I may have two unrelated problems but because of a stripped 10mm nut I am not sure. To begin with I have a 1992 240 with 211,000 Miles. Last night I had to drive a fair distance but before I left I needed to replace the thermostat as it appeared to be stuck open (registering very low engine temp and blowing only warm air in the cabin). After pulling the upper radiator hose and removing slightly less than a gallon of antifreeze I found the lower nut stripped. Some people should be taken out back and...

Anyway, for a variety of reasons (conducting the repair in 20 degree weather, next to the curb, with a bad cold and needing to drive 400 miles), I put the top nut back on along with the hose and refilled my coolant reservoir. At the time the color was green but seemed a bit dirty so I made a note to flush it.

200 miles into my trip I pulled over for gas and to check the antifreeze. The car is running extremely cold, sometimes the temp gauge would climb just slightly above the cold (bottom) line and it was blowing warm, not hot air. The coolant was green but opaque, not translucent, Both the oil and transmission fluids were just fine. The car was running fine with no loss of power or while smoke out of the exhaust.

I didn’t have much choice but to continue to my destination and made it without any overt problems. Not that it should matter but I did get an oil change two days ago. Oh, and the only time I know it overheated was last winter. It had been in the shop for. an auto-starter issue and when I started it up it got very hot, so I quickly returned it to the shop (literally one block) and they flushed and filled the antifreeze and I had no problem after that.

Thanks!

Mike

 

I liked your comment that somebody should be taken out back ,,,, and then your next statement was that you put the bad nut back on.
Now if the engine is still running cold on the gauge and if you feel the upper radiator hose and it is not hot then either you have a bad thermostat or the gauge or sender is bad. Pull the thermostat and test it in a pan of water.

 

Jag, I appreciate your response. I finally was able to use a nut extractor and replaced the thermostat. There was some RTV sealer on the studs and the thermostat was wedged in the housing so it had been replaced at least once. Quality work throughout.

The good news is I cleaned out the reservoir tank and no more milky antifreeze. I am now concerned there may be something getting into my transmission as there appears to be some fluid separation, so I will be changing my transmission fluid next.

I really like this car.

 

Based on everything you have said, I'd investigate the radiator for possibly leaky tranny cooler. And do it fast before more coolant enters the trans and ruins it...

 

Lev, there is no outwardly visible damage. I know there is more to this than simple observation so can you give me some ways to investigate? It has over 210,000 miles so I was thinking of a transmission flush. I suspect that will tell me a lot. My antifreeze stil looks great after replacing My thermostat and scrubbing out the reservoir. Perhaps because of relative pressures, it is easier for the antifreeze to enter the transmission line than the opposite?

Thanks for your assistance.

Mike

 

Good luck with the trans flush. Depending when it was done last it may be something that you don't want to do. I have 370K on our 89 740 but I do a recommended trans flush every 50K miles along with a timing belt change. If you don't do it regularly you take a risk that you will damage the gear box. Good luck.

 

"don't change old trannny fluid if really old" is an old wives tail! Some dispute that but it makes no sense. Shops claim that because they don't want to be accused of tranny failure after a change--if the fluid is really old they assume bad things are due to happen and they will get the bill... I'd avoid power flushes but just a drain and refill should not do damage.

 

McCavity, you mention "fluid separation"? Not sure what it looks like but it could be due to coolant mixing...

 

OK we'll see how it goes.