Cool running '97 E420 - what's normal temp?
 

My recently acquired E420 seems to run on the cool side, but before replacing the thermostat I hope that I can get some feedback from other owners. I'm in Seattle, so it isn't exactly super cold here. When I start the car, it seems to take quite awhile for the temp gauge to start to register, and in most driving conditions the temp never seems to run much above ~65C, frequently below 60C. In city traffic with lots of sitting time temp rarely reaches 80C.
Other owners of this model, where does your temp gauge read in different driving conditions? Do your engines warm up quickly, or does it take more than 5 minutes to move into the 40-60C range?
My understanding is that this car should have an 80C thermostat, so I'd expect the temp to run close to that. But maybe MB just does things differently - any feedback or advice will be gladly acccepted!

I have a '85 380SE and my gauge barely goes to 60°C when on the highway/expressway. In city driving, it goes up to about 80°C and when idling in drive for a period (10 minutes), it will rocket to 110°C. Then back down to nearly 60° (sometimes 55°C) on the freeway. :rolleyes: I am sure my thermostat is broken. A new one is $30. vs. $8. for my 95' Suburban and it looks like more work to change- which makes me crosser still. NABD though.

I am sure someone with a car like yours will reply with a more detailed analysis of what your car should be registering.

Both of those cars ought to be at about 80 to 85°. You're not those engines any good by running them that cold.

Len

Cool running E420
 

I have a '95 E420 and I noticied it runs a lot cooler than my 300E. I checked the radiator sizes and the E420 is almost twice as large (capacity) than the 300E.
It does take a while to get uo to 80C but eventually it makes it. Having lived in dreary Seattle, I can understand why it takes so long.
Anziani

standard working temp for that model is 85 degrees those models are equipt with a vacuum to increase its throttle position until the minimum temp is achieve, nothing wrong with working it below 85 degrees, technology dictates that you don't have to seat and wait for your vehicle to reach a certain temp before you drive, maybe only on models below 1970's

What happens?

hi, my 97 E420 runs at 80-85 deg C, no matter how cold/hot ambient temp

1) Engine oil doesnt get to temp, so acids and moisture don't boil out.
2) Exhaust doesn't get to temp, so moisture causes it to rust faster.
3) Engine runs richer at cooler temps, so you're getting worse MPG.

Those are 3 major downsides to running an engine too cool. A new thermostat is well worth the investment, and do a coolant flush while you're at it. 10 year-old coolant should be changed by now :)

Oh my! Thanks!

I do not mean to sound like an imbecile, but how to you "FLUSH" the radiator?

Thanks for all the info! It sounds like time to put in a new thermostat, and probably to change the coolant. Any hints on how to do that with this car? In other cars I've owned (non MB) I've put the Prestone flush tee kits in to make the job easier, but I don't want to cut up any hoses in my E420 if that isn't called for.

When you change your thermostat don't be surprised if your E 420 starts running at or near 100. At least here in the tropics they all do. The M119 is too tightly fit on the W124 engine compartment, hence it tends to run much hotter than it does in the S 420, for example.

I replaced the thermostat this weekend. Definitely a major PITA, it took over three hours and lots of skinned knuckles. Whoever designed the placement of the thermostat, especially the rear bolt on the thermostat housing, must be a class-A sadist! Placing it behind a hose was truly inspired, especially since the hose is so short that gettting it loose was also an experience I hope NOT to relive anytime soon. After lots of misfires I finally managed to get a socket (with many u-joints and extensions) onto the bolt, and finally got the thermo off. Putting it back again was nasty, but not as bad as getting it off. Now after warming up the temp gauge reads right at 80C and holds there, so I guess it was all worth it!

hmm. upon closer inspection, my E420 never gets to 80, but rather sits at 70 deg C or so. car warms up fine, blows warm air, etc. is my thermostat also busted..?

when its not broken don't fix it,

Yes. As mentioned in the posts above, an M119 will, if anything, run hot. Replace ASAP.