that thing directly to the right of the ABS control unit? It keeps ticking, and it sounds similar to a spark plug firing. should i be worried it's making these noises? TIA!

BTW, this is my first time posting! You guys really know your stuff, and thanks to this forum i just successfully completed my first oil change and spark plug change! The best!

Hi, and welcome to the best Mercedes forum on the web... !
As you note, there is much expertise here and open sharing of knowledge is common.
Unfortunately, I don't know anything about the W210, but many here do...
It might be helpful if you were to take a digital photo of what you're attempting to describe and I'm sure someone can indentify it for you.
Congrats on your doing some of your own maintenance... ! A rewarding experience that will save you a bunch of money.
KenP

If it's that cylindrical-looking thing with the electrical connector on top and the two fat rubber hoses on the bottom, and it only ticks when the engine is running, that's the purge valve. It's part of the evaporative emissions system. Leave it alone. If the noise is really bothersome you can try replacing it. With the hood open you'll probably always hear it though.

Gilly

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Thanks guys! I guess it is the purge valve and therefore i'll leave it alone. I hope it's working correctly. At any rate, i appreciate the replies!

-will

If this valve operates incorrectly, eventually it will lead to a check engine light.
Sometimes they will get a bit noisy, as you have noticed, and a new one will replace it. It can be noisy and still do it's job correctly though. Sometimes they will be a bit noisier in cold weather.
I would say yours is getting noisy but is probably operating (doing it's job) correctly.

Gilly

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Click here to see the items I have up for auction at EBay

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Gilly or others,

At what duty cycle should I expect to hear the "ticking" on the purge valve? Vehicle is a G500 (motor is 113.962 almost identical to the 1999/2000 113.961)

I just conducted a "test". outside air temp about 30 degrees F, tank about 1/2 full. I put my stethascope on and it's as quiet as church on Friday night.

A few days ago I popped some codes (all P0). Yes, I filled the car while it was running. Would that "break" a purge valve? The codes were:

- 442 EVAP system leak detected (small leak)
- 455 EVAP system leak detected (large leak). Gee I wonder why
- 150 O2S 1 circuit malfuntion
- 130 O2S 1 Circuit malfuntion

Not sure how 150 and 130 are related to the fuel cap issue. Thoughts.

Had expected the CEL to clear per the Mitchell's manual 3 "trips". But it didn't so I disconnected the battery to clear the DTCs. I'll drive it to see what codes pop, if any.

__________________
S, J.R. Brown
2000 G500 LWB Obsedian Black
2005 Toyota Tacoma Access Cab Off Road Sport
1993 Volvo 240 Sedan Anthracite
1980 450SEL Champange (owned it for 15 years. Great car)
1986 280GE LWB Anthracite (Sold it and kinda wish I hadn't)

The purge valve is normally closed at idle unless the intake air temp gets above around 40deg C (if I remember correctly). The duty cycle when openned varies by the conditions.

One of the ways that you get a large leak code is when the purge valve doesn't open. The evap monitor test closes the vent valve (sealing the charcoal cannister), opens the purge valve until a ceratin vacuum is registered in the tank by the tank pressure sensor or a certain time has elapsed. Once the pressure is achieved the purge valve is closed and the sealed system is monitored for a period of time. A large leak is determined if the tank doesn't reach the required vacuum and a small leak is registerd if it doesn't hold for the specified time.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Steve, THANKS!

It's a wait and see for me.

__________________
S, J.R. Brown
2000 G500 LWB Obsedian Black
2005 Toyota Tacoma Access Cab Off Road Sport
1993 Volvo 240 Sedan Anthracite
1980 450SEL Champange (owned it for 15 years. Great car)
1986 280GE LWB Anthracite (Sold it and kinda wish I hadn't)

The PO455 may or may not be related to filling up with the engine running. The self-test for PO455 is performed (initiated by the ME-SFI control unit OR Diagnostic Module) once per trip. It takes only seconds for this self-test to be performed. If you happen to be filling the tank while this test is taking place you'll set the fault code. If the PO455 code is set, the control unit will not perform the self-test for PO442 (small leak). If the vehicle "passes" the PO455 test, it immediately begins the PO442 test. Once these tests are performed and passed, you can drive without the fuel cap and not set these codes. The next round of testing begins with the next driving cycle. There are certain criteria that must be met in order for the self-tests to be performed. On earlier DM (diagnostic module) equipped vehicles the fuel level had to be between 1/4 -3/4. The vehicle speed had to be 0mph, and the engine had to be running for at least sixteen minutes (approx). As far as the duty cycle is concerned it's about 8% during EVAP system self-testing, and varies during normal tank vapor purging, depending on operating conditions. I could go on forever about EVAP system testing. I've seen SEVERAL different scenarios (including faulty/loose fuel caps) that cause the PO442 and PO455 codes.