Oliveri

So I have quite unstable temperatures on my car, or at least I think so, I’m asking if it’s normal or not
well to start with, the car is a 2002 S500
So the temperatures that I keep seeing is anywhere from 80-95ish as far as I can see it’s not going over 100 but it gets very close and as I said it’s up and down as it don’t look like there is a stable temperature
Also the cars engine tends to take up to 15min to hit the 80 degrees mark which to me seems like a long time, outside temps are usually over 8 degrees (all is in Celsius)
also unrelated to that the fans in front only blows cold air while the one in the back blows hot air, cold works on both like normal but front won’t get warm (4channel air conditioning)

wallyp

There is nothing magic about a temperature of 100C in your engine. The boiling point in your cooling system (assuming 50/50 mix of the proper coolant and water, and a proper pressure cap) should be somewhere between 120C-125C. The designed/desired operating temperature is usually considered to be 90C-95C.

The coolant temp is controlled by a thermostat that blocks flow to the radiator when the coolant temp at the thermostat is lower than the designed temp for that thermostat - which may vary. Coolant should be flowing to the heater matrices all the time. In the W220, coolant flow to the heater matrices is largely controlled by the duo valve, or in your case, duo valves (one front, one rear).

Coolant temp is affected by ambient temps. At 8C, radiation from the engine is significant, so the coolant tends to be cooler.

Thermostat operation is initially a batch process. Everything is at 8C ambient. When the warmer coolant from the cylinder heads hits the thermostat, it begins opening, and typically opens more than is ideally desired, thus slightly over-cooling the engine. This closes the thermostat a little more than is ideally desired, increasing coolant temp. This cycle slowly damps out, so that the coolant temp will eventually almost stabilize. Some initial fluctuations are normal, and not serious.

The cold air from the front heater matrices is very probably due to a failing duo valve. Cleaning and lubricating the duo valve pump motor and solenoid valves will often restore function. It is somewhat of a gamble, with the trade-off being your time and effort to remove the duo valve being the same whether you try to refurbish it, or whether you install a new one. You are balancing the cost of a new duo valve against the probability of the refurbishment being successful.

https://w220.ee/Duo_Valve
https://mbworld.org/forums/e-class-w...rol-valve.html

tusabes

These cars are fitted with a 95 degree thermostat and temps from 80-95 on the gauge are normal

bamberger_1

A slow temperature rise is obviously a defective Thermostat. Relatively cheap and simple to swap. And then see what happens.

cowboyt

In town driving with a lot of stop and go, I often see 90 to 95 deg C. temperatures. When I'm cruising on the highway, the temperature drops to 80 deg C. or just above. When I'm doing combined driving, then if I end up doing 40 mph for a little stretch, the temperature will come down from 95 C to about 85, and ultimately 80.

All of this is very normal for W220's, from the S350 all the way to the S65 AMG. Our S600 TT behaves exactly like our S430's and the S500 in this regard.

Have you been able to get an idea if your higher temps are happening when you're doing a specific type of driving? Same for your lower temps?

Oliveri

I would say I have noticed something simmelar, driving from red lights over and over tends to heat it up quite a lot (about 95) standing still after it’s that warm will usually bring it down to around 85-90
driving on the highway it’s usually around 80-85

cowboyt

Then you're just fine. That's absolutely normal. As long as you're not going above about 95 C, or below about 80 C after full warm-up, you're good.

tusabes

Yeah you’re fine .

Most people get concerned. Because Mercedes uses an actual gauge that fluctuates broadly , while others carmakers “gauges” are really programmed to stay stuck in the middle position at all operating temps and they only move to hot when overheating .

The Mercedes gauge actually normally heads between 1/2 to about 3/4 hot during normal operation.

theokgs

yes i i have exactly thesame problem as you....my w203 c230 the temperature fluctuating all the time as you between 80-96 C°.i think this thing is not normal because i tested that after 90C° the radiator fan is on and close to 96C° runs on high like a turbine and after 30 seconds the temperature goes to 80° and the radiator fan is off again...this thing is happening all the time.to mention that the AC is off and the temperature outside is winter about 5° C.do you have the same problem?and also the fan opens and to your car or only temperature is going up and down?

Futility2006

my 01 S500 has this issue however she. The temp gauge gets close to 100 I get serious lifter ticking, replaced all the lifters and the car still seems to do this. I have changed everything including the thermostat water pump radiator dual valve. How is this? I had the cooling system flushed and the car still does this. Maddening.

kraut56

lots of parts changed for what?
What kind of oil?

Status of car:milage?

tusabes

did you read what everyone said above ? Your coolant temp getting close to 100 is completely normal . The lifters tick is not normal