Mercedes b180 petrol temp fluctuating

[nav456]

My dad just got a mercedes benz b class

Has a 1.6 blueefficency petrol engine.

We took it for a long 2 hr drive

I noticed the temp gauge drops up and down from 85-70 depends on if we cruising along or in traffic.

When at a stand still and parked up engine on it sits at 90.

Never goes over 90 so it is not over heating

Never evee had or driving a mercedes until now.

All cars i have had temp always sits at 90. Wont fluctuate.

Is there something wrong here?

[nav456]

Bloody pain. Some forums online says its normal due to electronic thermostat. But this makes zero sense.

As you said how can water temp go down once operating at 90.

The car was freshly serviced i wonder if they did not bleed it.

Ill try get it in a garage to check it out.

[nav456]

So i did just that. Dug out the old obd reader got the coolant temp graph up and drove around.

What was showing on the graph matched the needle..off by few degrees but nothing major.

Which was odd. Personally i always thought that the operating temp was 90 and stayed there.

But as you just confirmed that is not the case. On my vw it fluctuates slightly too on the graph but the needle in the car will not drop or go up from 90 once the temp is at operating temp.

Im curious if the mercedes system is a more true operating temp reading. Which personally i have never seen. Aparently this is normal in mazda's. Which also does what this mercedes is doing.

I will do few more tests over next few days and see if i can find a bleed valve for the coolant system in the morning.

As said the needle and readings never went above 90 at all. So its not overheating at all.

[nav456]

No it seems to not really stay still. On the 2 hr motorway journey when was coasting it would still fluctuate and while cruising at 70mph would go to 85..drop to 80 etc after few mins. Would not really stay in one place for more then 5-10 mins.

I will try bleeding it today and see how that goes. The car is due a service so if the bleeding dont help will just get the thermostat changed while its in for a service.

[nav456]

Yes for now car is driving fine. Heaters working fine. Not overheating etc

When it goes in for a service soon will get it checked out. First time we have had a mercedes benz. Ans reading online these have some electrical thermostate or something. Not what you get in any other normal cars.

Prob because it is a blueefficency engine has these stupid readings and gauge. The MPG is great. So all signs that would indicate something is wrong are not there which is what is very odd.

Will keep you updated incase other mercedes owners come accross this

[nav456]

Yh i noticed that too..so i put in obd reader in my vw 2020 touran..and once the pbd reading was going above 75 the needle in the car was at 90. Even at few points the obd read above 90 and below etc..not by much tho as the mercedes just by 5 degrees here and there but the needle stayed 90. So yh defo think this may be a feature

[nav456]

So tried to "bleed" the system..left the cap off for about 10 mins before car to full temp. No bubbles etc. So there does not seem to be any air bubbles. Coolant level also has not dropped at all. Very odd.

I think the needle is showing real tempreture. So its a feature.

Will tell them to check it out when it goes for a service in 2 weeks.

I have done all my checks i could physically do myself