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Ted G.
Ted G., ASE Certified Technician
Category: Car
Satisfied Customers: 6091
Experience:  20 years auto repair experience, ASE Master Tech, Mechanical Failure consultant, Expert Witness
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CLK 320 Cab: I own a Mercedes Benz 2000 CLK 320 Cabriolet and

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I own a Mercedes Benz 2000 CLK 320 Cabriolet and have had a weird experience. Thursday evening, as I drove out of my sub-division I reached a traffic signal. It was HOT and raining at the time, and the light is timed for clearing the interstate. They, I-10, get about 2 - 3 minutes while our "green" is about 15 seconds. While waiting, my wife and I felt a jolt, like being hit in the rear. There was a big SUV behind us, and we tried to have it pull into a service station. No Luck, HA!! So, we got back in line, waiting for a "green." All of a sudden, another jolt, but I could see the small car behind us was 3 to 4 feet behind. At this point, we got the "green" to get on I-10. We drove 15 to 20 miles to our destination w/o any other problems. None of the other traffic signals required a VERY long wait, so we're thinking that caused our car's reaction. Any ideas??
Most likely what happened is the transmission went into low pressure mode at the light, this saves gas and is supposed to lower heat in the transmission. But if it sits long enough the heat can build up because there is very little fluid flow going on. At that point the temp sensor will signal the computer to boost pressure and flow in the trans. If that boost valve or solenoid was just a little sticky the pressure would spike up and it would bang, almost like you rev it in neutral and then drop it into gear. If it hasn't been done in a while I might service the trans, because it could have some debris in there making it sticky, but otherwise it was probably just a fluke of weather, time and temperature that caused a computer glitch and may never happen again.
Customer: replied 3 years ago.

Ted G. Is it safe to drive a few hundred miles? My service people can't perform the transmission clean-up until next week. And, we have a trip to check on parents, 97 & 96 in a nursing home. Probably 200 - 300 miles round trip.


Thanks for your answer.



Oh sure. What I'm recommending is preventative maintenance. Unless some other symptoms rear their ugly head the car should be fine indefinitely. All the best to the parents, 96 and 97 is pretty special!
Ted G. and 4 other Car Specialists are ready to help you
Customer: replied 3 years ago.

Ted G.


My service changed the transmission fluid and filter last Wednesday, but returning from a trip to take my Father-In-Lawn to the Doctor the problem occurred, again.


I notice that the car runs poorly just prior to the occurrence. I put it in "Neutral" and the idling becomes regular. Also, after the occurrence it seems to be idling better. I had asked that they check the idling, but they did NOT. Don't know if that gives more info.





Well that could mean the trans was trying to build pressure and pulled down the idle, but it could also mean the idle dropped out and that caused uneven pressures in the trans. To help them find this issue, pay attention and see if the idle seems rough at any time the trans bump does not occur. If it does it other times it could be causing the trans issue. If it only idles rough when the trans bumps then the trans is dragging down the engine, and that will give them an idea where to look.
Customer: replied 3 years ago.

Ted G.


Thanks, again for your input. This car has almost 270,000 miles so it could have more problems, HA! The service manager and the tech seem to think it relates to the worn engine mounts. The tech said one is almost metal on metal.



Mmm, Merc techs love selling motor mounts. Not that one wouldn't make it worse, but I think there is another problem. The bad news is you may have to wait till it's more frequent before they can find it. The good news is that if it's a sticking valve because of debris it could work it's way out and fix itself.
Customer: replied 3 years ago.



Again, thanks. Will try NOT to bother you again.





No bother, have a good day!