How do I know if I dodged the bullet? (longish)

LarryE9E10

LarryE9E10

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Warning: This story is not for the weak of stomach or the faint of heart!

Took the coupe on a 10 mile ride drive to pick up some spark plugs. Warmed up and ran normally. From there I drove 5 miles to a nearby town to drop off a package for a friend. That drive was high speed and high-rpm on full-on twisty roads, with full attention required out the windshield as the roads are forested, barely two lanes and full of deer (Note: This is my rationalization for what happened next). Pulled into the parking lot and, for the first time in that drive, saw that my temp gauge was in the red. No, it was at the TOP of the red. Don't know for how much of the drive it was overheating; the last 100 feet? All but the first 100 feet? Crap.

Made things worse by assuming that I had a broken ground on the temp gauge, as the needle has never run at higher than level (i.e. 3 PM), even when coming home from the Vintage at 75+ mph on I 81 in hot, humid weather. Drove another 100 yards or so at 25 mph before sanity returned and I checked the coolant, which was boiling. Waited for the car to cool down, started up a big hill for home and it overheated almost immediately. Had it towed.

Put the cooling system under pressure and discovered a couple of very small hose leaks, which apparently caused fluid loss only when under pressure as there was never any coolant on the garage floor (I am vigilant as I'm obsessive about the small oil seepage that I can't find.) Eventually it lost enough volume that it could not cool the car. Replaced all hoses.

Car is running as strong as ever. Took a long ride at high rpms. Sat in a
traffic jam for almost 15 minutes without temp gauge going higher than 4 PM.

So, have I dodged the bullet here? What, if anything, do I need to do to assess the status of the head, the head gasket, etc. Or should I leave well enough alone in the absence of any symptoms of a problem.

Any advice would be greatly appreciated as I am, obviously, stupid beyond belief.
 
M30 head

The m30 head does not usually tolerate ANY overheating. The original cooling system was adequate, but with 30+ years of silt sludge, old gaskets slightly blocked rads etc the system should now be considered marginal. Of course new rad, hoses, water pump etc will help but the key IMO is to use the correct antifreeze and change it regularly. The aluminimum in the head will corrode if the wrong type is used and then you have a whole can of worms to sort out.
You may be luck, I do hope so, in future keep an eye on the temp guage, perhaps fit a discreet audio warning should the temp move into the red zone. ( where there is no parking, "Airplane" quote sorry)
 
Scary. Time will tell, however you can occasionally check for oil in the coolant and vice versa. Also if steam (not the usual exhaust condensation) comes out of the tailpipe when started cold then goes away when engine warms up that's a danger sign. If this is the case you can put a paper towel to catch some and see if it smells of coolant.

Hope you dodged it.
 
Larry, I would continue to check the coolant as the days go by this summer. It is impossible to tell if there was any damage done just by looking at it but if the temp stays good and there is no coolant level drop then you are probably OK. I had an early 530 (1977 I think) that would like to over heat and vapor lock and run poorly but once we messed with the fan, lowered the thermostat spec and did a couple of minor things it was fine. I think I put an aux. fan in there too. At 140K the trans went out (automatic). Having it towed back the car finally gave up the ghost after the car transport dropped it off the truck . The piece of steel that ended up going through the oil pan and getting stuck somewhere between the piston rods finally killed it. Kind of like Meatloaf in "Americathon"
 
It seems a good sign that the car is 'running strong as ever,' as over-heating can burn valves, leading to loss of power. Such was the case w/ an Alfa Spyder I overheated when a hose gave out.
 
Hi Larry -- Not sure I have much to add about the potential for head problems, but as to potential for a faulty ground to cause the temp gauge to spike at the top of the red, it works the other way around. The circuit runs voltage to the temp gauge, which experiences less resistance as it becomes hotter. This diminished resistance allows a larger voltage flow to the gauge, and the needle moves upward in response to this increase in voltage. Thus, the way the circuit works, a broken ground would stop the voltage flow to the gauge and cause the needle to drop down to read no heat in the radiator.

Good luck with the aftermath.
 
The fact that you still had coolant to boil is good. If there was no coolant left, that would have been much worse.
 
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