what is this sensor
 

Can someone tell me what this sensor is and what it does i need to order it

That is a temperature operated vacuum switch that allows vacuum supply to pass through at a pre-determined temp (rising temp I am going to assume as in after the engine has warmed up). Sorry I can't tell you any specifics other than that. What kind of vehicle is it on?

It is on an 89 300e

Are you sure that's not a partially sheared off bolt? On my M103, there's a coolant "bleed" bolt in that spot that I use when filling the block with coolant. It prevents air bubbles from accumulating.
The 14mm bolt to the left of it accomplishes the same task.

Do you have a Euro version 300E??

It is, indeed the thermal switch for vacuum advance in a CIS system. It allows vacuum to the distributor during cold start and into warmup. I don't have an exact number for the shut-off point, but I think about 60C ( may depend on model year).

no dont think so take a lot at the pic again
i definitely need a part #so i can replace it

First, I ssume you removed one of the hoses so we could see the device. I still think it is a thermal switch for vacuum advance. Mine had a number stamped in the flat on one of the hex faces. I pulled it out and put a plug in its place, cleaned it off and found numbers. Then I tok it to my sort of friendly MB dealer and bought a new one, tested its function with near frozen and near boiling water, and installed it. Be carefule of the vacuum tubes when removing and installing.

Incidentally, why are you certain a new one is required unless one of the tubes is broken?

That is exactly what happen rcmktg one of the vacuum tube broke off
Would you happen to have the number to the one that you change from what you are saying looks like it is the same part

let me know please

Do you have vacuum to it????
 

Can anyone answer this?

I was just wondering if you have vacuum to the lines that go to this part at idle??

I have a slight missing (in my 300CE). I've just completed it's tune up with OEM Cap, Rotor, Wires, Bosch Plugs and still have this annoying shake at idle and a stumble when starting out. My "Economy guage" (VAC) is fluctuating and i've looked at every vac line in the car and can't seem to find a leak anywhere. I've also wet down everything in homes of finding a vac leak but no luck Every once an awhile it seems to stop completely for a few "traffic lights" and then returns. I've checked temp sensor which reads fine and wiring to no avail..

I noticed that I have no vacuum to either one of these lines on the part you are referring to until you rev the engine and then I feel just a bit.

Anyone have any input?? The car runs fantastic "off idle and crusing" but stumbles when starting out. It started one day "in an instant" which made me think is was "electronic or sensor related" but I'm stumped. I've removed and checked the idle valve (which is working fine) as well.

Sorry to "jump all over your post", I just wanted to comment. I've tried the search and gotten a bunch of good tips but can't seem to find the answer.

CE4me :

You likely have an injection system issue, but first, do check all vacuum hoses. One really hard to find and unusual vacuum leak is a bad check valve in the brake booster. If usign the brakes seems to cause more stumble, check there. Possibilities: Decel/cutoff microswitch not made or failing, 1 funky injector or leaking injector seal. More challenging problems: the hard to fix parts of the fuel injection system. Put the old diagnostics stuff on it and start checking.

Richard, are you sure about this. On my 89 it is called a thermovaccum switch and is connected to the intake under the airflow sensor and the other tube connects to the EGR gizmo on the fenderwell. My EZL vacuum line connects directly to the intake manifold.

No, I am not certain, forgot about EGR having a thermoswitch. Maybe if he followed the hoses I could guess better. Guess I need to look at the book again, and keep working on the old 190 ( see "of potentiometers and men", among others).

I don't think it's for EGR either, I think it's for the evaporative emissions system, in other words for the charcoal canister.
If you remove it, and use the correct fitting socket so as not to damage the flat parts of the hex shape (that the socket fits over) you should find the part number stamped into the metal on one of the flats.

Gilly

Oops!
 

Got my terminology wrong again. It's called the "regeneration valve" not an EGR gizmo, and it is located on the fenderwell and connects to the charcoal canister.

Well I wanna to think you guys for your help , I went to the dealer and the guy was kind enough to go outside in the parking lot to see what I was talking about , he told me it was a thermo-vacuum I ask him if that would cause my car to hesitate he said that it is possible the thermo vacuum sort of act like an egr valve how accurate this is i have no idea anyway the part cost $14.50 at the dealer i took the part # from him checked with fastlane it is $12.00 so i ordered it from the dealer.

Looks like the captain was right . thanks everyone

mpnye,

Welcome to the forum!

We could always use another MB technician.

I hope he doesn't keep SHOUTING at us!!!
 

:D :D Just kidding mpnye!! Welcome aboard!!

You can SHOUT all you WANT as long as the INFO is CORRECT!

Gilly

Thanks - rcmktg
 

Thanks rcmktg,.

I actually did check the check valve as well. I wanted to make sure I "had a handle" on all of the vac related issues before replacing injectors and digging into the fuel system. - Which by the way the injectors most likey need a replacement. (150K and the 1st problem I've had other than the Bearing Bracket) - It's been babied all of it''s life and has been very good to me.

1 question. Can the injector seals leak without causing a "wet area" or fuel leak / smell?? It's not exactly a "wallet draining" job and something I should do at this point anyway.

Thanks Again.

As lots of other, more current techs can tell you, injector seals are actually for preventing vacuum ( air) leaks around the injectors. Most often the problem is an age/heat cycles hardening of the elastomeric seals. We used to use a water bottle to find most of them, squirting a stream around each injector. Watch the tach and listen to the engine run.

this might be right in case of older or euros

mine does connect to the WUR & a quad with one of the legs being the distributor vacuum...

Both vents broke off
so I connected these 2 lines together by inserting a small piece of tubing until I can get it to the shop

$14.50
good for you
Price has doubled since then...

Still would really like to know what this lil devil really does
or doesn't do when its not working right...

:juggle2:

yup i was just gonna say thermo vaccum switch... i just had to replace this on my 88 300se as the shop that did my cylinder head broke the little tubes that stick up ..

my car actually has a diagram under the hood left of the radiator.. one of the lines goes to the charcoal and the other goes to the throttle body.. that switch operating temp is 70C.. and yes it can cause ruff idle. unhooked my idle fluctuated between approx 500rpm and 800rpm ..after installing it it ran smooth again. luckily here in cali we have quite a few junk yards ..and as my uncle always said about them places .. whatever u can fit in your pocket is free ..lol .. they actually have allot of nice chrome on the cars there .. gonna go get me a set of window chrome

just an fyi ... if you have the oart number or you can search it in partsamerica.com it usually list an option to "check what other vehicles use this part" and u can go hunting for those models ..

Thanks
That makes me feel better
even the pros make mistakes
I could hardly forgive myself
for hurting my benz
Hope it forgives me

Have to find some Benz graveyards...
I need the practice

:scream: