[W126 Coupe] Vacuum Regulator

[gerryvz]

90 percent of the time, a fast idle situation is caused by vacuum leaks in the intake system.

Indeed, the best way to diagnose vacuum leaks involving intake rubber components is to get a smoke test. This will tell you in 5 minutes where your issues lay.  If a smoke test doesn't indicate any vacuum leaks, then you can move on to other causes, such as the OVP relay, idle speed controller, slide valve, and so forth. But all of these are secondary to intake rubber air hoses, fuel injector holders and seals, and so forth.

This intake rubber and seals is not horribly expensive (a couple of hundred dollars US MAXIMUM for everything) and it is well worth the effort to replace. If you don't know that it's been replaced in the last 10-12 years, it's almost guaranteed that you are living on borrowed time and that a leak will develop.

Chet's splendid tutorial that he referenced in his reply provides an excellent guide (particularly when combined with the factory service manual) on removing the intake and replacing rubber.  I have done it now three times, and it the job be done with only common tools and a moderate amount of mechanical skill easily in a weekend, and even in a day if one has enough time. Figure about 4-6 hours for a first-timer to remove the intake, and about the same amount of time to re-install it.

You need to also get a new set of intake manifold gaskets which will seal the manifold to the heads. These gaskets around around $10 apiece.

One piece of advice: DO NOT SCRIMP and get aftermarket / Chinese intake rubber for your car.  I'm talking about cheap brands like "Uroparts" that are commonly sold by sites like buymbparts.biz and AutohausAZ.com. The factory rubber hoses aren't much more expensive (particularly when purchased through parts.com) and is MUCH higher quality and better fitting for your car.  You will NOT find the real MB factory rubber hoses & parts anywhere cheaper than via parts.com.  To use their site most effectively, you will need to have the MB part numbers in hand for the rubber bits -- do not use the "menu" system on parts.com.  If you need a tutorial, don't hesitate to contact me. But you will need to have the MB part numbers in hand (available free via the MB EPC site).

When you replace your intake hoses and seals, it's also imperative that you replace all of the plastic vacuum lines, as well as the rubber vacuum line fittings/nipples that the lines press into. There are 3-4 different styles/sizes of these rubber fittings and they are again very inexpensive ($1-3 USD apiece, and probably you'd need 12-15 of them or so). You can buy vacuum line by the meter, and I'd get a good 5 or 10 meters of it so you have more than enough.  Don't forget to replace the vacuum line & rubber fitting that attaches to the transmission, running from the back of the intake manifold down to the transmission!! Also don't forget to replace the three-way and four-way rubber vacuum distribution hoses that run through the inner firewall near the master cylinder and fuse box. These are often overlooked.

You will be amazed at how nicely your car runs just after replacing all of the soft items (vacuum lines and air hoses) underhood!

I will always be eternally grateful to Chet Hwilka for his tutorial and the invaluable assistance & courage it gave me to redo my top end.

http://www.facebook.com/album.php?aid=167571&id=821723571&l=946f984ee3

Cheers,
Gerry


- - - - - - - - - - - -
Gerry Van Zandt
+1 503 805-9316 (cell)
+1 281 518-2960 (work)
+1 832 764-0183 (home)





On Dec 06, 2010, at 11:15 AM, mbcoupes-request at mbcoupes.com wrote:


>

>

> As I have been plagued with the high idle problem,which even the German

> factory trained "Guru"could not seem to locate.The idle speed controler has

> been swapped(as well as the valve) so I have been thinking of fitting an

> adjustable vacuum regulator in the line between the valve and manifold,this

> may well be a crazy idea,but I have cut the idle down by 200 rpm by sleeving

>

> the valve with a plastic tube,but because it fluctuates from day to day I

> would be nice If I could fine tune it,any thoughts on the matter would be

> most welcome.

>

>

>

> Kind Regards Dan Gardner 1986 560SEC (Euro 220kw)

>

> The MB Coupes Website!

> W126 SEC Mailing List

> Postings remain property of MB Coupes, L.L.C.

>

>

>

>

>

>

>

>

> ------------------------------

>

> Message: 2

> Date: Mon, 6 Dec 2010 12:17:14 +0800

> From: "Dan Gardner" <cruftsk9 at tpg.com.au>

> Subject: Re: [W126 Coupe] Hi Idle

> To: <mbcoupes at mbcoupes.com>

> Message-ID: <CD27A7D2DD7A4156BEA7E288893D95AC at dane9tuc6ffoy5>

> Content-Type: text/plain; format=flowed; charset="iso-8859-1";

> reply-type=original

>

> Hi Folks

>

> Thanks for the information,I suppose with these vacuum leaks I need to

> have the "smoke test"(if they can do it here)just to verify if the system is

> sealed from leaks.From what I can gather the manifold rubber seals are

> notorious for leaking with age.Dont know if these can be bought in a

> silicone compound.

> Digressing I have just bought a few steering & suspension parts for my 450sl

> from "Autohaus" even with postage ($90)to Western Australia still I ended up

> paying less than half price than buying locally.So if you live in the US

> never complain about the cost of parts as you are spoilt for choice,price

> and availability.

>

>

>

> Kind Regards Dan Gardner 1986 560SEC

> (Euro 220kw)

>

>

>

>

> ------------------------------

>

> The MB Coupes Website!

> W126 SEC Coupes

> Postings remain property of MB Coupes, L.L.C.

>

> End of MBCOUPES Digest, Vol 78, Issue 5

> ***************************************

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