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Water Filters

Originally Published in MotorHome Magazine



For the past five years we owned a fifth-wheel and used an external water-filter system consisting of a sediment filter (changed twice a year) and a charcoal filter (changed once a year). This system made the water more usable for us, and saved us the extra cost and weight of carrying more drinking water. We now own a Class A coach with an in-line filter. We are still using our external-filter system, since we already have it. We know that most filters need to be changed at the most every year. By using my system, is there a need to still change the in-line filter once a year, or can we wait a little longer to change it?

Larry Danner | Appomattox, Virginia


By using an external water filter before the in-line filter, you are reducing the amount of particles that the secondary filter is receiving and being called upon to filter. This should have an effect on how often the filter should be changed. The micron rating of the filters is important, too. You should have the coarser filter first, then the finer one. Part of the consideration is that you may pick up a load of water, which might clog up the filter more than at other times. I suggest that, when the time comes when you would normally replace the filter, open it up and examine the insides carefully. This will give you an idea of how much crud the filter has trapped, and although it will ruin the filter, it will give you a guideline interval for future replacements.


Antifreeze Coolant Life
My 1999 diesel pusher has a Cummins M-11 with a side-mounted radiator and 110,000 miles on the odometer. I perform most of my own service, so disposing of waste fluids is always a consideration. Oil is easy to recycle, but few facilities take used antifreeze, so I haven’t changed the fluid since 2006. I check the coolant freeze point regularly, use Fleetguard test strips to check its condition and add supplemental coolant additive accordingly, as well as change the coolant filter. The antifreeze still looks new, and I haven’t had any issues with the cooling system. I’ve heard about bubbles that can cause pitting on the outside of the cylinder liners, but obviously can’t know if that’s occurring. I think I’m saving money by using what still works, and with the motorhome’s age, warranty is not an issue. Do you think I’m being foolish by not changing the antifreeze?

David Rossman | Corbett, Oregon


Have a tech question?That’s a great question, and the short answer is, I don’t think there is a definitive lifetime expectation for the antifreeze chemical mixture in terms of either miles or time. The easy answer is, follow the manufacturer’s guidelines. However, there’s certainly more to this. Manufacturers need to provide simple guidelines that offer clear-cut intervals, while covering a wide range of operating conditions (kind of one size fits all).

I’ve seen some vehicles that had very cruddy looking coolant after just a few years, and others that looked like new after a decade. I think some of the variance is due to the particular brand and mix, and some of the variation is caused by how often and how long the engine is run, plus the makeup of the metals in the engine and cooling system. Dissimilar metals cause electrolytic corrosion along with the usual oxidation and rusting. Problems such as air trapped in the system and head-gaskets leaking combustion gases into the coolant can speed up the deterioration of the fluid.

The coolant filter (which is typically only used on heavy-duty diesels, not gas models) does an excellent job of extending the life of coolant, as does adding factory-recommended additives to boost performance and extend service life. The use of distilled water instead of tap water also helps by reducing the amount of minerals in the cooling system, which can leave solid deposits that can reduce heat transfer.

Testing freeze temperature and using test strips are both good methods and are recommended, along with a Refractometer Coolant Tester. Using a commercial testing lab is an additional and definitive method of determining if your antifreeze coolant should be replaced. You can send in a sample, and in a few days receive the test results. You can Google “automotive antifreeze coolant testing lab;” one of them is Polaris Laboratories (877-808-3750, www.polarislabs.com). While this may be a little pricey, particularly for gasoline engines that have smaller system capacities, it starts to make sense with larger diesel-cooling systems on heavier coaches.

Some radiator shops have coolant-recycling machines, which filter and restore additives to further extend the life of the antifreeze mix. I suggest you check around for one of these places when it comes time to drain and replace the coolant. Of course, owners should use a product that is approved for use in their specific engine, in the correct percentages, along with any recommended additives for (diesel) cavitation erosion, etc.


Reefer Madness
We have a 2005 Damon Challenger with a Dometic RM2852 refrigerator, and the freezer gasket has been compressed and isn’t rebounding. I tested the seal with a dollar and there is no compression against the bill with the door closed. After cleaning the existing gaskets, will applying a self-adhesive closed-cell foam gasket (the kind you find at a home-improvement store) be sufficient, and will it last? Or, is there any way to rejuvenate the original gasket? The unit is still functioning well. If I have to, can I buy a new gasket from Dometic? I looked online and haven’t been able to locate an OEM gasket. I saw a kit that you tape onto the original gasket, but it received poor ratings.
Stephen Brown | Via email


I don’t recommend trying to glue one seal over another, except in an emergency. There’s no practical way I know of to “revive” an old compressed door seal, either. When Dometic builds its doors, the seals are integrated into the foam core behind the plastic liner of the door, and are therefore not replaceable, and Dometic recommends ordering replacement doors for your refrigerator. You can order parts such as doors for your Dometic RV refrigerator directly; call 800-544-4881 to be referred to a local Dometic factory dealer or service center. You can get aftermarket kits from other suppliers that are a double-sided tape, glue-on version, applied after cutting off the old ones; a Google search for “Dometic RM2852 refrigerator door gaskets” brings up a slew of them. Expect to spend around $200, and reviews, as you stated, are not very good.


Ken FreundRV DIYRV Tech SavvyTech topics

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