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Old 12-02-2001, 10:21 AM
Posts: n/a
Unhappy Temp/Vacuum Switch 300SE

I need help identifying a broken vacuum switch on the head of my '89 300SE. It's located just to the left of the dipstick and looks like a temp switch screwed into the head with two vacuum nipples protruding from the top. The problem is one nipple is broken. I need to identify the part to order from Fastlane tomorrow am (along with other parts).

Also, I "jumpered" the two vacuum lines together bypassing the vacuum switch. Haven't started the car yet, came in to determine what systems I would be effecting.

I most likely broke the nipple removing the idle valve for cleaning. The car "hunts" while at idle (fluctuates 0-50 rpm). Also there is a noticeable hesitation from a standing stop, especially when cold. Very similar to a inoperative accelerator pump on a carburated car. Have replaced the O2 sensor, injectors, cap, rotor, and plugs. Took resistance readings on Water Temp Sensor, at 20C it was 204k ohms, at 80C it was 505 ohms.

By the way, while removing the idle valve for cleaning, I understand now the previous posts I've read regarding replacement of the idle valve hoses. I'm going to order those tomorrow and replace them but am not looking forward to doing it.

Also have a bearing noise from the belt guide pulley, but that's another story.

Any help on the vacuum switch would be appreciated. Thanks in advance.

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