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Old 11-01-2007, 04:04 PM
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Join Date: Apr 2007
Location: boston, mass.
Posts: 5
1978 240D radiator--Boom! won't start...

So, I have a 1978 240D that i've had and have been driving at least 250 miles per week for 2 1/2 years. Has something like 275,000 miles. It never broke down before until two weeks ago when I was driving 65 mph on the Mass pike, and my wife started saying she was smelling something sort of burnt. Then I smelled it, I didn't ever see the temp gauge (which I normally watch carefully), then a plume of steam, then a giant cloud. Pulled over FAST! and I opened up the engine and shut it off (shut off valve never has worked). I think it got well over 250 degrees for a few minutes. And not only that, a 5-inch long gash was torn the top of the radiator (rad. less than 1 yr old, never overheated before).

Once it cooled, I tried to start it. It just turns over happily like this fellow who has a video of his car's
problem on youtube
, but doesn't start (sounds like his). I read this thread. From that, seems that it could be that the head gasket blew and those exhaust gasses escaped by pressurizing/blowing the radiator open before they could get out of the overflow tube. (???)

The only other events of note are that I had recently swapped the alternator, and tightened the belt (which I believe I did correctly). Now after stopping the car the belt was NOWHERE to be seen, the new alternator (seemingly undamaged) was hanging away, less one bolt, from the bracket. The water pump still turns, has no play, no squeaks. Could it have been the culprit still? The thermostat must have been okay, because there was no overheating (the temp needle always goes from 0 (cold) to 175 (driving). The other thing that occurred to me just now is that this little thingy in the thermostat housing (which I think is the temp sensor) isnt really connected to anything (no wire..) but what doesnt make sense is why the temp gauge would have been reading anything if it wasnt supposed to be like that.

Well, that's a bit long. But I hope someone has an idea what happened. Because I like this car a lot and really want to get it back on the road Help?

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Old 11-01-2007, 05:13 PM
Magoo's Avatar
Grease Collector
Join Date: Oct 2006
Location: Pennsylvania
Posts: 333
Sounds to me like your alternator came loose and the belt flew off. Loss of the belt means no coolant circulation and quick overheating at 3000 RPM.
Also, if your engine turns over as slowly as the one in the video, it will never start.
'83 300D Turrrbo 295K miles
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Old 11-01-2007, 08:17 PM
junqueyardjim's Avatar
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Join Date: Apr 2005
Location: Cicero, Hamilton County, Indiana about 30 miles north of downtown Indianapolis
Posts: 2,621
No doubt about this one

Your replaced alternator is the total cause. Either you didn't put all the nuts and bolts back in, or perhaps just didn't torque them up. Very important to do. There is a lot of tension on that belt, and if the alternator is not properly installed, it won't go far. It might have cost you an engine. Hope not, but over heating like that is very destructive. It could be a badly blown head gasket, could be rings and cylinder walls. You will have to get into it to find out.

Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis

1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!
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