The DPF conundrum.

[Thud]

Hello all...
Big fan of the Thomas C2. But pretty much gave up on finding one since most seem to be Mid-Western/North-Eastern rust-buckets.
Difficult to find a decent example on the West Coast; thus far anyway. Also looking for a shorty with a lift; even more difficult.
But alas, one has appeared. Decent condition, mileage, price, etc. Although no fuel-friendly Benz motor, it’s rockin’ a dreaded C7.
I’ve also ‘heard’ that “the early years” had problems, but I believe that model was created in ‘04, which means “the early years” swung directly into “the emissions years”; EGR right off the bat.
Anyway, to the matter at hand...
I know the answer to this, just wishful thinking I suppose.
DPF’s were mandated in ‘07, but I’ve read that in certain instances they went into effect in ‘08. The particular beast I discovered is unfortunately an ’07, and I don’t think the sellers know what they have. Been tearing through the internet but haven’t found any confirmation: Is an ‘07 Thomas Saf-T-Liner C2 equipped with a DPF?

 

[Sehnsucht-SKO]

Simple question to ask the seller is does it have a blue fill cap somewhere in proximity of the fuel filler cap? The blue cap is where you top up the diesel exhaust fluid or DEF which is a necessary additive in DPF systems. There will also be a secondary fuel level gauge and on a Thomas (Freightliner) it usually takes the form of four green LEDs beneath the fuel level needle. When these count down to 1 LED it then turns yellow and subsequently red as DEF level drops and if the seller has driven it any distance at all without ever replenishing the DEF the engine programming derates them down to 5mph! The only EPA rated engine that I know of which attempted to circumvent using DEF is the MaxxForce and you won't find one of those in a Thomas. That's where I would start.

Generally speaking although diesel engine manufacturers had until 2007 to deploy EPA mandated Selective Catalytic Reduction technology or SCR, most achieved it years ahead of that and it was broadly deployed in school buses in 2004 which is why this community generally eschews anything from 2004 on. I think a school district could probably order a non-SCR bus during that brief interim but I can't see why any district would knowing it would be mandated within a few years anyways. Of the major brands you can expect to find in school buses during this period, all except for the MaxxForce used DEF treatment systems. I think International Corporation was trying to avoid adding another perpetual cost of operation and attempted to achieve the EPA mandated reductions with an exhaust recirculation system which ended up giving the MaxxForce it's unfortunate reputation. It's kind of like the VW DieselGate scandal in reverse, the necessity of achieving a certain low emission level dumped far too much exhaust air back into the engine versus fresh air and the engine basically suffocated trying to reburn pollutants over and over again, robbing the vehicle of any power and performance. Lawsuits later, IC finally switched to a DEF system but by then the MaxxForce name was too tarnished and they actually paid some trucking companies to switch to Cummins or CAT engines! I'm not sure how prolific that issue was in school buses because they already go slow and may not have experienced a noticable lag in performance but nevertheless it's why you won't find MaxxForce fans here.

That's all I know

 

[cadillackid]

Simple question to ask the seller is does it have a blue fill cap somewhere in proximity of the fuel filler cap? The blue cap is where you top up the diesel exhaust fluid or DEF which is a necessary additive in DPF systems. There will also be a secondary fuel level gauge and on a Thomas (Freightliner) it usually takes the form of four green LEDs beneath the fuel level needle. When these count down to 1 LED it then turns yellow and subsequently red as DEF level drops and if the seller has driven it any distance at all without ever replenishing the DEF the engine programming derates them down to 5mph! The only EPA rated engine that I know of which attempted to circumvent using DEF is the MaxxForce and you won't find one of those in a Thomas. That's where I would start.

Generally speaking although diesel engine manufacturers had until 2007 to deploy EPA mandated Selective Catalytic Reduction technology or SCR, most achieved it years ahead of that and it was broadly deployed in school buses in 2004 which is why this community generally eschews anything from 2004 on. I think a school district could probably order a non-SCR bus during that brief interim but I can't see why any district would knowing it would be mandated within a few years anyways. Of the major brands you can expect to find in school buses during this period, all except for the MaxxForce used DEF treatment systems. I think International Corporation was trying to avoid adding another perpetual cost of operation and attempted to achieve the EPA mandated reductions with an exhaust recirculation system which ended up giving the MaxxForce it's unfortunate reputation. It's kind of like the VW DieselGate scandal in reverse, the necessity of achieving a certain low emission level dumped far too much exhaust air back into the engine versus fresh air and the engine basically suffocated trying to reburn pollutants over and over again, robbing the vehicle of any power and performance. Lawsuits later, IC finally switched to a DEF system but by then the MaxxForce name was too tarnished and they actually paid some trucking companies to switch to Cummins or CAT engines! I'm not sure how prolific that issue was in school buses because they already go slow and may not have experienced a noticable lag in performance but nevertheless it's why you won't find MaxxForce fans here.

That's all I know

DPF doesnt mean DEF.. DEF came along later for most when they had issues getting the levels down to EPA mandates by passive regen alone or when regen causes cylinder burnouts like happened in the IH and powerstrokes of the time. ..



thios is an easy one.. this thing is essentially a freightliner.. (Kudos by the way as I thought i was the only one who loves the C2 look).. get the VIN, call a freightliner dealer and ask for a DPF for it.. they will either give you a part number and a huge price or they will say "we dont show ione listed"..


if its a california unit then it will likely have had a DPF retrofitted if it didnt come from the factory.. those are the ones I run from as the engine and turbo werent designed for a DPF and ther backpressure it creates..



the C7 is a good engine.. not sure why all the hate.. I know plenty of C7s out running around doing their thing wuite well.. they are like any engine.. look for telltale signs of abuse or failure..



C7s when quite worn will produce a lot of blowby.. C7s when worn will run low oil pressure (like 25-30 at highway speed after warmed up) (a good one will stay near 50 at cruise ropm).


C7s dont like RPM.. dont plan on your C7 being happy if your cruising speed runs it at 2400 or 2500 RPM..



a skoolie is likely the bus type of environment for a DPF to do pretty well.. DPFs dont like short trips where the engine doesnt warm up. most skoolies are being highway run for many hoiurs at a time whch helps to keep your DPF clean..


if buying an emission bus be ready and able to read the computer before purchase.. any emissions related error codes then run away or be ready for a large bill to correct it before embarking on a long journey...


would Love to find a shorty Air conditioned C2 (Gen 2.. I detest the Gen 1 windows that dont close right)

 

[Thud]

Simple question to ask the seller is does it have a blue fill cap somewhere in proximity of the fuel filler cap? The blue cap is where you top up the diesel exhaust fluid or DEF which is a necessary additive in DPF systems. There will also be a secondary fuel level gauge and on a Thomas (Freightliner) it usually takes the form of four green LEDs beneath the fuel level needle. When these count down to 1 LED it then turns yellow and subsequently red as DEF level drops and if the seller has driven it any distance at all without ever replenishing the DEF the engine programming derates them down to 5mph! The only EPA rated engine that I know of which attempted to circumvent using DEF is the MaxxForce and you won't find one of those in a Thomas. That's where I would start.

Generally speaking although diesel engine manufacturers had until 2007 to deploy EPA mandated Selective Catalytic Reduction technology or SCR, most achieved it years ahead of that and it was broadly deployed in school buses in 2004 which is why this community generally eschews anything from 2004 on. I think a school district could probably order a non-SCR bus during that brief interim but I can't see why any district would knowing it would be mandated within a few years anyways. Of the major brands you can expect to find in school buses during this period, all except for the MaxxForce used DEF treatment systems. I think International Corporation was trying to avoid adding another perpetual cost of operation and attempted to achieve the EPA mandated reductions with an exhaust recirculation system which ended up giving the MaxxForce it's unfortunate reputation. It's kind of like the VW DieselGate scandal in reverse, the necessity of achieving a certain low emission level dumped far too much exhaust air back into the engine versus fresh air and the engine basically suffocated trying to reburn pollutants over and over again, robbing the vehicle of any power and performance. Lawsuits later, IC finally switched to a DEF system but by then the MaxxForce name was too tarnished and they actually paid some trucking companies to switch to Cummins or CAT engines! I'm not sure how prolific that issue was in school buses because they already go slow and may not have experienced a noticable lag in performance but nevertheless it's why you won't find MaxxForce fans here.

That's all I know

That's ALL you know???

Seriously?

Thought I was gonna receive some assistance here.

Sheesh.



Hahaha...

Are you kidding? Dude, AMAZING level of knowledge, And -super- helpful; now, and for the future.
I really appreciate you taking the time to lay that all out. You guys are always quite generous with your experience.

Update: I brought up the blue fill cap, but also an observation. I noticed they included a photo of the factory placard. Now I'm a car guy, so I have 0 knowledge regarding the manufactured by vs. release date on buses. But, the manufactured date appears to be 11/05. He didn't address the filler cap question, but seems my mention of the date gave him an 'oh sh!t' moment. He emailed back thanking me for the apparent oversight and immediately pulled the ad for further review. It's been listed for a minute, and a handful of others were also showing interest. They're surely scratching their heads now. Guess I imploded the entire process.

Hahaha... Oh well, hopefully it'll get re-posted as an '06. =)

Thanks again man.

 

[Thud]

DPF doesnt mean DEF.. DEF came along later for most when they had issues getting the levels down to EPA mandates by passive regen alone or when regen causes cylinder burnouts like happened in the IH and powerstrokes of the time. ..



thios is an easy one.. this thing is essentially a freightliner.. (Kudos by the way as I thought i was the only one who loves the C2 look).. get the VIN, call a freightliner dealer and ask for a DPF for it.. they will either give you a part number and a huge price or they will say "we dont show ione listed"..


if its a california unit then it will likely have had a DPF retrofitted if it didnt come from the factory.. those are the ones I run from as the engine and turbo werent designed for a DPF and ther backpressure it creates..



the C7 is a good engine.. not sure why all the hate.. I know plenty of C7s out running around doing their thing wuite well.. they are like any engine.. look for telltale signs of abuse or failure..



C7s when quite worn will produce a lot of blowby.. C7s when worn will run low oil pressure (like 25-30 at highway speed after warmed up) (a good one will stay near 50 at cruise ropm).


C7s dont like RPM.. dont plan on your C7 being happy if your cruising speed runs it at 2400 or 2500 RPM..



a skoolie is likely the bus type of environment for a DPF to do pretty well.. DPFs dont like short trips where the engine doesnt warm up. most skoolies are being highway run for many hoiurs at a time whch helps to keep your DPF clean..


if buying an emission bus be ready and able to read the computer before purchase.. any emissions related error codes then run away or be ready for a large bill to correct it before embarking on a long journey...


would Love to find a shorty Air conditioned C2 (Gen 2.. I detest the Gen 1 windows that dont close right)

Dude, love the C2. Not usually a fan of conventional’s, more of a flat-nose guy, but the C2 is a different breed.
Thanks for the tips on DPF determination, will definitely put those to use; especially with the CA units... Been looking at flat-noses out there because of the taller ceilings, but also C2’s because of the lack of corrosion.

And thanks for the pointers on C7’s, the more info I have the better. Seems to be the motor of choice for SB’s in my neck of the woods; they’re everywhere.
What would a rebuild run? The C7 in question has logged 160k. And “I’ve heard” that it’s possible to give the ECU a re-flash to unlock more efficiency/power; hearsay?
Anyway, I’m also not sure what’s up with all the hate. Fairly new to the bus world and I’m already hesitant on bringing up any power plant questions. Feel like mentioning anything other than a DT466 or 8.3/8.9L is askin’ for a bashin’.
As it’s been said, ‘every motor has an Achilles.’

But say for an ‘04-06 C2, if there was a choice, would it be the MB or the C7?
I know they’re both expensive to work on, the MB gets better mpg and is quieter, but finding parts and a qualified mechanic that’ll even look at it may be more of a challenge than with a Cat; just a thought.

I like the idea of DPF’s being more efficient on a highway cruiser, makes sense. But correct me if I’m wrong, aren’t they also exhaust/power chokers? And prone to failure, with repair costs being astronomical? On our high performance cars, the first thing we do is install high-flow intakes and high-flow exhaust. Considering internal combustion engines are essentially crudely-powered air pumps. Better flow = more power/better gas mileage/less strain = a win-win-win. I despise anything that’s air/exhaust restrictive; cats included.

And thanks for the error code tip; may have to pick up a code-reader. But are you referring to pre-04 emissions vehicles, or pre-07? Ha, or both?

And yea, a shorty C2 with a/c is on the wishlist (but with what motor?!?!?! hahaha). But when were the Gen 2’s released? I was under the impression that the larger-style upper window set up was swapped out in ‘07.

 

[Sehnsucht-SKO]

DPF is a diesel particulate filter (sorry, not talking down to you, just being concise for future generations who may be reading this) which while it does create an obstruction in the airflow from intake to exhaust isn't like a muffler that you can bypass or eliminate. The DPF equipped engines were designed with that restriction factored in and also the electronics monitor it so removal basically disables the engine without complicated and honestly illegal deletion programming. When the filter gets sooty enough the engine heats it up and cooks the impurities which is why a highway diesel is more efficient at this than a stop and go bus route or short distance delivery route vehicle. I think someone here said their school district bus fleet would do a half hour post trip drive around the city loop just so each bus got enough highway miles to allow the DPF regen cycle to perform properly. A parked regen cycle is also an option but I've heard it's less effective and frankly it's annoying to have to sit in a diesel vehicle that's parked and revving for up to an hour.

I'm a Jeep Wrangler guy myself and I too am a disciple of minimal resistance airflow. Bigger intake, straight and simple exhaust, a little fine tune programming, and even a puny V6 Wrangler can be quite peppy. The principle is the same in theory but diesels operate on a different set of rules and therefore that reasoning doesn't necessarily apply. I'm not a diesel techie just a daily driver but there are a few people on here who really know these engines well and hopefully if you have questions that delve into the principles of diesels they'll share their knowledge. This is a great community for that kind of thing.

As for whether your C2 will come back to the market and be what was advertised or something else, please do keep us informed. We'll all be on this journey together with you!

 

[Sehnsucht-SKO]

Oh, and I won't speak with definitive authority to this point but my understanding is that the introduction of the C2 coincided with the EPA regulation adoption so I am reasonably confident that every C2 has some type of SCR system regardless of which of the offered engines it carries. It's predecessor, the FS65, can be a roll of the dice because it predated the mandate and continued production into the EPA2007 era but once the C2 took the market the FS65 was discontinued. And as Thomas is a wholly owned division of Freightliner, the only SCR system I've ever seen employed by Freightliner and any of it's offered engine brands is the DEF system. Just a little Holmesian deductive reasoning on my part.

 

[Thud]

Yea, I’m certainly no expert, but I have done some research on diesel particulate filters. I know they accumulate soot then burn it off when a certain level is reached, and that highway driving would be more conducive for that. I know they can’t simply be bypassed, at least not easily. I know they’re programmed directly in with the ECU and the vehicle can’t run without them unless a ton of illegal work is performed. And that deleting them would also require gutting them but keeping the shell in place to get by the visual inspection (in most applications). I know there aren’t any official smog police out there tracking down potential offenders, but if caught, heavy EPA fines would ensue. And that no one really knows of any private owners who’ve actually gotten caught, but that it’s simply easier to run a pre-07 and be done with it.
Being a car guy, I view them as sort of a much more technical and advanced catalytic converter; basically a device inline with the exhaust to reduce the release of harmful particulates into the atmosphere. Except you can just swap CC’s out for test pipes. Although if one is concerned about the environment it isn’t recommended.

And yea, the C2 debuted in ‘04 so there’s no avoiding emissions regulations. Which probably explains why they were never popular with the aftermarket crowd. But as you mentioned, they ran selective catalytic reduction technology which does require diesel exhaust fluid. But from what I’ve read, it’s better than the exhaust gas recirculation system. Then of course, the DPF was added in ‘07. So I figure if I want a C2, the only way to go is ‘04-06. Not solely because the filter may cause a reduction in power, but also what repair or replacement may run; I’ve read it can be in the thousands. Plus they have to be routinely serviced. That’s why I was asking if anyone knew for a fact if Freightliner went with the filters in ‘07, or waited till ‘08, even though I knew what the answer would be.

And if I ever do acquire a bus I’m sure I’ll have a ton of powertrain questions. Like, where’s all that fluid coming from? Or, is that plume of smoke bad? For now I’m simply trying to figure what engine would be best in a C2 based on what’s available, from the standpoint of torque, reliability, overall repair costs, etc; in case I have a choice. Added emissions reduction equipment is a given.

Your Jeep sounds nice, bet it runs great... Just sold a ‘69 convertible Caddy we were restoring, now we’re finishing up a build on a ‘90 300ZX Twin Turbo, while I’m simultaneously diving into the world of buses. Diesels are a completely different animal for sure. Still have a fairly steep learning curve ahead of me. Haven’t really begun learning about the conversion aspect; I still know very little. Follow Skoolie groups on social media and cringe at some of the things I see people going through; not sure I have it in me. My demo/resto days may be behind me. Don’t plan on living in one full time; not yet anyway, just want it for travel. Gonna perform some fabrication on the chair lift so I can pull my (400lb) motorcycles up into it; hope the motor holds up, the 800lb limit should be enough. But to create a proper Skoolie, the right way, you’re essentially designing an entire, self-sustained mini-home, from scratch... It’s quite an endeavor.

But anyway, the gentleman that’s selling the C2 says he’ll repost it soon and to get a hold of him when he does, so we’ll see what happens.

Thanks again for all the help, appreciate it.

 

[musigenesis]

Been looking at flat-noses out there because of the taller ceilings, but also C2’s because of the lack of corrosion.

Do flat-noses generally have taller ceilings? My dognose is 6'7" down the center, as tall as they come. Maybe the really low 6'1" buses are all dognoses?

 

[cadillackid]

Both flat nose and dog nose come in low and high headroom models. The Thomas C2 may only be made in a high headroom