Brown Coolant

[Cooke95]

Have an 06 motorhome with a 400 Cummins on a freightliner chassis.
Recently had a low temp problem (module on radiator went bad), fan on high speed all the time. About the same time noticed coolant a little darker (light brown) than usual. Stopped @ freightliner and they said it must be the module we can order, but we are headed to Gaffney for service anyway will it hurt to drive it that way? Answer Nope so off to Gaffney for module and radiator flush. Gaffney flushed and flushed and finally got some Restore+ from Cummins and got it clean. Then however we have a leaking radiator. Change radiator and hoses refill with fleet guard and drive it ~ a little to chech for leaks. We don't know what caused it but you are good to go. Coolant is light brown again after ~ 800 miles. Engine has 50K miles, never been over temped, I use no oil and have no oil indications of problems, use no coolant, other than replacing what I drain from the radiator to check color, put coolant strips in comes out brown. No power loss, mileage no change. Where is my brown coming from?

[Perry White]

Do you have a steel expansion tank?( the tank that the rad cap is on). Sometimes they rust and let a film sit on top of the coolant.Drain some out the bottom and check color.

[Cooke95]

Yup do now. When changing the radiator found crack in the neck of the plastic one.

[spike45]

Quote:

Originally Posted by Cooke95 Have an 06 motorhome with a 400 Cummins on a freightliner chassis. Recently had a low temp problem (module on radiator went bad), fan on high speed all the time. About the same time noticed coolant a little darker (light brown) than usual. Stopped @ freightliner and they said it must be the module we can order, but we are headed to Gaffney for service anyway will it hurt to drive it that way? Answer Nope so off to Gaffney for module and radiator flush. Gaffney flushed and flushed and finally got some Restore+ from Cummins and got it clean. Then however we have a leaking radiator. Change radiator and hoses refill with fleet guard and drive it ~ a little to chech for leaks. We don't know what caused it but you are good to go. Coolant is light brown again after ~ 800 miles. Engine has 50K miles, never been over temped, I use no oil and have no oil indications of problems, use no coolant, other than replacing what I drain from the radiator to check color, put coolant strips in comes out brown. No power loss, mileage no change. Where is my brown coming from?

Usually brown coloration of engine coolant is due to a build up of degradation acids. These are the products of aging ethylene glycol. Also, the phenomenon is accompanied by an unusually strong odor that is more like stale paint thinner than coolant. The second cause of brown coolant is attributed to a reduction in pH resulting in rust formation. The third cause can be coolant that is contaminated with either lube or transmission oil. The coolant can acquire some darkening of color and accompanied by the strong odor. I recall you saying on the phone that the coolant before and after the change did not smell any different. There is also the possibility that the system when it was first flushed by service facility did not accomplish what they started. Engine flushing with straight water can accomplish removal of old coolant but the process requires high engine RPM and sufficient heating to open the thermostats to get positive flow through the radiator. You also had the engine flushed with Fleetguard Restore Plus cleaner. From your description of that process, I would say that it was not executed correctly. Restore Plus is a mild acid (citric and phosphoric) based chelating cleaner. It does very well in removing corrosion and scale formations. I do doubt that you had either of those to much degree with only 50K miles. You did indicate that after flushing you had a leaking radiator. That is not uncommon after flushing as leaks do develop into slow minute leaks that become self-sealing due to dissolved chemistry building up on the air side. The flushing agent removed this "self leak stop". Running that fan constantly did not create this issue. I do not see anything in your operation of the engine that caused this.

[J Walker]

Has the SCA filter been changed regularly? It prevents cavitation but it may do more such as pH control. You could get test strips that can tell the pH and the state of the coolant. That is too bad about the radiator going bad since it is a major expense. There may be a cause such as pH or it could be a defect in the radiator. There are companies that analyze coolants and I would use one if you can't get this cleared up.

[spike45]

Radiator leakage due to small pin holes in the middle of the core or at least not at the core tube-to-header plate are not caused by chemical corrosion. Aluminum radiators are especially susceptible to stray current induced corrosion. Stray currents are due to inadequate ground return path of the engine electrical system. The most common source point is using the steel frame rail as the major electrical return. Most OEM chassis builders do it right by having a (-) battery cable from the electric starting motor back to the (-) terminal on the batteries. Plus the alternator and all coach DC wiring grounds connect to a common ground location at the starter (-) terminal like the spokes on a bicycle wheel to the hub. This will provide one ground potential in the system. There are some OEM chassis builders who "save" you money by using the steel frame rail as the major ground return path. While the engine and electrical system does function, the engine starts and the alternator charges, there can be differing ground resistances due to the multiple connections using the steel path. When these connections get corrosion at varying degrees, the ground resistance can be such that the electrical system will use the engine cooling system as part of the electrical return. For aluminum which is a low nobility scale metal, it will be the first sacrificial metal in the electrically caused corrosion reaction. When radiators were made of copper this was not much of an issue as to corrosion but was still an issue for insufficient ground return low resistance path.

What do you look for? Trace your starter (-) post coming from the end of the starting motor. Some starters are now built that have removed this terminal post and ground through the electric motor frame into the bell housing. In either instance there should be a negative (black) battery cable equal in size to the positive cable. That starter (-) cable must go directly to the battery pack (-) post connection or to a cable junction. If you encounter a short (-) cable or braided strap from the starter to the steel frame rail you have the system that is prone to aluminum radiator failure. Some systems may still use a short strap to the steel frame while running the correct (-) cable in addition to the large return path cable. That is fine.