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Coolant temperature query

KLP 92

MB Enthusiast
Joined
Nov 28, 2003
Messages
2,671
Location
London
Car
Mercedes S600, SL600, C250TD
After getting my SL500 back from repairs my coolant temperature still rises to 105 degrees once i have the A/C on. When the A/c is off it the temp creeps up to about 95 degrees. The coolant temperature only comes down after i go above speeds of 30mph+.
At 105 degrees my electric fans don't cut in but the viscous fan does. Normal driving on motorways, the temperature is at 85 degrees.
I have just had a new water pump, radiator and coupling fitted due to another problem! This has made no effect on the water temperature. The temperature never goes above 100-105 degrees but is this normal?
Done the carrot test and the new coupling does work. When are the electric fans meant to cut in?
The electric fans cut in at 85-90 degrees with AC on when the car is parked. But when the water temperature is above this they don't seem to cut in.
 
bet its the same temp sensor prob as me - its only 10 or so quid, and takes 30 seconds to change (well, it has to, cos as you undo it water comes out of the hole....)

or its the relay...

its supposed to keep the temp below about 90 imho

edit
on the thermost housing are two senders, one looks vertical, one at a slight angle. the angle one (560 Sl 84 - closest i could get to yours - if you give me the first 6 digits of the engine number ill double check) is the one for the fans - short this wire / s together / to ground, the fans should come on. if not, then its the relay.
 
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Guy,

The car in question is a 1992 sl500 and not my old one. Do i check it the same way?
 
I am no expert but I would have thought 105 deg C is fine for engine water temp. I know nothing about the electric fans you mention but assume they are controlled by the HP side of the aircon - so if this has a slight undercharge then this may account for the fans not kicking in. Hope an expert happens along real quick!


PS: I only say 105 is OK because it is a pressurised system by design and this raises the boiling point of the coolant mix above 100 - as long as your expansion cap is Ok and it is not farting out water in an attempt to relieve any excess pressure - then ergo!
 
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Guy, thanks for the web link. I got one of the Cool Harness's, shouyld be here with me next week. In the meantime i will adjust my coolant mixture.
Its probably fine running at 105 degrees, but it is slightly on the high side and puts the engine extra pressure.
 
guydewdney said:
[snipped]
if you have a look at the s 500 coupe page http://pages.prodigy.net/jforgione/MB_CTS.html
[snipped]

Yes, nice one. I had quite forgot about Jim Forgione's site, it is really good and he has put a lot of effort in there so I do not begrudge him some income from it. But being a tight wad - I would be tempted to solder a resistor in myself - I would have thought easily available @ Maplins.
 
I know its easy but i'm just lazy!
But he's only charged me $30 for it. I emailed him a query and he said that if i wanted it premade then thats what he'll charge me. So i thought i'd go fo a professional look (even though theres a cover over that area) and saves me soldering it and screwing something else up in the process!
The resistors 28p at Maplins but have no stock.
 

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