I'm posting for a friend who is having overheating issues with his 1995 C280. He has replaced the radiator, water pump and thermostat and the temp gauge is still hovering just below 100. Any help is appreciated as we're working on it as we speak. Thanks in advance... Bill

Use an actual contact thermometer to determine coolant temp, we need to be sure the in car gauge is correct.

Next is a leakdown test where air is pumped into each cylinder ( with both valves closed to build pressure ), remove the rad cap and look for bubbles in the coolant. If you get bubbles, the head gasket or head has a problem.

What is the history of this car? Is the higher temp a recent development?

I believe that is the normal operating temp. Why does he think it is overheating?

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Normal operating temp.

I have same car and long ago questioned the temps.

What might be a source for a bit higher temp is the water pump. Some have different fin designs and cool at different efficiencies.

mine goes higher than 95C when driving up hill.

if it is not boiling coolant, and not in red zone, you are OK.

use appropriate motor oil and MBZ coolant.

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1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

Ambient temperature matters as does if the AC is running. On a 85 * F day with no AC my SL320 runs at 80*C. My recently on the road 97 C280 on a so far 80*F day runs just over 80*C.

cars are funny. my former 1989 300SE ran at just over 80C regardless of ambient. Lots more room in the engine bay than the C280.

My 95 C280 began to operate warmer after the first water pump change. design differences might make for variable temps compared to OEM pump.

Average out known running temps and go from there !

and keep cool !

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

That is running below spec. That is usually caused by a failing thermostat.

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

My m103 runs at 80°C or just above sitting in traffic with the a/c on. But, I installed a 80° thermostat. When it stats getting over 100°F outside all bets are off.

There's someone on the forums that sells a widget that kicks on the aux fans sooner. Supposed to help.

Been driving the 97 C280 lately. Car has variable coolant temp. On a 70* F day, motor runs cold 170* F . on a 88* F day it runs 203 * F at road speed , 225 * F when sitting. I'm using the HVAC control to read temp. Time to change the thermostat as a precaution. It also might be time to change the fan clutch, if the idle is raised to 900 RPM, the temp drops.

Now that I think of it, my 97 SL320 runs 197 * F regardless of outside temp.

THIS!

And this.

If it's staying out of the red and not boiling over, you're good. My 123 wouldn't get over 60 C with the old bad thermostat it had when I bought it. Since the new one went in back in '05 or '06 it parks at 100 and stays there. I think I got one of a run of thermostats that run hotter than marked, but it's still within the normal operating range and I think it partially explains why I get better fuel economy than most despite driving like Lewis Hamilton and/or Nico Rosberg on the last few laps at Bahrain this year.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

If truly running hot, esp at low speeds or idle, consider the fan clutch,

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Prost!

Up date on my 97 C280

On a recent cold AM day ( 60*F ) the engine never got above 160. When temps rose to 80*F, engine temp was 200 ish and would rise to 220 at idle. If I brought engine speed to 1,200 RPM, temps would drop to 190 ish.

Pulled thermostat, found bridge was broken ( where the stem presses against ) the valve was off center allowing for maybe 20% coolant flow. More importantly, the bypass blocking disc was not shutting off the bypass and allowed most water to recirculate. Luckely, half of the bridge was still holding the stem off to the side, otherwise it would have snapped shut and overheated the motor quickly.

Bridge was cracked for a long time based on the brass being dull. It probably finally broke completely just after I started driving the car. ( it was sitting for a few years. ) Given air temps were low the problem was unnoticed. Changing the T stat as a precaution was on my rebuild list and just hadn't gotten that far. This is a perfect example of why I life parts when the get high hours rather than wait for them to fail.

Looking at engine temp through the HVAC on 97 system is easy and more accurate than a needle. Fan on, key in 2 run position, press and hold REST, wait for 01 and a number to flash back and forth. Use fan - + buttons to scroll through the values. Coolant temp is in the range of 05 or 06. There is a chart for the values on the net. ( heater core / evap temp / pressure, bat voltage, AC high pressure and lots of other stuff. )

Car runs at 195 / 7 when warmed up even in 92* weather, at 60 temps engine does not run below 188 and will creep to 195 after everything heat soaks.

Hey thanks for posting a follow up. It makes this forum valuable.

Glad you got your temps straightened out.

Your persistence and gut feeling was right !!

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

Here is a pic of the broken thermostat bridge.

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