overheating and coolant

[ptmar]

hi im from the philippines and the weather goes up to 95-100F everyday . i have a mercedes benz fintail 200 gas and my engine temp. goes up to 190-200F in traffic without airconditioning. Is this normal? i changed engine fan to a 6 blade flexifan, removed my thermostat and permanently covered my bypass using aluminum that i custom made so that water will circulate throught the radiator all the time. Is this right ? will it lower my engine temp. ? i installed a custom made fan shrud to maximize air flow to the radiator. i placed a elec.cooling fan if i use my airconditioning. i changed my radiator to 3 holes for more water capacity. but still my temperature goes up to almost 200F in traffic and without airconditioning. what more if i use it surely my temp will go higher . but if car moving steadily to 40-60 mph my temp is 160 F. or lower and my car runs better. i dont know but are older mercedes benz car designed and more suitable in colder countries ? Do u recommend using Mercedes benz coolant. will it not eat up my aluminum head? will it lower my engine temp. ? need help thanks

[nachi11744]

Hello,
I would:
1.Replace waterpump
2.Flush the cooling system, including engine block
3.Replace the radiator cap
4.Run water+corrosion inhibitor instead of coolant
Hope that helps

[Oreo]

Hi

The thermostat diverts water from the block to the radiator when warm. It also acts as a restrictor to control the water flow thru the radiator. The theory is that the water has to loose some heat before re-entering the block. If the water is flowing too fast to loose any heat, then the hot water continues to go back to the block and the temp will continue to rise. Instead of the blanking plate, take out the valve of the thermostat and leave the housing. Personally, I don't think the thermostat is your problem at all. In my 123, the electric fan still kicks in often at 30+ celcius. Does your electic fan setup not have a thermo switch? Is it possible to install one?

Oreo

[patmccusker]

Hi, It's good that you are concerned. If it ever seriously over heats shut it down quick. My '63 fintail with gas M180 engine got driven a while when over heated and it warped the head and blew the head gasket. I had to remachine the head and it was kind of a pain that could probably have been avoided. PAT.

[ptmar]

hi dont have a thermo switch but instead have a switch for the fan which i can turn on/off manually. i placed a plug to the bypass because if i had a thermostat it will just do the same. it would stay open and have no time to cool down to close the valve . am i right?? anyway i think i would just try to custom made a larger radiator 4 or 5 rows. or maybe try to fit a larger and faster elec. fan. with the kind of weather reaching to 100F and hours in traffic any car would over heat .? thanks for all your help

[psfred]

You have a circulation problem. I would definitely do a citric acid clean and flush of the block, it's likely you have a buildup of crud in there, and this will cause overheating because the coolant isn't reaching all of the block like is should.

Always run either a thermostat or PROPER restriction plate. The coolant has to move slow enough to both remove heat from the block AND dump it off in the outside air, if it goes past too fast it won't lose any heat through the radiator and the engine overheats. The thermostat is sized to give correct flow. Put it back in, you may be surprised at how well it works!

Also, you need to have the actual temperature of the engine checked! You may just have a bad gauge!

Do not use plain water with anticorrosion additive, you will boil over. You need the increase in boiling point given by the coolant more than you need the better heat exchange properties of plain water! You are in the tropics, after all!

Also, if you have a visco clutch on the fan, you may consider replacing it with a plain fan, it's gonna be running almost all the time anyway. The problems you are having a characteristic of a bad visco clutch!

Peter

[300SDog]

Originally Posted by psfred

Also, you need to have the actual temperature of the engine checked! You may just have a bad gauge!

Do not use plain water with anticorrosion additive, you will boil over. You need the increase in boiling point given by the coolant more than you need the better heat exchange properties of plain water! You are in the tropics, after all!

With all due respect, I disagree that superior heat exchange should take backseat priority to increased boiling point. If water boiling temp is 225 degrees, then the guage would have to be very inaccurate for the car to be boiling over in current circumstances at 195- 200 degrees.

I think the positioning of the guage sensor at the cylinder head galleries is probably the hottest spot of the engine.... and I have never in my life seen an MB temp guage that was so insensitive and/or inaccurate that it couldnt register minor 5-10 degree drop in temp when the heater levers are opened up.

Regarding non-corrosive coolant, look for alternative orange coolant instead of the green stuff if you cant get MB dealership fluid. Meanwhile as little as 4 ounces of orange coolant is likely too raise the boiling temp to some degree, if you have worries about boiling over.

And hell yes, swap the water pump if it hasnt been done in the last 40k miles or so. The blades on those critters are made of cast steel which corrode down to nubs after awhile, even if the rest of the water pump is okay.

[psfred]

Boiling point of water at sea level is 212F, fully pressurized to 15 psi about 240F, boiling point of a 50:50 mix of glycol is 240 or so unpressurized and 260 or so at 15 psi. This is a very significant difference, as he would be near boiling point of the cooling system isn't staying pressurized for some reason.

The gauge may very well respond nicely to temperature changes and still be way off, after all, it's over 40 years old!

ptmar:

I would get the cooling system pressure tested. If you have a minor leak, it will prevent pressure from accumulating, lowering the boiling point of the coolant and allowing steam pockets for form in the head. This will cause overheating as the heat can't transfer to the radiator.

[ptmar]

hi thanks for your replies. I checked my radiator after a short drive and found some particles in my water. i drained it put distilled water and start the car . i noticed that it takes longer for the car to reach the normal engine temp compare before . so i guess that solved my overheating problem . i will test drive it tommorrow . i just have to flush my radiator and engine to take out all the impurities. now what kind of flushing agent should i use ? any brand would do? im afraid it might damage my engine head. what is the acceptable engine temp. is 180F-200F normal? up to what temperature is considered overheating?

[Mark DiSilvestro]

I don't have a 200 but the owners manuals for my '61 180b and '72 250 state that, on very hot days, in slow traffic or mountain driving, it's OK for the temp guage to go above the 'normal' range as long as it doesn't enter the 'red' zone.

The cooling system needs the thermostat to function properly. There are colder thermostats availible. I had a 75 C in my 250 which limited my heating in winter. Replaced it with an 82 C which seems to work just fine in my area.

If you're using antifreeze, use no more than a 50/50 mix. Too much antifreeze inhibits heat transfer in the coolant.

On the subject of aftermarket cooling fans and electric fans, recently, someone in the vintage Sunbeam sportscar club experimented with various combinations of aftermarket and electric fans. He found that many of the aftermarket fans didn't work all that well and proper spacing from the radiator was critical. Actually, the original cheap-looking four blade Sunbeam fan was one of the best performers!

Happy Motoring, Mark

[abe g]

I have a 77 450sl that runs normally at 200 degrees F. Sometimes slightly lower, or slightly higher. On a straight run on a hot day, temp stays constant (except heavy traffic) I would only be concerned if runs into or near red zone. You may have over-reacted with all the changes etc made. Good luck, Abe G

[Oreo]

Hi

Here in the tropics we actually do not need the 50:50 coolant mix as it is for winter conditions. The higher the gycol content the lower the heat transfer properties. The pressure in the system will prevent the boilover. Actually I read that just plain water with Redline Waterwetter is the best. I use 1 litre of MB antifreeze just for the anticorrosion properties. I haven't used the Redline WW as I do not have an overheating problem but you can check their website for this info.

I think you are already seeing some improvement. I would keep flushing out the system with plain water a few times, driving a few days in between each time. Once the water remains clear, add some Redline WW. And definitely replace a new thermostat. The car will warm up faster and the temps will be more steady. You can rig up an auto fan system with a thermoswitch and a relay. But placement of the thermoswitch is very important.

Oreo

[230/8]

As I read your question, you asked whether 190 - 200 degrees (I assume degrees F, not C) in traffic on a hot day is excessive. Basic answer is NO. In an unpressurized system water boils at 212 degrees, and with 7 psi (0.5 bar) pressure it rises to about 225 degrees F. As I recall your radiator has about 7 psi. Maybe more if you have replaced the cap, which would raise the boiling point even higher.

Some suggestions have been good, to summarize:
1. flush the system and check the soundness of the radiator to hold pressure.
2. Replace the thermostat with the correct number, ensure the pump is tight with no leaks, belts are snug, and there is no hose restriction.
3. A 50/50 mix of antifreeze and water raises coolant boil point higher, and even though not needed in your climate may assist with high temperatures. It will also assist with corrosion control, something to be wary of with aluminum heads.
4. Do not run without the thermostat, the radiator is a heat exchanger, and as such there is an amount of time the coolant must be in it in order to transfer the heat from the coolant to the radiator and then to the air flowing through the radiator. Even racing cars which do not use thermostats use a restrictor plate to ensure the coolant spends the proper time in the radiator.
5. Oil plays a vital role in cooling your engine. Use the highest quality oil available and select a grade in keeping with your environment. In the Phillippines this may be a single grade 40 weight, but a synthetic multi-grade such as Mobil 1 15/50 would be a good choice, too.

In short, your initial information indicated no reason to be concerned, your experience (160 F) when speeds, and air flow under the hood is better bear this out. But if you continue with the modifications you have made then trouble may be awaiting you. FYI, I have some experience with hot climates, having lived 6 years in Saudi Arabia where temps of 125 F are common.

230/8