So after seeing quite a bit of oil on the lower cover when I did my last oil change, I decided to chase down the leak. Pretty sure I found it when I noticed that the oil return hose coming from the oil separator (MB’s version of a PCV valve) had a substantial crack in it where it meets the dipstick tube.
New hose was only $13 at the local MB dealer, so that was a no-brainer. I’ll keep watch to see if I discover any more oil.
However, in the process of removing the oil separator, I managed to crack the brittle breather hose that goes from the valve cover to the oil separator. I epoxied it back together until the new part comes in later (another $20).
I recently replaced the Mass Air Flow (MAF) sensor with a new one. Next up are three parts that I hope will smooth out the idle. I have a camshaft position sensor, throttle position sensor, and new coil packs coming within the next few days. I’m hoping these will be the last parts I need for some time.
Rebuilding Hydraulic Cylinders
A while back I noticed my hard top was giving me issues. I soon noticed a rather large puddle of hydraulic fluid on the ground under the driver side rear fender. My trunk lid cylinder had blown. Now, if any of you know these cars, the hard tops are driven by a hydraulic pump and five (5) hydraulic cylinders: 2 that open and close the trunk lid, 2 that move the roof itself, and 1 that locks and unlocks the front of the roof. One of my trunk cylinders had leaked out and the seal was apparently bad.
I read a lot about rebuilding these cylinders. Most of it was good, with most people saying it was easy and that their repair was several years holding. Some cylinder rebuilders (professional ones) pretty much bad-mouthed the idea of using “inferior” o-rings in the cylinders rather than cup seals, per OEM design. I figured $20 o-ring kit wasn’t a huge expense, and I already had a bad cylinder, so I gave it a try.
First, taking apart the trunk lining can be a daunting task, but having done it a few times, I can pull it all apart in about 10 minutes. There are plenty of instructions online (Pelican Parts, youTube) on how to take it all apart. Second, removing the cylinder is a piece of cake. However, unless you want to completely pull all the hydraulic lines, I found it simpler to do the repair with the cylinder still attached to the lines. I just put a heavy towel over the edge of the car fender and did the work there. By the way, I broke two drill bits trying to get this done, so use fresh, sharp bits!
The cylinder is rebuilt by first drilling out the five dimples nearest the piston, then inching out the large bushing there. Removing the clamp end makes it simple to slide off the bushing. The hardest part is removing the old seal completely without scratching up the seat or the piston. You have to use extreme caution here, as one scratch will forever ruin the entire assembly. Carefully I removed all traces of the old seal, installed the o-ring, and re-installed the bushing. Now, some heavy-duty aircraft wire threaded through the holes assures the bushing will not come out again. Re-install the cylinder, re-install the trunk lining, and voila!
I did have to refill the pump, which is time-consuming as it is pretty much done with a baby syringe and some tubing about 50-80 mL at a time. I had lost quite a bit, so I had to fill a lot. My top works again, although coming back up is a bit slower than before, signaling the eventual death of my hydraulic pump. I expect I’ll have to drop the $150-$200 for another used pump in the not too distant future.