What is considered NORMAL W124 engine temps? - PeachParts Mercedes-Benz Forum

G-Benz · #1 07-23-2001, 08:38 AM

I have heard that the article in the STAR about cooling was VERY informative...unfortunately, I am not a member (maybe someone here will post the article). I checked my manual and my Haynes manual, and there is nothing in there about when to be concerned about the reading on the temp gauge.

It's been hot here in Texas (I think it got to 105 on Sunday). My 93 300E with 107K miles shows the temps around 85 - 87 when the outside temperature is around 75 - 95. This is with stop-and-go driving around town with the A/C on. If I sit at a light for a LONG time, then it creeps up to 90.

Trouble is, when it's REAL hot (over 100 outside), as long as I'm driving, everything remains normal, but if I make a stop, shut off the engine, and come back a few minutes later, the needle climbs to 105, and by then, I can't get things to cool down by driving, unless I shut off the A/C. Sometimes I see a bit of coolant on the ground from the overflow.

By the time I get home and shut off the engine, I'll open the hood, and can pretty much bet that the expansion tank will overflow (and it has a couple of times).

The water pump was replaced half a year ago, and the radiator, about 3 months ago (thanks FastLane). Got the cooling system flushed and replaced with a mix of water and MB coolant by a trusted tech (don't know the concentration). I just replaced the thermostat and coolant tank cap last week for (cheap) insurance. No oil in the coolant, and no coolant in the oil.

My ML320 doesn't seem to mind the heat, and it's always reading around 85, no matter the outside conditions.

Am I seeing the first signs of an impending head gasket failure, or am I just a little too nervous?

Mike Murrell · #2 07-23-2001, 11:16 AM

I went through a similar situation recently with a 103 cooling system.

It turned out to be a leaking overflow tank. It's pressurized and because it was not holding pressure, it was leaking as it would if the cap were weak. It's also possible that your cap is bad in spite of it's recent replacement, or you "might" have air in the system. These are but a few of the possibilities.

G-Benz · #3 07-23-2001, 11:41 AM

I forgot to mention that I had the expansion tank replaced for just the situation you described, Mike. On searching some threads, I did see a few posts regarding "air" in the system. Things were fine up until the week after I had the system flushed. Can you get air in the system that way, and how do you evacuate the cooling system if air is detected?

Mike Murrell · #4 07-23-2001, 01:54 PM

G-Benz:

I may stand corrected, but I "think" your 300E and my 300SEL have the same engine - M103 - single overhead cam - 6 cyl.
If I'm wrong, what follows may not work in your case.

Looking ay my engine from the front of the car, one sees 2
14mm bolt heads on top of the cyl. head just to the left of the engine oil disptick. The M103 engine manual coolant section shows a picture of this area. In this book, you're told to remove the 14mm bolt closest to the front of the car and refill through here. In other posts here and at one in particular that was answered today by a pro(Randy Durrance), it's recommended that you refill through the top radiator hose in order to push out trapped air. The approach offered in the 103 engine manual has served me well.

If you do not have this manual or the CD-Rom, send me your emailid and I'll email you the coolant section on the CD-Rom when I get home tonight.

G-Benz · #5 07-23-2001, 02:35 PM

Thanks Mike! My e-mail ID is gvforstall@aol.com.

Mine is the 3.2L 6-cyl version.

The Haynes manual says to remove the temp sensor and refill from there. I never did find the darn sensor yet, and the picture in the book is of no help. So I will look for the bolts and go from there.

In the meantime, send me the info anyway. More is better when it comes to useful info...

joel · #6 07-24-2001, 02:55 AM

G-Benz:

before you do anything fancy, i think all of the
temperature you have stated are quite normal to
the given circumstances. just my opinion. cheers!!

pmizell · #7 07-24-2001, 03:11 AM

Here's the bolt that Mike speaks of:

When refilling your system with coolant, it says to remove this bolt and fill until it overflows here.

G'luck!

~~Paul

David C Klasse · #8 07-24-2001, 04:53 AM

G-Benz,
I can assure you that your temps are MORE than normal. My 95 M104 motor gets hotter temps than you 93 104.
I have been frustrated with this also. I have gone to a 20/80 mix of MB coolant and water, respectively, and added a bottle of WaterWetter.... but my temps seem higher than ever. I don't know what to do...! I have recently replaced the thermostat... and coolant, but that's about it. And I'm only in So CA! I live on the coast, so temps RARELY ever get above 85.

G-Benz · #9 07-24-2001, 11:16 AM

pmizell: thanks for the pic...unfortunately, I have the M104, so it doesn't do me any good.

David: I'm frustrated too! This morning, I added a couple of glasses of water to get the expansion tank level to the arrow. Drove to work (about 40 minutes, highway/city combo, speeds between 30 - 70 mph). Outside temp got to about 90 this morning, and I ran the A/C at full tilt during the last half of the trip.

Engine temp got to 100 by the time I arrived to work. I opened the hood to watch the inevitable...coolant, boiling over in the expansion tank.

There IS something wrong! I just don't know what!

Mike Murrell · #10 07-24-2001, 02:20 PM

Paul - nice picture of the head.

Taken another shot at this.

- Coolant cap - is it a 1.4 bar cap? This equates to 20
lbs. approx. They used to be 14-15lbs. Do you have a
1.4 bar cap? I know the cap is new, but....

- Air in the system remains a possibility.

- Is the radiator healthy?

- The T-stat has an air valve that must be positioned at
the highest point. Is it?

Check out the following posts. While they may not address issues in 104 motors, I think the basic ideas carry over to just about any car. Comments made by JeffSr, MBDoc; Benzmac
are especially worth considering.

http://www.peachparts.com/shopforum/showthread.php?threadid=6029

http://www.peachparts.com/shopforum/showthread.php?threadid=7231

DMITRY · #11 07-24-2001, 03:05 PM

One more thing to do is to clean the radiator. When I was instaling a new one in my car, while it was removed I took a hose and washed the A/C radiator ("Star article recomends that too). Bugs and dirt get in between the cells and clog the airflow. It actualy droped the tempreture down a litle.

G-Benz · #12 07-24-2001, 03:18 PM

The cap says 140 (although I didn't check the type of cap it replaced, but this is the third cap, replaced just to be on the safe side).

Forgot to check the thermostat orientation..I just popped it in. Might be the problem.

Radiator was replaced 3 months ago with the OEM Behr radiator from FastLane. Just recently flushed coolant 2 weeks ago.

Aux fans seem to kick on appropriately.

I can keep things cool enough under any condition while its hot outside (driving, stopped at lights, idling) if the A/C is OFF. Otherwise, with the A/C on, I need to be pushing air through the radiator via driving at 50+ mph.

I will pull the thermostat off tonight to check if its installed properly. Also gotta figure out how to get air out of the system if there might be an issue there.

G-Benz · #13 07-24-2001, 03:54 PM

I hear gurgling in the system after the engine is shut off (not including the sound of coolant dumping itself in the expansion tank)...is that a symptom of air in the system? If so, how does one go about removing air in an M104?

Also, a couple of times when things got hot enough to purge coolant out of the expansion tank, the upper hoses were collapsed when the engine cooled down. I had to relieve pressure by opening the cap. This doesn't look normal either...

[Edited by G-Benz on 07-24-2001 at 03:57 PM]

G-Benz · #14 07-25-2001, 09:13 AM

OK, I pulled the themostat cover off and verified that I had indeed installed it properly. Also starting to rule out air in the system, as the air valve in the thermostat should take care of that.

New theory though...everything fine when driving fast, so outside forced air cooling adequately at speed. Things are fine around town and sitting at stoplights if A/C off. Therefore A/C radiator heat is causing radiator to pull in hot air. This is a problem if the aux fans aren't coming on like they should.

Noticed the aux fans were running when I started the car and left it idling this morning, but it was (relatively) cool this morning (79) and A/C was on.

Everything was fine, normal temps until I got off the highway. Then engine temps creeped up to the 90's. Didn't want coolant boiling over again, so I shut off A/C. When I got to work, lifted hood and aux fans were NOT running at all. Pulled off lead from water pump (I guess it's the aux fan sensor switch) and fans ran, and engine immediately cooled to nominal temps.

Question is, what temp do the aux fans kick on, and did I guess the function of that sensor correctly. Could it be at fault, and how do I test?

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