w124 running hot (120C) in traffic
 

1993 300E with 3.2 L M104

On very hot days (temp over 90F) the engine coolant reaches 115-120C when stuck in traffic. It's not 'boiling over' but comes close. When the car gets moving again the coolant temp returns to nomal range. The high coolant temp in traffic basically nulls the AC effectiveness and it becomes very hotinside :( I want this fixed!

Here's what I've done so far towards resolving the issue:

- Two new Aux Electric cooling fans (& check to make sure they come on correctly)
- New Fan Clutch
- New water pump & temostat
- This past week... a New Radiator and cooling system flush

None of these items has made the problem go away. The new radiator help the most but I'm still pushing 120C when idling for long periods of time.

Am I missing something or is the cooling sytem just undersized for operation in these very high tempatures?

PS
I had this problem long before my blower install, so I don't think that's it.

I would try running more water and less antifreeze and adding Redline water wetter. instead of 50/50, try 75/25 in the summer. change back to 50/50 when it gets cold. It could also be your radiator is partially clogged and needs to get rodded out or replaced.

Are you certain the auxiliary fans are working correctly? A/C pressure will activate the low speed stage, while coolant temperature activates the high speed stage. Check the fuse in the low speed relay.

I have also heard of the little auxilary water pump not working and causing the hot running. Was the cooling system bled for air after all these new parts? Air trapped in the cooling system can cause these high temps.

I just posted a very similar problem with my 1994 C280 with M104 engine.

http://www.peachparts.com/shopforum/showthread.php?t=128169

I noticed that my high-speed aux fans were coming on at irregular temperatures. Arthur Dalton suggested the culprit was the coolant temperature sensor and based on his recommendation I now have a new one. It was a $50 Canadian part, and about a 5 minute job with simple tools.

Based on what I've learned about the cooling system on this site, I'd be looking at aux fan operation. If the car cools down when you get moving again, then your coolant is clearly circulating properly. This should eliminate the water pump, radiator and thermostat as problem areas.

Jonathan

Problem Solved !!!!!
 

:) First thanks to everyone for their 2 cents! This Forum is a great tool because of folks like you.

After reading your feedback I was 99% certain my problem was the 2nd stage of the Aux cooling fans. Having never heard of the second stage I was convinced that was the problem.

I parked the car with the AC running...
- Stage one fans ran fine
Coolant Temp started to rise and then to my surprise...
- Stage two fans kicked in running hard

Just before I slamed the hood in disgust something about the passanger side Aux fan caught my eye.... The thing was running CCW !!! (Driver's side was correct CW) Appearantly when the passenger side Aux fan was replaced some bonehead plugged in the connector reverse. With the fan pulling instead of pushing air the system had no chance of catching up.

5 minutes to rewire the fan in the correct rotation and my problem is gone.

Now here's the hard part:
I'm the bonehead that last plugged in the fan connector.

Wow that was hard to say, but I'm just glad I'll be enjoying some nice AC on the way home today.

At least you can admit that you made the mistake :)

Know where good judgement comes from? Experience! Know where experience comes from? Bad judgement!. We have all mad bonehead mistakes. You are back in business and a bit more wise than when you started out. Sounds like a win to me.

does the m103 motor with the single fan have a two stage? as mine with a new water pump, thermosat, clutch and now aux fan, still in traffic heats up, I usually put in neutral and give it a lttle rpms

yes, it does.

hahahh... thats funny... my bonehead is the dealer!!!!!!! charged me 220 bucks to install my new radiator!!!! see that makes me mad!!! something as small as this should not happen at a factory authorized dealer!!!

As with all parts being installed on the vehicle it is wise to inspect them prior to installation and here’s why

1) M103 Water pump flange, three holes to mount pulley were not threaded-taught me the value of a thorough visual inspection

2) Spark plugs, performed a 60K service & the car ran like crap (misfired) discovered two spark plugs had broken porcelain insulators which would cover the center electrode once they were installed in the engine-taught me to shake the spark plugs before installing them if they rattle I look closer

3) Auxiliary fans, reverse wired from the factory-taught me to double check replacement item for proper operation

4) Power steering pump, threaded hole for high pressure line not threaded-refer back to line 1

These were the few experiences that helped me remold my thinking when it came to replacement parts. It also provided me the opportunity to be more focused on customer service. No, wait a minute. I think I learned real customer service by working the MB service wagon for 2+ years.

For me nothing was more frustrating then going on a road call for a flat tire only to discover the spare tire was flat. It was even more frustrating when the customer would stand there and say “I just had the car serviced last week by (name withheld for privacy) and paid over a thousand dollars, I wonder what other items were overlooked or neglected.”

WOW! Road side service was the real eye opener to customer service, Flat Spares taught me to focus……..hm ;)