help with overheating 79' 308 USA

“ The water temp went up just before 250°f”. In the scorching sun. Setting in a traffic jam. (his words). I’m going to bet the AC was on max setting also while setting idle.

“When the outer temp got down, I drove it back home. I had been watching the water temp gauge, but as long as the car was running, I did not face any troubles.
(After this trouble, as long as I did not drive under the scorching sun, no troubles”.(his words)

The 308 cooling system is simply not robust enough for some driving conditions and thus gets its reputation for marginal cooling design. The 328 design addressed this issue. OP goes on to say that after this last maintenance he sees the cooling as being even less adequate. Couple of thoughts here.. There was a thread a few months ago where one of the members changed out his original fans for a Supposedly high performance new set of fans only to discover they moved less CFM through the radiator then the originals. Would suggest to the OP that mounting the third “Puller type fan” behind the radiator and the homemade shroud possibly inhibits the flow of air through the radiator? Have the fuse blocks been checked over for issues or been replaced? Are the radiator fans receiving enough current to run properly? AC and other electrical‘s running while sitting in a traffic jam in excessive heat is going to make this more prevalent.

 

The engine suffered a critical overheating event that caused it to stop running.
That's what I'm reading. Given the issues now experienced there's a more fundamental reason at to what caused that event.
Pertinent to that would be, did the engine "heat soak" and boil over once it stopped running?
Thermal induced shutdown of a running engine causes mechanical failures, possible failure points are,
headgasket
Liners
Piston rings
Bearings, connecting rods and/or crank
Water pump

At this point I'd be starting with coolant pressure testing both cold and warm. Warm engine leak down as well as compression test. Does the engine turn over by hand with the expected force needed, though that can be difficult to know without experience. Is each cylinder running the correct exhaust temp? And most importantly is be using a infrared laser temp gun to verify.

The over heating shutdown is concerning, engines don't just shrug that off and run correctly again. Need to sort out what caused the shutdown and why it got that hot.

What were the repairs after that event?

 

"The engine suffered a critical overheating event that caused it to stop running."

Hmmm...I didn't read it quite that way but I agree if that's what happened then a head gasket issue would be first on my list of "usual suspects!"

 

Honestly, has anyone read this thread and it’s entirety?
“- I felt power down. When I tried to connect the clutch, I met engine stall. “ Sounds as if he stalled the car trying to get it rolling again in traffic. Also sounds as if it’s not running it’s best.
OP (with step by step instructions by members here) checked for blown head gasket pages ago and reported that all is good. OP is reluctant to verify/deny temperature readings shown on gauge with a thermal temp gun and validates overheating by the engine stall event. As mentioned posts ago, if this vehicle got hot enough to quit running it’s not going to just start right up again and run normally. Given his list of items replaced/refurbished, including a total system flush, there is nothing in this cooling system that isn’t brand new except for the 6 foot cooling tubes mounted underneath the car. I’m done but sincerely hope this gentlemen is able to find an acceptable solution to this issue.

 

There may be a translation issue at play, I don't think the OP is a native English speaker.
Out sounds like that it got really hot, started to bog then stalled out. He left it to cool down for a couple hrs, as it would not restart.
That points to issues other then just the cooling system needing attention.
I've seen more then one set of warped heads from overheating. And a couple cracked liners, scorched rings and scuffed skirts.

 

Failed head gaskets can happen in a variety of 'flavors' everything from catastrophic to subtle. Pressure testing the coolant system is only one of many tests. The system should hold overnight, at a minimum I'll test for 4hrs. Start with a 'dead cold' engine and if need be run the pressure test on a warmed up engine.
The cooling system is very large on these engines and should have very little trouble keeping the temps where they need to be at idle for extended periods. If it can't manage idle then something is wrong and short of a failed pump, blocked radiator or leaks, then something is amiss with the engine.

 

Looking at the photos within the OP's original link (radiator replacement) the fan blades are on correctly to push air through the condenser and radiator. It would be a good move to verify the motors are spinning in the correct direction though just to confirm the airflow is correct.

 

If anyone has been watching the 308 rebuild by Lou Trottier on youtube he just tested old versus new fans and indeed the stock fans push more CFM. But they are not shrouded to the radiator like newer ones should be. He did a quick test with the stock fans showing how much air blows up or out and around the radiator versus through it with the newer ones properly shrouded. Pretty interesting and telling to see.

 

That series should be entitled: "Bringing a parts car back from the dead"