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sublettm 08-26-2005 07:42 PM

'87 300D Vacuum Problem
My '87 has developed what I am guessing to be a massive vacuum leak. The symtoms are as follows. My door locks do not work, my tranny is flaring, and it is also jerking really bad when accelerating when car is cold. I have done much troubleshooting on the 123's but have yet to tackle a vacuum problem on a 124. Does it sound like I have one big leak, or two separate issues? How similar are the vacuum system 123 vs. 124? I will be tackling this problem this weekend so a little help will be appreciated.


sublettm 08-27-2005 11:02 AM


Brian Carlton 08-27-2005 11:17 AM

The procedures for looking for a vacuum leak are identical between the two vehicles.

Start at the vacuum pump and make sure that you have over 20" there. I presume that you do, because you mentioned nothing about the brakes giving you problems.

Then proceed down the vacuum lines and look for bad hoses and/or connections. When you find a connection, hook up the gauge at this point and ensure that vacuum makes it to the connection. Then move on down the line.

If the brakes work properly, you may have a bad hose inside the vehicle that prevents the door locks from operating, however, I'm more inclined to believe that the issue is under the hood, because the transmission is flaring.

Something else seems amiss, however. When the transmission loses vacuum, it acts in just the opposite behavior of a flare. You typically get a very hard shift. Flaring occurs when the trans has too much vacuum, or, when there are worn components within the transmission, or a combination of the two scenarios.

sublettm 08-27-2005 11:30 AM

Thanks Brian. I have been thinking the same thing regarding the tranny, but all of this started at the same time. When I first start the car, it jerks and bucks down the road until it warms up. I have got to get this fixed today...I can't stand another week of this.

sixto 08-27-2005 11:03 PM

You have multiple problems. The door locks of your car have their own electric pump. Loss of vacuum causes the transmission to slam gears, not flare. The engine has no dependency on vacuum for smoothness warm or cold. IMO, none of these problems are related to the engine vacuum pump.

How long before the engine smooths out? A couple of minutes could mean a bad glow plug or two.

95 S420
87 300SDL

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