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Discussion Starter #1
Hello-

I just finished bypassing the vacuum switches on the valve cover following the mercedeshop forum guidelines. I am hoping to make sure the vacuum is correct before I adjust the trans. I tested the black line that goes to the trans and it is not holding vacuum. I am guessing that the connector is swollen from excess oil. I had the car up and looked at it from the underside but could not see how to get at it. Is there an easy way to access the vacuum connection?

One more question. After I removed the two three way connectors close to the lift pump, I disconnected the two vacuum lines that connect right next to the thermostat from the top of the valve cover and plugged the vacuum connector that is next to the turbo. Does that sound right? It runs good.

Any help would be much appreciated.

Thanks,

Bill
 

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Discussion Starter #2
Ok I am too long winded sometimes, can anyone tell me where to locate the trans vacuum connector?

Thanks,
 

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It is on the passengers side on the rear part of the transmission. Its a little hard to get at, but if you follow the vacuum line, you will see it. Once you clean the grime off, it will be either red or green I believe.
 

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I just confirmed 100% that mine is toast. If you find a good source to purchase one, let me know. I have called Adsit, since they are in my town, but I think I can find it cheaper than $69. dieselgiant has it for $70 something (i need the red one) but I'm holding out for cheaper as he is great, but expensive. No luck at the partsbin, alleuropeanautoparts.com or ANY of the local places.
 

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Discussion Starter #7
I just followed the line and it connected to yellow mechanism right above the transmission pan. If that is indeed the connector I don't think I would be able to get it out without dropping the trans.
 

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That would be the modulator on the tranny. Sometimes just replacing the rubber cap on it fixes the vacuum leak.

Did you run the vent line into the cabin ad directed? I did the same mod. Brian Carlton's write up was great.
 

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Discussion Starter #9
Well I found the trans modulator and replaced the connector hose, no luck, and then tested the modulator itself. It does not hold pressure. I will replace it and let you know how it goes. Is it hard to get out?
 

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Hello-

I just finished bypassing the vacuum switches on the valve cover following the mercedeshop forum guidelines. I am hoping to make sure the vacuum is correct before I adjust the trans. I tested the black line that goes to the trans and it is not holding vacuum. I am guessing that the connector is swollen from excess oil. I had the car up and looked at it from the underside but could not see how to get at it. Is there an easy way to access the vacuum connection?

One more question. After I removed the two three way connectors close to the lift pump, I disconnected the two vacuum lines that connect right next to the thermostat from the top of the valve cover and plugged the vacuum connector that is next to the turbo. Does that sound right? It runs good.

Any help would be much appreciated.

Thanks,

Bill
Bill, I need to do this as well. Were are those guidelines for bypassing you refer to in the beginning of this post???
 

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Discussion Starter #12
yes, that is how i bypassed the switches on the valve cover. here is the info i used.

EGR elimination, 617 engine - ShopForum

and for a good vacuum diagram, go to vacuum diagrams and choose your model.

MZF, Inc

I ended up eliminating two three way connectors and all of the lines going to the top of the valve cover. You will need to replace the tees with rubber vacuum line and be sure to keep the green check valve and yellow connector in the same place, if you have them on your particular car.

The thermo valve is by the thermostat and the egr is closest to the air cleaner. If you have questions let me know. You should be fine with the diagram.

Anyone know how take out a vacuum modulator correctly? I would hate to wrench on it in a blind fury and mess something up!
 

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I'm going through similar steps. Reference the attached diagram.

Item 71 (Central Plug) had a broken hard line inside and was leaking. I disconnected the three lines going in and did the following:

(a) The wh/br line going to 36a is currently open and not connected to anything.

(b) The wh line going from 63 is plugged. This solved the transmission hard shift problem. The transmission now works GREAT!

(c) The bk line going from 65 is plugged.

Question 1: Should (c) be plugged or should it be tied into (b)? I don't understand the function of this line but this is due to the diagram not showing that is happening in the spaghetti behind Item 71.

Question 2: What does 36a (Thermo-vacuum valve) do?

Question 3: Is vacuum involved in the wastegate control? It appears not from the diagram. The engine has very little power starting out. More so than I attribute to turbo lag.
 

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Discussion Starter #15
I did the procedure the same way and had the exact same questions. From the posts I have read all lines to the valve cover are to be discarded. I would also like to know what the thermo vacuum valve does and if I need to plug up the connections. Does the EGR valve connection need to be plugged or should it be left open?

The vacuum changes were not enough to fix my shifting. I found information on changing the modulator and have been reading the Brotherton article on vacuum tuning and am getting excited for this thing to shift nice.
 
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