M-Class (W163) Produced 1998-2005: ML 230, ML 320, ML 350, ML 400 CDI, ML 430, ML 500, ML 270 CDI

Broken coolant sensor.....

Old Aug 26, 2025 | 07:13 PM
  #1  
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CE3
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From: Erie, co.
2001—-ml55
Broken coolant sensor.....

Hi folks,
Not sure if this is the appropriate forum since it's kind of generic to 113 engines. Let me know.
After almost five years of trouble free performance, I have a significant issue......My ML55 (01) stalled twice, in town. Wouldn't restart until it cooled for five minutes. Then fine all the way home.
I went to the same place each time with identical behavior. So I idled it in the garage when it got to the same temp as in town 165f it stalled again. Seems to stall at the same temp each time.
Replaced the crank and cam sensors. Same issue. So, I looked to the coolant temp sensor. tried to wiggle it out and broke the plastic....flush with the engine.
Sorry to belabor this, but....anyone have any experience with a solution...?
P.S. if the post would be better off in a more general forum please let me know.
TIA all.....
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Old Sep 16, 2025 | 01:28 PM
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Originally Posted by CE3
Hi folks,
Not sure if this is the appropriate forum since it's kind of generic to 113 engines. Let me know.
After almost five years of trouble free performance, I have a significant issue......My ML55 (01) stalled twice, in town. Wouldn't restart until it cooled for five minutes. Then fine all the way home.
I went to the same place each time with identical behavior. So I idled it in the garage when it got to the same temp as in town 165f it stalled again. Seems to stall at the same temp each time.
Replaced the crank and cam sensors. Same issue. So, I looked to the coolant temp sensor. tried to wiggle it out and broke the plastic....flush with the engine.
Sorry to belabor this, but....anyone have any experience with a solution...?
P.S. if the post would be better off in a more general forum please let me know.
TIA all.....
Oh Boy.  Yes I just had this happen, and it’s difficult to get it out.  Basically, I used some dental pics to essentially remove all the remaining plastic.  What is then left is essentially the Outer Shell.  In my case, it was for lack of a better word, fused to the block.  Again I used the dental pics to carefully pry the edge around the casing and the block.  This more or less mushrooms the casing enough to allow gentle pulls with needle nose pliers alternating from side to side, top bottom et
Oh Boy. Yes I just had this happen, and it’s difficult to get it out. Basically, I used some dental pics to essentially remove all the remaining plastic. What is then left is essentially the Outer Shell. In my case, it was for lack of a better word, fused to the block. Again I used the dental pics to carefully pry the edge around the casing and the block. This more or less mushrooms the casing enough to allow gentle pulls with needle nose pliers alternating from side to side, top bottom et
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Old Sep 17, 2025 | 01:44 PM
  #3  
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From: Erie, co.
2001—-ml55
Hey Casman,
Thank you for the reply. If you don't mind.... were you prying against the bore with your picks ? I'm paranoid about scratches. If I'm not mistaken, the o ring / seal gets compressed when the clip is installed, so the bore may not be that critical. Obviously, I haven't seen the layout inside since mine is still in there... Did your sensor seal correctly...? In retrospect, do you see any other alternative means of extraction ? I'm also too paranoid to use an ez out, for the same reason.
Thanks again....
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Old Sep 17, 2025 | 03:06 PM
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The pic would go straight in, then I’d pull it upward. Of course you’d want to be cautious, but once in, the upward pull isn’t a concern. Do not use or try an EZ out. I lightly sanded the bore after I got the old one out. There are reported issues with installing some aftermarket replacements specifically related to the size of the O-Ring. Just make sure you get it all the way in before pushing the retaining clip in. If you think it’s in, and when looking straight down you see any part of the outer casing, it’s likely not all the way in. Obviously if it leaks afterwards you’ll know. Good luck.
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Old Sep 17, 2025 | 03:28 PM
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Once I got some separation, this tool worked very well.
Once I got some separation, this tool worked very well.
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Old Sep 19, 2025 | 03:24 PM
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From: Erie, co.
2001—-ml55
Thanks again Casman.I didn't see your post with the tool. I have some lightweight O ring picks. Hopefully they wont bend too much. I was thinking about modifying a punch or drift to be a little stouter...As you can see I'm trying to sneak up on it.....
Cheers

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Old Sep 19, 2025 | 08:13 PM
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You’re getting it. Next what I did was grab it with some needle nose pliers, and pull on it. Alternating side to side, top and bottom, anywhere you can get a grip. It’s only fused around the bore. After awhile, it will jar loose. You got this.
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