Antifreeze Doesn’t Last Forever

What makes antifreeze go from alkaline to acidic? Does combustion gas leak from the head gasket and contaminate it or is it the heating and cooling process? Regardless, we have had two corrosion situations from acidic coolant recently, a pair of 330 cylinder heads and the core plugs in a 365 GTB/4 Daytona. To be fair, the core plugs are very soft alloy in comparison to the engine block so they are kind of sacrificial, unfortunately they are difficult to change. These plugs were so delicate that just by scraping the crusty coolant off to find the source of the leak, the screwdriver poked right through them like they were made from waxed paper.

Daytona engine block

Ferrari 365 Daytona Engine repair

Core Plugs for Daytona Ferrari 365

Ferrari 365 Core Plugs

The 330 heads are a combination of a bad casting and corrosive coolant. I saw a youtube video showing the process of building a modern Ferrari 612 engine where an MRI test was used to determine the thickness and integrity of a cylinder head casting. They didn’t have this technology in 1966 and this is the evidence of it! The deep pores in the exhaust port aren’t from corrosive coolant, it’s from a horrible casting. The pitted areas around the water passages are due to corrosive coolant rotting the material away.

330 Head Gasket leak

Head Gasket leaking on Ferrari 330

Cylinder head Leaking on 330 Ferrari

Welding holes in Ferrari 330 V-12

Like a dentist, I drilled and scraped the corrosive material out so I could weld the holes that were leaking coolant into the exhaust and intake ports. I don’t often remove valve seats and realize what a difficult job it is but I found a great way to get them out easily. I take a valve with the same size stem as the original (8mm for Ferrari) but has a slightly smaller head. I weld the head to the seat and drive the valve and seat out with a hammer from the back side!

Ferrari 330 GTC Head Repair

Repairing 330 GTC Heads

Anyhow, after welding, grinding, pressure testing a number times, I finally have the heads sealed up and looking great. After grinding and cutting the core plugs out of the Daytona block, we installed the new ones and sent the car home.

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  1. Peter R. said,

    August 5, 2012 @ 1:34 am

    Interesting technique for removing the valve seats but how do you get them back in?… Am I correct to think that the originals – at least the exhaust seats – were a bronze material, so do you at least replace them with iron seats for unleaded fuel?

  2. Sam H. said,

    August 8, 2012 @ 3:56 pm

    To quote a reasonable source “From the time the coolant is introduced into any type of engine it starts a gradual degradation process into corrosive acids. This degradation is a function of time, temperature and the types of metals used in the engine and components construction. Once the coolant turns acidic all engine metals start to dissolve. The results are leaking water pumps, heater cores and radiators.

    With the increasing number of aluminum engines and components the corrosive process is accelerated since the coolant degrades much faster in contact with aluminum than in typical cast iron engines. During the preventive maintenance of any engine, in addition to the freezing point, the pH value of the cooling system should be checked.”

  3. Peter P said,

    October 24, 2012 @ 10:04 am

    Thanks for posting this — I did not know this was a potential issue. After seeing the post, I picked up some coolant ph testing strips and an anti-freeze hydrometer on Amazon. Everything tested fine (ph 8, protection to -40) as I expected since coolant was recently changed, but it’s good to be able to test for piece of mind.

  4. DougD said,

    November 7, 2012 @ 10:39 am

    Antifreeze doesn’t last forever, but I think this posting might.

    Looking fwd to the next interesting & informative installment of your progress…..

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