Mark, My Words | July/August 2017


By Mark Nemeth #45776, Escapees Technical Advisor

Q. My last two fifth-wheel trailers have had external axle grease fittings, and I need to know how many miles I can drive before the bearings need greasing and how many pumps from a hand-held grease gun should be applied. At the advice of a mechanic, I applied grease with about three pumps of the grease gun every 1,000 miles on the way home from Alaska, and I had no trailer brakes. When I arrived home, I took the trailer to my local RV shop and had to have the magnets and brake shoes replaced to the tune of $884. The entire inside of the drum was coated with grease. Now, before my next trip, I am having the bearings packed for $200. It seems to me that with external grease fittings, I could avoid both these expenses if someone would tell me how to correctly grease the bearings.

A. You received bad advice. The Zerk fittings on the axle are there to make it easy to load the bearing with grease. Once you do, the hub is greased and does not need additional grease applied over time. Once the grease is in the hub and the seals are intact, it can’t go anywhere. If none is being lost, there’s no reason to add more.

The grease does not break down significantly over time, so there is no need to replace it annually. The only exception is when you pull the wheel hubs to inspect the brakes, which should be done every few years. Since you have the wheel hub off, it is a good idea to clean and repack the bearings, and replace the inner grease seals before you reassemble the axle.

Repacking trailer bearings annually, or after so many miles, is strictly applicable to boat trailers because they are regularly submerged in water. The water leads to contamination of the axle grease, making it necessary to repack those bearings regularly.

If the hubs are operating at normal temperatures and there’s no sign or symptom of grease leakage from the hub, then leave them alone.
Tire Temperature
Q. I’ve read many articles on tire pressure and heat, but have never learned if there is a maximum temperature that will damage tires. I have pressure and heat monitors on my fifth-wheel trailer and have seen temps as high as 105 degrees. Is this too high when the ambient temperature is 90 degrees?

A. While in operation, tire temperature will generally rise several degrees above ambient temperature. This is caused by rolling resistance and friction, and it is normal. I have seen my tires exceed 140 degrees on an exceptionally hot day. Bridgestone published the following info that will give you an idea of the “acceptable” range. “A general rule is that a properly inflated/loaded tire, when up to operating temperature, which is one hour or more of operation, will typically run about 60 degrees F hotter than the ambient temperature. Anything above 200 degrees F could lead to tire degradation, and you need to investigate for a problem.”

Since a lot of factors are at play, my suggestion is to buy an infrared, handheld thermometer, and ritually check the tire and hub temperatures each time you stop during your travels. This will allow you to get a feel for what is typical for your RV. It’s not so much the absolute temperature of a tire, but rather that it is not diverging significantly from what you have established as “normal.” If you usually see tire temps that run around 120 or 130 degrees, and you discover that one tire is running at 160 degrees, this indicates something is wrong, and you need to investigate further.

Danger of Degrading DEF for Diesels
Q. For diesel owners who may not be aware, DEF degrades in heat and should not be kept in the back of a truck. Degraded DEF can contaminate fuel in your truck if it reaches the wrong temperature. This could cause potential damage to the engine, wreaking havoc to its system and sending you to the shop. DEF should be kept in the cab or anywhere that is temperature controlled.

A. You are correct. DEF should be stored at temperatures no lower than 12 degrees F and no higher than 86 degrees F. In fact, the shelf life of DEF stored below 80 degrees F is stated to be two years, but if stored above 80 degrees, that shelf life drops to one year. All users should be aware of the need to store DEF in a climate-controlled location in hot or cold weather.

Undercover Tear Repair
Q. I have a 26-foot Salem bumper-pull trailer. While traveling down the road, I noticed fabric flapping around the wheels of the trailer. After pulling over and checking it, I found the undercover was torn and coming apart. Is there a fix that a handyman can do?

A. It depends on the material and how badly it is damaged. If it is a cardboard-like material, it is hard to get anything to stick to it permanently. If it is plastic, it is easier to patch. If the damage is not extensive, you can try aluminum duct tape, found in home improvement stores in the furnace duct area. This tape has an aggressive adhesive and may be enough to fix the tears, but it isn’t strong.

Another possibility is EternaBond tape (www.eternabond.com). Designed to repair roof leaks, this product comes in various widths and, in my opinion, is the stickiest stuff on the planet! It can repair larger damaged areas and is strong enough to make a permanent repair. It is expensive, but it’s a useful addition to any RVer’s toolbox.

If there is major damage, It’s best to remove the damaged area and either run without it or replace it. It may be possible to purchase replacement material from the manufacturer or a local RV repair shop. In a pinch, thin foam wall panel insulation found at Lowe’s or Home Depot can be used, but it isn’t ideal.

EternaBond tape, cleaner, and primer are available at: www.eternabond.com

Black-water Tank Repair
Q. I developed a jagged crack in my black-water tank. I tried to fix it with silicone caulk and then sprayed it with automotive undercoating. It held for a while, but has now developed a small leak. I have situated a tub beneath the leak that captures the liquid, but it is an unsatisfactory solution. I noticed in a prior issue of the magazine, you mentioned that you repaired a leak in a holding tank using EternaBond tape. My question is threefold: What would be the best tape to buy, the Alumibond or the Flexible WebSEAL? Do you think I should try to remove some of the silicone and undercoating or apply the tape directly over them? Should I use a cleaner, such as alcohol, MEK, acetone or paint thinner, before applying the tape?
A. I’ve had good luck with EternaBond on tanks, but it is necessary to prep the surface first. You must remove all traces of previous sealants, especially silicone, as nothing will stick to it, not even EternaBond. Once the area is pristine, EternaBond offers both a spray cleaner and a primer, if you want to use them. I’ve used acetone with good results to clean and prepare the surface, but be aware that it will soften and melt ABS plastic, so use it sparingly. The foil or white-backed tape is fine for flat areas. The WebSEAL is intended to be more flexible to follow curves and contours, so if the area isn’t flat, WebSEAL would be the correct choice. WebSEAL has no UV protection, so you need to coat it with something after it is in place if it will be exposed to light. Surface preparation is the hardest part of the job, but it’s the key to a successful repair.

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