308 Leaking Antifreeze Overflow Problem LOOK!!!!

That cap looks really old. Radiator caps are cheap, and it's a good idea to change it periodically, though not with every oil change. If you are using the old "green" antifreeze, you should be changing coolant about every three years. That's the normal life span of the anti-corrosion additives in the coolant that you really need in there. So that's a good time to check the cap and if there is any signs of deterioration, just get a new one. I use the Stant cap 1.1 bar on my 328 and it works fine. I used one on my 308 as well, same thing, worked fine.

 

Where does one buy a Stant cap? I've looked locally and asked wherever I've gone, and still no luck.

 

Try ordering online if your local outlets are useless. There are part #s for the Stant caps in the 308 Parts Cross-Reference Thread, here:

http://www.ferrarichat.com/forum/showthread.php?t=64460

Check the very first post, very first part cross-ref... Hope that helps.

 

I use a Stant but still use the .9 bar one. Doesn't seem to be a problem with my 77.

 

Going 1.1 cures this problem - at least until THAT wears out too.

I had the overflow problem happen about a month into ownership (1997). I put a 1.1 and never looked back. Not another drip in 15 years and 50,000 miles.

 

I bought my replacement cap from Superformance, as I wanted to replace the tired original spring, seal, etc......no cooling problems whatsoever. Coolant is the local auto parts store brand, pre-mixed 50/50. The only time that she drops coolant on the floor is when I've over-filled the tank. I've learned the "sweet spot" for the car, and it doesn't happen any longer.

 

I opened a thread here about cooling problems. Under no circumstances should you replace a cap of 0.9 bar to 1.1 bar against one because if you overheat your system, constituted by the valve cap begins only 1.1 bar at a temperature so higher than originally planned. This could cause damage to your engine.

http://www.ferrarichat.com/forum/showthread.php?t=326049

Theodore
http://www.f400club.com/forum

 

While any overheating event - regardless of pressure - can cause (substantial) damage to your engine, switching from a 0.9 bar cap to a 1.1 bar cap does not materially change the risk of damage.

The reason for this: the increase in boiling point going from 0.9 bar (1425 mmHg) to 1.1 bar (1575 mmHg) is minimal, only a few degC. (Going from a 0 bar open system to a 1.1 bar system pressure raises the boiling point by 40 degC.)

A higher-pressure cap, causing the cooling system to endure higher pressures when stressed, will more likely result in a burst hose or gasket, or extrusion of hoses from clamps / fittings. This stuff definitely shouldn't be ignored, but as far as risks go, they are minor. (Watch the large diameter hoses and the large circumference water pump gasket carefully; both LaPlace and experience say they experience the largest tension from the pressure.)

But a 1.1 bar cap is a very minimal band-aid for a bigger underlying problem, so it's still not much of a solution: if you have a problem that is somewhat mitigated by a 1.1 bar cap, your underlying problem is still there and it will come back to bite you. And boiling off your coolant, regardless of whether you have a 0.9 bar or 1.1 bar cap, runs a very high probability of doing real internal engine damage, even if you shut it down quickly, etc. And besides, no one likes a sports car that smells bad and piddles all over the street!

A better approach than a higher pressure cap would be to reduce the coolant concentration to 30% glycol, rather than the standard 50%. A 30% concentration gives up only a few degC of boiling point, but has more than 10% more heat carrying capacity improvement versus the 50% mix. Also, the 30% concentration has an improved viscosity, so pumps better (lower load on the water pump) and flows faster, again further improving the heat carrying capacity of the cooling system. A 30% concentration freezes at ~2 degF (-16 degC), so this is definitely a three season approach (no F-car excursions to the ski challet). But then, not many of us drive these cars in winter temps.....

A 30% glycol concentration should really be a standard approach in street performance summer fun cars, IMHO: this is actually more than just a band-aid. (Further reducing concentration, to 20% or 25% say, is not a good trade: too much reduction of boiling point for less heat capacity and viscosity improvement, and operation near freezing becomes somewhat risky.)

-frank