Bottom Line
Maintenance Q&A

Paul Abelson
technical editor

Question: My 2001 Freightliner Century Class started dripping coolant from the steel radiator pipe leading to the engine. When I went to examine it, I noticed quite a few rust patches. I touched one and my thumb went right through the pipe. I wound up with nearly all the coolant on my shop floor. My dealer said this is not covered under warranty. I have a little over 200,000 miles on the truck. What can I do?

Answer: This seems to be another example of how the new mixes of chlorides and urea-based chemicals, used for easier snow removal and ice control, are aggressively attacking our trucks. From the mileage, I’d guess this truck has seen at least two winters, plenty of time and enough exposure for corrosion to get this bad.

The pipe in question is by the right front frame rail, near the front tire and suspension. The pipe is primed and painted steel, with a chassis paint coating. In its location, the pipe is exposed to road debris and chemical spray kicked up from the front tire. All it takes is a few stone chips to expose metal to the aggressive chemicals, and problems start. Corrosion can get a foothold through openings too tiny to see with the naked eye.

I urge everyone who travels north of I-40 to power wash the bottom of their truck at least weekly, and to inspect the bottom of the radiator and all pipes at every PM, especially in winter. If there are any signs of corrosion, replace the part.

To protect from stones, I would wrap the replacement pipe with self-bonding silicon tape (available at West Marine and truck parts jobbers). The tape is about 1/16 inch thick, and with an overlapping spiral wrap, it can be made thicker. The tape conforms to curves, and will protect the pipe from minor impacts. It fuses to itself, so there will be no open seams. Being silicon, heat is not a problem.

Protect a new pipe before installing it, but don’t try to patch an old pipe. Once the corrosion has started, the pipe has been weakened.

When you’re under the truck inspecting, also check metal headlight, parking and fog light frames and mounts, wiring and connectors. Be sure that all wiring connectors and plugs are covered liberally with dielectric grease. I carry several tubes of Truck-Lite’s NYK in my toolbox.

The new road salts and brine sprays are insidious, penetrating every nook and cranny on your truck. Be alert for their effects.

Question: The batteries on my Mack Vision are not holding a charge, but the dealer says they test just fine after recharging. The alternator also tests good and the wiring seems tight, too, with no unusual rust or corrosion. I’d rather fix it myself before spending more money at the dealer. Also, the engine sometimes runs hot for no apparent reason. Then it goes back to normal. Any suggestions for either of these?

Answer: Since the dealer tested the batteries (I assume under load) after recharging, we can rule them out for now. You’d be amazed how many perfectly good batteries are returned under warranty because of erroneous diagnoses. The next thing I’d look for is a bad connection or a bad ground, but you indicated you checked the wiring.

How about the fan belts? The Mack engine has a poly-V belt that drives the alternator, the air conditioner compressor and the water pump. That could be what ties your problems together.

If there is not enough belt tension, the belt could start to slip when the A/C kicks in and puts a sudden drag on the belt. That would slow both the water pump and the alternator, reducing water flow — your heating problem — and lowering alternator rpm. Many alternators need high rpm to reach full amperage output. The alternator may test well in the shop with the A/C off, but on the road, it may not produce enough current to drive your accessories and recharge the batteries.

Mack engines use both manually and automatically tensioned drive belt systems, depending on specific engine configuration and application. Most on-highway engines have an automatic tensioner.

Check the poly-V belt for tension. It should be between 260 and 280 pounds for a new belt, to between 220 and 240 pounds for a used one. It should never be allowed to get below 150 pounds. Don’t guess. Measure with a tool designed for these belts. Mack recommends the Kent-Moore J41251-B for 10-15 rib poly-V belts.

Mack automatic tensioners cannot be adjusted or repaired. If belt tension is low, check the tensioner for free operation before replacing it. Mack provides specific instructions. They call for removing the belt by pulling the tensioner back with a breaker bar, then moving the tensioner to see whether there is any roughness or hesitancy, or if there is any metal-to-metal contact between the arm and end cap. If so, replace the tensioner. Also replace it if there are any cracks or if stops on the spring case are broken.

When reinstalling, make sure the belt is properly seated in all pulleys.

Question: My Kenworth T-600 has a small stone chip in it on the passenger side. I’m afraid if I leave it, it will grow into a big crack and I’ll have to replace it. They cost a lot, not like the old two-piece flat ones where you could just do one-half. I saw a glass repair kit at Wal-Mart. Can they be used on truck windshields?

Answer: I couldn’t believe how expensive replacement windshields have become. It used to take only one person to remove and replace a flat half-windshield. Now it takes two to lift and maneuver the curved one-piece glass. So whenever possible, you should consider repairing rather than replacing. But remember, the windshield is a structural part of the cab, and its optics affect safety.

The Cab and Controls Study Group of The Technology and Maintenance Council wrote a Recommended Practice, RP429, Windshield Replacement and Repair. When deciding whether to repair or replace, consider the rest of the windshield and the location of the damage. If the glass is cracked or broken or if it is pitted or abraded, replace it. Also, if the chip is in the driver’s area of direct forward vision, replace the windshield. Repairs are close to, but not perfect optically. There will be enough distortion in repaired glass to cause headaches after looking through the repair for several hours.

If the damage is on the passenger’s side, is within repair guidelines and if the windshield is otherwise OK, repair could be a good option.

The next question is, should you do it yourself or should you call a repair service? “Glass repair procedures call for extracting all the air from the damaged area and replacing it with polymer resin,” according to the TMC RP. “This resin, when cured, has similar properties to the glass.”

Glass industry association standards and practices require equipment that will “remove moisture and contamination, access the damage through drilling or probing, remove air and inject repair resin, protect the resin from premature curing, properly cure the resin and fill in the finished pit.”

Those are the procedures to be followed. If the kit from the store has the right equipment, the procedures parallel the industry guidelines, and if you feel competent to use the kit properly. I’d say go ahead. But if you’re not completely comfortable, call in a professional and check his methods and references.

The RP states, “Quality repairs require good equipment, quality resins and careful technician selection.” A good outsourced repair will be more expensive than an automotive department kit, but not nearly as costly as a new windshield.

The RP also cautions, “Since it is possible for the windshield to crack during repair, TMC recommends ... have the proper windshield available for replacement.” That’s another reason to consider using a qualified professional to do the repairs.

By the way, the RP on windshields was written by a committee led by OOIDA member Gail Swiger before she was elected Study Group Chairman.

Correction: In the October Land Line, I wrote that the TMC RP Manual costs $140 if you are a member. That is for a second copy. One copy comes free with membership. Non-members pay $195.

Do you have a maintenance question?
You can write to Paul Abelson, technical editor, in care of Land Line Magazine, PO Box 1000, 1 NW OOIDA Drive, Grain Valley, MO 64029; or you can fax information to (630) 983-7678; or e-mail your question to Please mark your message Attention Maintenance Q&A. Although we won’t be able to publish an answer to all questions in Land Line, we will answer as many as possible.