Help - '04 CH AC310/330 backfire under load, intermittent boost

[convoyduel]

hoping my new purchase wasn't a terrible decision....'04 CH613 built 2/3/03 with an AC 310/330 and 184k on the odometer. VIN 155261.

Truck has driven around bobtail just fine for a week locally while getting it ready. I was getting an intermittent 8-3 code, which according to my VMAC3 manual is an injector code. It was occasional. Called the dealer, they said as it was intermittent, it wasn't anything critical and could be looked at during next service. I did notice a slight whistle at high RPM (not road speed related, RPM related) and something that sounds kind of like a door slapping or a clapping when the engine RPM's drop back and bottom out during an upshift. I didn't pay too much concern as the performance overall was fine.

Last night, the truck started running pulling a 53 trailer with a very light load. Maybe 40k gross - truck, trailer and cargo. Started out ok, but after about 45 minutes, the driver said he heard what sounded like a tire blow from the front right. He stopped and checked everything was fine. He went back on his route and maybe 25 minutes later, it happened again. He rechecked everything and found nothing. Maybe another 10 minutes went by and it started to lose boost and what he described as a backfire. On a 2 lane rural with not shoulders or turn-offs, he limped it another 5 or 6 miles not getting above 40 with the problem occurring during boost demand conditions but not coasting or downhill. He was able to make it to his next stop safely. He also stated that the engine malfunction light would come on before each of the backfires occurred then would go out. The driver is very careful and dilligent

He had already called me after the second "boom" and I met him with a different tractor. From his description, I expected to find a blown turbo clamp or tube but nothing. I pulled the intake at the turbo and the turbo wheel was clean with absolutely no play. After we switched out, I bobtailed the truck back 60 miles to the yard without any problems, other than the same whistle and occasional clapping sound I heard before. I also occasionally got the 8-3 code but it always went back out on its own within a minute.

Any ideas?

[Mackpro]

Look at the tag on the turbo and see if the part# ends in something like 631GC5171M***. Hopefully you have the newer 631GC5176M** series turbos. The 5171 series had some weird issuses with them. You rarely see them much cause the had a high failure rate and probably have all bee replaced. Check for soot leaking around the exhaust manifolds and the EGR piping as the EGR piping actually had turbo boost pressure on it when under a load. Make sure this thing doesn't have an exhaust brake on it under the cab. Check the muffler for a broken baffle , rattling around and sometimes blocking air flow through the muffler. 8-3 code is the #3 EUP pump and shouldnt cause the noise and whistle issue.

[convoyduel]

Spent a couple of hours pouring over it this evening and driving it around. The clap I'm hearing is actually a bark that comes back through the air cleaner when you decel thru most of the Rpm band. Does it with the hood up or down so its not an issue with the air cleaner seating on the hood. It's barking around 1000rpms. Only does it once per decel. I can even get a very mild bark if I'm running it at full rpm's while parked and let it decel. Best way to replicate it is to have the cruise throttle set to a high rpm then turn off the cruise and let the rpm's drop thru the band. I can't replicate the "boom" or backfire our driver was experiencing with a load.

The whistle comes in around 1400 to 1500 rpms and whistles thru a boost, regardless of the gear under load, even bobtail. No, this is not a typical turbo whistle, its more of a piercing nails on chalkboard kind of whistle. Sounds like when someone runs their finger around the rim of a crystal drinking glass. I can't find any obvious leaks on the aftercooler or piping. I followed the stainless braided line from the turbo actuator over to the driver's side of the engine. It doesn't attach to the venturi pipe, it attaches to some sort of valve mounted up behind the centrimax approximately at the 5th cylinder position. I couldn't find any relief valve on the venturi pipe, but I'm not sure it was on the 310/330's. I've only seen it mentioned on higher horsepower engines.

I've looked for soot leaks on the manifold, turbo mounts and other exhaust and EGR components but find none. Also, there is no smell of smoke anywhere around the engine, even when I use the cruise to set a high rpm and walk around.

The truck has what looks to be all new gaskets, studs and nuts on the exhaust manifold. Everything on the turbo side is very clean and appears recent, but then again this truck is pretty immaculate so its difficult to say for certain. I spoke with the previous owner tonight who said he ran the truck in service even on the day he sold it to the dealer I bought it from. He said it was a shop queen its first year or so with all of the ASET problems and recalls, but that it had been a very good truck after that.

One thing I did notice is on the coolant lines from the EGR cooler to the block. As the lines go to the block on the front right side of the engine, there is a short piece of hose (maybe 1" or 1.5" diameter, 3 or 4 inches long) that goes between a stainless coolant tube and the block. That piece of hose really seems very swollen between the clamps when running.

[Mackpro]

I wonder if the VGT/wastegate is sticking. Take the stainless braided air line off the turbo actuator (VGT/wastegate) and lightly blow air into the wastegate and see if the rod moves down full stroke then springs back up when air is removed. The pivot pin can sieze up and the turbo will not work correctly. The pivot pin can be removed and cleaned and coated with hi-temp anti seize. An "E" clip holds it in. You might have to shoot a little air in the VGT to get the pin in and out. Dont put to much air to the VGT or you could blow the diaphram in it. I dont think the lower HP engines had the boost pressur relief valve in the intake manifold piping.

[rsb502]

sounds like vgt issues for sure, the swollen hose to the egr cooler doesnt sound good either, check for bubbles in the coolant with the cap off when revving the engine and excessive coolant system pressure you may have a bad tube in the cooler pressurizing the coolant system with boost pressure.

[convoyduel]

I loosened the braided line to the turbo actuator and it had a fair amount of pressure behind it. I didn't pull it all of the way off though. The valve was in pressed all the way down against the lower stop. I'll have to pull the line completely off tomorrow.

We don't have any coolant push issues showing with the truck, but the coolant line in question definitely has some sort of pressure behind it to make the hose swell like that. When the engine is off, the hose appears basically normal with only minimal/normal swelling between the clamps.

The truck has decent throttle response when bobtailing and responds well when pulling some decent grades, enough of a grade even bobtailing that I would expect the issues to reappear. What I don't understand is why it pulled fine yesterday for the first hour or so then started giving the fits as the night went on. There were bigger hills and higher boost demands before it started backfiring.

Are these VGT issues intermittent at all?

What are the indications of needing a new venturi tube or a new EGR cooler?

I've seen a few others use the word "burp" also with these ASET's and mention it going away when using higher rpm's. Is there a known burp problem with these and if so, what's the issue?

[Mackpro]

The "burp" was on the first orignal 2004 ASET turbos (631GC5171 series turbos) . The very first MP-8 turbos habe the same issue as well , a software update solved the MP-8's. When replacing the old style ASET turbo with the new style ASET turbos (631GC5176 series) there was a software update that should have been done. Pull the large hose on the front of the EGR cooler off ( going to the "S" shaped pipe that goes over the engine) and check for wetness/antifreeze. If dry its ok. The EGR valves on the early ASET's would sometimes break inside and cause EGR flow when there should be none but this would usually set a code for EGR issue.

[convoyduel]

Checked today, it has the 71 series turbo. Wound up taking it to the dealer to go thru and check for recalls, updates, etc. They were shocked to see a 71 series turbo still on the road, even with only 183k miles. They were aware of all of the common issues and said right off the bat that the bark is almost certainly the result of the 71 series turbo. REALLY dreading the bill. I'll keep everyone posted.

[Mackpro]

I was wishing you had the new style turbo too, but when they do replace it you will have the newest style turbo they make. They started with the 631GC5176BM**, then upgraded it to a 631gc5176CM** then a DM** , so atleast you should get the newest thats available.

[convoyduel]

With the price on these turbos, I'm afraid they're going to use a 631gc5176AR** to denote the anal rape feeling when I get the bill. Nothing against the dealer, just dreading the parts and labor expense in general.

[Mackpro]

With the price on these turbos, I'm afraid they're going to use a 631gc5176AR** to denote the anal rape feeling when I get the bill. Nothing against the dealer, just dreading the parts and labor expense in general.

LOL, that's a good one!

[Lmackattack]

sorry to hear of the troubles Dan. I was kinda suprised to see you buy one of the early 2000 macks as even you had commented before that they had issues. The truck looks great I just hope you did not get one that is a basket case. I looked under the hood of some othe these new macks and I can only imagine what it takes to work on them. i thought the engines in the R models were tight...not!!!

keep us posted!

[convoyduel]

We will be ok. We ran the history on this truck and it looked as thought the 71 series turbo had been upgraded but maybe not. I'm holding my breath. Won't mind a little more investment in the truck up-front as clean as it is and with everything that came on it. I'll wait and see what we find out. At the end of the day, my biggest problem is a truck, not an IED in Afghanistan. Keeping it in perspective, overall life is good here.

[convoyduel]

Just an update to complete the thread for future reference.

The dealer flashed the ECM with the latest software update applicable. It retains is original 71 series turbo. We have had it back and been running it without any further issues other than a persistent burp on decel. The truck still throws an 8-3 EUP code and an occasional 1-8 code which I believe is a fan speed code. A few pictures are attached for fun.

[Superdog]

Sure got it shined up nice,but you're missing a couple lug nut caps,Dan.Mikey said to tell you it's too damn short and needs another stack.

[staxx]

Low fuel presure will cause it to pop and backfire and 83 code have had plenty of supply pump issues to go with the turbo problems too.

[convoyduel]

OK, still having issues after a number of tries. Truck still backfires underload seemingly at random. The dealer replaced the #3 EUP this past week and replaced the fan belt to cure the 1-8 fan speed code. The EUP solved the 8-3 code, but the fan speed fault still comes and goes at random.

The truck ran perfectly for 7 hours saturday grossing around 50k. The dealer worked with Mack and they put in some new data files that makes the truck run with more power than it's ever had.

Truck still has the 71 series turbo. Truck has 184,000 original miles.

Tonight, its throwing a 4-1 road speed sensor code when it pops and derates. I searched on here and found a thread from 2010 about Lost Pulling Power on a 355/380 ASET. There were two comments that caught my attention. One was about a speed sensor and the other was about transmission programming.

The only other thing we found odd with this truck is that it shows having a T309 transmission, but the decal on the HVAC was for a T310. The truck shifts like a 10 speed transmission.

Could this all be because of a road speed sensor or the ECM expecting a T309 versus a T310? How do I know which transmission is in it? (I know that sounds incredibly stupid, but I've got to ask)

[staxx]

Ok I would still want to know what the fuel psi is doing when this happens those fuel supply pumps have a high failure rate. There are 2 engine position sensors one on front engine cover that watchs cam timing and one in the flywheel housing watching crankshaft timing and speed rpm dont think trans would be issue havint seen that before but theres a first for everything , are we sure it backfireing broken hood springs make alot of noise too .......my best guess is the exhaust brake the solinoid on the rockershaft has too orings and when the one in the bottom fails it splits causing exhaust brake to come on randamly have seen exhast manifold studs run in too far on bottom making contact with push tubes also, look and make sure they all look even ...hope this helps.

[convoyduel]

Thanks, Staxx. My '00 CH612 has the blinking engine malfunction light at high rpm's from the cam position and flywheel position sensor issue. Just a minor annoyance and a very slight derate.

This '04 CHN613 with the ASET does not have an engine brake so that's out. The hood springs are fine. This is a very prevalent backfire, sometimes in rapid succession like a machine gun. The 4-1 code is coming on when it is occurring.

[convoyduel]

Forgot to add, this has never occurred bobtailing, only under moderate load i.e. empty 53' van or up to 50k gross. Seems to like to do it at night versus during the day. That's probably a fluke. Has occurred in ambient air temps from high 60's to low 90's. Like I said, it ran perfectly all day Saturday. Really thought it was fixed.

The thread I was referring to about the similar problem on here is :

[staxx]

Can you tell if its coming from intake or exhaust 41code speed sensor on trans can check adjustsment turn sensor in till it bottoms out the back it out one turn also check mack sure the tone ring is not loose make sure trans output yoke nut is tight.....sensor ohm check should be around 300 .

[staxx]

Still sounds like a fuel pressure issue .

[convoyduel]

The backfire seems to be the exhaust. It's a backfire under fueled conditions. The truck also has the loud burp when the rpms drop such as when shifting or disengaging the transmission and the engine returns to idle. It is throwing a 4-1 code.

[staxx]

valve train related have seen broken rocker shaft mount bolts could be camshaft issue, trying to think of cheap easy stuff first.

[staxx]

If its backfiring the camshaft rollers will not put up with this for long you have ceramic rollers in there very hard surfface but do not absorb hard hits like a backfire.