Overheating

[garvard]

1995 S350TurboDiesel.
When I turn on the A/C the tepmerature of water in radiator going to red zone (120 degree Celsius).
What I have to do.? Thank you for help.

 

[television]

Does it move instantly, or slowly creep up to 120, does than fan cut in.

Malcolm

 

[garvard]

Malcom, It going up almost instantly (during 7-8 minutes).

 

[jberks]

By turning on the air con I assume you mean that you put the 'heater' on to cold (plus aircon refrigeration obviously).
The 2 relationships between the aircon and the engine cooling (as far as I am aware) are
1) The 2 radiators are in the same place so compete for cooling airflow.
2) Aircon on cold presumably means that no engine heat is being extracted into the cabin. If your car's cooling system is not working properly, having the heater on may be enough to compensate.

In any case, it shoudn't reach the red.
So, I suspect one or more of the following
1) your engine cooling fan isn't cutting in
2) Your theromstat is stuck partially shut (using the cars heater to cool the engine)
3) The cooling system has sludge in it and is inneficient.

The fan is easy to check, just let the temp rise and see if/when it cuts in.
The rest will require the use of spanners.

 

[Jay Kilby]

yeah check fan first though in this weather if you are moving even with the aircon rad the car should stay cool so my money is on the thermostat. i have had the same problem on my SL500. i also went to the trouble of flushing the system as well she now holds temp lovely and it only cost me £35 to fix!!
just as a thought have a look at the front of the car and make sure nothing like plastic bags or leaves are obstructing airflow first! if there is an obstruction then this could be the problem.

 

[garvard]

I have checked and found that the fans doesn't work even the temperature goes to 120C. What I have to do?

 

[Stevie A]

You will need a new fan or maybe just the switch that tells the fan when to work. It may even just need a new fuse on the fan circuit.

 

[kanda]

Check the output to the fan (after switching on the aircon)and see if there is power to it and if no power check the relay. If there is power then the fan is faulty and replace it.
Hope this solve your problem

 

[aazapf]

Overheating S500

I have the same problem.

The fan is not turning on at all.

I understand that it could be a fuse or the aux fan control unit.

The fan is apparently a large 150 amp unit located under the passenger floor pan. (got this from the US forum).

But I can't find it.

Did you find the fuse and relay?

 

[garvard]

I have changed thermostat and coolant temperature sensor twice.
But the problem is not resolved.

What I ned to do?

Thank you for any advise.

 

[Stevie A]

If the fan still does not come on when the temperature goes up either the fan is broken or the power to the fan / fan clutch switch is not getting to the fan.

You need to figure out what type of fan you have - is it an electric motor fan or is it one that has the clutch that cuts in and the fan is then turned by the belt that drives the alternator etc? Someone else on the forums should know.

If you have more than one fan then it is most likely the power not getting to the fan / fan switch. Change fuse on fan circuit, or loose cable or electric fault etc

You could go to an auto electrician to get them to check it. I would try myself first though.

 

[turnipsock]

You can try shorting out the switch that turns on the fan.

My car has two elecctric fans that are controled by two relays on the nearside wing.

You should be able to here a relay clicking.


The fans only make a difference when the car is stationery, does the overheating happen when you are on the motoroway?

 

[garvard]

Thank you, Stevie A,
I have to say that the fan is working properly. Do I need to change fan clutch anyway?

Aux fans did not work, but when I taken off the plug from water temperature sensor, aux fans work always, even in the mornings (when I just start motor).
But water temperature is going to 100-110C during first 15-20 minutes. When I turn on the AC the water temperature going to 120C and more.

Can you advise.
Thank you.

 

[turnipsock]

Sounds like the coolant system is blocked somewhere.

You can get things from Hellfords to clean the system.

 

[shayes]

I've just had a similar expeirence with my SEL. Not got far down the road and looked at the Temp guage to find it has rocketed to red - panic, slow down car ready to stop and suddenly the temp drops as fast as it rose.

As the Air con is not working anyway, resolved not to switch it on - no problem (if a little warm these days). Needs re-gassing and must say all the tech stuff is mind boggling at this unearthly hour.

Must get to bed.!

 

[oigle]

Just a quick thought. Have you actually verified that the water temp is as high as it reads? Gauges can be faulty too. Suggest you borrow a proper mercury type gauge and insert it into the top of the radiator whilst running - start when cold so as not to burn yourself - and run the engine. See if the temp on the mercury gauge agrees with the car gauge as the motor warms up.

 

[MDMB69]

I've been searching the forums for the same problem on a 96 E280.
The electric fans should have twin speeds, inside the relay box behind the fuse box if yours is the same there are 2 relays with a fuse plugged in the top of each.
The blue one is the low speed relay and fuse for the a/c. The green one is the high speed relay for when the engine gets real hot. I've just been and checked mine and the blue fuse was blown. Explains why the a/c never got very cold when the car was idling in traffic.
I'll find out tonight on my way home if its worked.
Check both of your fuses.