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Discussion Starter #1
1998 E320 just hitting 150k miles gauge was steady just above 80oC.

On highway, thought I smelled antifreeze enough that when I got off exit, looked under car at lite to see if I was leaking. There is no leak and there is no antifreeze smell. I don't know if what i smelled was real or in my head.............

I'm now noticing temp gauge much closer to 100oC both on and off hway and slightly rough idle (also, could be in my head). It hasn't really overheated, though I haven't pushed it. I changed water pump about 5000 miles ago.

I can change coolant and thermostat. I need to ask best way to check fans (but it is higher even on highway), and I need to ask (don't want to hear it but)if it might be symtomatic of bad head gasket.

PS I have a vacuum leak setting off P0170 code. Having a little trouble finding it. It comes and goes; I mention it, but can't imagine it is connected to temperature

Thx
 

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Dangerous "overheating" would be red zone, but so far you have been able to avoid this.

Preemptive, plan on a thermostat change now, but more importantly you need to take a strong flashlight and from under the car take a hard look at the water pump. Water pump failure will start with minor "weepafe" which in many cases evaporates on the hot block and/or blow back along the block due to airflow - however signs of that weepage should be visually apparent.

It's a blow out water pump failure that needs to be pre-diagnosed pre-emptively.
 

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Discussion Starter #4
Changed water pump 6 mos ago. checked it anyway and it is ok

Ordered a IR thermostat ($35 tooltopia- sounds like a great deal) Don't know exactly what I'm looking for but when I get it, hopefully I'll take a bunch of readings and get a clue.

Will change thermostat hopefully tonight. Drove it yesterday, and city (going by hash marks on gauge) is about 95 or 98, where hway is actually less, maybe 88. I don't anticipate a fan prob, because it is still higher on hway, but maybe should check anyway.

I know I'm not in red zone, but what makes me nervous is there was an exact moment in time where something changed. Also, I don't want to know what will happen when i get stuck in traffic.

Just because I'm paranoid, doesn't mean they're not out to get me
 

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Your P0170 could be the MAF, at least it was on mine. Do you see a CEL as I did? I'd start with the thermostat and if it's been over 3 years, fresh MB or Zerex coolant. To rule ouit head gasket you can always send an oil sample to a lab to look for antifreeze contamination.
 

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Discussion Starter #6
Thanks Musikmann

Actually I snapped the vacuum line from intake manifold to master cylinder when doing other work. I repaired it, but believe there is still a small leak there. That's when the code started, and it is intermittent. I want to change the line, but am having a real hard time getting piece out of intake manifold. I've been trying to just pull it out, but it is a tight spot and can't get a great grip on it. Everything around it is brittle. Can you tell me; does it just pull out; are there any tricks to getting it out??
Thx
 

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Discussion Starter #8
So it seems i just panicked when I smelled the anti-freeze; past experience was head gasket.

I promptly took all advice; got a thermometer; can't find any area over 90o. Changed thermostat, using xerex g-05. Nothing changed

Aux fans do not go on, which i should have checked first. I'm guessing there is a resistor somewhere, and possibly a switch. I ran 12 v directly to fan and got nothing. So I'm guessing fan needs to be replaced.

If I'm correct, what is procedure to get fan out?

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Aux fans are secondary way of cooling, but since you checked them bad, fix what you know and worry about potential other problems later.
If directly applied power is not moving the motor -most likely the brushes are gone. You can spend the time finding the replacement brushes, or buy new motor.
 
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