Coolant temperature high

[A250 Bennyboy]

Out in the car today and this warning flashed up with a ping sound as well. Pulled over for 20 mins with the fan going crazy, crawled home but temperature was fluctuating between 80 and 120.
Cars been parked for half hour now and still the fan is going, can't work out how it's got so high as I was driving like I had miss daisy in the car.
I'm going to leave till its fully cooled down and check all the levels

 

[A250 Bennyboy]

 

[Dave.tam]

Not good!

Wish I could be more help......but I can't!

 

[A250 Bennyboy]

Oil level looks good so not to sure why it's got so high?

On earlys tomorrow so will monitor the oil temp on my way to work 8 mile away

 

[zipdip]

Oil level looks good so not to sure why it's got so high?

On earlys tomorrow so will monitor the oil temp on my way to work 8 mile away

Why are you looking at the oil,it is the water that is too hot,with the engine cold look at the small plastic top up tank to the radiator,if there is water in there then you may have a thermostat stuck closed,bad luck if it has they normally fail wide open and so the car runs cold,but I might be too late as you have driven to work,

 

[Dave.tam]

"Stop and switch off engine!" Is always a good clue not to drive it

 

[Flackadder]

You have an issue. Needs sorting. Check WATER level. Look for possible leaks. Talk to MB or a reputable mechanic.

And I am guessing you were checking the oil to ensure there was no oil in it ;-) Never a bad idea.

 

[A250 Bennyboy]

Thanks for the advice I thought it was the oil temp that was climbing high? Oops I'm a thicko lol, I'll check the water now.

Going take it strait to MB when I finish work.

Cheers
Ben

 

[camerafodder]

Thanks for the advice I thought it was the oil temp that was climbing high? Oops I'm a thicko lol, I'll check the water now.

Going take it strait to MB when I finish work.

Cheers
Ben

If there is a fast coolant leak don't drive it anywhere Ben, get it recovered to the garage. Do you have AA, Mobilo etc..?

 

[Dave.tam]

Call MB recovery and give them your reg. It may still be covered by them. (No idea the age of your motor!)

 

[markjay]

1. If the coolant level is OK, then you do not have a leak, and the most likely cause is a failed thermostat (stuck in partially-closed position) as others said.

The other possible cause would be a failed coolant pump. This can sometimes be diagnosed by a visible leak or by excessive or grinding noise, or it may be seized. Removing the belt and turning the pump by hand can help get a feel if it has failed. But sometimes the only way to know for sure is by removing it and inspecting it (And, if removing the coolant pump, then depending of the age and mileage of the car, it might be advisable to just replace it with new anyway, I.e. even if no obvious fault is found, given that ultimately water pumps are wear items).

In theory this can also be caused by a failed cooling fan, but if you can hear it running then this is not the issue.


2. If the coolant level is low, then the overheating is the result of a leak, which needs to be investigated. Possible causes are:

Cracked or collapsed coolant hose

Leaking coolant hose joint

Corroded cooling system alloy part

Leaking coolant pump

Cracked expansion tank

Failed explanation tank pressure cap

Leaking radiator

Head gasket failure

The issue with coolant leaks is not just the actual coolant loss, but the fact that the cooling system is being depressurised as result, which lowers the coolant boiling point and caused the coolant to boil over - and vapour and air bubbles just don't conduct heat as well as liquid coolant does.


3. On some automatic MB cars fitted with the infamous Valeo radiator, coolant could leak into the transmission heat exchanger. However this issue affects older cars (from memory circa 2000?) do not likely to be an issue on newer cars.


4. On a general note, 'overheating' might turn out to be no more than a faulty temperature gauge or faulty temperature sender, so its always a good idea to have a second indication, and in this case the fan working overtime is proof that the issue is more than just a faulty gauge or sender.

 

[Dave.tam]

What he said! Lol

I wish I knew more about cars lol

 

[A250 Bennyboy]

Thank you Markjay very informative reply thank you very much for all the info and possible courses.
Checked the coolant level and it looks to be ok, I do have road side assist. MB only 8 miles away so going drive to them and leave car with dealers to sort.
On the drive to work this morning the temperature was fluctuating between 40 and 80 didn't get any warnings come up so I'm thinking I should be OK to drive it to the dealers.

 

[Benzowner]

I had a problem with my S Class a few years ago with overheating and looked at and tried all the usual tests with no resolution. Later found it was a failed impeller in the pump. The bearings were sound.

 

[A250 Bennyboy]

Well MB have had my for the second day now, didn't take it in till late Monday so probably not looked at it till today.
Finish at 3pm bricking it on the QT hoping my babe's ok and not going put a big hole in sky rocket.
It's got 12 months MB warranty thank goodness.
Cheers
Bren

 

[Dave.tam]

Keep us updated

 

[A250 Bennyboy]

MB had my car for the 3rd day now, got a phone call telling me it's two sensors sending faulty readings that's what was making the temp to fluctuating from 40 to 80 every time it changed gear.
Got the parts late today say it's a 3 to 4 hour job as they are located at the back of the engine.
Should have my baby back tomorrow hopefully, oh I have been fretting lol
Cheers
Ben

 

[Dave.tam]

Glad it's just a sensor!

 

[A250 Bennyboy]

Thanks Dave yeah was a big relief, just quite a big ish job to change.

 

[Dave.tam]

At least that's their problem nd not yours