PeachParts Mercedes-Benz Forum

PeachParts Mercedes-Benz Forum (http://www.peachparts.com/shopforum/index.php)
-   Tech Help (http://www.peachparts.com/shopforum/forumdisplay.php?f=1)
-   -   transmission vacuum on gasoline engines... (http://www.peachparts.com/shopforum/showthread.php?t=100904)

sjcruiser 08-05-2004 09:58 PM

transmission vacuum on gasoline engines...
 
Hello all,

I've read a few documents regarding about the tranny vacuum check/adjustment; but all of them have been for diesels. Do we have any article for gasoline engines as well ?

One of the prong of a three(3) way vacuum connector that goes to the vacuum check valve (mounted on the engine firewall) is quite loose on mine (rubber harden, and does not grab tightly). Another prong has a line that connects to the rear of the engine, where appears to be a metal orifice(sp?); and on the bottom of this orifice there is an vacuum output that goes to the transmission modulator.

My mechanic reassured not to worry about the looseness at the check valve since vacuum sucks :) in anyway. However, when going up hill, or under heavy load, my economy gauge shows very little vacuum, given that I do not have a heavy foot. In short, the tranny shift very smooth at times; but also very harsh at other times also.

Any tips are greatly appreciated (as I'm very itched to correct this problem) !!!

Thanks for keeping till this point,
Frank.

slfan 08-06-2004 06:46 PM

Frank,

Sorry, but I don't have a cure for your engine. I have similar economy gauge indications as yours ("84 380sl):
@ idle..all the way left
@ cruise..nearly full left (1/8 deflection or so)
@ slight accel (barely depressing the pedal)..at least halfway
@ normal accel from stop..nearly full right

The engine has a very noticable loss of power compared to previous performance. I hope someone will be able to point us in the right direction. Thanks in advance.

stevebfl 08-06-2004 09:31 PM

The reason for an issue with diesel vacuum is they don't have vacuum naturally so the system is created to mimic gas cars. Well gas cars don't need to mimic gas cars......except...

Gas engines have the most vacuum at every load when they are running best. An engine running poorly will have poor vacuum and the trans will shift bad accordingly.

sjcruiser 03-29-2005 05:12 PM

(another) vacuum leak identified...shifts much better now
 
Haunted by Steve's post...on my never ending quest on improving my old girl...

Found another vacuum leak last month...the connection hose between the idle air distribution hoses has a large crack on it. Since these hoses are pretty brittle (very old) and might break if I try to remove them, I just put a dab of RTV clear goop on the leak. Let it cured for a while and took the car out for a test drive. My economic gauge no longer bottoms out on moderate accelerations (shows more vacuum in general); and the transmission shifts much better.

Have been playing with the transmission/throttle linkage and adjusting the vacuum modulator since - very very smooth shiftings.

Just wanna share my findings...
Frank.


All times are GMT -4. The time now is 06:26 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website