Replacing idler pulley and AC V-belt on W126 Mercedes M116 M117 V8 

Replacing components is a good thing and a great start, but what was the problem to begin with? Throwing parts at any problem can cause more issues. One thing you have to do now is make sure that the idle air mix is set correctly, the fuel pressure is set correctly, and that the idle air and throttle control system is set up correctly. Also, make sure that ignition timing is not an issue.

Ha, ha! Good point. It just sits there and does nothing other than spin around - that is why it is called an idler pulley. It is indeed only there to help tension the belt.

Yeah, these kinds of issues can drvie you mad.At idle neither visco or electric fans help much with coolant cooling. The cooling capacity of the radiator is massive and as long and the water pump and thermostat are okay the temp hovers around 80C in average climates. When did this issue start? Do you have the full vehicle and service history? I hope for your sake that no one ever used a radiator leak stop - that stuff has been known to block engine coolant passages. Have you inspected the water pump yet? The impeller can wear depending on how dirty the coolant is/was. Also, have you been able to verify that the coolant temp is actually that high? It would not be the first time for either gauge or sending unit to be off. It is a bit difficult to measure - I give you that. Finally, there is the reservoir cap. Is it ok and rated at "140"? Too low a system pressure lets the coolant boil sooner, too high a pressure usually causes for the radiator plastic end caps to crack. Viel Glück!

@@straybenzes Thanks for your response. Unfortunately I don't have that thorough of a service history so I can't quite tell my issue started about february this year. Mostly it's a "non issue" since i rarely take it out during rush hour when there's a lot of traffic. I haven't checked the water pump.. however I do have a spare water pump which I just haven't installed since the location is hard to get to Funnily enough, I did change the reservoir cap! but I forgot to mention it, now that you mentioned it being rated 140, i checked it and turns out it says 120 on it You think this would make that big of a difference? I guess the best course of action is to first replace the reservoir cap with a 140 one and see if that makes a difference before taking on the work to change the water pump - altho I don't know if the reservoir cap will make any difference at all Seems like it will either be the water pump or the reservoir cap. Don't know what else it could be Thannks for your response!

@@PirateNightsuN I agree with you. The cap is unlikely the root cause, but it is a good idea to install the correct one. All the best!

The symptoms you describe may be related to the EHA needing an adjustment. The EGA determines the fuel differential pressure of the KE Jetronic which mainly determines the fuel enrichment during acceleration. Usually the older the car gets the EHA internals aged and lean out that mixture and therefore the engines stalls under acceleration. I highly recommend using a fuel pressure gauge set as described in one of the two videos, That will also help determine what the main fuel pressure is and thus help establish if pumps and / or filter need attention first. Good luck. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Hs8w5zBxHvY.htmlsi=moVjVrry-dr2N2dA ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-wGPKINfu_Hs.htmlsi=WbdVf4LFvh3OxTzU

@@straybenzes Thank you very much for such a quick response. I will start by changing the pumps since they make strange noises and I have already bought them, perfect, I have just seen the two videos, I have understood how the EHA works. FANTASTIC!

That should be this one: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-rJ54IkT_ai0.htmlsi=ewx-QCre4h-8VByU&t=246 and there is a list shown for all older Benz cars right after it.

Oh wow, it sounds you have a few things to sort out with that one.

As you can see, Ralph, in this video clip, the dashboard lights do not work when he turns on the switch, what is the cause and how can I solve it, because no one has talked about this phenomenon!

Oh boy, that is quite the sound. Question: What model year is that car? Before assuming the worst, let's check the most obvious. And that is the relay itself. Did you happen to replace it with a new one? If this is an early 90s model I suspect that it can be the dreaded wiring insulation issue. Good luck!

@@straybenzes I apologize for the late reply. Well my car model is 92 class E200. The problem started about 3-4 months ago. I have never replaced the relay. When I remove fuse #5 it beeps.

@@W-124s This is very difficult to remote diagnose. So if I understand correctly, your instrument cluster lights are not working and when you remove fuse 5 the N10 combination relay starts to make that sound, correct? Start with the simple stuff. Are the light bulbs from the cluster in working order? If they are check the dimmer switch for the cluster. These have been known to cause issues. Check for broken wires and cracked solder joints. Check if you have voltage going to the bulbs with the main lights on. Be careful when doing this as you may cause a short and your wiring may go up in smoke. Have someone stand by at the battery to disconnect it quickly.

@@straybenzes Thank you, Ralph, but can you explain the methods of examination at this stage or in particular how is the method of diagnosis that you wrote to me and add some advice and thanks again