The mercedes overheating flowchart - Mercedes-Benz Forum

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post #1 of 18 (permalink) Old 09-15-2016, 11:09 AM Thread Starter
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The mercedes overheating flowchart

Hello everyone, I usually post about in the W202 section, but since 1/3 posts on this forum are about overheating mercedes', I've made a flowchart! I tried to be as general as possible to include as many models as I could. Please, if you think you can improve something about it, post below! I'll gladly discuss and change it. If you are moderator for a particular section and like the flowchart, feel free to post it in a sticky in your section! I'm just trying to help the community out



Also feel free to download it and save it on your computer, just in case my online version ever gets deleted or something.

EDIT: Added coolant temp sensor check. To download in high-quality, right click it go to view image. Then you will see it in much higher quality.
mrboca and Deplore like this.

Last edited by Patman1; 09-15-2016 at 08:26 PM.
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post #2 of 18 (permalink) Old 09-15-2016, 03:20 PM
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Lol, that's applicable to most cars, not just MB.

Good graphic! I'll print it and post it in my office.

--1998 MB E300TD 285k
--1998 MB ML320 207k
--2004 Dodge Ram 5.7L 212k and holding (damn gas guzzler)
--2011 Suzuki DL650 44k
--1997 MB E320 161k. SOLD...loved that stupid car.
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post #3 of 18 (permalink) Old 09-15-2016, 06:25 PM
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Quote:
Originally Posted by Patman1 View Post
Hello everyone, I usually post about in the W202 section, but since 1/3 posts on this forum are about overheating mercedes', I've made a flowchart! I tried to be as general as possible to include as many models as I could. Please, if you think you can improve something about it, post below! I'll gladly discuss and change it. If you are moderator for a particular section and like the flowchart, feel free to post it in a sticky in your section! I'm just trying to help the community out



Also feel free to download it and save it on your computer, just in case my online version ever gets deleted or something
Great chart.. However maybe you could include how overheating is defined ? The maximum coolant temp I had seen was (as monitored at the clima control display) is around 93 deg. C and some are perfectly happy if it goes a bit over 100 from time to time. If I see 100 I would be concerned because something had changed ? My car has a visco fan and the airflow capacity will degrade over time, and the coolant temp will creep up at long idles. At what point I should decide to change it ?

I guess the coolant temp sensor over time can drift and give false readings, maybe it should be the part of the chart as most people use gauge readings to monitor overheating condition.
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post #4 of 18 (permalink) Old 09-15-2016, 07:58 PM Thread Starter
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Originally Posted by mrboca View Post
Great chart.. However maybe you could include how overheating is defined ? The maximum coolant temp I had seen was (as monitored at the clima control display) is around 93 deg. C and some are perfectly happy if it goes a bit over 100 from time to time. If I see 100 I would be concerned because something had changed ? My car has a visco fan and the airflow capacity will degrade over time, and the coolant temp will creep up at long idles. At what point I should decide to change it ?

I guess the coolant temp sensor over time can drift and give false readings, maybe it should be the part of the chart as most people use gauge readings to monitor overheating condition.
Those are actually fair points! I made my chart under the assumption that the coolant sensor (or in fact which ever method was used to determine coolant temperature) was giving an accurate reading. That should go near the top of the chart, I'll give it an edit. As for the temperature at which an overheat is considered, I'll leave that up to the user to determine, since it could be different on some engines.

EDIT: updated the chart to add coolant temp sensor. It's a good to have flow-chart, I feel like fixing an overheating issue is a gateway drug to DIYing your car.

Last edited by Patman1; 09-15-2016 at 08:29 PM.
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post #5 of 18 (permalink) Old 09-15-2016, 08:43 PM
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From this forum feedback, lot of overheating problems on MB come from using Zerex or other non-MB coolants.
Than I replaced a number of radiators in my life and all of them had internal build-ups that chocked the passage. Everything worked, just not worked enough.
Meaning the chart above might be just a tip of iceberg.

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post #6 of 18 (permalink) Old 09-15-2016, 09:03 PM Thread Starter
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I don't see how Zerex would cause a problem. Isn't it the factory stuff anyway? I'm pretty sure Mercedes doesn't actually make their own coolant. I could see how non-approved coolants could screw things over. Especially the generic green crap. Using any MB approved coolant will be good, same as using MB approved oils.

Fact checked myself, Zerex G05 and Zerex G48 have MB approval 325.0. The problem with those radiators could be that someone used tap water instead of distilled water. Coolants MUST be mixed with distilled water.

Last edited by Patman1; 09-15-2016 at 09:15 PM.
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post #7 of 18 (permalink) Old 09-15-2016, 11:01 PM
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You are correct about the Zerex G05 and G48. They are not the reason for failures if used in the correct models/years.
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post #8 of 18 (permalink) Old 09-16-2016, 09:06 AM
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Charts are useful on generic problems for people who have no education on the subject.
Using chart from Oldsmobile 20 lb manual -I was able to repair electronic module with my mechanical skills in the past, what made me very happy.
But chart will always be one person- more, or less educated opinion who at some point has to be wrap up with not much room for expansion.
Forum topic on other hand is "living thing" with direct feedback and creating "brainstorm" can deal with those rare problems that chart did not predict.
That is why we have members who after watching youtube, or other technical helps (charts), come to the forum with lot of additional questions.
We do have good sample how using charts on daily basis can affect human mind.
Noodles, who has great technical mind, can't step outside charts borders.
He could never understand how cooling system can work properly with engine fan removed and now he can't understand how inferior coolant can lead to system failure.
Would you Patman create a chart that can be continuously updated, that would be great thing.

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post #9 of 18 (permalink) Old 09-16-2016, 09:24 AM Thread Starter
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Originally Posted by Kajtek1 View Post
Charts are useful on generic problems for people who have no education on the subject.
Using chart from Oldsmobile 20 lb manual -I was able to repair electronic module with my mechanical skills in the past, what made me very happy.
But chart will always be one person- more, or less educated opinion who at some point has to be wrap up with not much room for expansion.
Forum topic on other hand is "living thing" with direct feedback and creating "brainstorm" can deal with those rare problems that chart did not predict.
That is why we have members who after watching youtube, or other technical helps (charts), come to the forum with lot of additional questions.
We do have good sample how using charts on daily basis can affect human mind.
Noodles, who has great technical mind, can't step outside charts borders.
He could never understand how cooling system can work properly with engine fan removed and now he can't understand how inferior coolant can lead to system failure.
Would you Patman create a chart that can be continuously updated, that would be great thing.
You bring an excellent point there. The forum is definitely an excellent place to brain storm. The point of the chart however, was to help those who are trying to DIY some of their work. Lots of posts here are about overheating, but the person is not sure where to start looking for the problem. This chart can help them get started. Most of the items on the top are pretty easy DIYs, and would be almost universal to every car. This even covers I'd say about 99% of all overheating cases. There can be more complex issues, which I why I added the bottom section for considering some of the following, but of course, including every possible explanation fr every overheating issue on any car could make for an impractically large chart. Again, this is mostly as a place to start, and I expect most issues to be resolved by the time they get to the thermostat on my chart. If however, there is a possible complex issue that is recurring on some cars, I'd be glad to update the chart to include it.
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post #10 of 18 (permalink) Old 09-16-2016, 09:36 AM
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Than again, your experience is different than mine.
That was pretty obvious in W124 section. Where after checking everything else, the owner would disclosure running on inferior coolant.
Bottom line, your chart might have good use on newer cars, where the problem is mechanical or electrical malfunction.
On aged cars, that we usually discuss in the sections I frequent - the most common problem is chemical build up and my first suggestion is get infra-red and read the radiator temperatures.
Meaning what you put as 7th on your priority ladder, would be the first step for me.
Just real-life variations.


Last edited by Kajtek1; 09-16-2016 at 10:59 AM.
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