M929 Questions

[Russ Knight]

If you want to get stuff out of the tank and lines, then yes. You can also run biocide if its been sitting for a while.

If you want to purge the pump, injectors, etc and clean them out, then you disconnect the supply line going to the IP/PT pump, and your mix of seafoam, power service, ATF/OIL mixed into a gallon jug and have the engine suck it all in directly instead of pulling from the tank.

That's one of the great things about older diesels like the NHC250, and to some extent the 6cta8.3.... looser tolerances mean it's not as picky about fuel... Do NOT let it run out of fuel though.. It uses fuel as lube for the pump.

I literally ordered a gallon of MMO, a gallon of TCW3 (2 stroke oil), 2 cans of seafoam, 2 cans of wallyworld version of seafoam, and a gallon of ATF, because this convo reminded me I needed to do it to my new truck.... I plan on doing a pump/injector purge which means I'm gonna take half of the above, dump it in a pail, and suck it directly in, and the remainder will be dumped into the fuel tank and diluted. By sucking it in directly, it's not diluted with fuel.

I couldn't get powerservice diesel kleen, otherwise I would have added that to my list...

The seafoam will provide the immediate cleaning ability, the ATF has detergents, the TCW3 and MMO provides lubricity. All of which are readily combustible in a diesel engine with no issues.

You really don't need to do a purge that often, but my truck is 30 years old and I guarantee it's never been done.

TCW3 is something I suggest in every tank...1 oz per gallon, but more won't hurt. the ULSD of today doesn't have the lubricity that older diesel does... which the engine was designed to run on..

It's actually very common to dump seafoam 100% strength into diesel fuel filters when changing them.... to clean things out... This is just a longer, more complex version, on steroids.... when purging....

By diluting it with fuel in your tank you have a gentler effect over a longer time, as the chemicals work in the tank/line.

That's why I do both. Half to do a quick deep clean of the injectors/pump, the other half to continue cleaning the rest of the system, for the remainder of the tank.

You will notice a quieter running engine on the TCW3 alone..


View attachment 896524

Awesome information! Thank you for taking the time to share. Very informative.

 

[Russ Knight]

To the above - If you're looking at cleaning/freeing up the fuel selector valve, then you can disconnect both lines and run both of them into your pail that you're sucking your purge solution from, then just keep moving the valve back and forth as it's sucking it in, 30 seconds or so on each side, alternating...

The problem with that, though, is it goes through the fuel filter, which is MASSIVE, and already full of fuel. You'd be better off pulling the valve and cleaning manually, IMO... or just wait for the mix in the tank to make its way through... if it's not critical right now.

Also, as with most things on these trucks, they tend to bind/seize when not used... so use it... alternate tanks frequently.....

--Also, if you don't believe me on the TCW3... dump a gallon in your fuel tank (half tank or more is better, so it's not being wasted)... Start your truck and wait a couple minutes..... you'll notice it gets quieter as soon as it makes its way through the filter and into the engine... Funny what happens when things are getting lubed properly..

Once I broke the valve free, which didn't take an excessive amount of force, it works good now. I will be alternating tanks on a regular basis as well. The fuel filter on the Freightliner is kind of odd. It sits on top of the engine in a housing with a removable lid. It would be the perfect / easy place to fill with Seafoam and see what happens.

 

[TechnoWeenie]

Once I broke the valve free, which didn't take an excessive amount of force, it works good now. I will be alternating tanks on a regular basis as well. The fuel filter on the Freightliner is kind of odd. It sits on top of the engine in a housing with a removable lid. It would be the perfect / easy place to fill with Seafoam and see what happens.

If you don't remove the return line, it's gonna suck it all in pretty quick....and dump most back in the tank and dilute it.

I forgot to mention you'll want to put the return line in your bucket 'o purge, so it's cycling through nothing but your mix. If you're using just seafoam, or a light colored fuel/cleaner, you'll notice it gets pretty dark pretty quick, as it cleans everything out.

This was on a small diesel in an MB 300D. You'll notice it's near clear when it starts, and gets darker the longer it runs...









and another extreme example.....





That's just the stuff recirculating through your pump and lines...

Imagine what the injectors looked like...

 

[Russ Knight]

If you don't remove the return line, it's gonna suck it all in pretty quick....and dump most back in the tank and dilute it.

I forgot to mention you'll want to put the return line in your bucket 'o purge, so it's cycling through nothing but your mix. If you're using just seafoam, or a light colored fuel/cleaner, you'll notice it gets pretty dark pretty quick, as it cleans everything out.

This was on a small diesel in an MB 300D. You'll notice it's near clear when it starts, and gets darker the longer it runs...


View attachment 896561
View attachment 896562





and another extreme example.....


View attachment 896563View attachment 896564


That's just the stuff recirculating through your pump and lines...

Imagine what the injectors looked like...

Wow! I must do this.

 

[Russ Knight]

I put a gallon of ATF, a gallon of high mileage 5-20w oil, and a gallon of Lucas fuel treatment in the drivers tank which had about 1/4 tank of fuel and ran it. Is it normal for junk to come out of the exhaust when doing this because the truck has little specks of something all over it now. Initially the truck was driven about 15 miles at 1800-1900 rpm to my farm, then lower rpms while working it most of the day. It burned most of the tank, and I swapped it back to the other tank. Should I do this again when the passenger side tank gets to 1/4 tank?

 

[TechnoWeenie]

I put a gallon of ATF, a gallon of high mileage 5-20w oil, and a gallon of Lucas fuel treatment in the drivers tank which had about 1/4 tank of fuel and ran it. Is it normal for junk to come out of the exhaust when doing this because the truck has little specks of something all over it now. Initially the truck was driven about 15 miles at 1800-1900 rpm to my farm, then lower rpms while working it most of the day. It burned most of the tank, and I swapped it back to the other tank. Should I do this again when the passenger side tank gets to 1/4 tank?

Did it rain? Could be water capturing soot particles coming out of the exhaust, and dropping onto the truck. If it's a light rain/mist it'll do that. It'll also do that if the truck hasn't been driven for a while and condensation builds up in the exhaust stack. The second you give it some gas it spits out soot water.

Shouldn't be overly sooty/bad, but if you're cleaning out the tank/lines, and it's already past the filter, then anything is possible. Shouldn't really be chunks, though.

I'm assuming you noticed it running quieter/different tone?



I'd probably run a purge cycle, as mentioned above... but that's just me..... then just run the TCW3 and PowerService (gray bottle summer, white bottle winter) in every tank (following dosing instructions).

Nothing that you listed has any super harsh chemicals in it... Lucas is fairly mild, and ATF and oil have mild detergents which won't shock the system.

Seafoam does have some harsher chemicals in it, and if you do the purge, it can shock the system, and if you have a failing part, or gunk holding back a leak, it can clean it out and show the leak. But it's not going to hurt anything, only show what weaknesses already existed. Seafoam is mild enough that it's suggested by the manufacturer to put directly in the fuel filter when replacing the fuel filter, so... they wouldn't suggest that if there was any possible chance they'd be liable for any damage.

 

[Russ Knight]

It isn't soot, more like small oil droplets. To be honest, I can't tell much difference in the way the 929 runs. It ran well before the treatment. My freightliner is the one that is running like crap. I've added the above (less Seafoam) to both tanks, but unfortunately they are tied together and neither tank is very low. I'm going to do the Seafoam trick directly into the fuel system and see if it helps.

 

[TechnoWeenie]

It isn't soot, more like small oil droplets. To be honest, I can't tell much difference in the way the 929 runs. It ran well before the treatment. My freightliner is the one that is running like crap. I've added the above (less Seafoam) to both tanks, but unfortunately they are tied together and neither tank is very low. I'm going to do the Seafoam trick directly into the fuel system and see if it helps.

Is it more on your tailgate? or all over?

Oil that's coming from a leak below the truck, especially from the driveline, will cause oil spots on the rear of the truck if you're driving at speed.

Nothing I can think of can cause oil spots other than that.

If your exhaust has OIL in it, and being propelled at enough speed to cover a truck, something is seriously wrong.


The purge isn't a miracle fix. It's just to clean out a system that hasn't been cleaned out before, or if you're concerned about contamination.

The seafoam in fuel filter is about the safest thing you can do that will help clean things out, but nowhere near as much as the purge would.

 

[juanprado]

M939 mufflers are notorious for holding water. Especially if it sits up any time. Then as mentioned, when warmed up; they blow all the crap, oil, soot, and water out of them. Put a rain cap on the pipe will save you a lot of trouble down the road and a rusted out muffler and intermediate pipe. I had a muffler almost literally blow apart as it was severly rusted from the inside. Dump trucks use the same muffler but a different tip.