How "Hot" Do You Run? - PeachParts Mercedes-Benz Forum

slimak9 · #1 03-17-2006, 12:21 AM

In my '90 300D 2.5 Turbo, which I purchased in Nov 05 (needed major work), I changed the head gasket, rebuilt the head, and changed little things along the way. (New thermostat, new fan clutch (too much play), new glow plugs and new filters and flushes all around).

With current outside temps of 30 oF - 40 oF (-1 to 5 oC) the engine temp at most gets to 80 oC if its driven hard throughout the city. But most other times it stays at a constant 70 - 75 oC.

Is it safe to say that the NEW Termostat may be stuck open?
Or the temp sensor / needle displaying incorrectly? (Any way of testing this?)

In my '87 300D Turbo, at normal driving, it stays constant between 85 - 90 oC. While in the summer weather w/ A/C it gets easily in city traffic to 100 - 105 oC.

Could this significant current lower running temp be that the '90 has 5 cylinder vs. 6 in the '87?

Feel free to post your running temps and input.

86560SEL · #2 03-17-2006, 12:26 AM

Not sure. My 85' is erratic as well. I have only owned mine since December, but we have had a couple of lower 80* days since then. The warmest day, I noticed that my needle went to the line between 80*C and 120*C - I am assuming this line represents 100*C, since it is perfectly in the middle there. This was in slow city driving. That was the highest I noticed then I hit the highway and it went back down to 80*C. I replaced my cap, as it was not sealing properly, but that did not help. I know that when it it below 45*F outside, and I am on the highway, many times the needle will stay around 55*C-60*C. I am thinking perhaps my thermostat is at fault - maybe your problem as well. I would like to change mine, but I am sure like everything else with Mercedes, there is something difficult about changing it.

Biodiesel300TD · #3 03-17-2006, 12:40 AM

Mine ran at 60C until a month ago when I put a new t-stat in and now it runs at 90C, and I actually get hot air throught the vents. YEAH

slimak9 · #4 03-17-2006, 12:41 AM

Changing the termostat is not too bad once you get the coolant from the rad out as it should also drain what is sitting against the thermostat. Then at least on the w124 its a matter of two screws which then are torqued back at only 8 lbs-ft.

Well my cap & thermostat as both new, so we'll wait it out till it hits 25 oC.

Regards.

slimak9 · #5 03-17-2006, 12:49 AM

Quote:

Originally Posted by Biodiesel300TD

Mine ran at 60C until a month ago when I put a new t-stat in and now it runs at 90C, and I actually get hot air throught the vents. YEAH

Its funny though, with my car garaged (not connected to a block heater) the temp as it rises to approx 60 oC on the morning drive, I begin getting immediate heat and then really hot heat (what should be expectd) once it reaches the 70 - 75 oC range. And this at most takes maybe 2 - 3 miles while its 40 oF outside to reach the crusing temp.

Like I said, did MB sell me a faulty termostat which is now stuck open? I'll probably do another complete flush in the spring, as I still have some traces of oil sticking to the top on my expansion tank from my cracked head gasket.

2.5Turbo · #6 03-17-2006, 01:00 AM

Mine parks itself at just under 80 during normal driving, and when I'm going up a hill or getting on the freeway or something, it goes up to just above the 80 notch. Highest I've gotten it was climbing the big hill on I-82 in Yakima, it was about halfway between the 80 mark and the one above it.

sailor15015 · #7 03-17-2006, 01:04 AM

My wrecked '85 would climb to 99 degrees C within a few minutes no matter what the temp. Sometimes cruising at 75mph+ would bring it over 100C. My '84 climbs to 80C within a few minutes and won't break that for a long time unless I hit the highway, 65mph+. Running it with the a/c on brings the temps closer to the 100C mark.

Hatterasguy · #8 03-17-2006, 11:40 AM

SDL runs just a tick above 80C regardless of the exterior temps. I can get the guage to move if its real real hot out and I get on it, not over 90C though.

It depends on how good your cooling system is. SD will come up to 100C all the time I suspect the cooling system is marginal.

babymog · #9 03-17-2006, 02:25 PM

Constant 75c most of the time here in below freezing outside temps. Running freeway 75-80mph will raise it to ~80c, but I haven't seen any changes. Heater is HOT at this temperature, engine runs well, 190D 2.5Turbo.

- Jeff Miller
190DT

jotunheim · #10 03-17-2006, 03:10 PM

85C most of the time for me. Highest ever was 105C last summer when pulling a utility trailer through the hills in northern WI.

Since then, I have flushed the coolant and replaced the fan clutch, so hopefully it won't even get that high.

Pete Burton · #11 03-17-2006, 04:04 PM

85c

dougand3 · #12 03-17-2006, 04:33 PM

83 300SD

95c - heat off
90c - heat on

Mike J · #13 03-17-2006, 06:18 PM

Steady 82-83.
It ran up a little when it was sunny and we hit 85 the other day.
I have the MB coolant and should get it into the car, I guess...

Zerohour3k · #14 03-17-2006, 06:20 PM

Mine is dependant on the ambient temp outside. In chilly weather, the car runs 80-85c, city driving. Once I hit the highway (taking her up to 70mph, usually), it climbs to 90-100c. Summertime with the AC on or off (doesnt seem to matter much), the engine runs 84-90c local, and 100-108c highway, which seems rather high.

Think my fan clutch is bad, or do I just need a coolant flush? Or.. is this normal?

Boardmonger · #15 03-17-2006, 06:24 PM

The euro (81) runs at 90 degrees all day everyday, driven soft or hard, on flats or up hills.
The 83 300d turbo runs at 80 except on tough grades will climb to about 95-100 but cools down real quick on the downhill.