses out (to find out how long each is) and have the car out of commission for a few days while I wait for an order to come in. Another option would be if anyone knows of local sources for vacuum tubing (particularly if I can find multiple colors). Is the size (thickness or whatever) a standard tube that can be found in Autozone or NAPA? What should I look for if buying from a non-MB source? If there is a local source (Dallas), I could pull all the tubing and take my roommate's car to NAPA to get the right lengths.

Thanks in advance for the help. I have learned so much in the last few months from reading the vast amount of knowledge available here. I really appreciate this community and the experts who continue to share their experience with us novices.

Thanks,
Aaron

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Gisele: 1985 300D (430K miles)

Flaring between 1st and 2nd??!! I think that would point to more than just vac problems...

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1989 300E 144K

Why does that indicate further problems?

I looked for the posts but couldn't find them. But I came across something (I am pretty sure it was in these forums) that led me to believe that my combination of symptoms were indicative of vacuum leaks instead of tranny wear:

• 1-2 Flaring (not slipping)
• Shifts into Reverse without problem
• Solid 3-4 shifting (for that matter all other gears shift without problem)

Please set me straight. I think I got this diagnosis from only one source. So what do I look for to diagnose transmission problems? What symptoms are indicative of transmission wear as opposed to vacuum?

The other reason I came to believe it was vacuum is it cropped up suddenly. When I got the car two months ago, the transmission shifted like a new car. But the power locks were not working at all. None of them react to the driver's lock. And the passenger front door locks itself every time the door is shut. Then, after a month and a half the tranny started doing this kinda suddenly. At first it was only one in ten 1-2 shifts, now it flares three out of every five shifts. And it only shifts smoothly when I take off VERY slowly.

Any input?

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Gisele: 1985 300D (430K miles)

I agree, flaring is vacuum related. I tried forever to get rid of the flaring and finaly did when I replaced the vacuum converter, unseized a switchover valve and tweaked with the vacuum modulator.

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1981 300SD 512k OM603

Do you have a vac tester? Best place to start. My 77 300D, has most of the original vac lines, especially the hard plastic and they work fine. I have replaced the vac boots on all 3 door locks (rt f, rt r, lr) always a problem, test them from the rt fr floor position. What shape is the vac pump in, do you build pressure after start up then loose it when you shut it off, any trouble with shut off. You will put a lot of effort into something that might not be broke by replacing all of the lines.

my thoughts
ron

Tubes tend to last its the rubber "T and X" that tend to dry rot. Save some money and time. Use the MiniVac and test lines/components.

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92 300D 2.5L OM602 OBK #59

Yes, those hard lines last, the rubber connectors are the fail points, usually. Available at the buy parts button above.

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83 SD

84 CD

I have a vacuum gauge and a pump. When I push it (it is not really a tight seal) against the line going to the brake cylinder (against the firewall) it shows 22-15 psi with the engine running. The needle bounces quickly between 22 and 15 psi. The rhythm of the engine seems to match the bouncing of the vacuum needle. I will try later tonight shutting the engine off and seeing if it retains a vacuum.

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Gisele: 1985 300D (430K miles)

Okay, I just got in from trying the vacuum gauge again. Once again I am just holding a rubber connector that came with my vacuum gauge against the metal pipe/hose that goes into the brake cylinder on the firewall. I am getting a pretty good seal but I have to hold against the metal end of the pipe/hose. If i let go it just falls off.

When I connect it with the car running it bounces between 19psi and 22psi. When I have a friend kill the engine the pressure drops in about 2-3 seconds to 5 psi and holds there until I remove the gauge.

Does this mean I need to rebuild the vacuum pump?

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Gisele: 1985 300D (430K miles)

I just had a vacuum pump issue
Lost everything while running 65 down the motorway...sucks!!!
I got the rebuild kit and rebuilt my pump...then I find the seals in the kit are to small.
I pulled a pump off a parts car and bam i'm back on the road
My vac pump reads 25 in/Mg solid it doesn't bounce
If you pull it I have learned watch the placement of the gasket.

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On the hunt...
1985 300D----Sold
1985 300TD---Sold
1983 300SD---Sold

I don't think so, as you're producing vac, sounds like a leak, or not having a good seal when you check.
Did you notice if there is any oil in the line you took readings?
In the pic, the red arrows, I plug the one nearest the firewall, and take readings from the front most, the rubber connectors can be plugged with a golf tee.

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83 SD

84 CD