1995 S320 overheating

[S320 newbie]

Hi, I have just purchased a 1995 S320. I live in a very hot desert climate, and my engine temperature is currently reaching almost 120 while driving in traffic. Does anyone know if it is advisable to remove the thermostat completely? Could any harm come to the engine if I try to do so for a couple of days to see what happens to the temperature, and if it helps in reducing it could I remove it permanently until cooler winter season comes? Cheers and thanks.

 

[paulcallender]

There should be no reason to, since they are designed to open fully once the engine is warm. Its function is to speed up warm up, so if you remove it you may have side effects such as poor fuel economy, poor idle, during the extended warm up.

What ratio water:antifreeze are you using? You could go to something like 75:25 to assist cooling.

Is everything else working fine, eg the fan coupling (search on carrot test)?

 

[Silver Arrow]

First, check if it is really overheating. I have an IR thermometer which I use.
It could be a sender unit, or a bad connection.

 

[guydewdney]

do both fans come on? And re-stress the carrot test mentioned above (when its hot, try to stop the fan with a root vegetable or soft thing, I have used a bit of hose pipe). If you can stop it when its hot, you need a new coupling. They are about 25 quid in the UK, IIRC..

fan control relays are known to go wrong.

Temperature senders are known to go wrong (easy to replace, its at the top / front of the engine). depending on the type, there are 1 2 or 3 senders.
if 1- then it does everything (fan, engine ecu and gauge)
if 3 then they are all separated
2 is obv a mix of the above.
ask your local friendly stealer to tell you which one it is.

 

[S320 newbie]

Thanks everyone for the hints.....I believe I have a problem with the fan control - at lower temeratures it goes on and off without any seeming logic (why should it turn on at lower temperatures?), but at higher temperatures (say above 110) I don't see it spinning sometimes. Shouldn't it turn on and work for longer periods at higher temperatures?

 

[guydewdney]

switch the a/c off (press EC button so light is ON... light on = a/c off....) and check again..

air con 'talks' to the fan system

ABOVE 110?? it shouldnt get that high... if the fans come on, then the relay is OK (i assume) - and it must be the sensor / switch?

i have had a look on here:- http://www.autolib.diakom.ru:8001/CAR/Mercedes-Benz/1996/S320/SYSTEM WIRING DIAGRAMS/
but i cant see the temp sensor - just the 'air control module' which controls the fans. Have a dig?

 

[Sullivj]

Adjust the cut in temperature??....

Take a look at this site. The guy has posted a load of technical stuff. One of the modifications he's done is to adjust the cut in temperature of the fan. He also sells a plug in gizmo that does the same thing....

http://pages.prodigy.net/jforgione/MB_S500.html

Some good pictures also. A worrying one of the whole dash removed when he resolved his aircon problem!

 

[S320 newbie]

A friend mechanic has suggested to wire the fans to be on permanently....would anyone have any comments on that? By the way, living in a desert climate, outside temeratures are rarely below 20 Centigrade in the coldest months, and in summer months are anywhere between 35 and 45 Centigrade. Cheers.

 

[Mid_lfe_Crisis]

I dont know why it bothers you that the car runs at 120.If it went into red then i would start looking at obvious overheating, but its not i asume that the car stays at 120 after warming up and stays there????

Ps how far up the gauge is that 120 ?? close to the red???

 

[S320 newbie]

At the highest its just below the 120 mark, probably around 115 or 118. It drops down about 5 degrees when the fans kick in.....the reason why I'm worried is that I'v been browsing the other threads in the forum about the right engine temperature, and this seems to be around 90, especially after the fans kick in. I've tried flushing the radiator, which didn't help. I'll now try changing the sensor/switch (temperature senders) as suggested by Guydewdnay, and if that doesn't work I'll see what to do next....Mid Lfe Crisis, are you implying that 120 is OK for desert conditions?

 

[guydewdney]

Do you have 25% antifreeze in the coolant? You should, even though it doesnt freeze? It works as an extra coolant...

also - try removing the air con radiator and cleaning it. it might just be a blocked radiator.

 

[S320 newbie]

After flushing the rad, I did add more water than antifreeze, but perhaps not as low as 25%....but something else came to my mind, which is to check the temperature when the car is idling, so I turned the engine on as well as the air conditioner (with the kids listening to some music) and even after 30 minutes the temperature (in a shaded garage) was dead on about 97, which was a (pleasant) surprise seeing that while driving it reaches almost 120....you MB buffs, would anyone know if this is an indication of anything, and of what? I would expect the temperature to be lower when driving, since the airflow helps in cooling....?

 

[Mid_lfe_Crisis]

At the highest its just below the 120 mark, probably around 115 or 118. It drops down about 5 degrees when the fans kick in.....the reason why I'm worried is that I'v been browsing the other threads in the forum about the right engine temperature, and this seems to be around 90, especially after the fans kick in. I've tried flushing the radiator, which didn't help. I'll now try changing the sensor/switch (temperature senders) as suggested by Guydewdnay, and if that doesn't work I'll see what to do next....Mid Lfe Crisis, are you implying that 120 is OK for desert conditions?

In a nutshell yes 120 would be ok for me so long as it was allways 120 if it climbed into the red then i would start looking at senders , blocked rads therostat or head gasket even the water filler cap and the cap seal but from what i can make out it gets to 120 at max .

 

[S320 newbie]

Something else came to my mind, which is to check the temperature when the car is idling, so I turned the engine on as well as the air conditioner (with the kids listening to some music) and even after 30 minutes the temperature (in a shaded garage) was dead on about 97, which was a (pleasant) surprise seeing that while driving it reaches almost 120....you MB buffs, would anyone know if this is an indication of anything, and of what? (I would expect the temperature to be lower when driving, since the airflow helps in cooling....?) Cheers.