Thermostat opening temperature

[Peter]

The official thermostat opening temperature is 87 degrees Celsius.
SLS is selling thermostats which open at 79 and 83 degrees Celsius. The story is the otherwise the engine gets to warm.

My engine has been completely overhauled, one should expect the running at factory specification is 87 degrees Celsius should then be possible. 

What is the experience you have?
Which openings temperature should is take?

Thanks for information Peter

[WRe]

Hi,
the 79°C thermostat is correct. There are some recommendations to use lower thermostat temperatures (71, 75) during summer and overheated engines but I don't have any experiences with this.
There is a note in the Workshop Manual to use a 87°C thermostat during winter times to increase the heating capacity but nothing more.
But I tested this summer, which was not a really hot summer, a fan shroud and a original 6-blade-fan with the closest distance to the radiator possible and I can say that this increased the cooling performance very much, means no overheating even during drives over mountain passes in the Alps.
...WRe

[wwheeler]

One thing you have to be careful of when selecting a cooler thermostat is that its temperature is NOT below the WRD shut off point. Depending on how you have the WRD set up (round shims) to shut off at "X" temperature, a cooler thermostat may be lower than that. In that situation, the thermostat opens and allows the engine temperature to stabilize below the WRD shut off and then the WRD will never completely shut off! Here in Texas, I messed around with cooler thermostats and found that indeed overlap with these two devices is possible. Find out what temperature your WRD shuts off at before selecting a cooler than factory recommended thermostat.

If you are looking at a 71*C, I would really be careful and check your WRD shut off temperature. 71*C seems too low to me.   

[Peter]

Thanks Gents, very helpful, Peter

[mauro12]

I’ve been told to avoid using the 87 degrees thermostat , for this reason I bought a 79celsius and at the same time I replaced the water pump and put only mercedes blue coolant . The car never overheat even in 40degrees in Sicilian summer .

[Peter]

The Haynes manual is indicating 87, but when I changed the old thermostat it turned out to be 79 degrees Celsius and the car never got too hot. So 79 degrees Celsius is correct.

Peter

[Pawel66]

79 is what you need.