Reality Strikes

As optimistic as my last few posts were, there just had to be a reality check.  Unfortunately, it came in the form of a coolant leak on Monday, so the trip to the mountain for MLK Day was scrapped.  I'll explain that today.  I haven't gotten around to looking at the problem, but I have a theory.  I'll hit that at the end.  First, a quick snow update from Saturday and the state of C's concussion.

Saturday Sliding

looking up the Multipor lift

The 6 of us (Boo plus boys in one car, me plus my boys in another) hit Mt. Hood Ski Bowl on Saturday for some afternoon and night skiing.  C, of course, couldn't slide because of his recent concussion.  He spent the day in the lodge with Boo's younger son (K2) playing on a laptop, playing chess and by the end of the day, making a snow-fort outside the lodge.  C's concussion symptoms are completely gone and he's back to his old self again.  The snow on Saturday was probably the best I'd seen all season.  Fluffy, yet quick, so you could get some good speed going, but if you took a spill, you had a nice soft powdery landing.  The lifts and slopes were not that busy.  In fact, look at this picture.  There was no one on this lift except us.  Nothing but empty chairs extending into the falling snow.  Even the run under the chairs was empty.
The cafe and Beer Stube were busy, though, because of the NFL playoffs.  I found that a little amusing, actually: drive 2 hours from home through chain-required conditions to watch a football game on tv.  I admit I watched the end of the Saints-49ers game while having a pint, but I spent the rest of the day and night on the slopes, eating up that powder until my legs couldn't take any more.  It was fantastic.  I'll be up there again this next weekend.  Maybe I can get the bus fixed in time... which leads me to the reality check....

My Outlet Flange History
If you've been reading this blog a while, you'll remember the troubles I've had with the coolant outlet flange on the front (pointing towards the front of the bus is "front") of the engine.  This flange attaches to the cylinder head where the valves live and allows for the passage of coolant from the engine out to the heater core, the radiator and the coolant bottle.  There's also a little coolant temperature sensor in there that connects to the engine harness that I've had all my troubles with.  I don't recall how much I complained about the difficulty in getting the coolant sensor in-place and the harness clicked into it.  It was a real PITA.

Flange Drives Tank Design
This area at the front of the engine is also the cause of the modification to the fuel tank.  The flange sits just above the bellhousing where it connects to the bus frame and it juts into the space where the fuel tank is.  So, getting your hands in there for maintenance can be challenging.

Flange Placement

sensor for ALH TDI engine

Last, the way the coolant sensor is set in place in the flange is a bit strange.  The sensor is about an inch long with the 4-prong plug at one end and a bronze post at the other.  The bronze post extends into the passing coolant, collecting temperature readings.  Between those 2 ends is where the trouble lives.  First, an O-ring needs to be placed around the wider throat of the sensor as it sits against the opening in the flange.  Then, the sensor is held tightly in place while a "U"-shaped plastic holder (U-clip) is set into the slots in the flange.  Getting all of this to work is much easier when the TDI engine is in its more native placement.  In my bus, this 3-handed job is performed while hanging over the top of the engine with your hands slipped between the engine and the fuel tank.

Leaks
When I swapped out the original harness for the borrowed one, I had challenges getting the everything right.  The coolant sensor was a real bear.  I had leaks.  I broke a U-clip, lost another one.  Lost a washer.  Then lost another one.  Finally, I got it all together, and I was able to drive around eventually.  When I swapped my original harness back in, I had some challenges getting the harness to reach properly.  I didn't really think about what the impediment was, I just worked it and worked it until I had enough cable to make it, and then clicked it together.  My test drive seemed fine, but I ended up low on coolant.  Later, there was what looked like water on my garage floor, but I chalked it up to rain.  Once I saw the puddle form under the bus at the gas station, though, I knew there was a leak, and the ski trip was off.

Cause Theory
What I didn't think about was the stress I placed on the sensor trying to get the cable to reach.  I believe that effort affected the sensor such that the U-clip no longer is holding the sensor flush against the flange.  I think the stress of the cable effectively pulled the sensor out enough to allow coolant to escape.  The sensor location is the epicenter of the leak, so this theory does seem reasonable.

I'll be digging into this tomorrow night after work (and a trip to the gym).  I hope the U-clip is undamaged.  I plan to remove the sensor, re-seat it, re-clip it and test for leaks.  I need to re-route the harness to eliminate the stress as well.  I wish I had a trip report instead of another "guess what I found" post, but that's what happens on this adventure.  Thanks for following along...