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LCG -
On an 80F-90F day around town, the coupe's M104 runs between the 80-100C range as you've mentioned. Mostly around the 100C line with the A/C roaring on a 90F day. Sure, hit the 85F scale on the thumbwheel, (heater on high) and the temp needle drops fast. However, hit the mountain passes and were running way close to hot, hot for my taste. There's no cooling system headroom here at altitude.

P.S., Yes, yes. Running a 50/50 mix of M-B glycol and distilled H2O is the way to roll.

P.S.S., It's said,, neg -3% specific output (HP/TQ) for every 1,000Ft elevation above sea level. 8,200Ft elevation at our garage - neg 24% output yikes!

Cheers, M/S
You're not answering the question; whether or not you're using G05 or G48 in your system. You're just answering with "i'm using Mercedes glycol." OK, is that "Mercedes glycol" for a 2019 engine? Because it won't be the right one. So, once again, are you using G05 or G48?

Turn your heater on to maximum heat and highest fan speeds if your temps are approaching 120*F. If that doesn't lower the temps you can dilute your coolant mix to have more water in it. Water has better heat dissipation properties than coolant/ anti freeze. That worked for me in Los Angeles, where I drove to Phoenix regularly. Be careful to correct the mix for winter.

If that doesn't do it, you probably have leaves/ debris between the ac condenser and radiator, blocking your airflow. A cooling system in good nick shouldn't struggle to dissipate heat at high altitude. My 2.6 got over the passes just fine, albeit in 3rd gear. And I was hauling ass! Temps didn't get that high.
 

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Neanderthal -
All good ideas.

The time-honored "envoke the heater on high" has the desired effect immediately in our w124 coupe, and yes the MB coolant being used is the G-48 "Blue" flavored coolant.
Having both of the external electric fans/shroud removed in addition to the engine mounted clutch/fan assembly also removed, it seemed like a good time to disinfect the A/C condenser.
After a couple of Wurth specific cleanser applications, the condenser is ready to eat on.

This just in from the MB HQ technical office in Sandy Springs, GA . . .
1. Check compression.
2. Check for head gasket failure; exhaust and/or oil present in the coolant.
3. Check gauge and sender operation; resistance-voltage.
4. USA 124.052 / M104.992 does not include older w124 models oil filter/H2O/Oil
circuit heat exchanger core assemblies.

All good ideas to run to ground.

Cheer's M/S

Edit/delete
If that doesn't do it, you probably have leaves/ debris between the ac condenser and radiator, blocking your airflow. A cooling system in good nick shouldn't struggle to dissipate heat at high altitude. My 2.6 got over the passes just fine, albeit in 3rd gear. And I was hauling ass! Temps didn't get that high.
 

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Neanderthal -
All good ideas.

The time-honored "envoke the heater on high" has the desired effect immediately in our w124 coupe, and yes the MB coolant being used is the G-48 "Blue" flavored coolant.
Having both of the external electric fans/shroud removed in addition to the engine mounted clutch/fan assembly also removed, it seemed like a good time to disinfect the A/C condenser.
After a couple of Wurth specific cleanser applications, the condenser is ready to eat on.

This just in from the MB HQ technical office in Sandy Springs, GA . . .
1. Check compression.
2. Check for head gasket failure; exhaust and/or oil present in the coolant.
3. Check gauge and sender operation; resistance-voltage.
4. USA 124.052 / M104.992 does not include older w124 models oil filter/H2O/Oil
circuit heat exchanger core assemblies.

All good ideas to run to ground.

Cheer's M/S
You removed both the electric fans, engine driven fan and fan shrouds? I assume you did that clean out the space between the condenser and radiator, and that you reinstalled all the above.

The fact that turning on the heater immediately lowers the coolant temp is what would make me think the air is being blocked somehow. But if you already cleaned that out, ...

The 4th point from that response suggests that the coupes don't have the radiator with oil cooling. (Take a look at your radiator; right at the bottom, are there pipes/ hoses leading to/ from it? That's where the oil cooler is. Perhaps adding an oil cooler would help?)
Also there was a guy on peach parts who sold a doohickey that fooled the electric fans into turning on sooner. Perhaps you might want to look into that.
 

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Discussion Starter #24
Temp sensor

Now when I come to think about it... since the temp goes down when I turn on the heat I do not think it is a faulty sensor. Since when it is normally (when fine not broke like now) running at 80-90 and I turn on the heat it doesnt change the engine temperature at all.
If the sensor was faulty and showed a too high value now, then it should not go down when I turn on the heat.
I think I have a blockage in the radiator, will do a flow test later this summer. Now I am (hopefully) of to vacation with my trustworth Peugeot with AC :)
 

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Transmission VS Engine oil cooler . . . Later w124 E-Class 320

The E-Class w124 uses a cross-flow class radiator, and as typical has an internal transmission oil cooler. This internal trans cooler is located inside of the end of the radiator, passenger side. Those pipes/hoses you've mentioned could be just that,, a transmission cooler's supply and return.

Earlier USA w124 models have/had an H2O assisted oil cooler-exchanger/oil filter housing assembly. This managed the engine oil temperatures, both hot and cold.

My understanding is across the board the USA 1994/5 E Class 320 production did away with this Filter/Oil Exchanger housing.

So,, no soap on an actual stock oil cooler for this 1994 E-Class 320 coupe. For now at least.


Edit/Delete text

The fact that turning on the heater immediately lowers the coolant temp is what would make me think the air is being blocked somehow. But if you already cleaned that out, ...

The 4th point from that response suggests that the coupes don't have the radiator with oil cooling. (Take a look at your radiator; right at the bottom, are there pipes/ hoses leading to/ from it? That's where the oil cooler is. Perhaps adding an oil cooler would help?)
Also there was a guy on peach parts who sold a doohickey that fooled the electric fans into turning on sooner. Perhaps you might want to look into that.
 

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Afternoon road test - Heater temp at 85f, windows down, driving up Vail Pass

I'll drive (70mph) up hwy. I-70 the 12mi 3,000ft elevation climb approach to Vail Pass (11,100ft) - As we speak.

Stay tuned.
 

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W124 heater on hi - Coolant temp stayed normal; 100C

The w124 coupe was stone cold when started for this Vail Pass run. Ambient temp was 82F, elevation 8,200Ft., sunny skies.
With the coupe's tempo stat rotary dial set to high (85F) from the git-go. Throughout the 12mi 3,000ft elevation climb from Vail Village to the Vail Pass summit the engine temp gauge barely exceeded the white line loosely referred as 100C. Operating the heater core on "hi" provided the cooling system headroom sought.

Fellow Neanderthal offered up a restricted a/c condenser's "diminished airflow" for consideration. A very potential.

At this point, a partially restrictive A/C condenser is a strong potential. The a/c condenser is the original production. (25yo)

I'll drive up the 12mi 3,000ft elevation climb approach to Vail Pass - As we speak.

Stay tuned.
 

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'94/'95 E320 Cross-flow radiator's flow scheme?

Removed the coupe's newly replaced cross-flow radiator today - taking notice that both the supply & return hose couplings are located on the same end. (top and bottom of the left end can.) .. The right side radiator end houses the trans cooler and a 3/4 inch return/supply hose coupling.

That said, which of the two 1.5inch left side hoses is the supply/return? The left end can has to have a mid-point divider of some kind??

There's a new MB OEM A/C condenser & receiver-dryer in route, in an effort to cure an air-flow restriction condition. New condenser/radiator and H2O pump should assist in cooling performance. We'll see.
 

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There's a new MB OEM A/C condenser & receiver-dryer in route, in an effort to cure an air-flow restriction condition. New condenser/radiator and H2O pump should assist in cooling performance. We'll see.
I'm curious to see the result. Does this running-hot condition show itself in traffic/stopped as well, or does it only happen at speed up mountain passes?
 

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Removed the coupe's newly replaced cross-flow radiator today - taking notice that both the supply & return hose couplings are located on the same end. (top and bottom of the left end can.) .. The right side radiator end houses the trans cooler and a 3/4 inch return/supply hose coupling.

That said, which of the two 1.5inch left side hoses is the supply/return? The left end can has to have a mid-point divider of some kind??

There's a new MB OEM A/C condenser & receiver-dryer in route, in an effort to cure an air-flow restriction condition. New condenser/radiator and H2O pump should assist in cooling performance. We'll see.
Just look at the fins of the AC condenser. Make sure they aren't bent and blocking airflow to the radiator behind them.
 

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Running-hot condition w/new radiator . . .

jlaa -
Yes. .. The w124 coupes 3.2l running-hot condition show's itself in both traffic/stopped, and running a 12mi stretch at 70mph in 3rd gear up a 3,000 elevation rise highway stretch.
Cheers, M/S

I'm curious to see the result. Does this running-hot condition show itself in traffic/stopped as well, or does it only happen at speed up mountain passes?
 

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Hi M. Schneider, I just read that that the following items were recently replaced:

Mileage 135,000mi, A new MB OEM A 124.500.24.02 radiator installed June 1, 2019 @ 132,100mi. Also, 2 elec fans, relay, Fan clutch, H2O pump w/rollers & adjuster-etc., All coolant system hoses, Belts, 50/50 MB glycol w/distilled H2O ... All components MB original except one,,,, an authentic Beru/Hella radiator.
As well, I read that you have the following avenues to chase down:

Neanderthal -

This just in from the MB HQ technical office in Sandy Springs, GA . . .
1. Check compression.
2. Check for head gasket failure; exhaust and/or oil present in the coolant.
3. Check gauge and sender operation; resistance-voltage.
4. USA 124.052 / M104.992 does not include older w124 models oil filter/H2O/Oil
circuit heat exchanger core assemblies.

All good ideas to run to ground.

Cheer's M/S
I have a spare 300E fuel/oil/econo/temp gauge on my shelf if you want me to test it vs. any reading that you get off of your own. I'd be happy to test it if you want a baseline.
 
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