Bottom Line
Maintenance Q&A
Hot engines and bad bearings

By Paul Abelson
Senior technical editor


Q: In the June issue, you answered a question about an engine running hot. I came across a product at a local speed shop. I think it’s called “Keep Kool.”

It claims to make engines run 30 degrees cooler. What do you think about the product?

A: You may be talking about LubeGard’s Kool-It, which is a product of that nature. I don’t have personal experience with the product, but there are a number of coolant additives that do lower engine temperatures.

Before we see what they do, let’s look at what coolant does. Coolant is a mix of water, antifreeze and additives. Glycol antifreeze lowers freeze point and raises boiling point. Pressure also increases the boiling point, so make sure the pressure cap is operating at its designed pressure. Always premix antifreeze, additives and only de-ionized water. Use the premix to top off coolant.

Antifreeze doesn’t cool as well as water. Water absorbs heat better and transfers it much more efficiently.

Engines develop hot spots because of scale build-up, especially if tap water is used to mix the coolant. Tap water contains minerals that form deposits that insulate, causing localized hot spots. Hot spots cause water to form steam bubbles when it is heated above its boiling point.

Many racing organizations do not allow coolant with antifreeze because it is slick and hard to remove if an engine blows or a hose fails. Racers found that by using wetting agents – chemicals that reduce water’s surface tension – the steam bubbles are smaller, keeping more water in contact with metal surfaces. Heat transfer improves, so engines run cooler.

Be careful using wetting agents. Some are incompatible with antifreeze. Read labels carefully. Make sure chemicals are compatible with your coolant’s additives. Don’t use wetters if your cooling system is performing satisfactorily. Diesels run efficiently when warm. If you cool them excessively, you’ll lose fuel mileage.

To answer your question, wetting agents are good but only needed in special circumstances.

The coolant question also prompted some readers to share their experiences. David Harris found his high temperatures were caused by hairline cracks in his charge-air cooler. They are difficult to locate visually, often being right on seams. A leaking air cooler can raise temperatures from the intake through the engine and into the coolant.

David Hilsdorf controlled temperatures by altering driving. His Detroit Series 60 would pull hills in 9th gear (10-speed) at 1,300 rpm but it would run hot. He dropped to 8th at 1,600-1,700 rpm and easily pulled the grade. Higher rpms pull more air through the radiator so the truck runs cooler. In 7th, in cruise, he “… enjoyed air conditioning while the gauges all stayed where they should be.”

Q:  My Volvo has almost twice the wear on the passenger side steer tire as on the driver side tire. Alignment checks out, and everything seems tight. Changing tires hasn’t helped. Can you help?

A:  OOIDA member and Land Line reader Frank Swicord also had excessive wear on only one tire. He also found oil leaking from the wheel seal. While replacing the seal, he checked the bearing and found it loose. He replaced the bearing installation, paying close attention to the tightness and play in the wheel end.

TMC Recommended Practice RP618, Wheel Bearing Adjustment Procedures, describes proper procedures. Torque the adjusting nut to 200 lbs.-ft., then back off one full turn. Adjust to 50 lbs.-ft., then back off again up to one-half turn, following recommendations of the RP. Never use an impact wrench. Always hand-tighten wheel bearings.

Swicord reports that after a year, the tire still runs true. He adds, “You can’t shake the tire to see if the bearing is loose.” You should still take the measurements to be certain. LL


Paul Abelson can be reached at