W251, R320 CDI, 2006 - Silversi

[Silversi]

Nonii.. Tervis lubas täna üle pika aja jälle auto kallal toimetada. Kuna tihendid veel ostmata ja aega oli ainult mõned tunnid siis otsustasin turbo üle kontrollida. Jama oli siis selles, et täiesti suvalisel hetkel läks auto mootor limp home seadesse. Väljendus see sedasi, et kui pöörded jõudsid 2000 ligidale hakkas auto 4 korda nõkutama- nagu piirajas oleks. Seejärel ladus käigud kõik üles ja see kestis kuni taaskäivitamiseni. Kusjuures ühtegi tuld armatuuris põlema ei läinud ja see muutis möödasõidud loteriiks. Mu pisike 8 eurone ELM veakoodilugeja näitas turboga seotud koodi. Eks see koodimajandus selline kahtlane ole aga vähemalt sain aimu kus viga otsida.

Keerasin siis turbol "electric turbo actuator" junni küljes ära ja avastasin, et seda on juba valesti remonditud. Sama aktuaator on peal tegelikult paljudel muudel markidel.. Jaguar, Ford, BMW, Audi.. Ühesõnaga hella teda toodab ja müüakse koos turboga. Nali ongi selles, et selle pisikese disainivea tõttu müüakse kliendile üldjuhul külma kõhuga uus turbo maha.

Ma kahjuks pilti enda masina konkreetsest detailist ei teinud aga kasutan siin teemas ühe Jaguari foorumi materjale. Minu autol oli siis samamoodi keegi varemalt parandanud ühendust plaadi ja klemmide vahel. Seal tekib külmjoode ja tänu sellele see kogu komejant käibki. Kuna see karp asub kohe turbo küljes, kus temperatuurid kõiguvad päris tihti, on originaal ühendus tehtud varuga. St. jäetud on soojuspaisumiseks ruumi. Kui sinna otse mingi pulk vahele joota, on see ainult aja küsimus kui probleem on tagasi. Tuleb kasutada õiget materjali ja jätta korralik aas nagu pildil näidatud. Igastahes kui kellegil on sarnane probleem, siis enne uue turbo ostu tuleks see karp ära kontrollida, kas ühendused on korralikud ja terved.. Lisaks veel seda, et om642 mootoril ei pea selle karbi eemaldamiseks turbot maha võtma.

Following removal of the Turbo Actuator/Control Unit from the car, after removal of the spring clips the metal body and black plastic casing were easily separated from one another. Inspection of the ceramic circuit board in the black plastic part of the casing immediately revealed the problem(s).

There are connection pads around the periphery of the ceramic circuit board that are connected by small wires to connection pads on the black plastic housing that have been spot welded to their respective pads.

These spot welded connections are prone to fatigue and break, usually at the point of the spot weld.

To repair the connection one might imagine that a new wire could be soldered in place, however the metallic plating on the connection pads cannot be soldered with standard tin/lead solder. Thankfully the connection pad appears to be copper underneath the top surface, copper of course can be soldered. So it is necessary to abrade the top surface of the metal pad away until copper is exposed which will take solder.

Now back to the problems exhibited on my circuit board.
It can be seen from the attached photos that the previous repair was an incredibly poor attempt at soldering and very hand-fisted. The solder joint was a “dry” joint, the solder had not flowed properly onto the wire. You can see that the solder is “dull” instead of shiny in appearance. Also it is clear that whoever had done the soldering was not very dexterous, much of the surrounding area has been burnt/melted with the soldering iron.
I have circled the problem area in the following 3 photos:-







This is a photo of the original repair - how not to do it - presumably someone had to pay good money to an outfit for this, shocking!





The dry solder joint would explain the intermittent problem of the MIL (coil light) and limp-home mode, which gradually became more and more frequent as the connection degraded, eventually becoming an open circuit. In addition to the dry joint, the connection immediately to the right of this was on the verge of breaking – I checked the strength/integrity of all the wire links and the one next the dry joint became detached with the very gentlest of pressure, so I removed and replaced both. The following image shows the pads having been cleaned up and abbraided to expose a solder-able surface. Be careful when rubbing down the pads on the ceramic circuit board, don't be brutal, the ceramic is brittle and can crack if mistreated. Also be careful about the swarf you produce when rubbing the pads down, make sure ALL swarf is removed.




The next image shows the new wire connections that I soldered on, I used a small gauge wire and formed it up into a loop to avoid having a short wire that would have very little compliance under vibration/thermal expansion/contraction.



Re-assembly of the two halves of the Turbo Actuator is just a case of putting the two halves back together again and putting the 6 spring clips back.

For those of you who are intrigued as to what is in the other half of the Turbo Actuator (the metal part) I have included a couple of photos. Basically it is a motor that drives a worm drive that causes the actuator arm to rotate. There is a cream coloured wheel with a grey pattern on it (reminiscent of a radio-active symbol) that is part of a position sensor, the other part of the position sensor is the pretty Catherine-wheel type pattern on the ceramic circuit board.





A quick test drive yesterday followed by a 70 mile round trip to work today on the M3 today reveals that my handy-work has fixed the fault that was causing the MIL (coil light) to flash and lapsing into limp-home mode.

Hope this is of some benifit to others who are having similar trouble.