Evans antifreeze and bad heater valves

I am on my 4th heater valve rebuild by Old Air. Looked at my history on rebuilds and I’m getting 6-10 months out of a valve and it starts to leak at the diaphragm. VERY unhappy.

I am using Evans waterless antifreeze which has worked out well and has good characteristics for alum…

In talking with the Evans tech on the problem he said they may be using old timey rubber on the diaphragms. He said Evans is not compatible with genuine rubber.

Old Air says yes they are using rubber diaphragms that they have made for them.

Anyone using Evans?

And if so has anyone experienced this?

I don't have any experience with Evans, but have used GO5 coolant for 25 years and am impressed at how well it keeps the aluminum bits. It is what MB used for years and I used to have to go to a MB dealer to get it. Now you can find it at AutoZone. Prestone GO5 in a gold jug. I read a bunch about this 25 years ago and use it in all my cars. It isn't the green stuff and it isn't dexcool. From what I read dexcool is probably the worst especially for old cars like ours that have a bit of air in the system.

Thinking about this some more. if Old Air is using Buna-N or something similar and not EPDM for the rubber components, they are selling bits that are not compatible with modern glycol based coolant. Buna-N or regular Nitrile just swells and deteriorates with glycol. I have used it in a pinch until I could get EPDM parts, but it does not last long when in contact with coolant. I am not sure you can get any coolant these days that is not glycol based. I know they use water wetter with deionized water in racing cars (SCCA, IndyCar, etc) and that may be compatible with nitrile, but why?

Evans seems to think its more of an issue with the additives, perhaps anticorrosion additives, in the antifreeze. I maybe wrong but I don’t think its the glycol as most do use some glycol in their formulation.

Not familiar with GO5 but I’ll check it out. Using the “Pet safe” Peak Sierra classic green in my other cars at this point and change out per recommendation every 2 years

In discussing the issue with Fusick back in Sept, they and everyone else i talked to use old formulation rubber, although he wasn’t familiar with the Evans problem he agreed there is a similar problem with Dexcool. They had previously looked at going to Viton but there was additional cost so they elected not to. .

But, in light of this issue which is only likely to get worse, he said they would now work up an OPTION for a Viton diaphragm. About $20 additional cost.

This option should be available in January per Fusick. No concrete affirmation at this time. They have already done a prototype build of the diaphragm. Talked to them about 2 weeks ago.

BTW per Fusick this same diaphragm is used in lots of different valves.

For those wondering why hoses don’t have a problem, I’ve been told modern mfg hoses whether for classic cars or not are a modern formulation of “rubber”.

Well, any hoses for my newer Saabs all are stamped EPDM. I just assumed that EPDM was used for all rubber bits in the cooling system.

I read this about 25 years ago and have used either MB or G05 ever since and had very few issues with cooling systems.
Saab Coolant Story

Not saying the diaphragm is epdm. It doesnt look like they are using that. All they told me is they are using regular old timey rubber.

Looks like EPDM is a more modern formulation per Wiki which would then be more resistant.

EPDM rubber (ethylene propylene diene monomer rubber)[1][2][3] is a type of synthetic rubber that is used in many applications.

Fusick Olds now has a diaphragm made of Viton which is resistant to the Evans, Dexcool, or other with problem additives. They rebuild valves, buick Skylark same as Olds F85