Cooling System Contamination: Repeat Component Failure Requires Heroic Efforts

By Kevin S. McCartney. There are currently four areas that I see as overlooked opportunities for automotive cooling specialty shops:

1. Al₂O₃ Contamination & Cooling system filtration
2. Lubrication, oil gelling and coolant heated PCV systems
3. Fuel tank contamination
4. Electrolysis Damage

Modern engines rely much more heavily on the lubrication system for cooling than ever before. Oil coolers and coolant heated PCV systems present some new opportunities. But, there is a great deal of overlooked technology in modern motor oils that should be understood before this opportunity is addressed.

Fuel delivery systems have changed and contamination related repeat fuel pump failures are increasingly common. The demand for fuel tank cleaning and reconditioning is increasing dramatically and radiator shops are well equipped to step into this niche. That subject is also a bit too involved to cover here. There is a lot more to fuel contamination than just the fuel tank.

Electrolysis damage is actually extremely rare. But, parts distributors and general repair shops almost always blame corrosion erosion damage and cavitation damage on electrolysis. I’ve written several articles on both electrolysis and cavitation that can be found on the internet.

Corrosion erosion from abrasive aluminum oxide contamination (also known as Alumina or Al₂O₃) is already well known to most cooling system specialists. It can be the end result of damage from water pump cavitation, electrolysis and other failures of aluminum components. It may be accelerated by air intrusion and the improper use of some coolant formulas in some applications.

Once corrosion erosion has reared its ugly head, the original cause is overshadowed by the destructive power of Al₂O₃ circulating through the cooling system. Some OEMs have claimed that extreme cases require replacement of the engine block. I haven’t seen any cases that can’t be rectified by slightly more conservative efforts. But, extreme cases are far beyond the capability of a typical general service shop.

Al₂O₃, or alumina, is a very dense and very effective abrasive. It is used to make sand paper and grinding compounds. When the engine is shut down, it settles into the deepest cavities of the engine block. Normal flushing fails to extract Al₂O₃ from these hiding places. General Motors developed a 3-step flushing procedure to address this. That 3-step procedure is extremely labor intensive and usually requires far more than 3 separate very difficult flushes. It is more accurate to call it a 12-step program instead of a 3-step procedure. It also creates a huge volume of waste water that may require special disposal in some municipalities. The GM 3-step flushing procedure is covered more extensively in other articles and training programs.

In the most common failure mode caused by Al₂O₃, a heat exchanger fails after a fairly normal life cycle. The Al₂O₃ left in the system by failure of the original component causes the first replacement part to fail within a year or two. The second replacement component then fails in 6 months or less. Subsequent replacement components fail with increasing frequency as Al₂O₃ from each failed component continues to accumulate in the system. The above cycle continues until heroic efforts remove contamination from the system.

One of the best ways to address Al₂O₃ contamination is to run the engine at normal operating temperature all day long with a large full flow filter installed in the cooling system. A very few commercially available cooling system service stations allow this capability. Installing an appropriate high temperature residential water filter at the radiator outlet can be a very effective alternative. As long as the filter has sufficient flow capacity, the car can idle in the shop all day long with this filter attached. It may help to rev the engine once in a while to kick up some of the Al₂O₃ a little faster.

Splicing a separate filter into the heater circuit will also help. The temperature in this circuit will be higher so additional care should be taken to use a filter that will handle the heat. Remember that the thermostat will allow less flow through the radiator than there is through the heater or bypass circuits during idling and other low load conditions.

The filter must be able to handle normal cooling system temperatures, pressures and flow volumes. It only needs to filter particles of about 100 microns (0.0078 inch) and larger in size. Filters that trap extremely small particles are not necessary and are more likely to restrict flow to the point of overheating.

It is fairly easy to find a residential/commercial hot water sediment filter that can withstand 175 o F and filter 50 micron size particles. Most of these filters can tolerate the heat at the radiator outlet of an idling engine.

Stainless steel filter assemblies are available that can withstand temperatures up to 250 F and extreme pressures. These are a great investment for shops that do a volume of cooling system service.

Filter housings are available that accept 10” tall filters and have 3/4 inch inlet/outlets with up to about 5 gallon per minute flow. One of these could be adequate for some applications but I recommend using two or more of these together in parallel for typical automotive applications. There are some housings that have 1.25 or 1.5 inch fittings and accept mesh screens that allow greater flow.

Residential and commercial hot water filters are NOT appropriate for permanent installation or street use. They should be used strictly within the shop. The flow and temperature limits will handle radiator outlet water under shop conditions. But, they are not appropriate for road use.

NOTE: Ultra fine filters (5-20 microns) are readily available but will cause more resistance to coolant flow and become plugged more easily. A 100-200 micron filter is more than adequate but a little more difficult to find. Ultra fine filters will clean the system very well but may require additional filter assemblies in parallel to provide sufficient flow. Some filters will also not tolerate the temperatures and pressures in the system.

Al₂O₃ contamination stays in the deepest cavities of the block until the engine warms up and then begins to gradually mix and circulate. So, filtering this stuff out can take a full day of idling in your shop with occasional higher speed operation to stir things up. Residential filters are not really designed for this use so steps should be taken to insure safety in the event of sudden leaks or ruptures.

After the system has been thoroughly filtered, it still must be treated as a slightly contaminated system. An on-car filter should be installed and a coolant with increased abrasion protection should be used.

The heavy duty truck industry uses coolant filters. These are the size of large automotive oil filters and are mounted in parallel with the heater. If there is sufficient room, one of these filters should be installed. Until you are sure that the contamination is under control, you may want to install the filter in series. After you are sure that contamination is under control, the hoses should be re-routed to provide parallel filtration. Many cars will lack the required under hood space for a filter of this size.

A small inline filter that can be spliced into a heater hose is an ideal way to prevent Al₂O₃ contamination from developing or returning. I have searched for years and have not found any suitable inline coolant filter assemblies. However, you can make a small inline filter assembly from brass pipe fittings and the filter washers that are often used in residential and commercial washing machine hot water faucets. A filter washer will fit nicely between a 3/4” barb x 3/4” MPT (male pipe thread) fitting and a 3/4” Barb x 3/4” FPT (female pipe thread) fitting.

The brass filter assembly will be relatively heavy and may cause increased flexing of the heater hoses. This may shorten the life of the hoses. I recommend mounting the brass assembly so that the weight is supported. You should also make sure there is a low area upstream of the filter for trapped material to collect.

If you use two filter washers, you can sandwich some filter media in between them. Be aware that increased resistance to flow will reduce heater output. The typical brass screen filter washers will not cause any noticeable reduction in heat. But, using two filter washers with a fiber filter media will be noticeable in cold climates. You can test the filter assembly and filter media for flow with a garden hose prior to installation.

The on-car filter should be checked about one week after installation. If there is evidence of Al₂O₃ , recheck again after another week or a full month depending on the amount of contamination. If extreme contamination persists, you may need to perform another full-flow all day flush and recheck weekly until it is under control. The on-car filter is in the heater circuit. So, you don’t need to worry about a restriction causing engine overheating.

Copper pipe and fittings can also be used instead of brass fittings. This is a great way to use the skills of typical radiator shop employees on slow days. Make sure you provide a small reservoir below the filter washer for filtered particles to collect in. And, be aware that edges of straight pipe ends will eventually cut into any heater hose that is clamped around them. I have used PVC fittings to construct inline filters but the temperature limits of many PVC fittings are too low to provide reliability in many applications.

An inline heater hose filter will protect the entire cooling system by preventing Al₂O₃ contamination from building up to dangerous levels. The heater circuit is an appropriate place to install a filter when any components are being damaged by the Al₂O₃ contamination. The heater circuit in most applications doubles as a bypass circuit. Coolant circulates through it even when the thermostat is closed.

I’ve always discouraged deviating very far from the OEM recommended coolant formula. But, when Al₂O₃ contamination is a problem, exceptions must be made to get things under control. Silicates are the fastest acting coolant additive for combating abrasives of this type. A good quality conventional inorganic additive technology (IAT) coolant, or a hybrid organic additive technology (HOAT) coolant is highly recommended when Al₂O₃ contamination has been identified. Once the contamination has been removed and the system has operated trouble free without any signs of contamination, you can switch back to the OEM style of coolant.

Make certain that the service is topped off with an appropriate new radiator cap. Drop center or gravity vent-return caps should be replaced with spring vent style caps. Check all radiator caps, even new caps, to insure that the top seal does not leak vacuum. Air intrusion during the low pressure recovery cycle is a major contributor to Al₂O₃ contamination. Surge tank pressure caps do not cause the same air intrusion problems. Radiator cap vacuum testing is covered more extensively in other articles and training programs.

In Summary, when Al₂O₃ contamination is a problem, follow these five steps:

1. Filter the entire cooling system through a full flow filtration system for at least a full 8-hour day. This gets most of the contamination out of the system.
2. Install an on-car filter. This traps any remaining contamination and traps any Al₂O₃ that is formed later.
3. Install a silicate bearing IAT or HOAT coolant. This provides an additional layer of protection that will hopefully prevent further damage as any remaining
4. Al₂O₃ is removed by the on-car filter.
5. Install a new high quality spring vent radiator cap (if so equipped) and test the cap to insure proper recovery cycle sealing.
6. Recheck the vehicle on-car filter weekly tapering to monthly for evidence of Al₂O₃ contamination.

With this effective method of addressing Al₂O₃ ”corrosion erosion” in place, you need to market this specialty service to general repair shops and parts distributors in your area. Your marketing efforts should include references to “electrolysis damage”, “Al₂O₃ corrosion erosion”, “Aluminum Oxide contamination damage” and “repeat heater core, radiator and water pump failures”. Most of the industry still thinks that repeat failures are caused by electrolysis. So, you should mention electrolysis when promoting this service. On rare occasions electrolysis will actually be the cause, so you need to be prepared for that also.

Promoting this service will bring in a few very profitable jobs. But, the more valuable impact is creating a reputation of being able to fix the most difficult cooling system problems. You will soon have parts distributors, manufacturer representatives and other shops recommending you within the industry and to consumers.