DPF saga issues - HEST discussion - 2008 Ambassador questions

[deanrd]

Hi All,
 

This is the saga of my DPF HEST light. I originally posted this on IRV2 and was referred over here for more help.

I have a 2008 HR Ambassador 40SKQ with 360 Cummins. Occasionally, up until now my regeneration cycle would run maybe once every 750 miles or so. I went to Florida the end of March and it came on maybe two or three times, so slightly more than normal. Coming home however it would come on 2 or 3 times a day. Should I be concerned? Is this an indication of looming problems? No other indications. It runs maybe 15 mins or so and done. I'll include pic of light. It's indicator 5, HEST High exhaust sys temperature. Says regen in process. These don’t match my owners manual, but match my dash 😞

I was asked about idle time and that is kept to a minimum. My DPF has supposedly been checked and is clear.

One reply: Another cause of high exhaust temps can be a leak in the pressure side of your turbo, as in your charge air cooler or the boots connecting the pipes. These were also checked as SAT.

Flash updates are supposed to be SAT also.

Well so far they had me replace fuel and air filters. They've scanned and no codes or any recorded. Took it to Vermont. Roughly 130 miles each way. Came on within 20 miles each way, once again about halfway and again towards end. Hopefully they can find something.

Well they said my vgt was only opening 22 degs. Replaced it, not cheap. Drove 15 miles yesterday and HEST light again. Back in Monday, grrr

DPF has not been cleaned, performance seems normal.  Actually slightly better with VGT replaced.

Always Ultra low sulphar fuel as far as I know. I’ve even started adding Diesel Kleen.

Lastly…

OK, time to find a new repair shop. After leaving it for over a month nothing has changed.. Even after replacing VGT the problem persists. Now my engine temp gauge will stay on cold and then suddenly will peg at hot, then warning light comes on. Ten seconds later the temp gauge drops back to zero. After being told everything was working I drove 5 miles to get the HEST light came on for a minute, then off about 1 min., then back for a min, then off, but Regen required light came on then started flashing. I think my DPF needs cleaning in spite of what they said. So frustrated...

Still flashing regen required light, regen HEST light on and warning light. Engine temp gauge still fluctuating hot to cold even at cold start. Waiting for return call for service, but looking for new technician.

I think it’s my dpf clogged, but they say they’ve tested pressures, so…

Thanx Dean

[K9 Exec]

Hi Dean,

If I were a betting man, I would say you have one of the possible following issues that I would address with a new shop:

1. Have them drop the DPF, if you haven't had it done in a year or two (never hurts since we have these crazy devices downstream now...) and have them clean/bake it. If you are dumping fuel/DEF ( I believe yours is diesel, but I could be wrong) in the DPF and it isn't burning, you could really be clogged up.

2. Check the sensors- I know, you have already done that. Here is why I say that: Once you bring it to a different shop- they can throw it on the laptop and do a 'forced Regen' and at that point the software does a "self check" and if you have issues, the software and tech "should" catch some of the faults that the previous shop had not and can correct it at that point.

3. It could be a bad "7th" injector (for the DPF), a harness that has gone bad, or a number of things I haven't mentioned. 

Also, I don't know your area otherwise I could suggest a reputable shop in the midwest but I would say find a class 8 (semi repair shop) that works on Cat, Cummins, Detroit, etc. Make some calls to find out if they have a scan tool/laptop that will work for you. I would call around 2-3 truck repair shops to get Diag quotes and find out what their 2 hr minimum is, etc. It won't be cheap but I can tell you I would probably find a new set of eyes to look at your ongoing problem.

Best of luck and plz let us know the outcome!

Edited October 23, 2023 by K9 Exec

[Frank McElroy]

The ONLY way to sort out what's going on is to look at the DPF regeneration history report on the last ten regens.  You can get this report via Cummins Insite software.  If your shop doesn't have this software you are only guessing about what is broken.

Is your check engine light on?  If so, it could prevent a dpf regeneration.  Also are you driving at highway speeds to do a regeneration?

[K9 Exec]

Hi Frank, I am relatively new to the group and don't know your background other than you are a legend around these parts, you are always spot on, always have great advice 🙂,  and I have the utmost respect for you. I am not disagreeing with your hypothesis, I just didn't explain the whole process in the reply to keep it short.  I am guessing they have done that last go around, but I am willing to eat crow on this one... We had one come in with the almost identical issue, HEST light on every time it tried to regen, stage 5, etc. I don't think he would be best served by going back to the same shop, IMHO. Whenever we throw the laptop on, we always do that amongst other things but the forced regeneration is usually the tell tale indicator. That one we had in would show that is was doing a  'passive' regen 5-6 times a day to the point it would start to derate. He brought in in and when we started a 'forced' regen- no dice, it puked.

The unit really wasn't regenerating 5-6 times a day, the dummy lights would all come on in the cluster for the customer. So, that's why I say get it into a new shop, let them throw it on the laptop and start the diag process, with a new set of eyes. 🙂

Again, not disagreeing and but willing to bet a dollar to a donut the last shop didn't do their due diligence. 

[Frank McElroy]

A really good shop would do a complete workup.  There is a very specific diagnostic tree that needs to be followed.  It's in the Cummins service manual.  Often times, shops get confused with no trouble codes and a plugged DPF.  So they do a forced regen but the root cause issue isn't solved.  Something is generating too much soot.  So, back to basics.  A sticking VGT can cause excessive soot.  Any history of a code for turbo actuator issues?  Has a cylinder load test been performed with the DPF off to see if running the engine on any 2 cylinders causes soot?  Then there are cases where the egr valve is opening when it shouldn't because it's plugged with soot.  A mass air flow sensor could also be giving a false reading.  Bottom line - diagnose why the engine is generating soot first then do a DPF regeneration.  On the ISC and ISL there is no 7th dosing injector.  Added fuel if needed comes from separate cylinder fuel injections at the end of the combustion stroke.  ISX engines have a separate exhaust manifold dosing injector.

All this assumes that the owner is driving under conditions to do a proper DPF regen, the check engine light isn't on and that the engine wasn't modified with an EGR delete or other modifications to the stock engine or emissions.

In addition, when that dash light comes on all it means is that the coach needs to be driven under conditions to do a dpf regen.  That's why it's important to look at the DPF regen history report and timings between regens.

[K9 Exec]

I agree with you 100%, but this is "post covid times" where techs decide if they want to come in to work, what they will work on, if the DC has parts etc. These are NOT normal times. He replaced the VGT which tells us a few things, but has a lot going on to say the least. Thanks for understanding that he was asking for help, and I put my $.02 in. 🙂

I only have 17 yrs in the diesel repair industry, but my 65 year old diesel tech has been doing this since I was in diapers. I sit back, watch, and learn. Btw Frank, you are a plethora of knowledge, I found you guys back when I bought my coach and had some Monaco specific issues. This group is one of a kind! I miss Tom Cherry, you and a few others posting what seemed to be, daily. I would wake up and see 10 hits on my phone from this site. I truly enjoy the camaraderie on here. 🙂

Well Dean, I hope this at least has given you an Idea of where to go from here.

Best of luck, and we will be anxiously waiting for your reply!

[Tom Cherry]

@Frank McElroy is truly the Guru…and most shops or techs should seek his advice as he actually “understands”, from a computer, scientific and mechanical viewpoint what is happening as well as what or why.  Follow his advice.

Not knowing if your DPF has the 7th injector or uses the “afterburner” or injecting raw fuel into the exhaust stroke….as my ISL does, i can only make an observation.

First….is your engine “REALLY” going from hot to cold as the gauges indicate?  Whether you have a faulty gauge, sending unit or thermostat is a mystery.  However, if you watch the tranny gauge and it doesn’t fluctuate, then one might, going out on a limb, assume the engine is actually “NOT” overheating.  Now, if the tranny “IS” pingponging, then one would suspect a bad thermostat.  My take….get the cooling system and/or gauges functioning properly and then focus on the HEST - VGT - DPF (our society is being destroyed by acronyms….  LOL.).

OK….MY ONE PERSON DOTH NOT MAKE A TREND TAKE.  MY DPF sounds like yours….rhetorically speaking.  Frank looked at my ECM history.  The epitome of “the rhythm method”.  Every 100 hours, the ECM said….OK, ITS TIME.  NOW… i can comment that if I drive in an urban environment, that pesky HEST light shows off like a spoiled brat.  It will flash on or stay on for a few seconds….maybe max of 30 seconds.  The more it behaves poorly, then the closer it is getting to needing to REGEN….and it usually does….but it is Engine Hours driven…not a “system” issue.

As Frank points out….your driving environment as well as whether you keep hitting the accelerator pedal like a rock band drummer….will heavily, IMHO, influence the HEST light.  I “used” to be Mr. Lightfoot.  I now do a full throttle dragster start at least 2 or 3 times per long trip.  That helps….and the Allison also doesn’t get lulled in to “Mr. Limpet” land….folks that constantly baby have had to disconnect the chassis for 10 minutes or so to let the TCM “RESET” and unlearn their flaccid driving habits.

BUT….ON a freeway, using cruise set to say 63 MPH….the HEST light should not misbehave or blink….or that is my experience….

[96 EVO]

1 hour ago, Frank McElroy said:

 

All this assumes that the owner is driving under conditions to do a proper DPF regen, the check engine light isn't on and that the engine wasn't modified with an EGR delete or other modifications to the stock engine or emissions.

 

Yep!

Last time mine did a regen, I got stuck behind this clown that couldn't even drive the speed limit on relatively flat, 2-lane road 🤬!

When I dropped below about 45mph, my regen lamp would go out until I got back to above 45!

I ended up having to complete the regen on my way home!

[K9 Exec]

Mr. Tom, what a surprise. I kind of figured you were bird doggin'. 🙂 I haven't heard from you in forever, and thank you for chiming in. I sure hope I don't have to eat crow on this one, lol. It has been a few yrs since that unit I referenced came in, but that was one of the trickiest ones I had seen. He does have a slew of other  issues, but the one that I hate the most is anything to do with DPF systems. Detroit, Cat, Cummins, Mercedes are all different and have their little intricacies. We can only hope he gets it to a good shop. 

[deanrd]

Thanx for all the suggestions. I'm making notes as my tech wants one more chance. I forgot a few things. 12/21 I had to replace turbo speed sensor. For clarification, this model doesn't use def fluid and the last time they worked on it they did a forced Regen. Also the temp gauge acts up within 5 minutes of cold start and it's not a slow rise to hot, it pegs out, then drops to stone cold.

I will take this list in for Fridays appt and see where we go.

 

Thanx again

Dean

[deanrd]

12 hours ago, Tom Cherry said:

@Frank McElroy is truly the Guru…and most shops or techs should seek his advice as he actually “understands”, from a computer, scientific and mechanical viewpoint what is happening as well as what or why.  Follow his advice.

Not knowing if your DPF has the 7th injector or uses the “afterburner” or injecting raw fuel into the exhaust stroke….as my ISL does, i can only make an observation.

First….is your engine “REALLY” going from hot to cold as the gauges indicate?  Whether you have a faulty gauge, sending unit or thermostat is a mystery.  However, if you watch the tranny gauge and it doesn’t fluctuate, then one might, going out on a limb, assume the engine is actually “NOT” overheating.  Now, if the tranny “IS” pingponging, then one would suspect a bad thermostat.  My take….get the cooling system and/or gauges functioning properly and then focus on the HEST - VGT - DPF (our society is being destroyed by acronyms….  LOL.).

OK….MY ONE PERSON DOTH NOT MAKE A TREND TAKE.  MY DPF sounds like yours….rhetorically speaking.  Frank looked at my ECM history.  The epitome of “the rhythm method”.  Every 100 hours, the ECM said….OK, ITS TIME.  NOW… i can comment that if I drive in an urban environment, that pesky HEST light shows off like a spoiled brat.  It will flash on or stay on for a few seconds….maybe max of 30 seconds.  The more it behaves poorly, then the closer it is getting to needing to REGEN….and it usually does….but it is Engine Hours driven…not a “system” issue.

As Frank points out….your driving environment as well as whether you keep hitting the accelerator pedal like a rock band drummer….will heavily, IMHO, influence the HEST light.  I “used” to be Mr. Lightfoot.  I now do a full throttle dragster start at least 2 or 3 times per long trip.  That helps….and the Allison also doesn’t get lulled in to “Mr. Limpet” land….folks that constantly baby have had to disconnect the chassis for 10 minutes or so to let the TCM “RESET” and unlearn their flaccid driving habits.

BUT….ON a freeway, using cruise set to say 63 MPH….the HEST light should not misbehave or blink….or that is my experience….

When I asked about 7th injector I was told there isn't any and it's done by the ECM. Not sure what it does different.

Temp gauge only goes from stone cold to boiling hot and back again, happens within a minute of cold start. Tranny temp is constantly good.

Curious about driving habits. I was told full throttle was just dumping too much fuel it couldnt burn so I'm a lightfoot trying for economy (haha) driving. When you say disconnect chassis are you referring to the battery disconnect?

Up until this last event the HEST light came on when driving about 62mph for 15-20 minutes. Last time was 35-45mph after driving 3 miles from cold start.

 

[K9 Exec]

Hey Dean, disregard the ‘7th injector’, we work on Detroit’s as well and they have the 7th injector, that is to spray diesel/ DEF fluid (urea anmonia) into the DPF. Just going off of memory for that repair. I’m getting ready to speak with my diesel tech this morning and will get back with you, I’m hoping we have some value to add to the conversation. 🙂

Edited October 24, 2023 by K9 Exec

[Tom Cherry]

1 hour ago, deanrd said:

When I asked about 7th injector I was told there isn't any and it's done by the ECM. Not sure what it does different.

Temp gauge only goes from stone cold to boiling hot and back again, happens within a minute of cold start. Tranny temp is constantly good.

Curious about driving habits. I was told full throttle was just dumping too much fuel it couldnt burn so I'm a lightfoot trying for economy (haha) driving. When you say disconnect chassis are you referring to the battery disconnect?

Up until this last event the HEST light came on when driving about 62mph for 15-20 minutes. Last time was 35-45mph after driving 3 miles from cold start.

 

Sounds like you are getting a handle on it.  Try to clarify or at least give you my intent and interpretation.

There is, if I learned properly from @Frank McElroy, a special regen sequence or fuel injection changes during the REGEN.  The ECM dumps or puts a microburst of fuel in to the exhaust stroke.  That is HOT and the fuel heats up (I assume) the exhaust....so that extra heat is what "burns off" any soot on the DPF screens or "elements".  You can google and get a fuller definition....

Your gauges should not be flip flopping.  TO ME (the novice), the engine temp sensor MAY be the problem....  I drive my MH periodically to "warm it up and keep things lubricated and flexible".  I also, when climbing steep grades or decelerating down ugly grades, use my digital display (a screen option on some Medallion Gauge systems) watch the TEMPS like a Hawk.  I know when there is even a 5 degree difference.  If I see the tranny heating up...which is common climbing or descending, I often downshift to get the engine RPM's up a little.  This increases the flow of coolant...and that results in the Tranny cooling off.  Now, that is rarely 15 degrees different.  MY CONCLUSION.  Your engine is probably NOT overheating.  BUT, if you have a faulty heat or engine coolant sensor (there may be TWO....one for the ECM and one for the Gauges....or at least some have reported or said that.  BOTTOM LINE.  Get this fixed.  The Check Light may be a false positive.  You should see, if you have analytical gauges or "needles" very little variation....on straight stretches....they should be like two peas in a pod.

We all, even those with less than my 40% "Scotchish - or Scrooge McDuck' DNA try to be light footed.  BUT, every once and a while, I sort of blow it out....when the engine is hot or at operating temperature.  I do that on all my vehicles.....and odds are, I can see the "SOOT" in the rear view mirror.  That includes a 2014 Caddy ATS V6 with a really well tuned and defacte and get power....as well as my C7 Vette.  So, I only do one or two per trip...  I THINK that sort of cleans things out.

YES...the Chassis feeds the Allison TCM. It has some "Semi (dumb?) Artificial Intelligence" that LEARNS your driving habits.  OPPS....it thinks you are the little old lady that drives 15 miles under the limit and only to church....the TCM starts acting like that is your personna....and it then shift or reacts very sluggish.  The fix....and it cost one of our members, who admitted this at a gathering, $150 to get it "RESET".  He and the tech drove it.  The tech told him....Every once and a while....get on it.  pretend you are a drag racer...engine and tranny warmed up of course.   Then, if it acts like this again....do that more frequently....and you can RESET the TCM yourself.  Kill the Chassis Battery (disconnect the LEADS as some have a connection that bypasses the Chassis switch.  Then you start a square one and it learns again...except don't repeat your mistakes...

I can't explain the HEST light....other than stating that mine will blink or flash.....and never again....particularly after a long stint in stop and go or urban or low speed driving.  Maybe just my rig....but Frank says the ECM is in control and no codes or any worries.

Once you get the Temp under control and do what Frank suggests and get the CODE history as well as the REAL regen cycles (100 hours....unless Cummins made yours different), then Frank, if you PM him, will probably help you out.

Good Luck.

[deanrd]

Well it's back in the same shop. They said they found a short in harness. Waiting to see what happens.

Hopefully by the end of the week I'll know more and so will you.

Dean

[deanrd]

Picked it up today and so far so good. They did find the problem area after pulling radiator. The wiring harness was routed behind the belt tensioner and idler pulley, but had enough room to move into the serpentine belt. This rubbed thru the protective sleeve and 4 wires were chafed thru. They repaired the wires and ended up replacing the idler pulley and serpentine belt that was ready to shred. They also made another clamp to restrain the harness to keep it from repeating. Thankfully they caught it now and not me out on the road. They actually ran a forced regen as the error messages I was getting had it thinking I still needed a regen, but not being driven fast enough to start. They told me I needed to let it complete a regen whenever it starts and I will when possible if I can. I read that if stopped before completing then it should restart after on its own. We will see.

Thanks for all the responses!

Dean

[96 EVO]

3 hours ago, deanrd said:

  I read that if stopped before completing then it should restart after on its own. We will see.

Thanks for all the responses!

Dean

That is the way it has worked for me!

Sure, I prefer to have the regen complete it's cycle before I stop, but, that's not always possible!

[Tom Cherry]

12 hours ago, 96 EVO said:

That is the way it has worked for me!

Sure, I prefer to have the regen complete it's cycle before I stop, but, that's not always possible!

Ditto.  Per @Frank McElroy, who is our Cummins engine Guru, my regen cycles are like clockwork.  I have had at least 3 or so interrupted.  In addition, the flickering, occasionally, HEST light did not throw any codes.  DRIVE ON.

Thanks for the followup.

[Jdw12345]

deanrd just curious how things are going?

 Me friend is considering getting a coach with the DPF on it and we are just educating ourselves on these types of issues..

        Thanks 

[deanrd]

Well I thought I was out of the woods, but here I am on my way to Florida and the hest light comes on after 50 miles, on for 20, then off again for about 50. Repeat repeat. Everything running ok. All gauges normal. Just gonna drive. Will find another garage when I get back or trade.

[96 EVO]

1 hour ago, Jdw12345 said:

deanrd just curious how things are going?

 Me friend is considering getting a coach with the DPF on it and we are just educating ourselves on these types of issues..

        Thanks 

Don't know if it's just the luck of the draw, but, I've had no issues with my '08 model (and yes, I'm knocking on wood!)

[Jdw12345]

Sorry to hear about your troubles deanrd!

 Thanks for the response deandrd & 96EVO, curious to know what mileage you are at? Assuming you have an ISL…

[96 EVO]

I'm at 60,000mi

[jacwjames]

I had been following a thread on IRV2 on a 2008 Cummins ISL regeneration.   Maybe this might help, has basically the same symptoms you have.

https://www.irv2.com/forums/f123/isl-8-9-fault-code-1691spn5298fmi18-634586.html

Toward the end of the thread the OP tries to remove the DPF, ultimately using a rubber mallet to beat the clamps loose but failed, but since doing that the problem has gone away.  One of the more knowledgeable posters commented that possibly using the mallet dislodged some of the soot buildup and then regen burned it up.  Seems plausible. 

 

Back in 2006/7 we installed a bunch of after market DPF systems on underground mining equipment in order to meet air quality standards.  These systems were not designed to regenerate.  The equipment that the DPF's was used on the had high engine load cycles (loaders & trucks) performed well.  Other equipment that never got hot the DPF's would clog up a lot, we had special computers to read the back pressure and could tell when the DPF was not performing.  We invested in state of the art cleaning equipment and spare DPF's so we could remove the clogged ones and replace.  The clogged ones were baked in a very high temp oven, and then put in a piece of equipment that would vibrate the DPF and use compressed air to clean, this was in an enclosed room to contain the dust/soot under negative pressure with special filters since the soot was considered a carcinogen.  

[Earl_Price]

I had a friend with the same issue. He did a delete and now he doesn't have that issue anymore.