Engine thermometer on 90 degrees

[Zerrin]

Hello,

I usually keep an eye on the thermometer and it is always on 80 degrees. Today when I was driving and I had the air con on, it went up to 90 degrees. I got worried as this has not happened before, is this normal or do I need to get it checked out?

 

[rayhennig]

I had the air con on, it went up to 90 degrees.

Mine sticks at around 87 C under normal circumstances. Up long hill, 35C ambient and aircon on it will rise to 92ish. No cause for concern.

This is as measured with a laser/infrared thermometer as my gauge actually reads 10 higher. Still no cause for concern. The gauge error started after it was replaced when the old oil gauge would randomly drop to zero - that really did cause concern and replacement underwear.

Mine used to rise to 105 when idling for long periods in hot weather and the aux fan would kick in and the temperature would drop. I never worried about it. After major overhaul at PCS in Horndean, all is now as described above.

In your shoes, I wouldn't lose sleep.

RayH

 

[Mr Greedy]

Most modern Mercs should be running at about 87 or 88 degrees rock solid, unless the engine is under extreme heat stress (e.g. as rayhennig example above).

If it is struggling to get to 88, and with the symptoms you are describing (the fact it can get to around 88 when under high heat load) suggests you have a thermostat that is slightly stuck open (faulty).

Other options could be a faulty gauge, or a fault with the control software that can electronically open the thermostat (if that applies to your model).


Welcome to the forum.

 

[mioba]

Thermostats do wear out and need changing. 80 is too low tbf. That said at 3 years old assuming we are talking about the 2018 A class in your profile, have you changed the coloant at all. is the right mix.

 

[flowrider]

Have you noticed the outside temperature lately? I'm not surprised car engines are reading a little high at the moment.

 

[mioba]

so does that mean when its a lot cooler the temp should be lower.

Its an engine they get hot regardless of external temp. The temp is "maintained" by coolant and should be steady solid 88 (give or take few).

The OP is concerened his temp has gone up to 90 whilst usually being 80. I would be more concerned with my car running at 80 than 90.

 

[rayhennig]

I would be more concerned with my car running at 80 than 90.

Yes, I see "around" 90 and feel that is normal. Upper limit is always with aircon on and climbing hills at lowish speed. Minor variations quite acceptable.

R