Its the same from stone cold upto around 95ish then gauge will stay the same even if the ac coolant temp read 101 or 105. I noticed also low fan kicks at 100 med. At 105 and high at 108 in ac diagnostic.I don't rely your average factory temperature gauges to have pin point accuracy but not a big gap between them either way. Do they read any different when the car has warned up and moving?
You can simulate temperatures with resistors via the gauge and sensor plugs if you want to find out what accurate.
I think i found the problem why my temp is high. My expansion tank has few leaks. And system i think is not pressurizing properly. Still, is it normal for the reading to be different? Gauge and ac diag.?Yep. Well its all quite simple to test if you want to but id check that your cooling system is up to scratch first if its getting that hot. Your viscous fan should be really going strong at that temp.
Just changed the water pump since the origanal pump was making noises. Together with the thermostat. Changed the rad. Too since the plastic are brittle. If this still persist i might need a head gasket job 😞Maybe not normal but probably not unheard of either being Mercedes, i dont really have much experience on that front, mine reads roughly the same but sometimes drops to 0 in the a\c panel.
Depends how bad the leaks are the location but sounds like you check the whole system and make sure its functioning properly first. Im guessing you are on original 1998 parts based on your mileage?
Would a very small leak in the expansion tank be the cause of high temp? Coolant level seems still spot onIf those items were bad then i would expect fan clutch would likely be worn too, your aux fans are going to be coming on a lot at low vehicle speed to try and compensate. Expansion tank caps can go bad also. I know these engines have headgasket problems but you'd want to make sure its the case via pressure testing.
Hmm. Might be pressure leak since coolant level is still the same. I ordered the new oem tank and will be arriving nextweek. Can this cause high temp.?Coolant leak or pressure leak? Either way should replace the tank anyway as a small crack in a closed system can give way very quickly when under pressure.
Doesn't seem like anyone addressed this specifically, so here I go:Still, is it normal for the reading to be different? Gauge and ac diag.?