Temperature showed just less than 100C
 

I hate to be posting repair questions, but my car is suicidal.

Today was amazingly hot and humid. I put on my a/c and drove to my destination. Half way there my A/C was barely blowing cold air.

My temperature indicator showed just less than 100C. After turning off the car I wanted to see how hot it was under the hood. The heat was incredible. Everything within the engine compartment was far too hot to touch, even the body panels.

The engine fans turn and the auxiliary fan was on all day.

Is something in needing of repair or should I focus on additional radiators or something?

Tons of posts on the forum regarding this subject. Have fun searching the different opinions.

My two cents is that you can spend a great deal of time and energy obsessing over the issue without much results. I was unable to bring my operating temp down (similar to yours) and eventually just lived with it. Nothing ever came of it.

If all the fans and cooling systems appear to be functioning, I think we're just victims of this unique MB quirk.

dp

100C is ok on a hot day. As long as you were not near the temp. red line, my owner's manual states that it is OK and will happen. You may want to have your sensor checked, however, just to be sure that you are getting the correct temp. reading. Do you have R134 in your AC? ( Get ready for a hundred different opinions. :D )

I have a different perspective of the 617 now that I have the SDL.

The 603 can warm itself up to 100°C. when under moderate boost, with the a/c off.

However, with the a/c on, it will have a difficult time getting over 105°C. even on a long upgrade.

So, look at the situation this way:

The 603 has no issues at 105°C. and it has an aluminum head.

Therefore, all you folks with 617 engines can relax and worry about other things. You can probably run the 617 up to 120°C. if you have proper coolant and sufficient pressure in the cooling system.

Keep in mind that the coolant at a temperature of 100C is right at the boiling point of water at atmospheric pressure. Other metal parts of the engine will be hotter in normal operation.

Engine oil is expected to run about 100C so that moisture will boil away, so the valve cover will be at 80C or so.

Heat under the hood is normal, and as human beings we are always impressed with normal underhood temperatures, since we cannot relate to them properly in our normal skin... :eek:

Best Regards,
Jim

Regards to temp sensor...
 

I have an '83 300D with 243K on the clock. It had 193K when I first bought it, and it ran cold (barely 80 degrees celsius in the Florida summer). After a new radiator, thermostat, fluid, etc., my temp gauge now reads at around 100 degrees celsius. However, I wanted to see for myself if it was really running at 100, so I brought it to my dad's firehouse and he put an IR or laser heat gun on it in various places where it would be hottest, and the warmest temp we found was 187 degrees farenheit when warmed up (about 86 degrees celsius) - so I know I'm getting readings about 14 degrees celsius wamer than what it is running. If you have access to a IR or laser heat gun, do it - you might be surprised.

I have see a product called Water Wetter, that is suppose to lower the temp in the engine by 10-20°F. They have one for gassers and one for diesels. I havent heard anything bad about the stuff yet, and was thinking of trying it myself.

You can check it out here:
http://www.redlineoil.com/products_coolant.asp?productID=70

If anyone has any input on the stuff from first, second or any hand experience please advise.

Damn, I had hoped people were not going to say "this is just how my car runs"

:pukeface:

It is R134A
Should I go back to R12 I'll pay 25 bucks a pound if it works.

Down in Texas, for the summer, I would be interested in seeing the result of running the 617 with no thermostat.

In this situation, the engine will stabilize at about 65°C. and will only climb if under heavy load or when it has reduced airflow. Starting off at 65°C. instead of 80°C. will give you that much more margin in terms of time.

You could leave it out all summer and report back on how it did for you.

I'm very sure that we would be interested in the results, and, additionally, if it still gets up to 100°C.

I figured the thermostat was wide open.

If you think it will help that bastards getting pulled Tuesday.

There is nothing wrong with your car, it is running fine. Under 100c is normal, that's the way mine runs on a 60 degree day. Check your owner's manual, page 12, quote "Up to red marking: Maximum permissible temperature" and on page 58 it elaborates: "If the antifreeze mixture is good to -30c/-22f, the boiling point of the coolant in the pressurized cooling system of your vehicle is approx. 125c/257f.

During severe operating conditions and stop-and-go city traffic, the coolant temperature must not rise above the red marking"

So your car is perfect, you don't need to do anything. Unless you think you know more about it than the people who designed and built your car.

Removing the thermostat or doing other modifications will do more harm than good.

Removing the thermostat in Texas for the summer will do no harm.

I believe that the engine will take longer to get to 100°C.

Dr. Bert has run the 617 in similar conditions and is quite pleased with the results. You can do a search on his name and read about it, if you wish.

Please, please report back as to exactly what that temperature needle reads when the ambients get above 90°F.

Removing thermostat is common practice here in India, especially in European origin diesels, the Japanese diesels never run anything over 80c and if they do, it is trouble with capital T.

Most OM 616 used in commercial LCV app would not only remove the thermostat, they would remove the radiator cap as well, according to them, it is the only effective way to keep it cool when loaded with 5 tons of goods.

My OM 616 turbo never goes a shade over 85c and that in a 45c outside weather day. I just wont feel comfortable at 100c as I know how high the hot spots inside the engine are by then, also it is like a psychological barrier once you cross 100c, overheating is on its' way. The turbo OM 616 is equipped with a 72c thermostat and I saw a big drop in temps when I modified the air intake to a ram air system as well a removed the muffler.

It is different approach I guess, I drive my brother's Toyota diesel SUV which never goes over 80c, fully loaded with a/c on at around 45c and yet, any MB diesel at that situation is showing the dreaded temp creep.

I have used Watter Wetter when I used to live in NY with my 240D as well as Accord V6, did not see any adverse reaction except for gelling inside the radiator which made me a bit nervous.

check me out
 

i never tried taking out a thermostat in a 617 but as i look at the diagram of the thermostat in my opinion it would cause additional heat to build up.thermostat is open to recirculate the block only when cold and as it heats the spring is compressed and finally closes the block port when hot and allows pressure to force coolant thru the radiator.
larry perkins
72 old cars

Mine hovers just below the 100C degree mark no matter what the temp. It can be below freezing or approaching 100F as it has been the past few days and it still stays rock solid at around 97C. The only time I've ever seen it break 100C is when i was installing my veg conversion and didn't fill it up quite enough. There was still coolant visible in the expansion tank but just barely. Even then it only broke the mark while driving 75 down the highway for about 15 minutes, and even then it was only about a needle's width over. Adding the proper amount of coolant fixed it. My brother has an 84 300D that a p/o modified so that the aux fan would run all the time. If I remember correctly his runs about 90C. Both cars appear to do fine at these temps.

It was 100F/36C here over the weekend. :sweatdrop

100F+ 70%humidity+a/c max. = 100C engine temps
Welcome to Texas! Were having unseasonably warm temperatures right now.

Removing the thermostat will only cause it to take a little longer to get there but once you reach 100C you will have to wait till 7 a.m. for it to get much lower. (Been there, tried that)

removing thermostat
 

On some gasoline cars if you remove the thernostat the engine will overheat because the coolant circulates too fast. In the past I have dismantled faulty thermostats so it will slow down water flow but never shut when I have been too cheap to go buy a new one. I know I'm a cheap bastard!

Not a good idea. The thermostat DOES prevent cooling until the temperature reaches the setpoint (usually 75-85 deg. C.) and then over the next 10-15 degrees closes the cooling by-pass port and directs the coolant thru the radiator. When you remove the thermostat you allow cooling to commence immediately (so the engine may take a VERY long time to reach proper operating temperature - which increases engine wear and drops fuel efficiency) AND the bypass port is never closed - so only about half of the coolant ever passes thru the radiator - and that reduces the capacity of the radiator to about half what it would be with a properly operating thermostat. The thermostat doesn't impeed cooling once operating temp has been reached and inded in the case of a Mercedes diesel, increases the capacity of the system to dissipate heat.

Water Wetter will increase the cooling capacity of the cooling system (modestly when using the apporved anti-freeze/water mix - more when the anti-freeze concentration is lowered) but under most conditions the engine will still run at between 85-95 deg. C. because that's where the thermostat is designed to keep the temperature unless the engine is really loaded down.

Marshall

If your thermostat is working correctly removing it WILL NOT improve cooling and it could result in overcooling which will reduce your mileage slightly and cause increased engine wear.

If it is not working correctly spend the $5 or $10 for a new one.

By the way it sounds like your air conditioning needs to be recharged.

It's a mystery to me why some people think Goober down at the filling station knows better than the design staff in Stuttgart.

By the way if you remove the thermostat restriction and the car runs hotter it's not because the water is going "too fast". It's because it's barely moving at all. Removing back pressure on the water pump can cause cavitation very easily and in hot water easier than cold. So you need the restriction and the pressure cap. You also need antifreeze to raise the boiling temp of the coolant and to prevent corrosion.

Car designers figured all this out years ago.

Do a search on Doktor Bert and his experiences without a thermostat.

Here is the thread for you:

http://www.peachparts.com/shopforum/showthread.php?t=114673

Read it first, before you jump to a false conclusion.

He's hardly the "Goober down at the filling station".

He's got a lot of real world experience without a thermostat in a 617 and the experience differs from "the design staff in Stuttgart".

Dr Bert has chosen to maximize cooling (even when it's NOT needed) not by eliminating the thermostat structure, but by removing the temperature sensor and thermostatic action - VERY different from running without a thermostat (even one that been eviserated) in place.

What he has done will increase the time it takes the engine to reach optimal opearting temperature. With a thermostat hanging open (rather akin to what he's done), most of my OM60x engines will never even reach 65-70 deg. C in temperate weather (may not reach 55 deg. C. in COLD weather) and the cost is seriously increased wear, slow boiling off of water and volatile accumulates in the oil and considerably lower fuel economy. When temps reach zero (F) the output from the heater isn't really even teped and at 20 below it becomes darned cold (and the engien does NOT run well and even the coolant operated fuel hear doen't do it's job.

As to his suggestion about reducing combustion/exhaust temperatures, that's what an EGR does and BOY does that increase engine wear and lower turbo boost. Boost pressure is absolutely correlated with exhaust temp. There may a a really good reason to run some engines without a thermostat, but I haven't seen one on this forum.

A thermostat is a device that is designed to PREVENT cooling until the engine reaches it's intended operating range. Then it should become invisible - allowing maximal cooling. The Mercedes design does that perfectly when the system is in good working order and is properly maintained.

Marshall

I'm starting to feel pretty good! I can't get mine to go above 90 C no matter what I do to it. It runs at a constant 85 C with the AC off, and will run a little cooler with the AC on. Then it starts to creep up as Mother Nature tries to cook me & my beloved Kraut, but the highest it's ever been is 90 C. Don't get too jealous of me, though. I think my AC needs a little freon, and the fact that my coldest air is being used to cool the windshield (vacuum leak, ACC vacuum disconnected) probably isn't helping much. The car is only comfortable if the outside temp is under 85 F, and it the highs won't be that cool again until September or October :( .

I notice your Doktor Bert lives in Visalia California where temps never go below freezing. Eliminating the thermostat is not recommended, but it is something you can get away with. You might not even notice the drop in mileage and the increase in wear, especially if you live in a hot climate. I see he makes the point about manufacturers using hot thermostats to increase mileage, and he knows that running an engine too cold will increase wear.

The other example he gives is industrial engines, which run at steady speeds for long periods and start from cold a lot less often than street driven engines. So eliminating the thermostats should do practically nothing.

I would ascribe the low cylinder wear to more modern rings and oils. Since 1980 car makers have been using low tension rings to reduce friction and increase mileage. Consequently these engines engines show little or no cylinder wear. Better oils have helped too.

By the way the only 317 cu in engine Ford ever made was the 1953 - 55 Lincoln engine. This engine was also used in Ford F8 trucks and as an industrial power plant. So if they were that old, no wonder they had the old 50's style rings and pistons, and showed cylinder wear typical of that era. And no wonder wear decreased when they were bored out and fitted with modern pistons and rings, and run on modern oil.

"I also inflate the tires on my vehicles with Nitrogen as opposed to air, because it allows tires to run cooler at sustained high speeds"

This is pure bull****. Nitrogen does nothing for keeping tires cool. It also does nothing to control expansion pressure, unless you have found some way to repeal Boyle's Law. The reason racers use nitrogen is because you can buy a cylinder of nitrogen @ 2000 PSI for $30 at any welding supply dealer, and it will take the place of an air compressor at the track. One cylinder will last a weekend racer a full season of inflating tires, cleaning parts, even running air tools. It's purely a matter of convenience.

Racers have been using compressed nitrogen cylinders at Bonneville since the 1930's and this is how the myth that nitrogen is better for tires got started. The reporters writing up the speed record attempts started it, or possibly the mechanics fed them a tall tale and they didn't know enough chemistry to see through it.

In other words, your Doktor Bert is a high grade Goober with a degree in bull****.

Since you are so knowledgeable about nitrogen, maybe you would like to explain why all jet airliners use pure nitrogen in their tires, as well? Tires that must achieve 200 mph on a daily basis.

I do agree that running cooler is not the reason.

Still think it's cheaper than compressed air to fill ten of those babies? :rolleyes:

"Since you are so knowledgeable about nitrogen, maybe you would like to explain why all jet airliners use pure nitrogen in their tires, as well? Tires that must achieve 200 mph on a daily basis.

I do agree that running cooler is not the reason.

Still think it's cheaper than compressed air to fill ten of those babies?"

I don't have to explain it. I never said they did, and I don't know what they fill them with. I just finished explaining that in a situation where you are away from the shop and away from your air compressor, nitrogen cylinders are a cheap, convenient, clean and quiet alternative to a gas powered portable compressor. Perhaps the explanation is that it is more convenient to inflate the tires from a service truck than to tow the aircraft back to the hanger when the tires are low.

In fact it is a lot cheaper and more convenient when you add up the cost of a gas powered air compressor, the fuel to run it, and the time and expense of servicing it. That's why racers started using it 70 years ago.

Simple
 

My w126 300SD (the 617 turbo) has and will run at 120C all day if the outdoor heat, driving conditions, and AC status warrent it.
With the AC on, sitting at idle in my driveway in about 80 degree weather...the temp will climb right up to 120 then the AUX fan will kick on and keep things between 110 and 120.

With the AC off, sitting at idle, same conditions, 100C is common with no AUX fan operation.

AC on or off, crusing temps vary from 90-110C depending on outside conditions and AC operation...nothing fantastic.

Keep your 617 turbo out of the red and you are fine. Period. :)

P.S. Just make sure your cooling system compoents are up to snuff! :eek:

Wow...........how's it feel to be the hottest guy on the board???? :D :D :D

no, no
 

dont remove your mb thermostat.

larry is right on.

mb's have a bypass thermostat not the more common type which just blocks all flow until it reaches temp. the bypass flows from the pump back to the block until warm thereby allowing no hot spots. after that it will flow all of the water to the radiator... if you take it out you will lose the full force of the cooling system when it is needed by splitting your flow betweent the block and the radiatior instead of flowing all of it to the radiator.

the only time to take one out is if it is stuck and no replacement is available and then only til you can put one in.

as far as the hotness under the hood... i always think of the heat sink effect on all those hoses and wires when the engine is really hot...like it would be in texas... when that happens when i am on a trip and have to stop and shut down i always pop the hood and leave it up a couple of feet to cool down. if i stop at a rest area or such i wil also do this with it running.

My right foot feels a little heavy :D

Again the aircooled VW reference...if you haven't experienced overheading VW heat...you haven't experienced engine heat :D

I heard that! I used to have a '72 Beetle, and that thing could almost overheat with the engine off. You have to open the hood with a shop rag, because touching the latch will cause third degree burns :eek: . When I'd stop while running errands in the summer, I'd always open the hood and remove the oil cap to let it cool. It didn't leak or consume any oil, but it cooked out at least a quart per month when it was hot outside.