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high soot in engine oil


bjcalhoun
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New to site and fairly new to Mack trucks. The problem is with 2002 to 2006 ASET/AMI 300 Mack engines. They have been oil sampling But not doing anything to correct problems. We are running five of these trucks and they all have Mack tm309m transmissions. Changing oil every 8000 miles, but the oil is very high in soot. When driving these every gear shift will lug the motor. Probably a mix of the motor being weak and the junk tranny. As far as I can tell we need more air intake and more power. The problem is we need to do this right and one time because of budget restraints. Everyone that I ask about a good economical fix has no answers. There are plenty of people who can make Cat, Cummins, and Detroit wake up, but no luck getting answers about Mack. Any proven ideas would be helpful. By the way I'm not a motor guy, just a parts changer that understands trucks.

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Macks can't be spec'd or driven like other trucks. 'Round here, they tried and are not happy with the results. Company trucks of all makes won't rev past 1300 or 1400 RPM...that's how the pencil-pushers in the office decided would make the trucks most "fuel efficient". Now I've never driven one of these new Macks to see how they drive, but my '01 doesn't really come to life until 1400+. Sure, it'll drive & pull at lower RPM's, but it smokes like a SOB and doesn't really have the giddy-up that it does in the 1400-1800 range. If the trucks were spec'd wrong, set up wrong in the computer, or driven by people who are used to driving Cats and other motors that are made to run at slower speeds and carry those habits over to the Macks that like to turn a little faster, it is lugging the engine more than it needs to be lugged. Have the drivers run it up to 1800 before grabbing the next gear...won't lug quite as bad, and might help with the soot situation.

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When approaching a 4-way stop, the vehicle with the biggest tires has the right of way!
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Let me welcome you to BMT, my experience with older Mack trucks is they were not designed to be lugged I am with Rowdy, have them try running the RPMs up and see if that helps any.

How is the truck set up in the computer?

I concur this concurement

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All AI and AMI engines seem to have high soot in the oil, mainly due to the design of the engine. The AI/AMI has 2 humps on the exhaust lobe of the camshaft and opens the exhaust valve twice. It will suck dirty exhaust out of the exhaust manifold (anyone notice how small the exhaust manifold is on a AI) and reburns it on the next stroke. Kinda like a EGR system. Thats how the AI/AMI got away with no EGR valve/cooler but the AC engine didnt. Also there are 3 or 4 ways of oil sampling. I know that the one the local CAT dealer uses always shows super high soot in the AI/AMI engines.

oil sample.pdf

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Thanks for all the feedback, but pretty much at the same spot in the road. Believe me you have to max out the rpm's before even thinking about grabbing the next gear. After just letting off of the pedal and getting back into it they pretty much fall flat on their face. The intake pressure goes to zero and it takes ten to fifteen seconds for it to come back up. We are running five trucks like this and they all act the same, and the Mack dealer around here is no help. My biggest concern is that we have two 09 Macks that are going to have to go way before any of these. I wouldn't wish one of these 09's to my worst enemy.

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On the poor throttle responce between gears, have you had the dealer do the "Step 12B" update to calibrate the throttle pedal? It seems to do wonders on some trucks. Just did one on a CXN this morning. Took me about 2 hr to reflash and download both ECM's. But with just a AMI-300 engine its just not much to work with. You could jump to a AMI-335 with just a download( HP upgrade) and it would give you 140 more FT LBS of torque. I dont know how much the download would cost as it has to be turned on at Mack and installed by the dealer. Also if these are MR or LE garbage trucks your limited to HP because of lack of radiator cooling.

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