PH Levels in Cooling Systems

[Gary Bishop]

PH in cooling System.

On Speed TV's show Motor Week Pat Goss talked about your cooling system and the PH levels. Pat talks about plastics but I gather it is really important for Aluminum also
He mentioned that the PH level should be checked twice a year.
Any one know about this or have done it?
What should the GM PH level be? Past and present?

http://www.mpt.org/motorweek/goss/2629.shtml

Info sites

http://www.radstrips.com

http://www.techmax.ca/coolant_service.htm

[Duke W.]

Re: PH Levels in Cooling Systems

Traditional IAT "green" is blended with "reserve alkylinity", which is reduced over the service life of the antifreeze. The RA of Dexcool is less and is not as critical on a HOAT conpared to IAT, and I'm not sure about HOATs like Zerex G-05, which is what I recommend for vintage Corvettes. So the "proper" pH range is a function of the type of antifreeze installed, and I don't think testing the pH every six months is necessary, but it will do no harm as long as you interpret the readings properly for the type of antifreeze installed, and in the case of OATs and HOATs reserve alkylinity is not the only measure of anti-corrosion strength.

Your best line of defense against cooling system problems is to keep all your cars on the manufacturers' antifreeze change service interval, which ALWAYS includes a time limit (regardless of mileage) that most people ignore, and use the type of antifreeze the manufacturer recommends. That's what I've done and I've never had any serious cooling system problems, but antifreeze changes are one of the most overlooked automotive services. So are brake fluid changes.

In the case of vintage Corvettes with G-05 I recommend a three year change interval, REGARDLESS OF MILEAGE, even if the car is in storage, because corrosion mechanisms work 24-7 regardless of whether the engine is running or not.

For long term storage the system should be drained, flushed, and dryed.

Duke

[Dick W.]

Re: PH Levels in Cooling Systems

Duke, on the older systems if you allow them to dry sometimes the microscopic holes in the radiators will leak the next time you fill them. You are a lot better off with fresh coolant for long term storage. We operated a radiator repair shop several years ago. Occasionally we would repair a radiator, test it for leaks, put it into storage dry, and when installed and coolant added would leak like a garden sprinkler.

[Duke W.]

Re: PH Levels in Cooling Systems

You and Joe Lucia are of the same school, and I don't argue with your anecdotal data, which I assume is mostly for brass radiators.

IAT antifreezes tend to plug small leaks due to precipitation of the salts. It could be that when radiators are allowed to dry out, the deposits shrink or loose mechanical strength and allow pinhole leaks.

I don't think this is the case with modern OAT and, perhaps, HOAT type antifreeze. So if you have a late model Corvette that has Dexcool or a vintage model with new radiator/heater core that has never seen IAT antifreeze, I think the best course of action is to drain the system rather than leave the system filled for long term storage.

Significant cooling system corrosion can occur even if the bulk corrosion inhibitor level is satisfactory. Lack of regular circulation from running the engine can lead to local galvanic action and do a lot of local damage. This tends to happen in nooks and crannies.

A good example is erosion of the tops of the cylinder barrels on Cosworth Vega engines. There are a number of "new" CVs out there that have been stored since new. One or two show up every year or two and are sold. Unfortunately, most were stored with the factory fill antifreeze and over the years localized galvanic action eroded the tops of the cylinder barrels and a few starts later by the proud new owner blows out the head gasket, which requires a major overhaul of the block including cylinder sleeves to restore the sealing surface at the top of the barrels. In these cases, if the system had been drained and dried, there would have been no galvanic action, and even if the radiator core needed replacement, it would be a much cheaper alternative than overhauling the block. So the answer may well depend on cooling system materials.

Unfortunately, I've never found any good engineering/scientific test data comparing "wet" and dry cooling system activity during long term storage, and the "correct" answer may well depend on cooling system materials and design geometry. But the industry is just not interested in what happens after 20 years of storage because this market is very small.

Cooling system corrosion mechanisms are like termites - all you can do is slow them down. No radiator will last forever, and aluminum engine components add greater risk because aluminum is a lot less forgiving than iron. It's a matter of using products and service intervals that get the most useful life, and that will probably always be a subject of debate.

Duke