This is an edit to my original post. Just drove the car and came back and my coolant light is on! Tank looks dry from outside, waiting for it to cool before opening the cap. Can I top off with normal Prestone pre-mix to hold me over until Monday/Tuesday when car can get into shop? My tank is brownish/redish looking. I know the MB fluid is redish, but the tank is not translucent red looking, it's dirty red/brown looking. Is this normal? Or sign of rust/air, etc... Just had thermostat done at dealer two weeks ago. In addition, the below cooling problem mentioned in the priginal version of this post has been going on for a long time. Car has been in shop 3-4 times since May just for this issue. I feel like they are charging me @$$loads of money and no real results. Even if the temp issue I'm having is normal or within spec, you'd think that they would at least mention a dirty tank on a car that is in the shop specifically for cooling problems. Not to mention that they have flushed the fluid when they did head gastket, and at least added fluid again when they did thermostat. I'll have to sepak to them on Monday...

Original post:
I know this subject has been visited many times, but thought I'd post a new thread in hopes of gathering any new info...An archive search yielded tons of info, but nothing very recent.

I have a '93 300E, 3.2 I6, late '92 build, only 70k miles on it.

Temp
For the last few years, the car runs hot in slow or stop and go traffic, especially on hot days. The temp needle stays around 80-85 on the highway, but then reaches up to 110-ish when in slower traffic, especially after coming off the highway into slower local traffic, red lights, etc. The aux fans and engine fan all work. I tried to turn the engine fan with engine off, and it turns as much as I want to turn it, all the way around. Old posts here say that would mean it is going bad, not spinning at full speed, but M-B mechanics and other service people say that it is normal, that it should turn when off (that being the purpose of having a "clutch", not fixed to engine). Did the turn-fan-by-hand test only apply to earlier models? Or are the dealer techs wrong? Dealer did the head gasket early this summer, and problem seems to have become worse since then, but that may just be the summer heat. Had the thermostat replaced a couple of weeks ago, little to no improvement in temp. No leaks found.

Idle
The car sometimes has a slightly "bobbing" fluctuating idle speed when sitting still in park or in D.

Tranny
Clunks into gear from park or R. Sometimes when I make a special effort to pause and wait a second or two when shifting from reverse to drive, I get a short slip and a clunk before car jumps forward. After that, when driving, car holds gear long before upshifting when cold. Hard, heavy acceleration pulls up to redline, shifts smooth and crisp.

Thanks for any help or advice anyone can provide!!!

 

Just went out and checked the coolant level in tank after car has cooled for over an hour. It is up to the level of the horizontal seam in the tank. Seems normal. But then why would my coolant light be on? Also, although the tank looks muddy, a look inside with flashlight shows clearish looking fluid..not very redish or greenish. Can see right through it to the bottom of the tank. Any ideas?

 

You said you just had the head gasket replaced right? Did you refill the tank with MB coolant? I have heard it's bad to mix regular coolant with MB coolant because the silicas they use are different and it will clog up your plumbing. After a refill of the cooling system it is not unusual to have the resevoir suddenly drop in volume. This is probably just air bubles in your hoses being flushed out. What mixture ratio are you using? If your car still runs hot you may want to adjust your coolant to water ratio closer to 40% coolant and 60% water. The reddish brown stuff is a mystery to me. Usually an oil leak from the head gasket makes white milky foam in the resevoir. Could be old "regular" coolant mixing with the new MB coolant.

 

Tranny
Clunks into gear from park or R. Sometimes when I make a special effort to pause and wait a second or two when shifting from reverse to drive, I get a short slip and a clunk before car jumps forward. After that, when driving, car holds gear long before upshifting when cold. Hard, heavy acceleration pulls up to redline, shifts smooth and crisp.

The clunk is from a bad flex disc, get that replaced. Since you're having the same problems re-occuring or rather not fixed from your mechanic. I would take it to another more knowledgable and trustworthy tech. You just had your head gasket replaced, I would have a compression test. A leak or crack in the gasket/motor would cause overheating. Flush out your radiator and use some MB radiator fluid, see if that'll improve your overheating issues.

~Cali

 

Thanks guys. The head gasket was done at dealer. So it is filled with MB coolant. Another "running-hot" suggestion I have heard from an MB Service rep here in the office (I work for MBUSA) is to directly ground the gauge. They say it may not be running hot at all, just guage inaccuracy. Apparently they have done this in the past on their own cars, and the guage reads more accurately. My argument against that is then why would it read around 85 on the highway, and 100+ in traffic. Wouldn't this mean the guage is in fact operating correctly?

But, we'll try another flush, maybe with some Shout mixed in, as I've heard form 2 people now including MB people. Will definately request compression test and also ask about flex disc in tranny. Would gassing the car in neutral and dropping into Drive mess up the felx disc? I believe my mother inadvertantly did this once, very long ago. Thanks for help.

 

Reving the engine and then dumping the car into drive would definately not help the flex disc, nor your tranny or rear end for that matter. I think this is a fairly common problem on w124 and w201 cars with over 100k miles. It would definately help to get the flex disc replaced, when they go they can "unravel" and turn into a giant nylon hairball and wrap around the propeller shaft and screw all kinds of stuff up. The only way to prevent these from wearing out that I know of is to #1 Don't rev the engine and drop the car into gear (realizing this was an accident and not intentional) and #2 make sure you have come to a complete stop before putting the car in Drive or Reverse so you don't place any additional stress on that part. Good luck with your cooling flush, mine was a huge pain. Make sure you drain the engine block as well as the radiator. I would agree that your temp gauge is probably working since it shows the correct temp at highway speeds. If it is the correct thermostat, it is set to open at 87deg. C. At highway speed my car never gets above 87C. however in stop and go city with the air on it will spike to 100C very easily, but usually peaks out there.

 

i have the same type of problem in my 91 300e. it runs hot while idling and relatively cool when running on the highway. it stays around 85 on highway, but if i slow down, it goes from 100-115.. kinda scary. my coolant light isnt on, recently replaced the oil (if that does anything at all). My dad had taken the thermostat out a while ago.. i dont recall why he did that, but he says the car is supposed to run cool all the time without it. any possible solutions for me?

 

There is a 'sender unit" at the bottom of the tank. When they go bad the light goes on. Mine is bad too. You can just unplug the thing, but of course then you loose the indicator for low coolant. I don't think it costs too much to replace the sender unit. I just have not done mine yet.

Your description of the coolant sounds normal to me. Actually, so does your temperature stuff. Just about all these cars tend to go to about 105 degrees in stop and go traffic on a hot day. It is "normal" as long as it drops rather quickly when the high speed fans go on. The low speed fans come on for AC pressure and that can help a bit so that the car does not go to 105 quite as easily. When it is hot, however, there are always a zillion posts about the exact same thing on many W124 cars. There are even modified parts to stop the "normal" situation. I purchased a "cool harness" that turns the high speed fans on at 95 degrees instead of 105 degrees. It works, but the fans seem to just stay on after they engage. The best solution is probably a switch so you can simply turn the high speed fans on or off as you like to compliment the normal function. I am planning to try that next.

There are also some additives that can help keep the car a bit cooler, although I am not a fan of putting extra stuff into my fluids.

 

The reason the fans never turn off with this mod is that the thermostat is only about half open at 90 deg C. The engine will probably not get cool enough to turn off the fans until it sits for a while.

 

The delayed shifts when cold are normal. It's designed to warm up the catalytic converter faster and improve emissions.

The dirty tank is really of no consequence. It just means the previous owner did not flush as often as he should have, or they used non MB antifreeze. My MB fluid looks clear in the tank, and the tank is clean.

115 deg is hot. How hot is it outside? Mine never ventures above 100 deg C. while driving, even when it's 100 deg F. outside, but I have the AC on all the time so the aux fans never stop.

 

Where do you live? Have you flushed your Radiator during your ownership of the vehicle?

 

i live in los angeles. right now weather is around 85-90's (or at least thats what my benz tells me). but it was this way in the winter too.. im not sure whats going on.

some people suggested to get the timing belt checked, or to get a tuneup..

 

I've got the same car, same year, same mileage, some of the same issues.

I was losing coolant, but saw no leaks. I put some leak tester in the coolant and was able to notice a leak at the water pump, ($700-800 job at an indy, I'm doing it myself, but it is rather involved). My coolant expansion tank is kind of discolored, but I feel that is normal for the type of plastic that is used. I'd check for froth on the underside of your oil cap when hot, test coolant with leqak tester, then check oil for contamination, check carefully around water pump.

As to the tranny issue, mine does that too. If I pause before applying throttle in either fwd or rev, it will not clunk. The clunking is also worse when the tranny is cold. I do not think this is an issue with the flex disk, but i will inspect my disks next time I jack the car up. I think the issue is with the tranny. The PO had taken the car, under warrenty to the stealer for this issue and they wrote on the ticket, to make sure the car is stopped before shifting to/from rev/fwd. I always make sure it is stopped. I'll be saving a bit of money for a rebuild if/when the time comes...

 

It sounds like the radiator is fouled, or partially clogged due to improper maintenance or mixing different types of antifreeze.