Another transmisssion/Vacuum troubleshooting thread

[bigblockchev]

I have recently acquired an 87 190D turbo & am going through it to solve some issues. The trans is not shifting properly. In order to get to the bottom of this I have started to test the various vacuum lines. What I know so far is that there is 23" of vacuum at the brake booster line takeoff T. This line tees off into a white line which goes up to some kind of device next to the fuse block. This device has a red and a green line attached to the top of it, both of these lines have a reduced vacuum of 10ish " coming out of them. The other line coming from the brake booster T is brown and seems to go to the engine shutoff keyswitch line. The shutoff pot system works perfectly. For the life of me I cannot find a vacuum source to the VCV valve to begin troubleshooting the trans. The diagrams seem to indicate that the vacuum is tested at the line pushed into the side of the VCV. I get nothing at this line. Am I doing it wrong?

[muleears]

Originally Posted by bigblockchev

I have recently acquired an 87 190D turbo & am going through it to solve some issues. The trans is not shifting properly. In order to get to the bottom of this I have started to test the various vacuum lines. What I know so far is that there is 23" of vacuum at the brake booster line takeoff T. This line tees off into a white line which goes up to some kind of device next to the fuse block. This device has a red and a green line attached to the top of it, both of these lines have a reduced vacuum of 10ish " coming out of them. The other line coming from the brake booster T is brown and seems to go to the engine shutoff keyswitch line. The shutoff pot system works perfectly. For the life of me I cannot find a vacuum source to the VCV valve to begin troubleshooting the trans. The diagrams seem to indicate that the vacuum is tested at the line pushed into the side of the VCV. I get nothing at this line. Am I doing it wrong?

What is the tranny doing wrong? It might not be a vacuum issue at all. My tranny problems have all been fixed by the bowden cable adjustment or K1, K2 spring replacement.

[bigblockchev]

The car has 431K (260K miles) & I assume the trans does too. I have tried snugging up on the bowden cable which had lots of slack in it. I got some improvement but it still has a slight hard 2-3 shift and a very soft 3-4 upshift along with a big flare on 4-3 downshift. I have tried increasing the modulator pressure by 1 1/2 turns on the key at the top of the modulator. This maybe made the shifts a little more definite but not much. I have temporarily disconnected the modulator vac line to see if all shifts got hard. Well they got a bit harder but not neck snapping hard like I expected. I want to go through everything before condemming the tranny , I have a 40K rebuild from my 87 190d na under my bench to put in if all else fails but I still have to get the adjustments figured out to do that. I also have a Superior shift kit which I might install but that is more difficult. I need to get to a baseline and work from there otherwise I will be going off in all directions. So to start at the VCV valve which is clearly not reading correct makes a certain amount of sense to me. Does anyone have a checklist or flowchart of items to logicaly go through. Cheers Dan

[jt20]

http://w124-zone.com/downloads/MB%20CD/W124/Index/602_603index.html


start going through the vac system and get it sorted.

I doubt this will solve your trans issues, but it will help.

On top of the VCV there are labels that help identify each vac line.

[Brian Carlton]

Originally Posted by bigblockchev

I have temporarily disconnected the modulator vac line to see if all shifts got hard. Well they got a bit harder but not neck snapping hard like I expected.

If the flare has disappeared under this condition, you might be able to get it to work for you with some careful vacuum adjustments..........but, it won't be easy as you have the combination of hard shifts and flaring, together.

If there is still flare under this condition, the game is effectively over. I wouldn't be spending a lot of time on a trans with over 250K.