Time for an update. After six years of driving this car I had relatively few issues and only twice was left at the roadside. First time was when the left rear air shock lost it height sensor and was undrivable, unbelievable how the car react when the shock is deflated, the car literally hop like crazy and even slow speed driving is impossible. Second time was recently after the heavy rains when I stopped at a shopping center and the battery drained in no time at all.
A few years ago Gavin pointed me to a accident damaged 760 at a scrapyard and it made sense to buy this car and use as a donor. This was one of the best decisions ever as I have saved loads of money and effort using spares from this car.
When the rear shock failed I ordered a new one from BMW and delivery took so long I got the donor car before the spare shock arrived. When I got the donor car I removed the rear shock and fitted to my car while I waited for the new shock to arrive. Once the new shock arrived I fitted the new shock but believe it or not the new shock did not last a year, exactly the same sensor failed and I fitted the donor shock again which is still fitted today.
The big advantage of having the donor car is to swap spares during fault finding. I might add that the car came without a key so I bought a matching set of key, DME's and CAS unit, fitted it to the donor car and I could start and drive the car to its parking spot, so engine and gearbox is still working.
When I got the donor car I swapped the rims for the original BMW rims getting rid of the low profile tires and could feel an noticeable difference in ride comfort.
I have used small bits and pieces of the donor to fix a few nagging issues, one was the lock pins in the doors that was rattling, turned out that my car was missing inserts around the pins. I also now have a full spare set of screws and bolts which is really handy, when I work on my car and miss a screw or bolt it is just a matter of stripping it from the donor.
One of the first times I really needed the spares of the donor car was when I had a very strange fault where certain functions of the car turned off randomly with the associated error codes. One of the error codes was gearbox related and I took the car to ZF for an opinion. At this stage the car was randomly making a squealing noise like when a fan belt slip, I knew it was not the belts as I had recently replaced all belts and tension pulleys. ZF was convinced the gearbox needed repairs but before I could decide to either use the donor gearbox or spend money on the repairs is turned out to be the two CIV air valves on the side of the engine, when the diaphragm tears the air leaking through the diaphragm produce this noise. Again I could use the donor spares to eliminate the gearbox repair. I must add that I will use spares like this to test a theory but like with the CIV valves, once I found that they were the culprits I did buy two new ones from BMW.
Eventually I took the car back to ZF for a gearbox oil change and to test the gearbox as I still had the random gearbox and other errors. ZF changed the oil, replaced the sump with the new oil filter but a few days later the errors was back. I started to read on the forums and somebody suggested that the slip rings on the steering wheel could cause this error. Back to the donor and I removed the sliprings for inspection, they were still in good shape. Another great benefit of the donor is that I can practice for instance removal of the airbag and steering wheel before I damage my car's
I removed my cars steering wheel and found the sliprings badly worn, definitely worth the effort to replace them.
Drove for a few days and the error returned, one of the strange symptoms was that it will disable the wipers, not nice when it was rainy season and I had to plan my trips carefully..
Long story short I started to notice a common component when I studied the wiring diagrams. Again I removed the suspected ZGM module from the donor and was very pleased when the errors never returned. One of the valuable lessons I learned during tracing these faults was to figure out a relation between all the errors and physical symptoms experienced. In hindsight it was pretty clear that all the symptoms like gearbox errors, wipers failing, indicator not working, radio buttons on the steering wheel not responding etc came through one common component. It turned out that if the gearbox module could not "read" the gear buttons on the steering wheel it turned on an error, same for the radio and all other functions coming from the steering wheel.
Once one start to trace an error code it is always wise to clear all errors and see how long it takes to appear again. Two errors which was present since I bought the car was the parking break and also the driver seat airbag warning. The forums pointed to a possible plastic gear failure in the handbrake module and I imported the steel gears for replacement. Again I removed the donor's handbrake module and it was still in good shape, on to my car and the gears was still in good shape, I replaced the plastic gear with the new steel gear anyway as it was due to fail sooner than later. When I removed my car's module I noticed the one cable was broken, removed the donor's cable and all was good.
For the seat error I bought a new mat sensor, removed the seat and replaced the sensor, this was a real difficult job to do as one has to remove all the clips from the padding, it was worth while in the end as this error was gone after the repair as well.
One of the more challenging repairs was to the interior heating system. Since I bought the car the heating was not working, as we had a trip planned to Clarence during winter I was eager to get the heating working. I replaced the three way water valve which was in a very poor state, the rubber seals inside the valve was perished. I also replaced the secondary water pump but had to leave for the trip without heating. when we returned I was determined to get to the bottom of this non heating as it is quiet important to work as you have to run the heater to bleed the air from the engine cooling system as well. After days of faultfinding I decided to reverse flush the water through the dual water heating radiators. I did took the donor's dash out to see how easy it was to replace the heating system but soon decided against it after I saw how much work it was. When I started to reverse flush the heater coils I noticed the flow was not what I expected so I persevered and eventually the flow increased till I noticed a steady flow, did this for both coils and all was good. Two years later and the heating system still work as advertised, no more frosted windshield during winter as well..
Recently I have also replaced a leaking oil seal on the alternator bracket, was not a to bad job, just work methodically and strip everything to get access..
Two days work all in all.
I mentioned the sudden battery drain earlier. After a very scary tow truck driver jump started the car in a parking basement I could drive the car home for investigation. All kind of errors were showing during the drive, gearbox errors, drive height, ABS, handbrake etc. Using my previous experience I studied the diagrams again and tried to figure out a common component, all joined at the ZGM. As this was a used component from the donor I suspected the ZGM failed again, I still had the old ZGM and replaced it for testing, no result, still the same, during the initial fault finding I could not detect all of this electronic modules using DIS. A day later all modules showed up, I cleared the errors and the car was driving faultless again. After the next heavy rain I started the car and all errors were back. Reading the forums I suspected a bus fault as all the units communicate on a common bus. This was a bit frustrating as DIS is useless once the bus failed as it can not see any of the units for fault finding. Turned out that there are two termination resistors in the bus wiring, one in front of the front wheel arch and one somewhere below the rear seat. I inspected the front resistor and tested it and found it to be in good condition and no corrosion as the forum suggested. Next I removed the rear seat in search of the second resistor. When I removed the rear seat I was surprised, or not, to find the area full of water, all wiring was submerged under the water. Even though I could not physically found the second resistor yet, the BMW TIS is useless with its descriptions and locations, I suspected this resistor is inside the wire loom that was flooded. I had no idea where the water came from but dried the water as best I could and a day later no more error codes. Needless to say after the next heavy down pour the errors were back and the area under the seats full of water again. reading the forums it indicated to two possibilities, either the sunroof seal leaking, or the sunroof drain pipe failure, and secondly the rear window seal failure. I have inspected the window rear seal and it is quite hard, so this need replacement in any case. The sunroof seal is hard as well but somehow I cannot see that much water passing it to cause this much leakage under the seats. I have removed all the panels inside the boot to inspect for any sign of water leakage but everything was bone dry. I have not yet found the two sunroof rear drain pipe outlets and this is my next challenge. In the mean time I have used PVC tape to tape the sunroof closed in order to eliminate one of the two leakage possibilities. It has not rained yet so I am still to determine or eliminate which direction to go next.
The car need to visit a panel beater again at some stage as somebody opened their car door against my door, opened is an understatement as I can only imagine the force to slam a door to get such a dent, and funny of all is my car was parked far from other cars but why is it that even if you park far somebody will park right next to you? Anyway, a garage door was closed scraping the front bumper, the car was reversed into a pole in the parking lot, none of my doing I might add...
One of the remaining things to fix on the car is to replace the rear door locking mechanism, this is disconnected at the moment as it cause the battery to drain if connected. This is a fairly expensive part and also a days work to strip the door and reassemble, might plan this during the spray touch up as they have to strip the doors anyway for spraying, ooh the only difference between my car and the donor car is that the donor does not have the comfort access, so I can not use the door lock from the donor.
Having said all this, yes it is an old car, approaching 15 years now and one can expect component failures from time to time, rubbers will start to perish and fail but if I look at alternatives with the same level of luxuries and pure driving pleasure I think all the money spend was worth while, no monthly installment, fairly reliable, all in all a good car, not a days regret since I bought it.
