Question: You have recommended changing coolant every 50,000 kilometres or three years. How does universal coolant compare to green, orange, etc., types of coolant?
D.B.
Answer: As coolants and engine technology continue to improve, I've softened my position on coolant changes. Assuming a long-life coolant and 25,00040,000 kilometres per year, I'm willing to go five years now - a huge step for me.
There are basically two technologies for corrosion protection in engine coolants - inorganic and organic. The conventional antifreeze used for decades, which is usually green in colour, utilizes silicates and/or phosphates to protect the various metals used in engines and radiators.
The so-called long-life coolants - often orange in colour - introduced in the mid-1990s utilize organic compounds to provide anti-corrosion protection. The benefit is these compounds last longer, thus the extended-life concept. There are also several hybrid coolants used by several carmakers that combine both organic and inorganic compounds.
Universal coolants typically use organic compounds like long-life coolants and claim to be compatible with any coolant.
As confusing as the different coolants can be, remember three important things: You own and are responsible for the vehicle; if the cooling system contains any conventional antifreeze, change it every three years; and, finally, no coolant is permanent, or capable of lasting for the life of the vehicle.
Q: I have a 2006 Jeep Grand Cherokee SRT8. I took it to the dealer, and they said I have a No. 1 cylinder misfire. They checked the compression and leak-down on all cylinders and everything was OK. Now they want to pull the cylinder head and check for carbon deposits on the valve and the valve possibly not rotating. The miss occurs while idling. Can you come up with any more possibilities?
C.T.
A: There are several steps in the diagnostic process before deciding to remove the cylinder head for inspection. First, decarbonize the induction system to remove any carbon buildups.
Next, connect the engine to an electronic engine analyzer to determine if the misfire is electrical rather than mechanical. This can show the actual voltage required to fire the spark plugs.
Comparing this information to the performance of the other cylinders might well identify an ignition problem with the spark plug, coils or harness. The 6.1-litre Hemi V-8 in this vehicle features twin plugs per cylinder and coil-on-plug ignition coils.
If the misfire is electrical, it may be possible to swap coil packs between different cylinders to see if the misfire follows the coils. A new pair of spark plugs in the misfiring cylinder might also help.
If the misfire is not electrical, try the same thing with the fuel injector from the misfiring cylinder. Does the misfire follow the injector?
If the misfire is neither electrical nor fuel-related, it may - and not having tried this on a dual-plug engine, I emphasize "may" - be possible to remove and disable the coil pack from that cylinder, disable the injector, remove one of the two spark plugs and install a compression gauge with the Schrader valve stem removed so that the gauge will not hold pressure. Starting the engine momentarily will show the actual running compression in that cylinder. If airflow into or out of that cylinder is restricted by carbon deposits or a valve problem, the running compression will be low.
Q: I would like to have information about two-speed axles - particularly the Gear Vendors overdrive in five-speed pickups. W.B.P.
A: The company you mentioned is a leading manufacturer of auxiliary transmissions for domestic car, truck and motor home applications. These bolt up behind your existing transmission and allow overdrive and gear-splitting functions.
An overdrive gear ratio allows the engine to spin more slowly at cruising speed, reducing fuel consumption, noise and engine wear.
Gear splitting refers to the practice of shifting the auxiliary transmission in and out of overdrive as one shifts the main box, allowing additional useful gear ranges. Some gear combinations fill gaps better than others. This sounds like a lot of shifting, but is particularly great when towing, climbing hills or racing.
In addition to the hardware, Gear Vendors supplies an electronic interface that can co-ordinate overdrive functions with your existing vehicle power-train controls.
Do you remember when some automatic transmissions had only two gears? There were only two vehicle speeds where the engine could be the most fuel-efficient or develop peak power, and every other vehicle speed resulted in a moderate to dreadful compromise. Transmissions these days have up to nine speeds, and some are continuously variable - they have infinite speeds, which allows the
engine to be highly efficient under every possible driving condition.
Your five-speed transmission already contains an overdrive ratio, in addition to the other four, so you wouldn't see the same benefits as the owner of an older pickup with a more sturdy three-speed transmission that suffers from wider gaps between gears and no overdrive.
From what I've heard and researched, the Gear Vendors units are very sturdy and expensive (their word). I priced one for a hypothetical pickup and the cost is around $3,000 plus tax, installation and drive-shaft shortening.
From a fuel savings standpoint, in a typical low-mileage pickup with three or four gears, and gas at current prices, the unit should pay for itself in perhaps 80,000 kilometres, then allow in-the-black fuel savings. If you work your truck hard, either heavily loaded or towing, the added gear ratios can improve performance and reduce driveline strain.
Then there's the fun factor - truck folks seem to love shifting gears. I can't leave the up/downshift and tow/haul buttons alone on my six-speed Allison.
Paul Brand, author of How to Repair Your Car, is an automotive troubleshooter, driving instructor and former race-car driver. Readers may write to him at: Star Tribune, 425 Portland Ave. S., Minneapolis, Minnesota 55488 or via email at [email protected].
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