Written by Jamie Avant
Written by Michael Patton
I love what I do, and that is a blessing. Focusing on the troublesome mysteries of the technical world, I get to figure things out: things that have no apparent explanation... the elusive.
What follows is one such mystery, wrapped in a clever disguise and hiding in plain sight for years. It remained undetected for so long because there is not a single vehicle sensor, diagnostic, or gauge that is set up to alert us to what I finally found with patience, a casual observation, a $15 gauge and a paradigm shift.
As you read, keep in mind that the principles in this article can be applied to all turbocharged vehicles, not just the Duramax. You may well find inspiration to look at other unsolved mysteries by the time we are done. If you do, I would love to hear about it.
Duramax LLY Disappointment
It was 2004 when the Duramax LLY model replaced the LB7. Promises of more power, an advanced variable geometry turbo (VGT), among other announcements, were considered worth the wait. Unfortunately, it became clear right away that there was a problem. The engine did not seem to live up to the promises. Economy was reduced, performance was hindered and many towing customers could not use it for the advertised load capacity. The vehicles even overheated. Compared to the first generation LB7 Duramax, the LLY seemed to be dragging an anchor behind it.
Written by James Langan
Steve Johns loves his 1993 AM General HMC4 (4-door hardtop), powered by the stock 6.2L naturally-aspirated diesel. After years admiring the AM General H1, five years ago Steve purchased this clean specimen from his local GMC dealer for $25,000.00. It had only 50,000-miles on the odometer.
Ninety-three was only the second model year for the civilian Hummers – basically modified military trucks. (You can see the tan military paint showing through on Steve’s Hummer where the factory white paint has peeled away.) This H1 includes a 12,000-pound. Warn winch, undercarriage protection, air-conditioning, rocker-panel protection, a brush guard, tow hitch, and the Central Tire Inflation System (CTIS). This truck has every factory option offered in 1993 except power windows and door locks.
Written by Dan Watson
In the preceding Lube Notes, we covered basic lubrication, oil functions, additives and base stocks. Now, it’s time to construct finished lubricating oils. From what we have learned, it may seem like the only thing we need to do is pick a base stock oil, mix in some additives and presto, we have lubricating oil. If only it was that simple. Of course, it’s not.
Previously, we looked at the refining of petroleum and classifications for synthetic and petroleum oils. The base stock with which we choose to start will obviously have a direct bearing on the quality of the finished product. If cost is no concern, then all finished oils would be made using one of the synthetic base oils since they result in the best lubricating oils. However, cost is an important factor and will always be a consideration in choosing base stock oils. Most oils are manufactured by a reverse process where the final performance requirements dictate the quality or lack of quality of the ingredients. If the manufacturer is making an oil to meet the minimum performance criteria for the current classification, then no money will be spent on anything more than an adequate base stock. On the other hand, if the manufacturer is producing a high performance oil, then he will spend what is reasonably necessary to produce the final product’s higher level of performance.
Written by Bill Heath
Our ’94 one-ton Chevy diesel seems to have a heating problem that we think began soon after we had the air conditioner pump replaced. The problem is, no one seems to be able to fix this for us. The temperature gauge goes up to 230ºF and back down; up and down it goes. It takes spells of swinging back and forth like this, then seems to be fine at other times. I am not convinced that it ever really gets hot, even when the gauge says it is. The mechanic at our dealership has replaced the thermostat, then the radiator, then the water pump, then the radiator hoses, then the temperature sensor, then the fan clutch and finally another new thermostat; all without solving the problem. After each visit, they tell me it is fixed and send me on my way with a lighter wallet, but the problem returns. Now, after all this expensive work has been done, we have noticed that the oil pressure gauge is reading lower than it used to and that the volt meter reads low. We also see that the speedometer jumps around when I rev the engine in neutral. Then, once in a while, the wipers will make an unplanned swipe across the windshield. Maybe I am being unfair to the mechanics, but none of these problems existed before the work was done. Understandably, I hesitate to take it back to the dealership for fear of the costs. Am I vexed? Can you offer help?
Written by Bill Heath
I have a question not related to my engine, but hope you can help. Our ’95 GMC has developed a variety of problems with its lights, while we were on a trip. The turn signals were sometimes dim and or they flashed rapidly. The brake lights often do not work at all and the tail lights are dim. All the lights are behaving oddly. A dealer checked it out for us and replaced many bulbs, but things are still goofy. He now says it needs a new turn signal switch at a cost of $620, but he will not guarantee this to be the fix. Do you have any suggestions?
Written by Bill Heath
Please help! We have a problem with our 1998 Chevy dually that has proven to be beyond the capability of mechanics, even so called diesel mechanics in our area. Our big red truck smokes like a freight train sometimes. It will be fine for a day or so then, when we need power most, it lets us down and only billows black smoke. So far, we have had to replace the turbocharger, catalytic converter thing, injectors, fuel filter and more – none of which fixed the problem. I am tired of trying to get results from people who seem to only be guessing; please help.
Written by Joel Paynton
I have just purchased an '05 LLY Crew Dually 4x4 and am learning about overheating issues (Summer Issue – thank you) and other design concerns. The most recent item to come to my attention is the EGR system. It appears that many DMax owners recommend blocking off the EGR, welding some ports, installing a fingerstick(?) to eliminate code generation and rerouting the PCV. All of this appears to eliminate intake contamination. Is this something important to do? If the system is so bad, how did GM let it go? Many have found carbon build up under 20,000 miles.
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