Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Mercedes-Benz SL Discussion Forum

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 08-22-2008, 12:47 AM
stix518's Avatar
Registered User
 
Join Date: Aug 2008
Posts: 6
I searched - really I did!!

Hey all!

Relatively new owner (2 mos) of a 1986 560sl with 165k on the clock. Have been lurking and searching and learning for several months here prior to that. I have read virtually every thread related to vacuum leaks (which I believe I have). I was hoping in my search to find a vacuum diagram for the 560, but to no avail. Nor have I found "exactly" what I have for symptoms but some have been close. Here's the skinny on what's already been done...
1. brand new plugs, wires, rotor, cap - all the right stuff based on info gleaned here.
2. Soon after that, took it to an indy/dealer tech (works at an MB dealer/techs on the side out of his house for the older mb's) for a quick once over to give me a heads-up on what it needs and to plan for any "larger" expenditures that he may have found (like needing a rear main seal - which will be done after driving season). He took off the air cleaner, attached some device to the engine and turned a screw around the (what I assume was the) EFI to "adjust the mixture". Ran great for a while after that.

Now here's the problem, recently the economy gauge is generally pegged to the right (although sometimes when I step on the brake, it moves to the left). Sometimes it will move to the left, stay there during idle or coast but as soon as you step on the gas, it slams back all the way to the right. It sometimes runs a bit rough at idle but not overly so and appears/feels to run fine under load.

I truly believe vacuum is the culprit (per the myriad of posts regarding same) but, being a relative neophyte in auto mechanics (but not afraid to get my hands dirty), I have no idea on how to chase down a vacuum leak - especially without a functional and readable (to me) schematic. There was a great one for a 450sl in one of the posts I read but I'd bet that it's not the same for the 560. Any help and/or suggestions about the problem I'm having and/or a diagram would be greatly appreciated! And thanks for the education you all have already given my with your great posts on any number of topics. This place is a wealth of info and I need it!!

Stix

Reply With Quote
  #2  
Old 08-22-2008, 01:50 AM
Carson357's Avatar
www.stonebrew.com
 
Join Date: Aug 2006
Location: San Diego, California
Posts: 1,116
i had similar issue om my 560 sel, it was a loose vacuum connection, rubber was not fitting securely on the valve causing leaks, i would check all under hood connections and verify they were tight
__________________
1967 250 S
1967 280SE
1968 250S
1971 280 SE
1973 220
1974 280 S
1975 450 SEL
1976 220 D
1979 300SD
1983 300 SD
1985 230 TE euro
1986 280SL
1986 500 SEL euro
1986 190E 2.3
1990 300 SE
2003 C230 K
2004 C230 K
1987 560SEL
1987 300SDL now in canada
2005 C230
1998 C43 AMG Sold to DON
1993 190E 2.6
300TD Former daily driver Totaled
current:
R320 CDI
Ram 2500 Cummins
Reply With Quote
  #3  
Old 08-22-2008, 06:00 AM
MB, love..hate..love..
 
Join Date: Apr 2003
Location: NB Canada
Posts: 1,173
I'd second that advice. Try spraying some 'quick start' (volatile, but safe if there is no open flame or red-hot metal) around the vacuum lines/connections at idle. A leak will bring the idle up as the stuff enriches the mixture in the incoming air-stream. There is a large rubber plenum under the air cleaner which is prone to cracking. I fixed mine with silicone, for now, and plan a tear-down to replace it next winter. You need to get a paper copy of the 117 or 116 engine manual, or the CD, and read up. Most of the vacuum diagrams won't help to find leaks anyway, but will aid in understanding functionality. Welcome to the forum too...
__________________
1986 560SL
2002 Toyota Camry
1993 Lexus
Reply With Quote
  #4  
Old 08-22-2008, 07:59 AM
Registered User
 
Join Date: Oct 2007
Location: Greater Metropolitan Beaverdam VA
Posts: 2,877
vacuum leak

I agree that your problems are vacuum related. If your "economy" gauge is pegged to the right much of the time the leak is massive.

The most overlooked vacuum fitting because it is hard to see is one at the back (firewall) end of the engine. It is located on the intake manifold near the center. The rubber connector for the vac line often deteriorates because it lives in a heat and oil-rich environment. If you look at the multiple vacuum lines that enter the firewall on the driver's side and trace the line that feeds them across the top of the firewall. it enters the intake manifold through that connector. You can use a piece of plastic tubing as a temporary fix until you get the proper connector. You need tiny hands and a lot of patience to reach in there. While you are under the hood, inspect all the other rubber connectors you can find also. The hard plastic lines seldom fail but the connectors do.

This fixed most of the driveability problems on my '88 560SL. Good Hunting!
Reply With Quote
  #5  
Old 08-22-2008, 08:48 AM
Dee8go's Avatar
Senor User
 
Join Date: Apr 2006
Location: The People's Republic of Arlington, VA
Posts: 7,193
Quote:
Originally Posted by donbryce View Post
. . . . There is a large rubber plenum under the air cleaner which is prone to cracking. I fixed mine with silicone, for now, and plan a tear-down to replace it next winter. You need to get a paper copy of the 117 or 116 engine manual, or the CD, and read up. Most of the vacuum diagrams won't help to find leaks anyway, but will aid in understanding functionality. Welcome to the forum too...
Is this plenum under the air cleaner common to all 117's or just the SLs?
__________________
" We have nothing to fear but the main stream media itself . . . ."- Adapted from Franklin D Roosevelt for the 21st century

OBK #55

1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
The Dee8gonator 1987 560SEC 196,000 miles - Sold
Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
2016 AMG GTS 12,000 miles
Reply With Quote
  #6  
Old 08-22-2008, 12:53 PM
Registered User
 
Join Date: Apr 2007
Location: Sierras, CA
Posts: 138
While I'm far from knowledgable I might suggest that you find a shop in your area that has a "smoke machine". That is the only way I found my vacuum leak(s) after weeks of searching. The test was $100.00 and I wish I had done it weeks before!

http://www.peachparts.com/shopforum/mercedes-benz-sl-discussion-forum/221171-380sl-hard-start-poor-mileage-post1920679.html#post1920679
__________________
82 380SL 41K miles sold, 98 SL500 44K miles, 13 C300 4Matic, 14 CLA-250 4Matic
Reply With Quote
  #7  
Old 09-04-2008, 05:10 PM
stix518's Avatar
Registered User
 
Join Date: Aug 2008
Posts: 6
Agree completely on the "smoke machine". But here's some new info that might help nail it down.

Changed the gas cap. Now, when I start the car, the economy needle stays to the left and moves when I rev the engine (like it's supposed to). When I put it in reverse, it works okay too. When I put it into drive and step on the gas, the needle pegs to the right and stays there although occasionally, if I put it in reverse, the needle will move to the right with pressure on the gas pedal and then return to peg/right. Is there a vacuum line to the tranny that could be causing this? Gonna have to find a garage with the smoke machine! Anyone know what it is actually called? Thanks again for all your help!

Stix
Reply With Quote
  #8  
Old 09-05-2008, 01:42 PM
Registered User
 
Join Date: Apr 2007
Location: Sierras, CA
Posts: 138
There are several manufacturers of the smoke machines. The brand that the shop used on my car was by REDLINE Smoke Pro. Hope this helps!

__________________
82 380SL 41K miles sold, 98 SL500 44K miles, 13 C300 4Matic, 14 CLA-250 4Matic
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 07:49 PM.


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 -    DMCA Registered Agent Contact Page