93 - 2.5 TD - Cooling Questions
 

I have a 93 2.5 TD. It has 208k miles. I purchased it 2 months ago and it is averaging about 28 mpg in mixed driving. The AC works great.

I noticed it has green coolant. I have heard this is not good for the MB.

Also, everyday on the way home in 95+ heat the guage moves to right above 100. My dad said I should invest in a new radiator. I found one for $243.

My questions

1. Should I replace the coolant first and see if that helps the high temps on the way home? or
2. Should I go ahead and replace the radiator and the coolant at the same time?
3. If I choose to replace the radiator how hard of job is this on the 93 2.5?
4. If I get the radiator replaced at a shop is there anything else they should do like flush the block?

Thanks,

roane3

PS - Nothing like 3 100 degree days in a row to get you thinking about cooling system.

There are so many things that can cause overheating, I wouldn't jump to the conclusion that it's the radiator. A few quick answers:
1. Don't keep driving that car if it runs over 100C. You are going to crack the head and/or blow the head gasket. It's not a 123, and doesn't tolerate the overheating. It's too nice a car to throw it away like that. At the very least, I would turn off the A/C to bring it down below 100C
2. The green stuff is bad, especially for these models with aluminum heads. Get MB coolant or Xerex, which is a lot cheaper and readily available and yellow also.
3. Drain the cooling system and flush the radiator. Stick a garden hose in it and see if the flow is constricted. If it's not, it's not likely the radiator that causes the overheating. It could be the water pump, or simply the thermostat, or other things like the fan clutch.
4. When you put it back together, better just swap the thermostat as a precautionary measure, they're not expensive. That might fix your problem, just as long as you bleed the system well, and seal the thermostat housing correctly by cleaning the surfaces carefully before closing it.
Good luck.

I largely disagree with the previous post. What type of driving are we talking here - droning along the freeway, or stop & go, flat ground or climbing mountains? The car is expected to run warmer in some situations than others, and near 100F with the a/c blasting will definately result in higher engine temperatures.

That said, it's running hotter than it should. I respectfully disagree with the previous poster; you're not about to damage the engine. But you do have a problem in the formative stages here.

I would not replace the radiator right away, that's an expensive option. Start with the simple stuff first, and work your way up the cost/complexity ladder. First, make sure the a/c condensor & radiator are clean and free of debris. A surprising amount of crud can build up in the narrow space between them, resulting in substantially blocked airflow. Give it a good inspection, clean it out with a hose, consider pulling the radiator to get a thorough cleaning.

Second, suggest you flush the cooling system. MB recommends a citric acid flush. You can find lots of information here using the search function. Refill using the correct MB or Zerex G-05 coolant. Changing the coolant won't make it run at a lower temperature, but it is the formula MB recommends for long term protection against corrosion and other nasties.

Let us know how it goes. There are a bunch of other possibilities, such as the radiator, electric fans, engine driven fan clutch, thermostat, water pump, etc.

- JimY

Mine runs at the same temp, it seems to be universal in 124 diesels in hot climates. I used to worry about it alot, but now i just turn off the A/C whenever it gets above 100C. The gauge doesnt turn red until it gets above 120C anyway!

I use the green stuff too, its what every indie shop ive ever been to uses.. And that stuff about it being bad for aluminum doesnt make any sense. All modern engines are aluminum so why would they even make it anymore? that being said, if i ever did flush it myself i would use the recommended stuff.

good luck

I am going to try the the flush and fill with Zerex G-05.

It has been over 100 for three days straight here and it still only barely goes above the 100 after 30 minutes of stop and go traffic.

Thanks for the info,

roane3

The green stuff had other things in it that tend to pit aluminum due to the speed and force of the coolant as it leaves the water pump. I had a Honda Goldwing that required usage of distilled water and non phosphate coolant, due to the eroding of the aluminum. The GW was a '75. It is now living in Florida with a new owner, on the original WP, and no pitting of the aluminum under my watch.

"Mine runs at the same temp, it seems to be universal in 124 diesels in hot climates. I used to worry about it alot, but now i just turn off the A/C whenever it gets above 100C. The gauge doesnt turn red until it gets above 120C anyway!"

Ditto. My temps easily hit 100 with A/C. I keep an eye on it, but no longer worry about it.

The flush and fill is happening today with Zerex g-05. I would like the car to stay under 100 if possible. Next will be a thermostat and then a radiator.

I will check the temps on the way home today. Even if they are still at 100 at least the correct coolant is in there and I can move on to the thermostat.

I cleaned the radiator this morning. I also confirmed the electric are coming on.

Next I will change out the thermostat.

I was still getting over 100 degree readings yesterday with the flush and fill of zerex.

My car will heat up to over 100 if I push it up a hill with the A/c on. I have flushed, changed thermostat, filled with Zerex, cleaned condenser and radiator, etc and it would still creep to over 100 when pushing it on hot days. I unplugged the temp sensor plug which defaults both fans to high speed all the time and now it barely gets over 90 when pushing it up a hill. I drove it really hard yesterday and today trying to get it hot and it won't now. I will plug it back in when it cools off in a month or so. Cheaper to replace the fans than the head.

Huck

2 other options
 

The Art Dalton manual over ride switch
http://www.peachparts.com/shopforum/tech-help/193757-high-engine-temp-really-all-about-ac.html?highlight=switch

Jim F's Cool Harness
http://pages.prodigy.net/jforgione/MB_S500.html

It should almost never hit 100°C on the gauge. Make sure the radiator fins are clean, and also the AC condenser fins. Clean with compressed air if possible. Make sure the radiator isn't cool directly in front of the fan clutch, or the clutch will never engage (even if brand new). The clutch is suspect, these are known to be problematic... to test, get the engine to 100°C or higher, pop the hood, and kill the engine with the "stop" lever on the IP. Watch the fan - it should stop within 1 turn, it shouldn't freewheel to a stop. Don't forget to check the temp ahead of the clutch before condemning it... a bad radiator can make a new clutch not engage.

After all else fails, a new radiator is sadly quite common... they seem to end up corroding internally, or getting buildup inside the tubes, although they look perfect from the outside and when peeking into the plastic necks. My '87 is on it's third Behr and it looks like it will be getting #4 before next summer. Note that the factory procedure for curing temps above 110°C specifices a citric acid flush followed by radiator replacement... the acid flush won't "fix" a radiator with excess deposits.

:cool: