tmryan

Coolant level checked out ok.

any ideas??

Arrie

Check the thermostat.

tmryan

Arrie,

How do you check it?

Another dumb question since you suggested I check the radiator coolant level by taking off the top hose, what would make the water level low in the radiator low while the radiator overflow tank appears full? I checked it seemed ok, but the next time I get a spike I plan to recheck it once the car cools down. What you suggest makes sense--coolant level is critical.

The weather in the Northeast has turned cold/snowy I plan to recheck all the suggestions that you guys has offered. Always double check problems.

I will let you know the results.

Again I really appreciate you experience and suggestions. Diagnosing a car problem long distance is difficult.

Darel

This behaves to me, as mentioned, like low coolant. Your LEVEL might be fine but you have a bubble that has not been purged out of the system, and as it travels through the system the temperature spikes when the bubble of steam reaches the sensor.

I haven't looked it up, but is there a SPECIFIC, by-the-manual procedure for bleeding the cooling system? For example, I had a Jag XJ-S with the V12. These cars are notorious for overheating problems, mainly due to the fact that people wouldn't follow the book procedure for bleeding the system. For the Jag, it involved such gyrations as jacking up the left-front of the car so that the corner of the radiator was higher than the rest of the system, running the car until warm, cracking a bleeder screw on the top of the radiator and continuing to fill / run until a fountain of coolant came out of the bleeder (not jut spurts, if it's spurting you're not done yet). You ALWAYS need to make sure the heater valve is 100% open when topping up / bleeding any cooling system so you should at least have the system in manual with all temps set to high. Otherwise a bubble can get trapped behind even a partially opened valve. Again this is for a completely different car, but it's possible there is a "book procedure" that needs to be followed here. I've been wrenching on cars for 20+ years and this is behaving exactly like what happens when you haven't purged the system completely.

And again, your "level" could be completely fine and you would still "feel" flow in the hoses with this problem.

Good luck.

Arrie

Thank You!!!

tmryan

Once weather improves will rebleed and check system.

to my knowledge there is on book procedure the bleed the w212. Suposed to be self bleeding/purging. In spite of that have done the old school bleed- park car on a incline,-take cap off overflow, start car and let it reach operating temperature while squeezing upper hose to get air out of system.

you would think that since the thermostat was changer 18 months ago any air pockets would have worked themselves out of system. will recheck again.

thanks

100k Pat

I recently had an issue similar to this one my 2011 E350.For a few months I noticed that I would get a coolant temperature warning on my dash and my coolant temp guage would be around the 100 degree mark. It puzzled me as usually it occurs when I have my a/c running and once it does the a/c starts to blow hot air, but after a few seconds of turning it off my temperature would quickly return to normal operating temps around 80 degrees and a/c runs normal temperatures. Later it would happen at extremely random times while driving. I knew my car battery was toast and due for replacement as I'm a tech (not for mercedes though, so I'm definitely not anyone qualified to give advice towards mercedes automobiles) and tested the battery multiple times to find out that it failed the load tests, which was evident by me needing to jump my cars even after as little as 10 minutes with it on accessory mode. I also noticed that everytime the warning came on, my fan would also stop spinning. And as soon as I turned my car off, it would automatically turn on at maximum speed. As you probably guessed by now, changing the battery definitely fixed this issue for me. Went on a drive with the a/c the entire ride for about 40 minutes not a single coolant spike to be heard of. Hope this helps anyone still looking into this matter like me not too long ago!

CaliBenzDriver

Thank you for stopping by to post your good fix... we enjoy undoing gremlin setups on these cars.


Would you be interested in going the extra mile to fix your car? I think your new battery may be masking an underlying issue here.

There's a chance proper ALT power is not supplying the chassis... causing voltage spikes under load.
-- we can see you don't have yoyo swing
-- we can deal with main GNS Strap

What sort of machines are you familiar with?


> I wonder...
-- how the ECT on the block tells stories to ECU when toast-battery voltage is allowed to swing.
-- Is that a "case of bad ECU GND at cowl" ??



++++ Ok, me read whole thread from OP...
It seems there are couple things that may have been overlooked. Thanks everyone who contributed smarts because it gets substracted during the process of elimination. Everything had to be checked - It's focused team work!

As far as I can tell this defect is impacting cars across the land. Sometimes gremlins get misinterpreted during growth stage... until chaos is fully ripe for harvesting.

-- At this point I see A/C compressor as a common contributing trigger... big draw makes sensor read wild over OBDII. Nice, but trust Bosch for a sofistication.... I can almost bet sensor is not grounded by engine - Too simple.

More interesting nuggets:
-- Sensor data nearly matches ECU gauge:
sensor lies and ECU doctors gauge matches.

-- Temps can ride up/down quickly :
> this style of rodeo is electrical, not mechanical related!!

-- Healthy/toast Batt :
Toat battery allows glitches
Fresh battery prevents glitchings like a large cap.
> crappy ALT/ECU YOYO??


> To summarize the above clues...
I can guess there's a poor connection somewhere that when loaded down causes ECU to read ECT sensor incorrectly.

Preliminary top suspects in that order..:

1. Main Strap or
2. cowl GND or
3. ECT circuit floating GND Source
4. (or footwell or yoyo?)

Hope this helps sweeten these meyers

S-Prihadi

Agree with Cali, 100K Pat main alternator positive wires ( F32) and more so the grounds ( W10 and the undocumented W-TF ) need to be inspected and cleaned.
They are 12 years today and if car has winter salt experience , the undocumented W-TF ground wire will suffer, along with all other big demand Ws ( ground wires ) like the
fan and ABS which are hidden behind front fender well plastic liner.

I wonder how would ECM yoyo charging strategy behave when main battery was that weak ?
Our charging strategy is not as smart as BMW which seems to calculate battery capacity in real time, instead of only voltage.
Hence BMW need new battery to be registered/programmed with/to the ECM to let ECM know and revised its algo to suit new battery.

As these W212s are getting older, we will come across more and more problem with oxidized ground wires.
More so the the undocumented W-TF ground wire