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1987 420 SEL
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Discussion Starter #1
Can any of you tell me where is the Ported Vacuum Switch located? Could it also be known as the Thermo Vacuum Switch? Any help greatly appreciated.
 

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1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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Hi Prochambers,

What systems would this 'Ported Vacuum Switch' be associated?

I can see 2 Thermo 'Vacuum' Valves, one associated with the EGR system, the other controls the engine vacuum feed to a purge valve for the charcoal canister.

Semantics, right?

Cheers, MBL
 

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1987 420 SEL
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Discussion Starter #3
Hey MBL. When I took my car in for the diagnoses of the ticking noise up front. The mechanic there said that I need a PORTED VACUUM SWITCH. Of course, he wouldn't show me what he was talking about. I believe that it is the THERMAL Switch. I searched Autohaus and some others and they all came back with the same info. If you have a diagram that would be very helpful.

Also, while were at it, we can I find the Coil Wire Connection? I want to change my oil again and have been advise to disconnect the coil wire before restarting the car after a oil change to prevent the chain from jumping a tooth. I just had my chain done about 4 weeks ago. Thanks.
 

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1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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Hi Prochambers,

Here are some vacuum diagrams part location, 79 is what you're looking for I think. Also included - the MB accepted way of disconnecting the ignition. MB says any other way will damage something, probably expensive (my emphasis).

Cheers, MBL
 

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1987 420 SEL
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Discussion Starter #5
Hey MBL. That's it. I will get on it. There is some advantages to taking your car in to a professional, especially when they point out things that need attention and you can do it yourself.

So, in your picture of the electronic control line. Is this what I have to disconnect before restarting the engine? It sounds like if I disconnect it, nothing will happen when trying to crank. Just want to be sure. That sounds like something serious that you don't want to screw up! Let me know. Thanks.
 

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1987 420 SEL
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Discussion Starter #6
Now that I know where it is. How is it removed? Does it unscrew or just pull off? Any advice.

By the way here is a picture of it. It seems like there are different colors pertaining to temperature.

https://autopartsworld.com/new/product_availability.asp?product_number=B7030-159712&web_brand_id=genuine&web_name_id=thermo-vacuum-valve&year=1987&web_make_id=mercedes-benz&web_model_id=420sel&x=77&y=7
 

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1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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4,286 Posts
Hi Prochambers,

YUP! That is line disabling the Ign, (looks like it pulls off in the pic) as recommended by MB, is the featured item in the pic I posted yesterday. That said, (I think it is a good idea to get the chain tensioner - tensioned B4 the motor starts!!) I don't do it, I just take the car to get the oil changed. Possibly I'm stupid or something. [8] When new, the car didn't get that treatment (blanket statement here) at the MB dealership. Now that we are dealing with teenage MBs, maybe we should be more aware... [8)]

Anyway, you've got the thermo valves, they're just different manufacturers & prices. 50 degrees C is the ticket.

I've been down to Greenwich, assisting a good friend move a car & clean out a garage. You now, separating stuff really needed - vs. the other. Then there are the 42 or so years of accumulation..... tools, more tools-measuring, machine lathe bits, BS & Whitworth, metric, SAE tools to sort, electrical testing......

His car, and 97% of the accumulation: spares & really special stuff has now been moved successfully. The remainder, the items that absolutely must be with the car....... are in the trunk of my Volvo.... getting a ride to western Massachusetts tomorrow, I think.

Cheers, MBL

BTW: I saw a gorgeous grey metallic 560SEC heading N on the Merritt Pkwy. late thisafter, on the way home.[:)]

3 smileys.... Prize?
 

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1987 420 SEL
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Discussion Starter #9
Is it best to change both of them at the same time? And are the temperature ranges the same for each?
 

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1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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Hi Prochambers,

On the CD they appear to be identical 50 degree C switches, my parts reference book is pics only, so I'm not in position to give you exactly the info you need. Perhaps jdc1244a might chime in, as he has more MB experience than I and can supply parts as well.

FYI: On page 137 (380SE-420SEL) of the Performance Products catalogue - (reference #87) there are 2 thermo-vacuum valves listed. One with a 4.2 suffix. Opens at 70C, not at 50C as the CDs suggest.
Performance Products lists both 50 & 70C switches for the 500/560.

As you point out, the swiches are color coded: Yellow = 70C, Red = 50C.

I've found the CDs to generalize at times. I'm also aware that, over time, parts can be superceded by the manufacturerer. I think a call to Ron at GermanStar or one to your MB dealer might be in order at this point. Either call could give you the info & get the parts in your hands PDQ.

Cheers, MBL
 

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1987 420 SEL
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Discussion Starter #11
I found out some more information as to how important the Thermal Vacuum Valve is. Read below:

PORTED VACUUM SWITCH

Another component that may be a part of your vehicle's EGR system is a "ported vacuum switch" (PVS), which may also be called a "thermal vacuum valve" or "temperature vacuum valve" (TVS). The switch controls the passage of vacuum that operates the EGR valve.

This device is a heat-sensitive switch that remains closed until the engine's coolant reaches a certain temperature. The PVS screws into the intake manifold, thermostat housing or engine so the heat-sensing element is in contact with the engine's coolant. Inside the switch is a wax plug that pushes a sliding plunger to uncover or block vacuum ports in the switch. As the engine heats up, the wax expands and pushes the plunger up until it uncovers or blocks the vacuum port. At this point, vacuum to the device that the switch controls is either applied or blocked. Severe engine overheating can damage the switch, making replacement necessary.

If yours is broken on the tip or missing a connector, then it's time to address the problem!!! Just sharing information that was introduced to me. Have a good day![:D]
 

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90 420SEL
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Hi Prochambers, Just wondering if you replaced that switch and if it solved your ticking noise.Don't see the connection between them,but can't hurt.I take it the chain tensioner uses oil pressure to keep the chain tight. I'll have to do some homework before trying to change oil myself. No MB dealers around here.Thanks!
 

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1987 420 SEL
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Discussion Starter #13
Hey 90 Benz. I have changed the Thermal Vacuum Valve and have noticed that the climate control system operates better. My ticking noise is a bad camshaft on the right side of my engine. Get yourself some of the repair manuals on CD that are on ebay. They are very helpful. Now that the weather has gotten better, i've been examining all my vacuum hoses, various lines and connectors for any damage. I noticed that I have to change my 2 transmission cooler lines, of course, i've already ordered them. So, I will be doing them sometimes this week.
 

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1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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Hi Prochambers,

If the climate control works better now, it sounds as though there was a vacuum leak at the valve or line. Was the unit you replaced cracked/broken? I never did ask why your tech advised replacement in the first place...

Way back in the previous millennium, when I worked on Volvos (during the Arab Oil Embargo and when the 55mph national speed limit was invented [xx(]), I remember a Technical Service Bulletin on the heater/defroster controls (vac. operated) advising that the engine valves be checked & adjusted if certain problems were happening with heater operation. **The specifics in this paragraph do not apply to our 126 cars at all.** The above does serve as an example of how vacuum supply can (and will) affect the climate control operation of our cars though.

On another note, what's the cam plan?

Cheers, MBL
 

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1987 420 SEL
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Discussion Starter #15
Hey MBL. The valve was broken on one of the connectors leading to the vacuum hose. See diagram. I'm planning on getting a complete upper cylinder rebuild job done. I know I need to have my valve seals and guides done anyway, so i'm going to pay the piper and get it done right. Thanks for asking, i'll keep you posted.
 

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