Engine Temperature - Is this normal? - PeachParts Mercedes-Benz Forum

Kynetx · #1 10-10-2006, 10:55 AM

Had some strange behavior this morning. Ambient temperature is 45° F.

I was going to work. My route is a bendy farm road where I never get up past 50 MPH. The heater was non-functional except for the defogger setting and blowing lukewarm air. The temp guage was reading in the vicinity of 45°C or so
The last section of my 15-mile drive is a 2-mile hillclimb (out of the Snohomish River Valley for you Seattle area folks) up about a 5% grade. I was turning onto the road from a stop so it was floored and on boost hard until I got to 55MPH or so. During this climb I really put the screws to the engine and the temperature climbed to just shy of 70°C in my estimation. The heater was now blowing nice, hot air on all settings.
So I have two questions:
1. Why did it take so long to get to operating temperature? Is this normal? Engine was running fine and had plenty of power (so to speak).
2. Does the climate control system have a feature that locks out all the heater modes except for defrost at low coolant temps?

I'm beginning to wonder if I have a stuck-open thermostat.

rrgrassi · #2 10-10-2006, 10:58 AM

Sounds like you either have a stuck open or even missing T Stat.

N41EF · #3 10-10-2006, 11:45 AM

My experience has been that in european vehicles, as a thermostat ages, it begines opening earlier. I had a Ford Thermostat fail stuck shut once. If it opens early, the car is slower to warm up, especially in cooler climates. I noticed my Eurovan didn't get above 80c this last weekend, and my 240d never reaches 80 on my commute in (similar to yours), but as I drive late in the day as it warms up it clmbs right up to 85 where it typically stays unless stopped in traffice with the a/c blowing on a hot day, when it gets up to just over 90c. YMMV.

Beautiful area out there, was in Bremerton for about 8 months back in 1995.

Good Luck, Chuck

pawoSD · #4 10-10-2006, 11:48 AM

I agree sounds like an open/stuck T-stat, my car gets up to about 75-80C within a couple miles or so when its cold out, even faster, and up to 85C (normal operating temp) when its hot outside.

2.5Turbo · #5 10-10-2006, 01:21 PM

My 124 300D has a temp switch in the block that only lets the heater blower come on high when the engine has gotten hot enough to allow the heater to blow hot air. Not sure if there is that feature in the 123 though. Using the defroster will override it.

I agree on what's wrong with your stat. Sure sounds like it's stuck open. My 602 usually gets up to temp (~80c) within 2 miles of home with normal driving. On a 2 mile hill-climb floored all the way, you should be a little over 80c if not higher.

Hatterasguy · #6 10-10-2006, 01:27 PM

Replace the T stat. Its either failed or starting to.