How much vacuum do you get at the T? Im getting around 21" Hg when one nipple is plugged or 10" when one is unplugged. Does this sound right? Im trying to troubleshoot a shutoff problem. The engine will shutoff with a mighty vac. All vacuum lines to AC and doors are OK. The tranny modulator wont hold vacuum but its been that way for years and car would shutoff fine. Could it be a weak vacuum supply?

__________________
'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles

I get 21ish when I connect to the system, nothing open or plugged. if you are getting 10, then you have a leak.
John

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

If you get 10 with the vac guage plugged in and the second T connected to the system, and 21 when you plug that line then you have a leak in that system somewhere.

__________________

Based on your article, I have eliminated the vacuum pump as culprit. Thanks for the link. Im thinking the modulator is leaking a lot more.

__________________
'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles

You just have to work your way through the system. Good to hear you are narrowing it down. There are LOTS of places that can leak. But it only takes a couple to cause all kinds of problems.

__________________

My HVAC has vacuum leaks, as does the locking system...still...

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

You might be getting different vacuum readings with different lines unplugged because there are little plastic "control orifices" in the system.....they look like hose couplers....be careful because there are different sizes in some cars....if you look around here you can find some Vacuum Schematics which will point these out......

SB

__________________

Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

I wanted to eliminate the vacuum pump as the source of the problem. Its already 300T miles old. My vacuum system is already quite simplified, no vacuum lines to the passenger side of the engine compartment.

__________________
'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles

Im getting 10 when one of the two nipples is unplugged from the vacuum system. Could the vacuum pump be intermittently working? I should get the v. modulator fixed first.

__________________
'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles

You have two T's in your main vac line right?

If you have one T in the main line open to the air and one connected to a vac guage, you will likely be getting a very low reading, beacause the open line creates a huge leak. But if you have the vac guage in one T and the other T is connected to the rest of the system and your are getting 10" than that system has a leak.

If your getting 21" with yoru vac gauge in one port and the other plugged then your vac pump is good, as well as your break booster.

__________________

Great! I really dont have time nor the desire to work on the vacuum pump right now. Thanks All.

__________________
'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles