Seafoam?

I've used Seafoam in my gas twice in the last 2500 miles, but have not used it directly in the intake. What are the benefits of doing that? Can it hurt anything?

My XJ (2000 model, 4.0L, 140,000 miles) idles a little rough and the idle jumps around between ~450 to ~600 RPM. :shiver: It has good power and gets 21-22 MPG on the highway, so I can't complain about performance. I've cleaned the IAC and the throttle body with spray cleaner, but I'm just wondering if Seafoam in the intake is the solution. Also, the engine, at idle, has a knocking sound that seems to come from the valve cover. My local mechanic said that it's piston slap and that it's perfectly normal for that engine and won't do any harm. Does that sound right?

I was leary about the sea foam trick, but I did it on mine (in the tank), and it did seem to make it idle a little smoother.

I would have to say that in my experience, the stuff really didn't do all that much.

In regards to the noise you are hearing, it is likely piston slap on #1. A trusted friend who is a mechanic/automotive machinist listened to mine and said (and I quote) "Yep, that's the ol' #1 piston slappin away, and is not uncommon at all on these engines". I asked why it was #1, and he said that it has to do with the coolant flow around that cylinder being different from the rest. He also said that while it was a deathly sound, to not be at all concerned about it.

He said that the vast majority of 4.0's he's been around (some with as few as 70k on them) that have had this light diesel-clatter at idle, lived to rack up 250k+ miles without ever an incident.

I have since racked up 30k since having him listen to it, -and it has not gotten any better or any worse. The engine runs just as good as it ever did.

On mine, the noise is only at idle with no load. As soon as the engine is loaded, -even slighly, the noise completely disappears. Going down the road, it isn't even audible.

Now, my cracked exhuast header, well, that's a different story!

For reference, my engine has 180k.

The slap at idle you've got sounds exactly like mine...nonexistant under load. I guess I just won't worry about it.

Thanks for the response and info.

Just as a second opinion I've had 5 cherokee's, both renix and HO and all have had some kind of noise at idle. I know this is a common problem and have never blown an engine yet. (Yes, I've tried on very steep hillclimbes in hot weather, very high RPM's). These motors are virtually indestructible as long as you keep the water temp down and keep oil in them!
I love the 4.0L.
P.S. current 98 Classic, 136,000. Just the header noise mentioned earlier.
Never used seafoam yet so no opinion 'bout that.

I use seafoam about every 6-8000 miles. I pull it through a vacuum line in the intake and let it sit in there over night. I have 94 and 96 Xj's both with about 127000 miles. Idle does improve along with gas mileage. P.S I use Lucas fuel injector cleaner and it helps immensely with noisy and clogged injector's. Piston slap on the 94 since i had it with 70,000. 96 is quite as the day it was new.

Jeepm@n said:

I use seafoam about every 6-8000 miles. I pull it through a vacuum line in the intake and let it sit in there over night. I have 94 and 96 Xj's both with about 127000 miles. Idle does improve along with gas mileage. P.S I use Lucas fuel injector cleaner and it helps immensely with noisy and clogged injector's. Piston slap on the 94 since i had it with 70,000. 96 is quite as the day it was new.

Click to expand...

My '96 has 147k. It starts instantly, idles perfectly, never has noisy or clogged injectors, has no engine noises and gets more than 22 mpg on the highway.
I change the oil every 10k (Mobil 1) and use the cheapest gas they sell at the local Shell station. Additives are clearly not needed.
Why would I think that oil conditioner, fuel conditioner or Seawater will do anything but cost me money.

Seafoam is great stuff. When I had my renix I would use it when ever I noticed a little rough idle or the injectors getting kinda loud. I would take 2 cans, one in the tank the other through the intake. If you do put it in your intake it will smoke like crazy for a while (longer than you are pouring it in) put about .75 of the can in slowley and then let the vacuum suck the rest in fast. It might stall it out or it might not. You want it to stall out. If it doesnt, then shut the XJ off and let it sit for about 15 minutes. Start it back up and rev it up to about 2500 RPM till it quits smoking. I always saw a pretty good improvement when I did this with my Renix 4.0L
Good Luck

Thanks for the advice, guys. I'm gonna do the Seafoam-in-the-intake thing here in the next few days and see if it smooths the idle out.

You will also be able to find out if/where you have exhaust leaks as the white smoke billows from the exhaust. just a little advertised benefit of sea-foam....lol.:dunce:

Yes on the Seafoam.

You might also remove the Idle Speed Control motor and clean it up. That gets gunked up too. Don't pull on the pintle. Just hose it down with brake cleaner and maybe scrub it a bit with a little brass brush. Clean the mounting bore inside the throttle body, so the ISC will work smoothly. Way easier to do that this description sounds.

have used Seafoam on all my rigs and I think it is well worth the $6 a can. I usually split a can between the gas and the vac. My neighbor always comes out when I am running it though the intake and is real dramatic about the white smoke....he really got pissed when I did it during his family reunion and they awere all outside at the barbecue!!! I tend to try and make his life as shit*y as possible!

little confused, you put the vacuum hose in the can and let it suck it up through the intake? From what it sounds like, it does a decent job.

Years ago my Dad and I used Marvel Mystery Oil thru the carbs on the vehicles and it would smoke up a storm. We'd run some in the tank too. Seemed to clean up the intake valves and cylinders pretty good. Based on all the stuff I've read here I tried Seafoam in my '01. I ran 3/4 of the can into the brake booster vac line, a touch of that into the intake directly, the rest I just dumped in the tank. I ran enough in the vac line to shut the engine down. After it soaked for about 30 min I fired it back up. Throughout the whole exersize I got just the slightest trace of smoke. The Jeep was running fine before and I've noticed no real change, actually it may be slightly closer to a "rough" idle: ie not perfectly smooth. No real complaints, but I might try the MMO again before I spend the cash on seafoam. :dunno:

i have better luck with the lucas in the gas tank and the seafoam through the brake booster. its great for getting rid of built up carbon. sometimes it will foul the plugs from the stuff it removes

nudosimmons said:

i have better luck with the lucas in the gas tank and the seafoam through the brake booster. its great for getting rid of built up carbon. sometimes it will foul the plugs from the stuff it removes

Click to expand...

Better luck at what?
What "stuff"?
Where does the "stuff" come from?
How do you know it's the "stuff" that's fouling the plugs, and not the Lucas and Seafoam "stuff" that's fouling the plugs?
Why does my '96 work perfectly when I haven't addressed the "stuff" issue at all?

Why brake booster line not the pesky CCV line(that tends to choked up) is it too small dia. to stall it?

Harlee&Tahoe said:

Why brake booster line not the pesky CCV line(that tends to choked up) is it too small dia. to stall it?

Click to expand...

because the CCV line doesn't go to the intake direct, it goes to the airbox.
the brake booster hose feeds straight into the middle of the intake.

I don't think you'll see such a dramatic plume of smoke and decarboning on an HO rig, since cryco deleted the EGR system.

For sure I've done it on both of my 87's, because I could look into the TB and see the nastiness that an EGR system creates.

Jim Mesthene said:

My '96 has 147k. It starts instantly, idles perfectly, never has noisy or clogged injectors, has no engine noises and gets more than 22 mpg on the highway.
I change the oil every 10k (Mobil 1) and use the cheapest gas they sell at the local Shell station. Additives are clearly not needed.
Why would I think that oil conditioner, fuel conditioner or Seawater will do anything but cost me money.

Click to expand...

As I can see you must take good care of your Jeep. When you by an abused Jeep things need to be cleaned out. Try looking at your plugs after pulling a trailer weighing in the neighborhood of 2800 lbs. a few hundred miles in a nice hot summer day in the hills then let me know how clean everything is then. All this stuff does is remove deposits left behind by petroleum products and combustion. Less deposits on lifters and engine components = longer engine life. You must be scared to try it or very happy with how things run on your Jeep. P.S good choice on the oil although I'm not as brave as you with 10K oil changes, mine are around 5K with the M1-301 mobil oil filter.

Jeepm@n said:

... after pulling a trailer weighing in the neighborhood of 2800 lbs. a few hundred miles in a nice hot summer day in the hills then let me know how clean everything is then.

Click to expand...

That's exactly what I do 5-8 times a year. Then I pull the trailer through the woods a little way.
I was a dealership mechanic for 27 years, I've seen sludge. You can leave a sludged up valve cover under running Safety-Kleen for 12 hours and it won't come off without a scraper. Pouring a little Coleman fuel + alcohol (see the Seafoam MSDS, those are the ingredients) through won't do anything but compromise the lubrication and overload the catalytic converter......and lighten your wallet.

87manche said:

because the CCV line doesn't go to the intake direct, it goes to the airbox.

Click to expand...

Not the fresh air line, the other one, that draws fumes from crankcase into the intake manifold.

or am I :greensmok