i just bought a 1981 c3 for a friend. the car is to be shipped to Italy.
i picked the car up in Oceanside and drove to National City. a trip of about 45 miles with a little extra driving thrown in and had no troubles other than a little stumble. I figured that was poor carb adjustment.
I had to drive to the forwarders in Torrance to ship the car, about 125 miles. i made it to San Clemente, 70 miles when the car started to act up. loss of power, no acceleration. laboring to maintain speed. the temp did not go much over 200 but you could tell there was big trouble. I pulled into a gas station and opened the hood. water was boiling from the overflow tank. i kept the engine running and poured water over radiator core and tanks to cool it off. i did notice diminished flow from inside the radiator and the water looked like mud. after clean water and new coolant i hoped all was well. two exits down the freeway and the car said forget it. after i unloaded it from the tow truck it started fine and ran with no knocks pings or bad noises.
questions are bad radiator? thermostat? muffler bearing? tell me what you think. also do you guess any lasting damage to engine?
i know that last one you could only guess...

 

It could be something as simple as the thermostat stuck in the closed position. If that turns out to be the case, be sure the replacement is of the type that, if it fails, fails in the OPEN position.

AutoZone, etc., sells them for only a couple of dollars more.

Jake

 

I had cooling system problems with my 84'. The radiator was clogged up (replaced it). The other thing you can do to improve performance is to replace the temperature switch. The factory switch doesn't kick the fan on until 228 degrees. Ecklers has after-market switches that can kick on as low as 180 degrees. I also replace the fan relay with a beefed up unit from Ecklers

 

this car is a c3 with a fan clutch. unless the clutch is bad i don't see that being the trouble. [ i ran a push button switch and indicator light in my 84] i agree that the thermostat could be the problem, the flow i was seeing inside the radiator when i was filling it was not at all impressive.
by the way weather was definitely not an issue today, cloudy and 65 with scattered showers.

 

Eckers S*ck, don't do it.... nothing personal oldtvman, just personal experience with them... You can add a manual fan switch, search forum, there are tons of posts on the issue, also do a search for overheating, etc, theres more info as this has been discussed 1000 times or more...

 

Driving at cruise speeds should not require a fan to get sufficient airflow through the radiator.

Is the lower air dam present? It does help to direct air upwards into the front of the radiator. Is there dirt and debris between the radiator cooling tubes? Are the fins bent to where airflow is reduced? Same with the A/C condensor, it has to allow airflow through to the radiator.

Another possibility is a collapsed lower radiator hose. Lower hoses typically have a coiled piece of wire that keeps the hose from collapsing and cutting off the flow of coolant into the engine.

The cooling tubes in the radiator can get clogged (you mentioned "mud") so the most likely culprit is a lack of flow of coolant through the radiator. The older metal tank radiators can be taken apart and cleaned out so that is something that should be done. A complete flush of the system is in order along with all new hoses and a new thermostat. Refill with a 50-50 mix of ethlyene glycol coolant and distilled water.

As radiators get old, the metal in the cooling tubes actually wears away from the constant flow of coolant and reaction of minerals in the coolant and the tube material. The tubes can get too thin to effectively transfer heat from the coolant to the outside airflow. It could very well be time for a replacement radiator.

I would consider doing a complete cooling system service that would include a radiator clean (or replacement if necessary), all new hoses, new 'stat, water pump, fan clutch, and belts. With the car going to Europe, replacement parts are going to be very expensive much less finding a supplier of C3 parts

 

Have the cooling system flushed, new hoses and a new t-stat. If that doesn't cure it, it could be the radiator or water pump. I changed all those on my 79 C3. Not a lot to go wrong, with the coolant like mud, you definately need to have the system flushed and the flow checked thru the rad.
Bernie

 

thanks for the input guys, my suspicion was always a plugged up radiator. but there can always be a combination of things involved. the car is already at the freight forwarders so i cant do any repairs. i supply parts to several people in Italy so I know all about the expense involved.

my hope is that no damage was done to the engine.

thanks again for the help, Terry.