Overheat?

The fans turn on via a thermal switch on the rad while the gauge gets its reading from a sensor on the engine. First step would be to make sure your system is properly bled as an air pocket can cause what you are experiencing.

To bleed the system park the car on an uphill grade so that the top of the rad is as high as possible. Then have the car up to temperature and idling. Make sure the heater is also set to full hot (important to avoid big air pockets). With the car idling open the thumb screw on the drivers right top of the radiator. Turn it a few turns and close it once you get a steady stream of coolant without any air in it. Be sure to wear gloves and have some rags handy. The whole procedure should take a few minutes and might need repeating with a drive in between to circulate things.

If your problem persists after this you may want to start looking at the sensors for the rad fans and the dash gauge. For now just try the bleed.

 

It sound more or less what most tell me of their 308's, they run a little hot in traffic and the temperature will drop when moving on the road, especially cruising at at 70/75 miles per hour - with the gauge settle around 195 or just below, your fans could be kicking out to quickly when idling in traffic not sure, if the thermostat got stuck the gauge will move to the far right past 250/280 and you would have noted more heat.

a good radiator flush with new coolant could help a little, when last did you replace this ?

 

When I bought my 308 15 years ago I immediately re-cored the rad and had the coolant changed. In all my years of driving I have NEVER had the temperature creep up (except for one time that was bleed related). I have been in the hottest and most humid weather you can imagine in absolute bumper to bumper traffic with zero air flow to the rad for well over an hour and the engine never ran hot. To me traffic related over heating is either air in the system or a partially blocked radiator. These cars have extremely narrow passages in the rad that cannot be effectively `boiled out`by a rad shop. The only solution is a new core and it is important to use a core that is of the same density as the OEM one. Most shops fit cores with larger and fewer passages and these rads never seem to cool well. Ferrari actually got their cooling system right and overheating cars are usually down to poor maintenance or parts over the years.

 

I wonder if it is a wonky fan switch?

Very few people make THAT claim!

Personally, I think it is an airflow issue. The fans don't push enough. People consistently report that once their cars get moving, things cool down. This suggests to me that it is not a radiator flow problem.

 

+1

I also have a two valve version of the 308 and it does not overheat.

If you have not had your radiator checked in over 30 years, it's now time.

If you do not open up your heater control valve, you are not totally filling up your cooling system.

If it has been 30 years plus since you checked the fans, temperature sensors, hoses, thermostat and water pump, it's now time.

If you do not have 4 pieces of foam rubber around your radiator, you are losing efficiency.

Some air is going around your radiator, not through it. Foam rubber should be on all four sides of the radiator. A large foam rubber piece is glued under the hood and rests on top of the radiator when the hood is closed. There are foam pieces on each side of the radiator and a piece of foam under the bottom of the radiator that rests against the bottom of the radiator and the front valence. These four pieces make a BIG difference. (An additional piece of foam rubber is further back and glued to the underside of the hood and rests on top of the spare tire carrier, this helps keep some of the hot air from the front compartment from going through the fire wall and into the cabin, which makes it hot. Also, if the four previously mentioned pieces are missing, you will have more heat going into the cabin.)

Don't blame the car, blame deferred maintenance.

 

only time I've ever had an overheating prob was due to failed thermostat. it was 10 years old.

 

A constant flow of coolant from the overflow tube? The first thing that causes that is an over-full system - IOW, when cold there is too much coolant in the tank and as soon as the engine starts warming up a bit and the coolant volume increases, it exceeds the pressure of the spring and begins overflowing. BUT, it will quit after the engine establishes the "correct" level. It will do that on its own, spitting from the overflow hose. So are you saying the constant overflow occurs regardless of engine temp or once the engine is up to operating temp?

If it occurs at operating temp, as you noted, a bad Rad cap can cause this but again, only after the pressure/volume come up. If the pressure spring is weak, it may allow the coolant to boil near the normal boiling point of water as opposed to 230-240F of a properly pressurized system. If the coolant boils, it will, blow coolant /steam from the overflow. The cap's spring pressure has no direct affect on the coolant's volume increase as temp goes up. The coolant volume increases based on temp, not pressure. The pressure cap/pressure in the system simply raises the boiling point of the coolant.

As noted, the problem might be air in the system and bleeding should correct that. But if there is a need for repeated bleeding, there is a leak in the system somewhere. The system can be bled per the instructions in the owners manual, and it will stay "bled" until the next time the coolant is changed or until there is a leak somewhere. A leak may not be a visible stream/puddle/seep. There may be no readily visible sign. A pressure test is the best way to find a leak if you find that periodic bleeding is needed and there is no visible leakage.

Of course, there are other, more serious issues that can cause a need for repeated bleeding, loss of coolant, or erratic temperature gauge readings. But usually it is just a simple issue of rad cap problem or minor leak somewhere.

 

The beginning of my coolant problems started with an old cap + overheating + gushing out the overflow tube. After I replaced the cap, I thought my problems were solved... but over the next few days, I started noticing a leak elsewhere which took quite awhile to track down and repair. I've wondered if replacing the cap led to older components now being at more pressure than they could deal with (due to their age).

So - keep an eye on your coolant level, and the garage floor for the next few weeks. Hopefully you're done with the issue completely.

 

"It looks just fine. Even the spring feels normal, wish I could figure out a way to do an actual test on it."

In the old days, every gas station did repair work and had a tester that could check Rad caps. Whether anybody has one now...well, probably not!

As Thorn suggested, keep an eye on things initially with the new cap and probably a bit higher system pressure. Check how the temp reacts in normal driving while out on the road.

 

And keep a full bottle of coolant in the trunk.

 

I would like to point out that on any North American 308 with the big fat bumper on the front the bumper is deflecting the air away from where it was designed to go. If you change the front bumper to a "European Style" bumper, which is the bumper designed for the car, you will not experience overheating under normal driving conditions.
I promise!

 

It can take 3-5 sessions (repeated bleeding) to get all the air from the radiator and the engine. But once bled, it should stay quite bled. If not, you have air leaking in from elsewhere.

 

Lots of threads here on overheating & assorted fixes.

My '83 consistently gets very hot in heavy, slow traffic. I dread stop & go and parking lot traffic. Forget the A/C when the car isn't moving. Start driving, the temps drop.
I've gone most of the whole route of rad cleaning, hose replacing, radiator foam. Nada. A buddy went further with Nick's radiator & new fans. Nada.
Someone on here was offering an autobleed kit with Euro hot-water bleed caps for the radiator & engine gooseneck. I installed them and they are great. No more bleeder screw rubber gaskets becoming brittle with age & heat cycling. No more scalding coolant spitting out with the air. No more constant bleeding. But if I'm sitting in traffic, the temps still rise into the 230 zone.

 

My 78 308 with the big fat bumper does not overheat, even in stop and go traffic. The air goes under the big fat bumper and into the grill. As ugly as the big fat bumper is, I have no intention of changing it.

With all due respect, I think when you make such a generalization that "on any North American 308 with the big fat bumper...you will experience overheating under normal driving conditions." is quite silly. So, with the big fat bumper under what conditions will it not overheat...only by removing it?

I have confidence that when the Ferrari engineers designed the big fat bumper they certainly were not planning on having it overheat their engines. Please give them some credit. Ferrari does tend to take pride in their engines!

 

Also My North American QV with the big fat bumper never overheated even driving in LA rush hour traffic during summer and I still have the stock radiator and stock water pump in eleven years of owning it. So I don’t know what the heck George is talking about.

 

"No more constant bleeding."

If bleeding is constantly required, there is a leak in the system. Once bled, it is bled until you drain/replace the coolant. When these cars were new, owners weren't taking them to the dealer every couple of weeks to have the coolant systems bled.