Saturday, January 9, 2010
Visit with Technician
I dropped by the dealer earlier today to ask one of the technicians what kind of tool they use to fasten the special miniature band clamps used to secure the various connections in the windshield washer system. As I walked into the maintenance area I was pleasantly surprised to find my technician in his bay working. Since he's the lead in the shop he doesn't typically work weekends so I was naturally curious as to why he was spending one of his few days off screwing around with BMWs. It turned out he was doing a simple valve cover gasket replacement on his own car. I interrupted his work long enough to show him the crimp-type clamp and he kindly explained that contrary to their appearance the clamps are not designed to be permanently crimped like some of the other factory band clamps. He used a pair of diagonal cutters to pull the mating surfaces together until they snapped closed, then inserted a straight pick between the two mating surfaces and twisted it just enough to slide them sideways as required to open the clamp.
With that small task out of the way my attention naturally gravitated to a nearby bay in which two N52 blocks in various states of disassembly were located on engine stands. This was the first time I'd seen any BMW bottom end fully disassembled (close up, anyway) and took a few minutes to look around. When I asked what was wrong with the block my technician pointed out that BMW now uses a combination of aluminum and magnesium to construct their blocks to save weight. The magnesium wraps an inner core made of aluminum for compatibility with engine coolant. Problem is some of these engines have started to experience leaks in certain locations where the two metals meet. This led to a discussion on the current quality of BMW engines, to which my technician responded (paraphrased) that the E36 and E46 engines (M52 and M54) are more or less bullet proof due to their relative simplicity, but the newer N52 and N54 engines are showing signs of technology failures (like this manufacturing technology defect, turbo failures, etc.) that may affect the long term reliability of the engines. He was quick to point out that the block leak issue is very rare so it's likely but a blip in the data for BMW, but I took this as another sign that it sucks to be on the bleeding edge. I'll take the old and proven systems, thanks.
I also noticed that the new block had been fitted with new stock pistons equipped with sizeable valve reliefs. That prompted me to ask if the engine was still considered an "interference engine" and he responded in the affirmative. Lose that timing chain and you're going to bend valves. But fortunately -- at least for now -- BMW wisely continues to use a chain rather than a belt and the chains still appear to be designed to last the useful life of the engine (250K+ miles in the case of the M52 / M54). Of course, no one knows how long the new turbo motors will run as they haven't been around long enough. They may be able to meet the same lofty goals as the older engines in spite of BMW's "war on maintenance" (15K oil changes, "lifetime" fluids, etc.) but we won't know for many years.
Windshield Washer System Overhaul
I received the parts necessary to repair the leaking windshield washer jet this week and completed the repair today. I also managed to overhaul the system and through the installation of a new thermostatic switch, fluid pump and hose. The temperature was hovering in the 20's by the time I got out to the garage so I fired up the kerosene heater and got to work. I'm not sure if this work warrants a DIY but if it does I'll post it later. In the interim I'll simply point out what I learned.
I determined that the leak in passenger side jet was due to metal corrosion rather than the heating elements. This jives with my earlier findings in that both nozzles appeared to melt the snow I placed over them. I did not discover the cause of the leak until I disassembled the old jets. The jet is in fact two pieces: an inner metal section to which the heating elements are connected and an external plastic shell that contains the part of the jet visible from the top of the hood including the two small jets that direct fluid to specific areas of the windshield. The inner section contains a single orifice that protrudes beyond its top face by about 1/8". This raised orifice fits into a corresponding cup of the same depth in the outer shell. Metal corrosion caused erosion of the face of the inner jet which resulted in a loose fit (thus a leak) between the interior jet and the external shell. Since the interface between the two sections is also responsible for heat transfer to the outer jets I now know why the leaking jet seemed to take longer to melt the snow.
While I didn't notice any operational problems with the driver's side jet I replaced it along with the leaking jet and noticed a much stronger and finer stream of washer fluid exiting the new jets. Substantial corrosion was found in the driver's side (working) jet but it obviously hadn't progressed as far as in the leaking jet. This means the driver's jet was likely to fail at some point in the near future so I made the right call to replace both jets. I imagine this is quite typical for these parts so in my opinion they should be replaced in pairs.
The fluid flows from the fluid pump through a single line to a Y fitting. The outputs of the Y fitting go to each jet. Since the washer fluid bottle and pump are on the right side of the car the passenger jet is connected through a small 4" section of hose and the driver's side is connected with a section that is slightly under three feet long. The piece I received with my parts order was 4 feet long so after cutting the necessary sections I was left with a spare piece about 8 inches long. I'm glad I replaced the hose because the old hose sections had hardened due to age and were not sealing well. I partially deformed the Y fitting during disassembly (the stressed area is recognized by its milky-white appearance in the picture) so I'm also glad I bought extras of that part as well.
Contrary to what the ETK (parts book) implied, no check valves are used in this system so I wasted a few dollars on those parts. Unfortunate, but unavoidable, as I had no idea whether the valves were hidden somewhere and wasn't about to disassemble everything earlier without the needed parts on hand. This isn't the first time this has happened and it won't be the last.
The new fluid pump is noticeably quieter than the original pump but that's about the only operational difference. I could have easily avoided replacement of the pump but I decided to file this under "preventative maintenance". I replaced the thermostatic switch for the same reason. Imagine spending $70+ on new nozzles only to have the switch fail and the nozzles freeze and crack. Replacement of the switch required removal of the passenger side protective panel under the bumper cover. No jacking of the front end was required to facilitiate access to it.
I found the special band clamps to be a bit temperamental. Some persuasion with the flat side of a pair of lineman's pliers were needed to bend the outer band down so it would grab onto the inner band sufficiently. I was careful doing this so as to not damage the brittle plastic fittings.
The last snafu of the day came when I attempted to replace the underhood insulation fasteners with the new parts: they didn't fit into the corresponding holes in the hood. I salvaged enough of the old fasteners to secure the insulation for the time being but I'm planning to bring the correct part to my local dealer and order a new set from them.
The job took about three hours of my day but that had a lot to do with my lack of familiarity with the various parts, my lack of interest in moving fast in the cold weather, and chatting with my brother. I estimate I could do the job again in an hour and a half. However, I think the job would be worth 2 hours of labor from the dealer simply because replacement of each item would likely add up to more than that due to book labor charges. So I'll call it two hours of labor saved or $256.
Mileage: 187050, Parts $157, Labor Saved: $256
Saturday, January 16, 2010
Aux Fan Runs Continuously (High Speed Relay Failure)
With the drive home completed for yet another day I stopped at the end of my driveway to pick up the mail. As I got out of the car I realized that the aux fan was running -- at high RPM, no less. Given that the outside air temperature was a balmy 26F, the coolant temperature gauge was pointing at the usual 12 o'clock position and I didn't have the air conditioning on (not out of the question in winter given that it is sometimes necessary for defogging the windshield, by the way), my instinct diagnosed the problem in an instant. One of the relays (likely the one that switches the fan to high speed) was fused closed. I'd read of this happening to other E36's and recalled that this failure mode would cause the fan to continue to run even with the ignition off (position 0), a condition decidedly unfriendly to the battery. Time to test that theory.
I pulled up to the house, turned off the key and opened the door with an odd sense of anticipation. Sure enough, the fan was still running. I got out, closed the door, and walked around to the front of the now dark vehicle with the fan eerily running with a mind of it's own. I stood there for a few moments contemplating the ghost in the machine before I set about to come up with a temporary workaround so I could sleep peacefully knowing I wouldn't come out to a dead battery the next morning.
I opened the hood and then pulled the cover off the fuse box. I began by tapping on what I believed was the low and high speed fan relays in an effort to free the contacts in case they needed a little persuasion. It had been a while since I'd messed with the low speed relay and while the fuses are labeled on the inside of the fuse box cover the relays are not so I wasn't sure I was hitting the right relays. When that didn't have any effect I decided to pull the 30A fuse for the aux fan (#41). Not surprisingly, with its supply of electrons cut off, the fan spun down to a halt. Problem solved -- for now.
While I waited for the wheat crust for my world-famous deep dish pizza recipe to rise I spent a half hour reading the schematics in the Bentley manual in an effort to further troubleshoot the problem. It didn't take me long to confirm that the aux fan receives power from the "hot at all times" bus through the high speed relay which in its depowered position delivers power to the normal speed relay. The normal speed relay contacts are normally open and break the path to ground (and thus keep the fan turned off) until the relay's coil is energized. And as it turns out, the coil of each relay is powered from the "hot in run and start" bus, so I quickly concluded that given how the fan was running in high speed with no power to either coil the high speed relay was faulty. The schematic also indicated I could have pulled the connectors associated with the refrigerant pressure switch or engine coolant temperature switch to rule those out but based on the symptoms I remained convinced that the relay was the cause.
Schematic for the aux fan (1998 E36)
Location of the fan relays (1998 E36)
The next morning I went out to the car and it started without any problems. I drove to the dealer to get some information from my technician and he was gracious enough to pull the wiring and fuse box layout diagrams for my specific model year from his archives and confirm the locations of the low and high speed relays. I pulled each relay and wrote down two part numbers to give to the parts department:
Normal Speed Relay (Yellow Case) - 61361389105
High Speed Relay (Purple Case) - 61361388911
While BMW is famous for supporting their cars far longer than most manufacturers, the one down side to maintaining a BMW older than 10 years or so is that the dealers tend to not stock parts for it and so it was in this case: I had to special order both relays. Cost for the high speed relay was $20 and the normal speed a mere $10 so given the critical nature of these parts, particularly in the upcoming summer months, I decided to replace both. They should be here in a few days. In the meantime, the car will run just fine with the aux fan fuse removed. All I have to do is treat this as an aux fan failure and keep the car moving if I decide to use the A/C to defog the windshield. I've never seen the aux fan run to address a coolant temperature problem in the winter so an overheat is of little concern.
Mileage: 187275, Parts: $40
Sunday, January 24, 2010
Replaced Aux Fan Relays
The parts required to fix the aux fan came in this week and finally managed to get to the dealer to pick them up. This morning just before I ran an errand I installed both the normal and high speed relays with no issues.
To test the system I reinstalled the 30A aux fan fuse and verified that the fan was not running with the key off. Then I started the engine, turned the HVAC temperature controls to full cold (60F), turned on the compressor (snowflake button) and verified that the fan was running (meaning, I had reconnected power to it successfully and the fan wasn't merely dead all the time now). I noticed the fan and compressor stayed off most of the time but that was likely because the 45F outside air temperature was below the HVAC setting. I could have pulled the coolant sensor connector and shorted the center pin to each of the other pins to prove the fan ran in both speeds but I figured that this was sufficient since I knew the fan worked -- I just needed to verify it no longer ran continuously.
As usual I conducted a post mortem on both relays (shown in the picture). I first inspected the high speed relay (purple body) and found the contacts in remarkably good shape, although they did have a bit of oxidation and one contact (used in the depowered state) showed a small amount of pitting. Overall, it looked like it was in relatively good shape so the reason for the failure is not obvious to me.
The normal speed relay was another story, however. With a mere 56K miles in service the contacts were in a condition similar to the last time I replaced it. I have always known that the normal speed relay takes most of the abuse and that explains why I specified a replacement interval for it in my maintenance schedule worksheet, but based on the condition of this relay I have decided to reduce the replacement interval from 72K to 54K to better reflect the wear pattern of this critical part. I don't like throwing money at the car even in the context of preventative maintenance but given the failure mode in this case I think it makes sense to be proactive.