Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: Madmerc on January 07, 2016, 13:15:55
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hi guys I haven't got a overheating problem but I thought I might just change the thermostat so I pulled mine out and it has 79 degrees stamped on it so I called my local Mercedes spare parts tech and he said I need a 87 degree thermostat . I placed it in and guess what she started to get hot .not boiling hot but certainly a lot hotter than the 79 deg. which one should I go for I am confused a little after reading the tech manual.any sugestions.thanks rob
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Hi,
79 degrees is correct.
...WRe
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Won't changing the engine thermostat rating also change your WRD settings? If the car is running hotter then the WRD thermostat pin is extending further, leaning out the mixture? Or vise versa?
I know there is some debate about the WRD being non-contributory above a certain temperature, but I have noticed the hotter my car gets the leaner the mixture gets.
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The WRD isn't active at the normal operating engine temperature. I forget exactly what the typical shut off temperature is but it is much lower. You can fine tune the shut off temperature of the WRD (or the time it stays active) with the round shims in the air valve piston. If the WRD shut off temperature is that close to the normal operating temperature of your engine however, it is set wrong.
I use a 75*C thermostat in Texas because of the summer heat. Yes it runs a bit cool now, but just perfect during the other 9 months out of the year. I wouldn't go any higher than the 79*C.
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You will run slightly leaner at full engine temps but you want your engine to run there anyway. Running cold is just as bad as running hot. The parts that can be damaged are different and it happens in a different way but it's still damage. Running too hot will cause rapid damage while running too cold, and therefore too rich, will happen at a slower rate. However, running too cold and too rich at the same time will quickly damage engine bearings from fuel dilution.
Our engines are designed to operate effectively at or around 80 - 85 C. Constant running at or over 100 C will warp the cylinder head. You are probably safe at 75 C to 90 C but I can't recommend operating much outside of those parameters. A 79 C thermostat will often give you around 82 C which is right in the sweet spot. The main thing to watch for is large spikes in engine temps which can be very harmful to your cylinder head. If you find this happening while waiting for a stop light you probably have a cooling problem. This is not normal and should be addressed without delay. I also highly recommend water wetter from my own personal experience.
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Doctor Dan, Any thoughts on the Evans waterless coolant? Anyone use it?
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Don't.