how hot is too hot
 

84 300D-I frequently drive thru the high and low deserts here in the west, experiencing 110 to 125 degrees in the summer. There are a few steep hills to climb where my temp guage shows halfway between the 4th and 5th white hashmark, sometimes creeping almost into the last small white hashmark. My a/c is on with the aux fan as well. Road temps were well over 140 degrees. I know these are extreme conditions but I've been driving them for a few years with no breakdowns, car runs excellently. A few times I've turned off my a/c to bring the temp down. Does this seem like a reasonable temp reading? I live in Ca. in the mountains and routinely my temp is at or over the 4th white hashmark when driving a steep 6% or greater grade in the summer, 90 to 95 degrees, with the a/c on. Driving flat city driving with a/c on temp guage below 4th white hashmark. Does it seem like my clutch fan and water pump are doing there job? I'd appreciate any comments or suggestions.

I never EVER let my car get above 100*c. a few times is fine, but it will cause head damage over time on aluminum headed engines. iron heads (like yours) are much more robust and should be ok with 125*c

In the pic is where my CD operates. I think it's a bit high, not overly so.
If you're running ~100 C (212 F), that sounds high, too high. In one of the charts below, a 50-50 mix boils at 107 C.
http://en.wikipedia.org/wiki/Ethylene_glycol

Too high, I'm surprised your head is still okay. Although the iron heads are more durable than the aluminum ones, repeated instances will eventually warp the thing enough. I would make sure that your radiator is in good shape, very few bent fins, good flow, etc.

I don't like more than 100*.

Others will tell you that it is fine, even 110*.

The heat button on the head will melt at 250*F I think, which is 120* C. This is supposedly the mark of an overheated head. I think all bets are off at that temperature.

I think he's saying the 110 to 125 are the ambient temp... Unless I'm mistaken.

When it is that hot & your going up a hill. I would give the poor thing a rest from the air con.
It wont get above the boiling temp of the coolant until it boils some coolant away and then you are in trouble!! At highway speed the fan doesnt do much as the air is being forced through the radiator by your forward motion.
Just back off a bit on hills & turn the air con off on the uphill bits.

KarTek I think so too, but if his gauge is like the one in the pic and it's between the 4th and 5th hash mark, his car is running ~100 C, too high.

no.
100C is fine on a 617
if it's going up to 120, then you are experiencing problems.
how is the cooling system in your car? when was the last time the coolant was flushed?
what color is the coolant in your car?
what radiator cap is on your car? what pressure?
what is the mixture of coolant to antifreeze in your car?
did you mix with tap water or distilled water?
in those extreme temps, I'd be sure not to use more than 35% antifreeze 50/50 is horrible for high temp driving. pure water is better, but it needs the antifreeze for it's antiwear and plastic conditioning.
you say it does it with your a/c on up hills... what refrigerant is in your a/c system? has it been converted to 134 or is it still (hopefully!!!) running 12?

I agree with the folks that say 100*C if fine but not for extended time period. I wouldn't let it go above the 100 mark. And when you get the engine temp above 90 I'd be turning off the AC. If it goes over 100* turn the AC off and the heat on, this will cool the engine down much quicker.

Is it possable that my TD has a 100° thermostat in it? Cause my TD is always at or just below 100... ALWAYS. The hotest heater I have ever encountered.

No, its more likely that your thermostat is stuck partially shut, not allowing your coolant to flow properly, and/or your coolant is not mixed properly, or it's old coolant. I'd seriously think about changing the thermostat and coolant. You could also have a blockage somewhere.

Additionally, ashedd, your temp sensor may be bad. My car used to hover around 100 before I swapped out the sensor.

how hot is to hot
 

[It's never been to 120. I kinda thought the cooling system was ok but maybe a few refinements will bring the temp down in the desert. The trip I make 6-7 times per year in the summer is 500 miles one way. The coolant was flushed 2 years ago. The coolant is brown to golden in color. It was a fifty-fifty mix so I used no water. The radiator cap looks like the original MB cap, it has the number 140 stamped at one corner. The a/c was converted some 5 years ago with the usual new parts when doing the conversion. I do not know how the ac was when r-12 was in. I bought the car with a frozen motor and faulty trans for $500 because the body and interior were pristine. The motor that was installed supposedly had 125k. The trans was rebuilt by a local german who only does MB trans. I've been traveling this route for over 5 years. The fan clutch and water pump were replaced when the engine was in stalled but I don't know if they were OEM parts. What about hooking my aux fan to run continuously with or w/o the ac on. Only in 100 degree and above. What do you think? 3QUOTE=vstech;2437721]no.
100C is fine on a 617
if it's going up to 120, then you are experiencing problems.
how is the cooling system in your car? when was the last time the coolant was flushed?
what color is the coolant in your car?
what radiator cap is on your car? what pressure?
what is the mixture of coolant to antifreeze in your car?
did you mix with tap water or distilled water?
in those extreme temps, I'd be sure not to use more than 35% antifreeze 50/50 is horrible for high temp driving. pure water is better, but it needs the antifreeze for it's antiwear and plastic conditioning.
you say it does it with your a/c on up hills... what refrigerant is in your a/c system? has it been converted to 134 or is it still (hopefully!!!) running 12?[/QUOTE]

Ok I will get a new T-stat. I also have a small leak from under the water pump. I think there is a hose there where it's leaking. I guess I should look in to that:rolleyes:... or just sell it as a "fixeruper"