Dodge Day Afternoon

Here is the text of a post I made on the Mopar web board I use. I mentioned (I think) half of my regular readers in it… so I thought I would bring it here so you guys could see your names in lights…

The Sludge Strikes Back:

Several people on the Mopar web board responded and introduced me to the concept of “short-tripping,” and told me that it was likely that there was plenty of carbon goo up in the intake.

Today I spoke to Mike the Mechanic and he laughed and laughed and repeated some words back to me that I said when I was drooling over the Dart, like “It’s a gen-u-wine little old lady car! She barely drove it!” etc….

SO, I have been obsessing about how to get that goo out of there. Two suggestions (of several) have caught my attention:

1. the slow but sure method: Frequent oil changes for a while, new hotter plugs, some frequent long drives to get the heat up. Clean oil will gradually get some of the sludge out of the case and sound maintenance practices should wear away at some of the impaction.

2. the sorta goofy but kind of fun method: Two guys I respect suggested using steam- one said lift the air cleaner off, turn the idle screw until the motor is running at about 1800 rpm, then mist some water over the intake, it will suck in the water, combustion will turn it to steam and melt the carbon deposits away. (Hi, Fixer!) Seems reasonable. Here’s my favorite variation on that idea:
Mike said we should rinse out an antifreeze bottle, put about half a gallon of water in it, then drop one end of a vacuum hose in it with an aquarium aerator on the end. Place the bottle in front of the passenger seat. Cut a hole in the lid of the bottle, and slip the running end of the hose to it. Attach the running end of the hose to the main vacuum port on the back of the carb. Crimp the hose with a pair of tiny vice grips, and go for a drive. On downhills, where the accelerator is not needed (and vacuum is peaking), uncrimp the hose by releasing the vice grips. This will pull water into the combustion chamber, aerosolize it into tiny droplets, which will be converted to steam (lots of it, since the vacuum going downhill is plenty strong) and the steam will force the carbon out of the tail pipe. Repeat until water in the bottle is gone, or all the beverages in car are gone. Sounds like a pleasant enough way to spend this coming Sunday afternoon, right?

Other suggestions that came along were “Run 1/4 quart of Dextron ATF in with each of the oil changes. It has dispersants that will push some of that stuff along.” (Hi, Gordon!) You guys have any thoughts on that?

How would you de-carbon-ize your top end?


Everyone said something we already know- “You’re getting good advice from your buddies. Do what they tell you.”

Duh, I knew that.

A couple of guys suggested Sea Foam, too. Might do that after the steam to get the residuals out. I am running the 1/4 qt of Dextron today. I drove the 17 miles to work with it in there, and I will drive home, drop the old oil and put in fresh at lunch and put on fresh filters.

I am starting to daydream about finding myself a Plymouth Satellite and putting a performance package in it. πŸ˜‰


  1. Maybe you should pull a valve cover off and have a look-see. I knew an ol’ gal one time (a lot of my stories start like that!) who had a DeSoto that had so much carbon built up in there that there was exactly enough room for the
    rocker arms to work.

    I see you have corroborated my ATF suggestion. If you pour it through the carb it will make tons of smoke, thus my ‘city’ reference. I recommend only doing this in someone else’s garage for revenge.

    Re putting it in with the oil change: Good idea, but I don’t see how it will help to decoke the top end unless you need a ring and valve job, and if you do, you can just scrape the pistons and clean the parts you don’t replace with old fashioned methods, like carb cleaner (the really strong kind that comes in a bucket), a wire wheel, an oxy-acetylene torch, and a bead blaster.

    You burn the oil out of the soft carbon buildup with the torch so it doesn’t contaminate and dull the blast media, which it will do instantly. Then you can blast the hard carbon remainder which will turn brown.

    An old way to decarbonize bikes is this: get it runnin’ down the road pretty fast and turn the fuel petcock almost off. It leans the mixture way out. Makes the combustion chambers run hotter’n shit. You can see burnin’ chunks of carbon come out the tailpipe. Do it for too long and the burning chunks will be aluminum from the pistons. I don’t know where the petcock is on a Dart. πŸ™‚

  2. Darren

    Yeah, Patrick, I like the valve cover suggestion. I can see that right bank leaking from here. Clearly you need to replace those valve cover gaskets; while you’re there, clean out all the sludge up top.

    You could always use that “Motor Flush” stuff. I think the instructions say something like pour it in, run the car for 20 minutes, then dump the oil. The stuff has always scared me, but it might work.

    And yeah, the long drives are pretty much taken care of daily, aren’t they?

  3. Darren

    And be thankful for the responses you’re getting on the Mopar boards. All I’m getting to a Benz question I posed this morning is, “yeah, I think my car’s doing that, too.”
    It’s like the Democratic Senate Caucus — everybody knows what’s wrong, but nobody has the solution.

  4. That motor flush stuff scares me too. What it is basically is a strong solvent. When Harley-Davidson came out with the Evolution motor and went to 20w50 from the traditional 60 weight (which used to be marketed as Regular Heavy 105 measured in Saybolt Standard Seconds – don’t ask! It’s a viscosity measuring system from before The Flood.), they recommended a motor flush at oil changes. We did it exactly once, and that was at a dealership using H-D brand flush. During the time period we were supposed to run the engine with that stuff in it, it got awful clanky and started to stink. I don’t think it actually did any damage, but it was scary.

    Air-cooled aluminum engines are different from water-cooled iron engines, so it’s probably OK. Anybody?

  5. I don’t know what Sea Foam is, but I had visions of you taking the car to the beach parking lot down on the Gulf, pointing it at the ocean, torquin’ it up with the brake on, and…

  6. Romulus

    The motor flush as a product does not scare me, however;

    Let’s assume the worst, and say the engine is completely sludged up inside… You pour the stuff in there and run it. Gordon was spot on…Solvent…Releasing all of that sludge stuck to the side of the cast iron. It releases it, but in the event the sludge does not break down completely, where does it (The schmutz) go?
    A) The filter. If the filter starts getting plugged, the engine goes clanky clanky as Gordon suggested. If you shut it down in time, no harm no foul. This is if you’re lucky.

    If you’re not so lucky, what does not get caught by the filter (Not all of it will) slides right on down into the oil pan and resides there if it’s too large or not viscous enough to come out the drain plug hole. Then it can get sucked into the pick up screen for the oil pump and can clog it. Then the engine goes clanky clanky but doesn’t stop after the oil change. Oil light comes on. Uh, oh…No oil pressure. Consult the manual and see section regarding “Oil pan, remove and replace”.

    Also, if the engine has ever been rebuilt:

    If the last person that fixed it decided it would be a good idea to paint the INSIDE of the oil pan,( So the oil will “flow quicker”) that could be trouble too. The motor flush has roughly the causticity of paint thinner. Need I continue? See above for “clogged oil pickup screen”. Picture the “post chemical stripping” consistency of paint…Where does it go? See above…

    Then again, you may pour it in there and it may be just fine afterwards…

    I say leave that poor old sludge alone until you are ready to build the engine. What did it ever do to you anyway? It can loiter in there for years and never cause a problem except lost sleep for you in lieu of rust.

    If you try to evict it, it can become vendictive indeed, but not always…

  7. The Romulan might be onto something: depending on what you find under the valve cover -‘schmutz’ is a good word – it might be worth it to drop the pan and take a look, if just for your own piece of mind. I have no idea how many ancient, rusty parts you have to take out of the way first and fix before you can put them back.

    I think maybe in the case I described, the engine got noisy because the solvent thinned out the oil. Thicker oil helps dampen noise. There’s no hood, firewall, or water jacket on a bike to mask noise, and the fins can amplify it.

    Just for fun, after you change the oil filter, cut the can off the old one and un-pleat and lay out the filter just to see what you can see.

  8. Darren

    As usual in this realm, Romulus takes our generalized notion: “uh, that stuff scares me,” and articulates the details of the problem.

    I think Gordon takes the right lessons from what Romulus says — go for the mechanical solutions instead of the chemical. Scrape it out where you can and otherwise keep on rolling down the road. If you really want to do something to loosen things up, change the oil every 1,000 miles for the next 10K. The small amount of detergents in engine oil will shake up the sludge a little bit, but will not be a major shock to the system.

  9. Leave us to talk about cylinder temperatures. Hotter plugs are nice, but you also have to richen the mixture a little when you do it and maybe back off the spark advance a degree or two. You see, higher combustion temperatures produce oxides of nitrogen (NOx). It also caused the motor to ping. Especially if it doesn’t have an EGR valve (memory fails whether yours has one or not). Pinging is worse for the valves than carbon buildup. It also plays hell with the tops of the pistons. Remember, pistons are aluminum.

    Mike’s ‘redneck water injection’ is a good idea but I’d like to have a little more control over the amount of water going into the engine. It doesn’t take much to hydrolock an engine, especially if it condenses before being turned to steam in the combustion process (steam compresses, water doesn’t). Big problems then; I’ve rebuilt my share (more often replaced) of engines thanks to water suckage.

    I also think Romulus has the best advice. Let the thing unsludge itself slowly. Adding an ounce or so of Marvel or ATF with an oil change is a help (also an ounce in with the fuel every other fill up. I’ve also seen many a motor destroyed by crap in the pickup screen on the oil pump. Mostly though it’s RTV silicone where guys get overzealous with the shit when they change the pan. (Rule of thumb: There are very few places on an engine where it is proper to use RTV. Use it sparingly. A tube will last a year around my shop with three mechanics using it.)

  10. And just a word about filters. If you walk into my shop, you will see we stock factory filters for every car we work on. Go one extra and by a couple filters from your Dodge dealer. Just one more thing to make you sleep better at night. πŸ˜‰

    Also, see my post from way back when on factory parts.

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