Merc 500 SL overheating

[anonymous-user]

My non petrolhead friend has recently acquired a 1980s Merc 500 SL. The big V8 tends to overheat in traffic. Big engine, small compartment, slowly turning fan. I have advised him to desludge and, if need be, replace the radiator, and maybe fit an electric fan, but wonder if anyone here has Merc knowledge and can point to any obvious gotchas on the cooling systems of these cars. Thanks for any, er, hot tips.

[Huntsman]

How is the viscous fan coupling?

[anonymous-user]

Worth a look, thanks.

[Pentoman]

If it's anything like my 190, and it probably is, the fan is a simple on off affair when the temp reaches a trigger point. On mine it's about 110 on the gauge. It looks scarily high but the key thing to look for is whether at this point it continues up into the red, or slowly comes down. If it comes down, the engine fan has cut in as it's meant to. When this happens there is a click and you will see the fan spinning very fast as opposed to just twirling loosely. It's pretty clear cut. Both my 190s got worryingly high on the gauge but always came down. Seems to be designed that way.

I would change the fan switch for peace of mind to make sure the fan does get switched in. It's about £15. It's a simple on off relay based on temperature. Note there are 2 or 3 temperature sensors that all do different things so you have to get the right one. There are discount ones but get a Merc one because my discount one didn't work correctly and so the fan was engaged 100% of the time. Only noticed when I wondered where all the engine's power had gone,

[mgroadster]

A good flush out also may be beneficial.

[anonymous-user]

Indeed, as I have told him. He isn't very car aware, so far, and didn't know, for example, that turning the heating on (he had the top down after all) might give some small measure of protection for the big fat sweaty engine. He also needed a good talking to about opening up boiling radiators, or (rather, not doing so).