Modulator adjustment - Help!! This cant be good... - PeachParts Mercedes-Benz Forum

dieseldan44 · #1 06-02-2007, 02:53 PM

hey all,

I am trying to properly measure my modulator pressure through the test port directly below the modulator.

I am following instructions that I have read in the acrhives and in this article at mbz.org:

http://articles.mbz.org/transmission/adjust/

I have the proper bolt, gauge and everything. Connected it up...turned car on and the clear line going to my gauge instantly filled up with tranny fluid!!

-car is up on ramps
-tranny fluid level before this was correct

This can't be normal...uhhh, advice? I am fairly certain I am doing everything correctly here.

thanks in advance,
dieseldan44

1985 300SD Sady · #2 06-02-2007, 03:38 PM

what kind of gauge are you using? I have never heard of anyone hooking up to that to measure modulator pressure. Seems ok that it is filling with fluid though, seeing as there is hopefully fluid in the tranny.

dieseldan44 · #3 06-02-2007, 03:42 PM

thanks for the reply sady...

im just using a 0-100psi gauge i got at the hardware store. nothing special.

dd

dieseldan44 · #4 06-02-2007, 07:23 PM

End if the day...tried the measurement a couple more times and the same result. If anything, the fluid spewed out more...yikes. It looks like it is leaking from the fitting itself, not the hose or anything like that.

Perhaps the wrong size washer etc. I think the screw is the right length.

I am still not sure that fluid should be spewing from here.

The pressure darted up to 60 psi - it should be 49 psi. Maybe the pressure is way too much or something like that. Which direction will tun down the pressure? Screw in or screw out, anybody know?

Thanks again for any help...
dd

Brian Carlton · #5 06-02-2007, 07:37 PM

Quote:

Originally Posted by dieseldan44

End if the day...tried the measurement a couple more times and the same result. If anything, the fluid spewed out more...yikes. It looks like it is leaking from the fitting itself, not the hose or anything like that.

Perhaps the wrong size washer etc. I think the screw is the right length.

I am still not sure that fluid should be spewing from here.

The pressure darted up to 60 psi - it should be 49 psi. Maybe the pressure is way too much or something like that. Which direction will tun down the pressure? Screw in or screw out, anybody know?

Thanks again for any help...
dd

I think you're going to have to explain exactly what you're doing to us dummies.........

The transmission is going to fill the hose to the gauge and will attempt to pressurize the test device.......hose........banjo fitting.........whatever you've got connected. 60 psi is a bit much for hose clamps and you'll probably get some leakage. Such a test is best done with hard piping and no hoses.

dieseldan44 · #6 06-02-2007, 08:34 PM

Here's a more rational explanation that doesnt relfect the fact that Im covered in tranny fluid and panicking

All of this is info I have gleaned from the forum and an MBZ.org article. Read beginning at step 12-16. http://articles.mbz.org/transmission/adjust/

Here's what I am doing:

-To measure the modulator pressure, there is a test port below it. It's a 12 mm bolt head. For my transmission, 722.315, I want to see 49 psi (2.9 bar) at the test port. forum member tomni has been kind enough to supply this info from the TDM.

-to make this measurement I purhcased a 100 psi gauge, some 55 psi rated vinyl tubing.

- for the fitting to the test port, tomnik correctly pointed out that the ALDA banjo fitting is the correct size. I got a bolt off of a yard car and cleaned it up with brake cleaner.

-I put the front wheel up on ramps. Plugged the modulator vacuum line per the articles instructions. Removed the 12mm bolt and put in the banjo fitting. I used the washers that were on the alda fitting.

-Checked everything was tight and prepared for an easy measurement. Turned car on - tranny fluid leaking from the bajo fitting and filling the measurement tube. Yikes.

-Tried two more times. Both times same result.

It seems the fluid is spewing right from the banjo bolt area. And its a lot of fluid really fast...not a drip.

Does this clear it up Brian? I can explain more...

dd

Brian Carlton · #7 06-02-2007, 08:58 PM

Quote:

Originally Posted by dieseldan44

-Checked everything was tight and prepared for an easy measurement. Turned car on - tranny fluid leaking from the bajo fitting and filling the measurement tube. Yikes.

-Tried two more times. Both times same result.

It seems the fluid is spewing right from the banjo bolt area. And its a lot of fluid really fast...not a drip.

Does this clear it up Brian? I can explain more...

dd

I presume that you wish the fluid to fill the measurement tube and not leak from the banjo fitting.........correct?

The banjo fitting, by itself, is certainly not leakproof. You'll need some copper crush washers on either side of the fitting to prevent any fluid from getting past the hole through the fitting.

Personally, I think it's going to be difficult to get such a device to seal completely. 60 psi for soft tubing and hose clamps is really pushing the limits.

A pipe nipple that extends from the port directly to the gauge would be the best choice........however adapting to the metric port will not be the easiest chore.

dieseldan44 · #8 06-02-2007, 09:22 PM

Brian,

Hmm, I am using a long tube - 13' - so I could road test it. Maybe if I got some different crush washers (had some on there already) and shortened the tube Ill have more success. If I shortened it enough, maybe the fluid wont even make it into the tube.

The only way to get a reading at that port would be with some sort of flexible hose - not enough room to go straight from port to gauge.

Id be interested to know what MB prcoedure is...but I think its not in the FSM. Its in the tranny manual which I dont have.

Thanks for confirming that it is not terrible for fluid to be present in that location.

Brian, do you know which direction of turning will increase the modulator pressure on the T handle- screw in or screw out? I know I am on the high side, maybe lowering the pressure to start with will also help.

Thanks again,
dd

Brian Carlton · #9 06-02-2007, 09:26 PM

Quote:

Originally Posted by dieseldan44

Brian, do you know which direction of turning will increase the modulator pressure on the T handle- screw in or screw out? I know I am on the high side, maybe lowering the pressure to start with will also help.

Thanks again,
dd

Clockwise will increase the modulator pressure.

Counterclockwise will decrease it.

.........as far as I can remember.........since I've never done it........

tobybul · #10 06-03-2007, 01:40 PM

DD, after reading this thread, I was wondering what symptoms are you experiencing that prompted you to do this? Thanks

dieseldan44 · #11 06-03-2007, 03:49 PM

Re-tried this morning with sucess! No spewing fluid. Woo-hoo. I had another banjo bolt. My pressure was set around 80 psi and needed to be 50, so needless to say it was off a bit.

tobybul - I replaced my leaking modulator valve back in december. I have meant to measure the modulator pressure correctly in this manner for months but have not gotten around to it. the car has been in the garage undergoing restoration so it didn't matter too much.

before that the car was shifting very harshly no matter what vacuum was set to. now after replacing the modulator it was still a little harsh, it just needed fine tuning.

I am going to write this experience up so others can benefit from my red fountain of fluid experience.

Brian Carlton · #12 06-03-2007, 03:52 PM

Good job.

I'd be interested in seeing the writeup as well........including a photo of the hose and gauge.

dieseldan44 · #13 06-03-2007, 09:42 PM

http://www.peachparts.com/shopforum/showthread.php?p=1525142&posted=1#post1525142

The write up from my experiences here...thanks for helping me in my hour of panic..