1982 300D Engine Temp
 

I just replaced the radiator on my car due to a split in the top tank. That job was not bad at all, thanks to TangoFox and Jimmy's input. There was no need to remove the fan and shroud at all.

I have an 84c t-stat. It was either that or a 90c one.

My car, from day one of ownership ran at 90c, during the summer running the a/c or not. I have owned the car for 5 years. With the radiator replacement, it still runs at 90c. I even removed the t-stat, and is still runs at 90c. When idling and the a/c on, it will creep up to 100c, and drop back down when traffic begins to move.

There is no oil in the cooling system. Water pump was replaced a few years ago.

I see lots of people saying thier cars run at 80c.

Is this normal?

Thanks!!!

probally get alot of crap for this but ive seen alot of post on here claiming 80c is what it should run. 80c is 176f thats low for a complete burn of fuel. my 87 with the horribal 14 head is well past 300k and runs 90-100 (based on gauge). which i think 100c is around 210f which is good and fine. the extra heat helps mpg's

80c is stock tstat temp on mine and 10-15f over that is to be expected. temps should rise and fall within a safe range which yours is so id say yours is good to go.

Those folks must live a lot closer to the Arctic Circle than you and I.

My stabilization temp ('82 300D) is close to 85 C. On a 100 F day, it will approach 100 C in stop & go traffic with the a/c (and aux fan) running. Like you, I recently replaced my radiator due to a leaking upper seam and saw no material difference in operating temps. The tubes in the original radiator were very clean. My water pump and fan clutch replaced recently.

Considering that an 80 C thermostat does not fully actuate until 94 C, any arguement that 80 C is the "normal" maximum temperature is pure poppycock.

80 C is, in fact, the normal "minimum" temperature. The entire function of the thermostat is to maintain a minimum temp; it has no control over the upper limits.

YEAH!!!! I'm 55 miles east of Dallas.

Thanks Tango!! Thanks 02!!

Removing the thermostat will not lower the max temperatures.

Paraphrasing from the FSM:

Until 80, the main valve is closed and the bypass valve is fully opened and coolant is not routed through the radiator. It bypasses the radiator.

Between 80 and 94, the main valve and the bypass are more or less open. Some coolant goes to the radiator, but some coolant still bypasses the radiator and stays within the engine, depending on engine load.

Above 94, the main valve is open and the bypass is closed. 100% of the coolant goes to the radiator. Verbatim quote: "It is therefore wrong to remove the coolant thermostat for better cooling of the engine."

"Full actuation" may depend on perspective. The thermostat seems to be designed to maintain between 80 and 94, since it starts cooling at 80 but above 94 it diverts 100% to the radiator.

Consistently running at around 100, unless there are high ambients and an A/C load, is probably a bit high. This is for a 617 motor.

My '83 300CD ran with the needle just on the upper side of the hash mark at 80 - call it 83 degrees since it was less than one-quarter of the distance between 80 and the next line at 100. With A/C on, in city traffic it ran closer to 100, on the highway around 90 (R-134 conversion, parallel flow condenser, aux fan running).

When you consider the non-linear scale, the coarseness of the measurement, and the fact that above the hashmark between about 80 and 85 the needle is pointing directly to the number 80, people saying "80" is hardly a big deal.

As described by the OP, the needle between the 80 hashmark and the 100 hashmark - with a thermostat installed - seems pretty normal.

Kindly list the factors that affect perspective.

I thought I did. See "between 80 and 94..."

In response, please define "full actuation".

If you mean completely shutting off the bypass in order to keep the temps from rising and staying above 94, then sure it's "fully actuated". If you mean opening the main valve in order to permit coolant to flow into the radiator, then no, that happens at approximately 80. And it's described as "more or less open."

By your own description, your car normally operates below your described "full actuation" point, does that mean it's not running hot enough?

The observation and question was "I see lots of people saying thier cars run at 80c. Is this normal?"

Somehow that became "pure poppycock" and was described as a stated "normal 'maximum' temperature". I can't say I've ever seen a thread that described 80 as a maximum. Normal, yes. Maximum, no.

And now, a first, that 80 is really the "minimum". Okay. Sure.

Since the OP described taking out his thermostat in order to run cooler, but not getting results he desired, I thought it beneficial to describe what was actually being "actuated" in case someone else may see the thread and attempt to cool their engines by removing the thermostat since they might have thought it didn't "fully actuate" until 94.

Enough perspective?

Mine have always run right about 90. A little cooler in the winter a little hotter in the summer. Anywhere between 80 and 90 is normal. Start pushing 100 and you're running hot, below 80 and your running cold.

What is the part number / brand for one of these? I have been looking for a true 84C t-stat for a long time and have never found one :D


With an 80C stat, my 85 runs at 87C on the gauge. With the same 80C stat, my 82 runs at 80C. Both have new Behr radiators.

Try shooting it with an IR thermometer and see how close the gauge is. I replaced the temp sender on my 82 and it dropped the gauge reading by ~~7C.

I would not worry about the difference between 80C and 90C if the car is running well and you're not seeing it get above 100C. 90C is a perfectly acceptable running temperature.