Paccar MX Engine

[LookAtMyPeter_____bilt]

Hello all. I'm about to buy my first truck to move more of orchard equipment for my business. I found a great deal (or at least what seems to be a good deal) on a 2014 Peterbilt 579. This unit has the Paccar MX engine which is a 12.9L (Not the MX-13) and is rated at 485 hp. I've searched the internet far and wide, but other than an opinion here or there that doesn't really answer my question, I cant find much about the regular MX. I was told by the dealership it was the predecessor to the MX-13 and other than a few minor differences they are practically the same engine. Does anyone have any firsthand experience with these motors? If so, what was your experience? Are they reliable, run good, any problems other than some emissions BS which seems like all trucks are suffering from? Also I'm aware roadside service for these seems to be a problem, but given my application I'm not concerned with roadside services and there's a Pete dealer down the road from me. Any info is appreciated, Thanks!

[Zhidden]

It's a mx13. Few issues with the unit pumps and can be a nightmare on the sensor side. Sw is expensive and you can't do much. Core engine is fine
You will struggle to find anyone with davie 4 and even then struggle to find someone would can diagnose them properly. Even peterbilt dealerships struggle. If a derate gets stuck in the ecm you will need to take it to a dealer and pray they don't hammer you with 4+hours of time instead of clearing power down memory.

Good motor. I wouldn't own one

[LookAtMyPeter_____bilt]

(02-14-2021 )Zhidden Wrote:  It's a mx13. Few issues with the unit pumps and can be a nightmare on the sensor side. Sw is expensive and you can't do much. Core engine is fine
You will struggle to find anyone with davie 4 and even then struggle to find someone would can diagnose them properly. Even peterbilt dealerships struggle. If a derate gets stuck in the ecm you will need to take it to a dealer and pray they don't hammer you with 4+hours of time instead of clearing power down memory.

Good motor. I wouldn't own one

Thanks for the reply! Yeah the little info I was able to find did mention a lot of sensor issues. I've heard that removing certain "special parts" eliminates a lot of the sensor issues and derate problems, if that's the case I will probably find someone that charges a pretty penny to get it done right. I'm probably going to drive the thing a max of 15,000 miles annually in all reality, maybe a little more, maybe a little less. Do the issues you're aware of seem to come after heavy use and abuse?

[tree98]

(02-14-2021 )LookAtMyPeter_____bilt Wrote:  I will probably find someone that charges a pretty penny to get it done right.

The ones that charge the most are the worst ones to use. Buy a cummins and don't mess around with stuff you can't work on yourself.

[LookAtMyPeter_____bilt]

(02-14-2021 )tree98 Wrote:  

(02-14-2021 )LookAtMyPeter_____bilt Wrote:  I will probably find someone that charges a pretty penny to get it done right.

The ones that charge the most are the worst ones to use. Buy a cummins and don't mess around with stuff you can't work on yourself.

Why is that? A guy I know paid a decent amount but they went through and made it damn near untraceable without cutting into things to figure it out. As far as the cant work on it yourself comment, that's fair. I'm pretty mechanically inclined but I'm assuming you're talking about the fact that Paccar is pretty well guarded with their info and as the other guy stated earlier that even Peterbilt has a tough time sometimes.

I heard the Cummins ISX had countless problems as well?

[Zhidden]

(02-14-2021 )LookAtMyPeter_____bilt Wrote:  

(02-14-2021 )Zhidden Wrote:  It's a mx13. Few issues with the unit pumps and can be a nightmare on the sensor side. Sw is expensive and you can't do much. Core engine is fine
You will struggle to find anyone with davie 4 and even then struggle to find someone would can diagnose them properly. Even peterbilt dealerships struggle. If a derate gets stuck in the ecm you will need to take it to a dealer and pray they don't hammer you with 4+hours of time instead of clearing power down memory.

Good motor. I wouldn't own one

Thanks for the reply! Yeah the little info I was able to find did mention a lot of sensor issues. I've heard that removing certain "special parts" eliminates a lot of the sensor issues and derate problems, if that's the case I will probably find someone that charges a pretty penny to get it done right. I'm probably going to drive the thing a max of 15,000 miles annually in all reality, maybe a little more, maybe a little less. Do the issues you're aware of seem to come after heavy use and abuse?

Only a few do then right. And they don't charge 3k+. I have had one done at close to 600hp and it's held up for years. Core engine seems solid.

Still does stupid shi#t sometimes. Still wouldn't own one.

[Zhidden]

Also any of the others are more o/o friendly than paccar.

[Rawze]

A)> your on the wrong forum if you want detailed info about MX?13's... this is mostly a cummins forum.

B)> your posts so far imply that you have no absolute clue that 90%+ of all de-mandate programming (delete) is absolutely harmful to these engines and severely shortens their lifespan --- and that "FINDING SOMEONE EXPENSIVE" like you put it ... is absolutely a complete sham!

c)> your posts also heavily imply that you have already made up you mind .. and that all your looking for is other ppl to back up your decisions instead of the reality of the situation.

D)> you seem to have this false bubble of thought that a de-mandate is going to be the solutions to all your problems .. and this simply is not going to be true... especially for a paccar. You will simply trade DPF problems for engine failure issues when that thing gets flashed with some over-priced garbage "delete" programming... We see it about 300+ times a year around here, hence the comments by other members on here about deleting it and the absolute joke of an idea towards "finding someone expensive".

-- People on here are not going to give you the answers you looking for, but instead are going to point out these flaws.

maybe start by educating yourself a bit further towards finding something that more closely matches your needs instead of getting stuck on one brand and make of engine etc.

Here are some somewhat related posts of the past on here. I suggest you browse thru them all...

http://rawze.com/forums/showthread.php?t...9#pid12429
and...
http://rawze.com/forums/showthread.php?t...7#pid32057
and...
http://rawze.com/forums/showthread.php?t...1#pid37721
and...
http://rawze.com/forums/showthread.php?t...9#pid40339
and...
http://rawze.com/forums/showthread.php?t...6#pid53226

.. and if YOU REALLY WANT TO KNOW if one of those super-duper delete shops is any good at all.. tell them to make an example program for a red engine (the easiest to get 100% right) and send it my way for a proper review ... I do this for free on a daily basis around here and what I find is beyond bad most of the time... FROM THOSE same damn exact "best of the best" tuning shops out there.

you might want to browse thru the bad delete collection and see some of these horror stories for yourself...
http://rawze.com/forums/showthread.php?t...5#pid13255

[Waterloo]

Cummins gives you all of the repair manuals and diagnostics, http://www.quickserve.com

You can buy a cheap Inline Reader from eBay for around $200 to $300 and have access to your own ECM.

The main issue with the Cummins are the lack of knowledge in how to properly drive them, RPM UP (1500 - 1800), Boost Low and stay off the cruise.

The fuel pumps on the CM-2250 and up have to be rebuilt every 400,000 miles.

Personally, I would not own a PACCAR product, but that is me, too many issues with these things.