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

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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?

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Jim

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??

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-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi

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

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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

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

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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