1992 600 sel came back from having a/c fixed ( not by MB)and started overheating- temp slowly rises (after abt 30 mins) to red under any conditions. Changed thermostat - was advised that v12 happy at 100-120 but new day burst a pipe in a hard to reach place. MB say water pump ok. Fans come on and stay on.
Then, when finishing repair of burst pipe, MB detected a new misfire. Changed f/s Air Mass Sensor. Result: "Limp home" mode (my analysis, MB call it misfire) / minimal power after 1-5 mins. Resets after ignition off. MB say no fault showing after they changed sensor, and who am I to question them. They want to change the wiring to the other Air Mass sensor because it looks melted but my amateur tests show good electrical isolation / connection to cap. I am not optimistic about that.
The Car runs well before it shuts down.
Could the overheating be causing the limp home mode or is it the result of faulty injection / ecu?
Before I have a new wiring loom fitted, I wonder if there is a trick cure or miracle answer which won't leave my car in the garage for another 3 weeks or cost as much as a luxury holiday. If not, any sensible input would be much appreciated.
After a run of 80 miles last Satuday with the air-con on (outside temp 30deg.)i turned the engine off and parked up.After approx 1 hour went to start the car('92 600sel)and it seemed like she was running on 6 cylinders!NO power whatso ever!When i managed to get airflow into the engine by means of the engine fan and some revs she picked back up on all 12 cylinders?The same happened the next morning but occured for 10mins whilst i was acctually driving the car!Spoke to my main stealers and they said it sounded like the ignition amplifier module going down,said that its a common fault on the 12's and they are £700+Ouch!Its going in for a diagnostic on Monday(16/08/04)so i will hopefully find out and MAYBE its the HT leads that are breaking down due to heat build up!.Fingers crossed,but £700+ for a module for a 12 year old car thats been out of production for 5+ years!Come on Mercedes.[:(][?]
At least you got to drive 80 miles and your car was only jiggered for 10 mins; you are the lucky one. I hope it is HT leads and at least you’ve got something to keep your spirits up until your diagnostic. My problem is definitely a major shut down- I can feel the accelerator pedal move as it happens and it wont go away until I switch off. Also, when it happens the snow chain light goes off or won’t go on so, in my case, I am pretty sure that the engine management is to blame. I hope, for your sake, that you don't have those symptoms.
I have spent the last 4 hours researching how our cars work and I didn’t read of any "ignition amplifier". I understand that the ignition system is linked to the fuel injection system(s) and that they are managed together. I understand that there is a separate control unit for each bank. They are programmed to retard the ignition when the temp reaches 203F- maybe that was your problem. Any way, there is a service bulletin from MB that says those units can store erroneous diagnostic data, so, in future, I am going to give critical consideration to whether or not I should replace expensive parts on the strength of what a diagnostic says. I don’t think dealers (in UK at least) know how this car works and just rely on what their computer tells them, which can be a load of rubbish. I am now convinced that my car will have stored a fault code for my problems (because it is supposed to) and that the garage somehow missed it. I am going to get someone else to retrieve the codes on Monday, which, at least, is a plan.
My opinion, as an unqualified person with a little knowledge, is that if one of the ignition control units was broken, your car would never run properly and that you are in the process of being ill-advised. Imagine how frustrated you will be if you spend £700 + (and ages without your car waiting for trivial parts) only to find that your car is still broken. If that happens more than once, you might start ranting, as have I. Good luck.
I know what you mean about MB diagnostics!Here in the UK they can get parts from Germany in 2-3 day's so thats an advantage over the USA.As i said my problem seems to be heat related BUT two days prior to the really bad runnind the black square plastic retaining clip on the throttle cable broke whilst i was over taking whilst going up hill.Now i managed to pull over and put a washer on it to get home!I also know that when the pedal went flat to the floor and the engine linkage went to the idle position causes to computers to miss-read and store an error code.MB say that you must never rev the engine from the engine bay linkage!Only use the accelerator pedal!So beware people!Anyway my car was showing my syptoms before this happens,it just seems worse after this?Fingers crossed for tomorrow. [xx(][;)]
Just back from the main stealers.Very bad news - it's the engine wiring loom,it's totally degraded and i've been very lucky not to have had a fire!Good news is the new one will be here tomorrow and it's only £328!As an electrical engineer i could not believe the state of the harness - basically all the wires are 'shot',i.e 5mm bare wire and 5-7mm insullation on ALL wires(it's just degraded and dropped off).To see if yours is OK just lift the black plastic strip off the center of the engine - it's very obvious if the looms seen better days![:0][xx(][:)]
My main dealer is in Scarborough N.Yorkshire.Part number is A140 540 47 05.Unfortunatly this HASN'T cured my fault!They can now see the problem as the old wiring loom was kicking lots of error codes up.What they can tell now is that the entire left bank of cylinders is shutting down.They can't tell as to what is causing it as yet - they've checked all obvious things like dis cap,rotor arm,plug leads,coil etc....all seem ok!At present there is no error codes stored so i'm running it for 4 days and then taking it back in for a diagnostics check.Maybe something will be logged by then!Fingers crossed.[xx(]Car is a '92 with 113k(miles) and full main dealer service history.
A MADMAN WITHOUT A CAR OVER THE BANK HOLIDAY WRITES
£300 plus vat rings a bell. That must be the temp gauge, aux fan sensor, cam solenoid x2 and engine management temp sensors x2 that go down the middle of the engine. In my car, which, of course, is still in the garage, the r/H air mass sensor (on the left of engine!) wires had also melted. A mere £60. I suspect (as a non expert) but I also ****ing well know that a fault there will cause more profound problems than in the £300 wires (because bad air mass data is treated as a more profound fault by the ecu s). Through all my troubles, I wondered whether it would be impertinent to mention to my garage the following, which I noted in my desperate search for an answer.:
1 The left bank intake system is on the right of the car and visa versa (so the diagnostic information described as relating to the right side comes from the parts on the left of the engine). I was most tempted to mention that when a new am sensor on the right of the engine (£300 I think) did n't help at all while the melted sensor wires were on the right.
2. A bad am sensor fault code (£300 plus) on some 1992 models can (say MB) be ignored.
3. As I understand it, diagnostic information has to be read from the l/h and r/h ecu's separately. As not many mercs (as I understand it) have separate ecus for each side of the engine, I wonder whether the mechanics know that. If it is possible to overlook that, it could explain why I was told that no fault was recorded when my ecu s detected a fault bad enough to justify limp mode. (Which I call dick for short, becuase its that much fun).
It might be arrogant of me to think that a main dealer is not perfectly aware of those things, but they are the sort of things that are easy to overlook (I imagine). I wish I had slipped them into the conversation.
That (once the leaks have been fixed) only leaves me with my overheating, the cause of which is still a mystery. I think it must be the water pump but none believes me.
I meant to say that I replaced the mass sensor on the right (called the left sensor)but had melted wires on the left.
Post Script
I ask, rhetorically, how it can be that a system that records tiny faults that a human might not even notice does not record a fault bad enough to shut down half the engine. THat has got to be a crock.
Linear Mode
