cooling system

[aaron marcus]

1989 SL suddenly running too hot (110+) while sitting in traffic on hot days. Does not come down when you race engine, but will come down to normal (90) when moving along.  Car is mint, 68000 original miles Any suggestions?

 

[dave elcome]

Aaron.

There are a few things worth checking here. Firstly go down the cheapest route, get the vehicle hot, and then check that the radiator in unifomly hot, I.E. no cold spots which would point to a blocked rad, if this is ok then check which type of fan coupling you have, either Viscous, or Electromagnetic, check that these are in good condition, and working correctly.

Now if you have not found anything decisive, i would change the thermostat, contrary to popular belief this is a not a "lifetime" item, they do get weak and sticky, and are so cheap that you might as well change it.

If the problem still there then you have probably got a problem with the rad, when i got mine i had the same symptoms, the rad didn't have any cold patches, but some of the cores in the centre section were a bit distorted, i got it changed under the warranty, and the problem was solved.

 

[Matt Crooke]

Echo Daves advice there, as, from own experience, the fan switches arent the most hard wearing part on a Merc engine.

 

[aaron marcus]

Dave, Thanks for your reply. I did replace the thermostat and the 212 switch for the auxilliary fan. I suspect the viscous fan clutch.  It seems to be working OK. With the car hot, I turned off engine but I still could rotate fan by hand. Should the coupling hold it stiff when hot?  Aaron

 

[Andy]

Hi all,

By the sound of it with the auxillary fans. The vehicle is fitted with AC. If so I would blast out the condensor and radiator with a pressure washer and test again. When you can see no more dirty water then its ok.

Regards

Andy @ www.mercedesservicing.com