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Calling Steve! - 500SLC Thermo Vacuum Switch???

11K views 26 replies 7 participants last post by  Fonzi 
#1 ·
Steve,

If you're about... or anyone else that wants to chime in.

Whilst my 500SLC was in the US, a lot of smag crap was added to it.

It's has a frequency valve, and O2 sensor, some charcoal canisters etc etc.

What I'm trying to work out is, should there be any Thermo Vacuum Switches (of the type pictued below) screw into the front/top of my intake manifold, behind the WUR?

The EPC seems to indicate that it has two screw plugs, and none of these switches, but I have two screwed in there.

One seems to have a line going to the charcoal canisters, and they also seem to be connected to each other, as well.

Anyone that has photos of connects for vacuum/fuel/air, etc on an unmolested 117.960 engine, I'd really appreciate any photos at all that you might have.

Regards and thanks

Shane
 

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#2 ·
Let me know what pics you are seeking and I will provide. I don't see any nonsense under my hood. All the nonsense on my car seems to be behind the firewall.

I will try to snap a few in a few minutes and post back shortly. If you can provide examples of what you'd like to see before I go out to the garage, I will get the right pics the first time around.

I don't recall anything like that on my car. Granted, mine is a much earlier 026.



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#3 ·
Thanks for that! Any pics are appreciated, but be aware that the were changes throughout the run of the engine, and would also need to make 100% sure that it hasn't been altered in any way.

I'm wanting mine to be factory original.

Any photos you have of the lines and sensors at the front if the intake manifold would help, along with fuel lines from FD and also fuel return lines.

No problem if if takes a whole to get to it,

Cheers
 
#4 ·
BTW, the reason the request was directed at Steve wasn't in any way meant to offend anyone, or to question the depth of anyone else's knowledge, it was more because I know Steve has what is most likely to be the most as original 500SLC's on the board.
 
#6 · (Edited)
I don't have any TVV's installed on 2053. The engine vacuum setup is very straightforward. The only smog stuff I have is a charcoal canister and the cats. I've attached a few pictures.

The first is a little out of focus - sorry for that !!! Here's how she's setup. There's three actionable vacuum line on the engine:
  1. from the plenum to the distributor
  2. from the switchover valve to the advance on the distributor
  3. from the air distribution hose to the WUR.
Everything else is either a leak line or the vapor line. I have a vacuum input at the plenum running to the switch over valve. From the switch over valve to the vacuum advance on the distributor. There's the line running to the WUR. There a leak line at the WUR and one at the fuel pressure damper. Finally, there's the line running from the throttle body to the charcoal canister.

Hope this helps....



 
#22 ·
Everything else is either a leak line or the vapor line. I have a vacuum input at the plenum running to the switch over valve. From the switch over valve to the vacuum advance on the distributor. There's the line running to the WUR. There a leak line at the WUR and one at the fuel pressure damper. Finally, there's the line running from the throttle body to the charcoal canister.
Can you clarify as it appears that this reference shows plenum to switchover valve to retard, not advance?

And it's really tough to be certain from this reference photo but it also appears that the charcoal canister sources vacuum from the manifold, not the throttle body.

Thanks.
 

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#7 · (Edited)
Hey. You guys are going to have to try a little harder to offend me.

Apparently my vacuum system is all pooched up according to Steve's pics, assuming mine are supposed to be like his. I just rolled through my mechanic's shop and he touched the vac line on the bottom of the fuel pressure regulator (edit: I am now thinking that is a damper, not pressure regulator, and that hose is a "leak connection" per 073-500.pdf page 3) and it crumbled. Same with the line to the charcoal canister. So I had to remove the fuel pressure regulator (edit: damper) to get a hose on the bottom of it, and now from Steve's pics it almost looks like there's not supposed to be one there. Anyway, the vacuum can't be all that strong on the rhode at the back of the valve cover where mine was hooked in anyway. I guess I got a wee bit of a clusterfuck on me hands. I'm going to need some vac diagrams! :)

The screwdriver is pointing to the buried location where one side of the dizzy vac line is connected.

Ignore these pics if you want to see how it should be!

Auto part Engine Fuel line Vehicle Carburetor

Auto part Fuel line Engine Automotive fuel system Automotive engine part

Auto part Engine Fuel line Automotive fuel system Automotive engine part

Auto part Fuel line Engine Automotive fuel system Carburetor

Fuel line Auto part Engine Vehicle Pipe

Auto part Fuel line Engine Automotive engine part Automotive fuel system

Auto part Fuel line Engine Automotive fuel system Automotive engine part

Auto part Engine Fuel line Automotive fuel system Automotive engine part

Auto part Fuel line Engine Automotive engine part Automotive fuel system



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#8 ·
Steve, Fonz, that is incredibly helpful, thanks!

I'm going to pull the two TTV's from mine and screw the plugs in, instead.

Steve, what is the charcoal canister on your hooked up to?

I'm going to get some more photos of mine, where my charcoal canisters connect to what appears to be a return line maybe, just below the brake booster. I need to know what is meant to connect to that, so I can remove my canisters.

Also, Steve, do you have any more photos of the lines coming out of your FD? I need to work out the arrangment for connections when I pull the frequency valve.

Your photos have given me something to apsire to there Steve, but i'm getting there, screw by screw, bolt by bolt, bracket by bracket!
 
#15 ·
Steve, what is the charcoal canister on your hooked up to?

Also, Steve, do you have any more photos of the lines coming out of your FD? I need to work out the arrangment for connections when I pull the frequency valve.
The canister takes its input from the gas tank, via a vent valve. It uses vacuum from the engine to suck vapors out of the gas tank and burn them while the engine is operating. The vacuum can be taken from any point - the most convenient usually being on the throttle body.

I don't have any other photo's handy of the FD. The stubby hard pipe on the fuel line will rotate once the connections are opened up. Spray your connections with some secret sauce. My 5.0 had a freak-valve when I got it. Pulling it was pretty straightforward as I recall.
 
#9 ·
here is the bastardised connection to my FD, with the freq valve line in between the feed line and the FD.

BTW, how the hell do you undo these without twisting the solid line??

I loosened the 'nut' closest to the FD, and it tiwst within the thread, but the hose twists with it. I thought the hose should stay in place while the nut twisted? Am I doing something worng, or is the connection all locked up?
 

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#12 ·
Thanks guys, and thanks rockcrusher. If it was a 116.960 I'd take you up on the offer, but i think yours might be a 116.962 and it might be best to avoid any red herrings!

I really, really appreciate the offer though!

hey Fonz, what is that hose on yours running (in the picture) below the reservoirs, is that going to your charcoal canisters? what's it connected to?
 
#13 ·
I really, really appreciate the offer though!

hey Fonz, what is that hose on yours running (in the picture) below the reservoirs, is that going to your charcoal canisters? what's it connected to?
I pulled up the cloth covered hose from the charcoal canister to show how it was connected to the hose on the back if the air filter to the valve cover. That's also where the damper "leak connection" is picked up. I assume that is all pretty low level vacuum. I jammed some new small hose into the big old cloth hose today to get it back together as a temporary fix.

The other side of the canister quickly drops down from big braided hose to more rigid small hose, runs back, crossed the firewall and disappears behind the driver valve cover as shown with my finger.

Fuel line Wire Auto part Automotive fuel system Cable


And here are the hoses on the other side as previously described.

Wire Fuel line Electrical wiring Cable Auto part


Wire Electrical wiring Cable Auto part Fuel line




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#18 · (Edited)
Still searching for a 117.960 vacuum diagram.

Hoping to confirm connections to the following vacuum ports and which should have check valves present:

EGR. Two ports.
Switchover Valve. Two ports.
Thermo Valves X2. Two ports each.
Ignition Distributor. Two ports. (Advance/Retard)
Throttle Body. Two ports. (Upper/Lower)
Intake Manifold. One port. (Driver's side/upward facing/next to throttle body)
WUR. Three ports.
Shaped Contour Hose. Two ports. (Idle control)
Valve cover breather hose. One port. (Passenger side)

Any assistance and/or suggestions would be greatly appreciated. Thank you! :thumbsup:
 
#25 ·
Sorry...I only have time for a quick response. Real busy at the moment w/ one of my other distractions - boats.

In the picture by the WUR you have some 'plugs' referred to as thermo vacuum valve.

The output from the charcoal canister can connect anywhere in the system. Throttle body or intake manifold makes no difference. It's only purpose is to burn stray fumes.
 
#20 ·
One of the differences as noted in the photo reference above is the WUR. The 026 utilizes the older two port WUR. (upper atmos and upper chamber only)

The WUR found on my 117.960 is using a later 3 port version. (#70 ports:i,g,h) All of the 3 port WUR diagrams I've come across thus far show the later 3 port switchover valve (#13) mounted throttle body + upper and lower ports.

Now, the throttle body found on my 960 has only 2 ports (upper and lower)

Can I assume the incorrect WUR was installed at some point?

If so, can a later 3 port WUR be used a 2 port throttle body?

As by the MB manual's definition (c) and (d) connect when no fuel enrichment is required. So, without switch valve (13) can the WUR port (h) merely connect to the manifold vacuum?
 

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#21 ·
And just for clarification, Fonzi can you confirm that the two lines noted in your photo below in fact run from contour hose to the switchover valve to the ignition retard?
 

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#27 · (Edited)
Sorry I missed this 48hp. Yes. Those run to the little pod behind/under the radiator overflow. The hose to the distributor is the one closer to the center of the car, and the vacuum source hose seems to go into the center of that pod, the only hose you can really see with a red stripe in pictures below.

I'm sure you have not only figured out the above by now, but also figured out that the vacuum to the distributor is a vacuum retard (not advance).
 

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#23 ·
Thus far no single or series of diagrams reference my particular system specifically and maybe by identifying each of the systems individually, I hope to piece one together.

Thank you in advance and I appreciate any feedback.
 
#26 ·
Thanks for the replies.

Yes, I have two thermo vacuum valves. (noted as thermo switches)



I do not have a charcoal canister installed currently but good to know.

lurker, the epc diagram does help with the individual bits that make up the system. Thanks.

I suppose the bigger question is whether I should revert back to a 2 port WUR (Upper and Leak Only) or can I retain the 3 port WUR (Upper, lower chamber and upper chamber)? As noted previously, the lower chamber ((h) 3 port WUR) is routed through the throttle mounted switchover valve in diagram below. Can the switchover valve be bypassed and connected directly to manifold vacuum? Or should I introduce a later throttle body with said switchover valve?

The following photo is merely for reference (upper and lower chamber ports differ on the 0 438 140 XXX WUR) but with the lack of switchover at the throttle body, a bypass would create a similar loop:





And back to the original post topic, the thermo vacuum valves as noted can technically can be eliminated all together but if an EGR is present should at least one be retained?

Any feedback is appreciated. Thanks in advance.
 
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