After losing most of my spare time over the last several weeks, I was able to track down the source of the weird climate controls issue with the Benz. As you may know, it started acting poorly last Summer when we drove to Lake Shasta for some fun in the sun. After a week of babying the car, it limped home. I replaced fuel filters, changed the oil, changed the air filer... nothing. I changed the fuel tank screen... little change, but no big kick. I cleaned the "banjo bolts" to no avail. That was all last Fall/Winter. We discovered that by playing with the climate controls, we could turn on the turbo. Well, kinda. So, for 6 months we drove the car with the kids in the back shouting "turn on the boost". Funny stuff, but harrowing for the driver when the boost switches didn't kick it up.
kill the button
The climate controls, like too many of the systems in the Mercedes, are driven by vacuum. When it works, its very slick. You push a button to change how you want the air toflow and the little doors inside the system slowly open or shut, gently changing the air routing to your liking. Its pretty cool when you push the defrost button and the floor vents slowly turn off while the windscreen vents slowly open. That coolness disappears when it doesn't work right, and you're just praying for the car to speed up. So, I removed the vacuum signal to the climate controls before I did anything else. Unfortunately, this removed the massive vacuum drain that "turned on the boost", so we now had a car that would barely break 45mph... ever.
the saga
So, I started spending every evening and weekend trying to get it running. First, I did a valve adjustment and changed all the filters. That didn't do anything. Then, I replaced all the boost-related tubing and found that the overboost protection valve was bad. Replaced that. Still no difference. Then, on a whim after reading about the "evils of the EGR", I removed the vacuum signal from the EGR. I figured maybe it was stuck open or something and it was gumming up everything. Maybe by removing that little door, I'd see some of the boost come back. Wrong. Suddenly, ALL of my boost came back. It was like driving a rocket! I felt the back of the seat pushing me forward like my old Camaro used to.
It seems the diaphram in the EGR went bad, and all of my vacuum was disappearing through that hole. You see, whenever the engine moves into a semi-throttle position, the EGR is supposed to open, letting in exhaust into the intake to improve emissions. When that vacuum signal was interrupted by my leaky climate control system, the boost would kick on. Now that it has been resolved, the Benz has been filled with B99, the keys returned to my wife, and I get some time back to work on Hapy.
Of course, first I have to clean the garage. Hopefully, the next post will be about dropping the transaxle to test-fit the adapter plate, clutch/pressure plate and engine. My new goal is to have the engine physically attached to the bus before the end of Summer / start of rainy season so I can roll the whole thing into the garage for Winter work.
Thanks for reading,
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