So I pick up this 88 300CE 145 miles away and am driving the 2/1/2 hrs home. I'm going 75 mph most of the trip and the car is driving nice, handling well. The temp gauge reeds 78 F most of the way. 3 miles from home, the temp creeps up to 110-115 F and I pull over , turn the car off and heat is coming through the center vents and the fan is making noise as it winds down for awhile after I shut off. AAA flatbeds me the 3 miles home. WTF? It's night now so tomorrow I have to check the hoses, water pump, radiator and tank. Curious about the fan noise and the heat gush coming through while the temp was set at 68. Before overheating, it was driving nicely and you can feel the road. I forgot how nice these early W124s were and how humongous the trunk is. I once bought a new 86 300E for my wife on her birthday many moons ago.

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__________________
85 300CD Signal Red/Tan sold
83 300D Manganese Brown 109K
97 E420 Midnight Blue 197K sold
98 BMW 328i Vert White 100K, sold
95 BMW 525i White 125K, sold
93 BMW 525iT Red 193K, sold
95 E320 Green Wagon 125K, sold
94 E320 White 127K, sold
85 300SD 156K Grey (Annie), sold
84 300D Lapis Blue 170K (Judy), sold
99 ML 320 Black (lease), 1998 C230 White (lease)
00 Honda S2000 Red (lease)
86 Mercedes 300E (sold)
84 Porsche 911 Red (sold), 1965 Porsche 911 White (sold)

Main fan also if fluid leaked out when you slowed down nothing to cool off the radiator. Also is the A/C isnt charged or the temp sensor on the drier isnt good then low speed isnt working on the Aux fan. If your strip fuse is bad for the Aux fan or the relay with built in fuse is blown you basically had no cooling when you slowed down. Thermostat would be next for me then water pump.

Good luck its a good looking ride.

It actually overheated while I was being pulled over by the cops who took 30 minutes to warn me for operating the new to me 300CE with my old plates. The car was insured so he let me drive home. I was trying to get it home but stopped at Costco and of course he spotted me. I'll register it today and switch plates. Today I put in 1 gallon of water in the radiator reservoir and so far I'm not seeing any leaks and the water is not going down in the reservoir. Would coolant be purged through the water pump weep hole if the car overheats telling me that the water pump is soon to go? Last night the temp gauge did not get to 120 F and stick. I pulled over at 115 F and turned off the engine and waited for the tow. Car is operating at 78 F now and the engine seems fine, wtf? The coolant leaked somewhere? Exhaust is normal and not white or cloudy.

__________________
85 300CD Signal Red/Tan sold
83 300D Manganese Brown 109K
97 E420 Midnight Blue 197K sold
98 BMW 328i Vert White 100K, sold
95 BMW 525i White 125K, sold
93 BMW 525iT Red 193K, sold
95 E320 Green Wagon 125K, sold
94 E320 White 127K, sold
85 300SD 156K Grey (Annie), sold
84 300D Lapis Blue 170K (Judy), sold
99 ML 320 Black (lease), 1998 C230 White (lease)
00 Honda S2000 Red (lease)
86 Mercedes 300E (sold)
84 Porsche 911 Red (sold), 1965 Porsche 911 White (sold)

I don't know how and why your car over heat with 120 F. (120F only equal 48.8 C Celsius and water only start boil at 100C.

Sorry, those temps should be C on my temp dial.

__________________
85 300CD Signal Red/Tan sold
83 300D Manganese Brown 109K
97 E420 Midnight Blue 197K sold
98 BMW 328i Vert White 100K, sold
95 BMW 525i White 125K, sold
93 BMW 525iT Red 193K, sold
95 E320 Green Wagon 125K, sold
94 E320 White 127K, sold
85 300SD 156K Grey (Annie), sold
84 300D Lapis Blue 170K (Judy), sold
99 ML 320 Black (lease), 1998 C230 White (lease)
00 Honda S2000 Red (lease)
86 Mercedes 300E (sold)
84 Porsche 911 Red (sold), 1965 Porsche 911 White (sold)

Apparently there was too much water not enough coolant in the mix. I flushed the system and changed it to a 50/50 mix. I tested the new mix by idling the car and waited 15 min to wait for the temp to rise above 105 C and the aux fan kicked in at high speed which brought the temp down to 95 C so no gurgling or boiling of coolant through the overflow. All is back to normal, thank goodness. The A/c is currently not working so I don't get a low speed aux fan?? That's the next job, then the left speaker comes on and off. Rear windows don't work, more likely the switch rather than the motor?

__________________
85 300CD Signal Red/Tan sold
83 300D Manganese Brown 109K
97 E420 Midnight Blue 197K sold
98 BMW 328i Vert White 100K, sold
95 BMW 525i White 125K, sold
93 BMW 525iT Red 193K, sold
95 E320 Green Wagon 125K, sold
94 E320 White 127K, sold
85 300SD 156K Grey (Annie), sold
84 300D Lapis Blue 170K (Judy), sold
99 ML 320 Black (lease), 1998 C230 White (lease)
00 Honda S2000 Red (lease)
86 Mercedes 300E (sold)
84 Porsche 911 Red (sold), 1965 Porsche 911 White (sold)

Water leaking from the purge hole in the pump means that the pump is shot.

Common problem.

Whole moving over 20mph the fans are not required. Airflow through the radiator will lower the temp of the coolant sufficiently. Even if you lose a fair amount of coolant while moving the temp can still stay low. As soon as you stip the low coolant level plus assuming the pump is not nopertaiong properly this will cause your temp problem.

M103 water pump changeout can be DIY - bit of slog though.


Don't know about your thermostats in your climate but the thermos here in the Southern Hemisphere are set to 87degree.