LMM Duramax Diesel Emissions System

Diesel Articles

Some time ago, there was a love-hate relationship with the Clean Air Act and many mechanics and owners who tended to view diesel engine emissions controls as evil. That was because most carburetors and vacuum control systems were not terribly reliable: as a result, fuel economy and survivability suffered. Entering the 80’s and the era of fuel injection, emissions systems suddenly became more reliable and usually improved the overall performance of an engine; at the very least, they did not hinder it. Computer controls allowed for much more precise engine operation. Despite this, diesel engine emissions controls sometimes still have that original stigma attached to them. In the early years, people often solved their drivability problems by removing all the emissions controls, retuning the engine’s performance – and pollution output – to pre-emission levels. This was illegal then, of course, and remains illegal today even though some people still remove EGR valves and catalytic converters.


LMM Duramax and Oil Bypass Filters

Diesel Articles

The LMM Duramax is certainly a step forward in its reduction of emissions into our environment. These controls, however, come at a cost. In Learning to Love the LMM Duramax Emissions System, Joel Paynton looks at what the LMM accomplishes and what it costs in terms of convenience and fuel economy. In this article, I want to take a quick look at what recycled soot does to the engine oil in the LMM and recommend bypass oil filtration as a worthwhile protection for this considerable investment.

Oil bypass filters for large diesel engines are accepted as a necessity and have been recommended by several aftermarket filter companies for many years. As a certified lubrication specialist, I have recommended bypass filtration systems as a solution for many diesel applications, though not for every application. Prior to the LMM, the Duramax engines were capable of dealing with soot. Even if they could benefit from a bypass system, they could certainly get by without one. Not so with the new LMM. I absolutely recommend bypass filtration for this engine.


Heath Diesel 6.5L Land Speed Racing Truck at Bonneville

Diesel Articles

Heath Diesel 6.5L Land Speed Racer at Bonneville

September 2008, Bill Heath raced the Heath Diesel Team’s 6.5L GM Diesel pickup at Bonneville. maxxTORQUE featured the vehicle in our Summer 2008 issue before the event. Now, here is a look at the Bonneville performance and what’s inside that makes this truck – that could pass for a daily driver – fast...

Heath Diesel Power’s 6.5L GM Turbodiesel Land Speed Racing truck ran a solid 153 MPH on its first trip to the Bonneville Salt Flats – that felt pretty darn good. Knowing that she has more speed in her yet – that’s even better. Here’s a look at our experience at Bonneville and the details of the build that got us there...


Lube Notes: Petroleum Oil vs Synthetic Oil


Lube Notes

The ongoing march to achieve more technologically advanced engines continues and certainly the GM Duramax diesel engine exemplifies that quest. The race between GM and its would-be competition has benefited you and me: the improvement in all aspects of these diesel engines is easily quantifiable in terms of horsepower and torque as well as fuel efficiency and endurance. Recognizing how vastly improved these diesels are to their predecessors, it should not surprise anyone that advances in the lubricants for these engines have also facilitated quantum leaps in performance.

Any oil, properly rated for use in a high performance turbo-charged engine, is a remarkable lubricant regardless of the base oil used. In this article, I will compare synthetic diesel engine oil to petroleum diesel engine oil and draw some conclusions and make some recommendations. Previous Lube Notes have established fundamentals of lubrication and how oil is made, so if you haven’t read those, a review might be in order. I am writing this article assuming you have read the preceding articles.

Click here to see a summary of costs comparison for petroleum oil vs synthetic oil...

To start, we should compare several performance criteria for petroleum oil vs synthetic oil...


Testing the Injection Pump for 1994-2000 6.5L Diesels

6.2/6.5 Issues and Answers

Hello, I hope you can help us out. Our 1998 Chevy 6.5 truck has been doing some odd things lately and the shop I took it to, told me it needs a new injection pump, but I am not so sure I believe their diagnosis at least I don’t want to believe it. Here’s the issue: Sometimes when the truck is stopped at a traffic light, the engine will surge against the brake and makes a puff of gray-black smoke when this happens. I thought maybe it could be caused by a bad throttle switch. Hope this is enough for you to go on. Thanks in advance!

Here is a quick and easy way to determine whether the injection pump of any 1994-2000 6.5 C-K truck is working properly.


Blow-By Test for 6.5L Diesel

6.2/6.5 Issues and Answers

I have always been a gasoline engine driver, however I am thinking about buying a used 1995-1998 Chevy or GMC diesel Suburban and need some advice in making a decision. Those I am looking at have more than 150,000 miles on them, which seems like quite a lot to me. How can I know whether the engine is OK? Do I need to have compression tested? Any help is appreciated! Jim – Amarillo, TX

Jim, we recommend that you check for crankcase blow-by vapor flow. This is the best way to determine the health of the 6.5.


Troubleshooting a Heavy Rattle Sound in a 6.5L Diesel

6.2/6.5 Issues and Answers

Our 1996 K-2500 GMC diesel has many mechanics stumped; maybe you folks have the answer. Last summer, while traveling through Oregon, we began hearing a rattling sound under the hood. A shop diagnosed it and replaced the air conditioner pump. No change and he threw up his hands and sent us on our way. Another shop in California, decided it was a bad water pump which they replaced. Again, no improvement and in fact, it had gotten louder as time passed by. Of course, the shop couldn’t very well switch the old pump back on, so we were stuck with yet another unnecessary and costly repair. Then, another shop in Mexico diagnosed the problem as being the alternator and this time, the mechanic ‘proved’ his diagnosis by removing the drive belt so we could listen. Sure enough, the rattle was gone when he did that little test, so on with the new alternator. Same old deal. When the drive belt is on the rattle is there and it is getting worse all the time. The engine runs well and has good oil pressure, so we are hoping it gets us back home to northern New Brunswick next September. Can you offer any help?

Most commonly, a heavy rattle, one that sounds like marbles rattling in a tin can is caused by


6.5L Diesel Starting Problems

6.2/6.5 Issues and Answers

We hope you can help us with our hard starting 1995 Chevy 6.5 diesel. When the wait to start light comes on and stays on the normal amount of time, it starts fine, like always. Often, the light comes on only very briefly and the start up is not so easy, with a lot of extra cranking. Perhaps this additional problem is related and I include it to help in the diagnosis: The truck often bucks and misses under heavy load. Two shops have diagnosed this as a failed fuel transfer pump. Between the two shops, they have installed 4 new fuel transfer pumps: no help. One shop replaced the engine computer: no change. Another replaced the glow plug relay: no change. Yet another replaced the ignition switch: again, no change. Sure hope you can offer a suggestion! Ray S., Maine

These problems may be related. Here are the things to check out.


How does the fuel lift pump work in the 6.5L diesel?

6.2/6.5 Issues and Answers

Can you help me understand how the fuel lift pump works in the 6.5 turbodiesel GM trucks? I’ve talked with several knowledgeable mechanics and get as many answers. I’m confused!

You did not specify the year of your truck and there is a difference between the 1994-1995 and those built later.  In the 1994-1995 models, the lift pump...


What are the effects of leveling and other suspension changes for towing?

Duramax Issues and Answers

Can you talk about effects of leveling and other suspension changes for towing?

As a GM technician, I get to drive all kinds of modified trucks, towing and empty. I have come to a basic, simple conclusion as regards the OEM suspension system: if you don’t know exactly what you are doing, leave it alone! Too many modified trucks that I have driven are absolutely scary. They can have an unstable on-center feel, pronounced bump-steer, excessive sway under load, memory steer, etc. The mods have butchered what would have otherwise been a great-handling truck.

So what modifications do work?



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