My 99 E300 (125k miles), until now a model of reliability, finally broke down. A week ago I took it into my local dealer (Cherry Hill NJ) due to the instrument panel readout reporting low coolant, but normal temperature. They (said they) checked it and the only problem was the coolant reservoir cap which they replaced. Car ran just fine before and after. Until last Friday. Driving up a steep ramp in a parking garage that "low coolant" message reappeared. I figured it was an artifact due to the steep incline and the car was parked within 30 seconds. When I got the car back I noticed that I was no longer getting cold air from the A/C but no "low coolant" or any other error message. A few blocks later the engine seemed to suddenly loose power and there was the "low coolant" message again. I immediately parked the car (noticed the temp gage was at max (120 degrees C+)) and MB sent a flat bed to haul the car to that dealer. While waiting in the 100+ degree F heat I removed the reservoir cap, very carefully of course and with a few layers of scrap cloth, and nothing happened. No hissing, no steam. The car started for the flat bed driver and within a few seconds he had driven it up on the flat bed and off we went. THe MB dealer will look at it tomorrow.

Is there a coolant problem with this engine? Can I have damaged the engine? I am obviously scratching my head about a connection between this failure and the dealer's "solution" to the original "low coolant" complaint. Coincidence or bad diagnostics?

I bought this car around 85k miles ago and planned to keep this baby to at least 300k.

 

Was the radiator full when you pulled the cap? When is the last time you changed the thermostat? What did the engine sound like when it was started to load it on the truck? Having only driven it a few blocks, you might only have blown out a head gasket if that.

 

Dodge, there was no coolant visible in the reservoir tank when I opened it. After the car sat for about 30 minutes I poured in about a half gallon of 50-50 antifreeze (that's all I had with me) v-e-r-y, v-e-r-y slowly but still saw nothing in the reservoir tank. Engine started immediately and sounded quite normal when the car was driven onto the truck. Thermostat? I have no recollection of when it might have been replaced. I have had all the servicing done at my local MB dealer. Maybe it was replaced somewhere in the course of schedukled service. Have to check back over my records.

A blown head gasket could certainly cause overheating and coolant loss. If this was the cause of the breakdown, I wonder if it should have been detected when I first complained about the "low coolant" error message. If it was not the cause . . .

 

If you paid "out of pocket" money to have the dealership look at your car, then you did not get what you paid for. For them to say, "they checked it out" in my book, that means they checked the coolant level, pressure tested the system, and made sure that everything was operating as designed. For you to loose that much coolant in such a short period of time would indicate either of two things...one would be a leak that should have been visible to the naked eye, or a blown head gasket. If it were a blown head gasket, you should have noticed a difference in the exhaust and or a difference in performance. As for the thermostat being the culprit, that still does not solve the issue of the missing coolant. Good luck!!

 

There is a possibility that the thermostat stuck after it was checked at the dealership causing overheating and the blown? head gasket resulting in the coolant loss. Thermostats are'nt normally checked or changed on routine maintenance, but if I was checking one that came in for coolant loss, I would at least look at the thermostat. If the engine sounded normal you might have shut it down before serious damage occured, but you're probably still looking at a blown head gasket, or a cracked/warped head. Check it out carefully

 

The dealer's people found a leak in the radiator and are confident all is well. Seems to run fine. They took a few hundred bucks off the work (new radiator) due to the embarassment of (1) apparently missing the leak the first time around, and (2) not working on the car promptly.*

*The service horror story: Car was carried in by M-B road Service late Friday afternoon. I was in CA on business Monday through Wednesday and heard nothing from them, which got me worried. Left voice mail inquiry with the service rep. I called Thursday and the service rep told me they had not looked at it--vacations, short handed, etc. I left a strongly worded voice mail with the service manager who finally called me back late Thursday all apologies. I picked up the car late Friday afternoon almost exactly 7 days after bringing it in!