What to check on overheated engine?
 

Folks,

Today the alternator belt on my 240D broke. I drove it six miles without the water pump or fan before I realized what happened. The temperature gauge has been spotty of late (you can bet I'm fixing that post-haste) so I can't say how high the coolant temperature got. I can say that the highest speed I got up to was 55 for half a mile. I ended up putting about 1.5 quarts of fluid back in after I parked it.

I'm replacing the belt tomorrow, and I have high hopes that the engine is not too damaged. With the transmission in neutral I can turn the crankshaft, so at least it didn't seize up.

The question is: how can I check if I damaged the engine? What is liable to break when an engine overheats?

Most commonly the head gasket.

You might find that it starts to consume coolant.

You might find oil in the coolant.

You might find that it won't maintain temperature..........various escapades of running higher than normal.

You might find pressure in the cooling system after it sits overnight.

Or.........it might be perfectly fine. One never knows with these.

if you had to pick a car that might b est survive such a stress, the 240 is probably the best candidate.

Tom W

You'll have some idea tomorrow when you start it up.

Thanks for the advice, folks.

The good: Engine starts. Alternator charges. No oil in coolant. Head gasket looks good.

The bad: Nothing 'bad' yet.

The ugly: A new low throbbing sound that seems to originate from the injector pump. A sort of 'shhh' sound from the area of the alternator. I will monitor them. The temp. gauge is still not working properly--the 'jumping' motion often reported by others; the sender doesn't seem to register any resistance when the engine is idling...time for another sender?

Overheating is not fun. I'm glad there hasn't been a serious issue after it happened

If you only blew out a quart and a half of coolant probably all is well. Of course the engine was hotter than usual but not hot enough to boil most of the coolant out. Could the swish noise be related to the new belt?
It is always important to keep the gauges properly functional. You may still not catch a condition in time even with them working. If not working generally you will not catch something till too late. You were lucky this time in my opinion. Also I wonder how many of our members ocassionally inspect the condition of the rubbber belts for cracking and wear etc. Always cheaper to catch them early.

That's what I'm hoping. I figure it will go down once I put some mileage on it, but I don't want to drive it until I get that gauge fixed. I'd like to know how warm it's getting.

I'm not sure if I'm troubleshooting the temperature sender correctly. With the engine idling and the lead attached to the sender, I should be reading some resistance between the stem of the sender and a firm ground (say, the engine block), yes?