Oil passage cleanning

I want to run something thru the motor, 91 - 4.0, to clean the inside of the block.
Heres my question.......
I have a small leak on my rear main. If I put something in the oil to clean out the block will this make the leak worse?
Also .... what do you guys (and gals, if any) recommend I use?
Thanks

My recommendation is to change over to Mobil-1 or Castrol Syntec synthetic. It will clean the engine out due to it's high detergent nature, just a bit more gently. You just need to keep an eye on the dip stick and replace the filter once you can't read the hash marks/letter on it. The other preferred method is to have it put on a flushing machine for an hour or two. Even after that though you still have to watch the filter as the cleaner/solvents will continue to break down any sludge.
The inside valve train area of our 2 TJ's and 1 XJ look like new, my XJ has run Mobil-1 since about 5,000mi and I'm at almost 207,000mi now. The TJ's we have no idea what was in them for their first 100K but for the last 20-40K they have been running Mobil-1.

Most conservative to more aggressive sludge flushing, (CAUTION: only from my readings, and what I have concluded and tried).

1. Frequent oil changes (500 mile intervals) and change when oil is hot!
2. Mixture of synth and dino, with a keen eye on the dipstick, about 1000 mile changes, maybe shorter for the first 2 changes. The higher the percentage of synth oil, the shorter the oil change interval.
3. Only synth oil, 300-500 mile oil change intervals, initially.
4. MMO in the crankcase, drive 20-40 miles, and change oil.

Note: all the oil changes I mentioned should include oil filter.

These are the only ways I'll do it (and have done it).

You may read about ATF and other stuff in the crankcase, but they are all too risky in my book.

Which ever way you go, keep two things on your radar. The oil pressure and the color of the oil on your dipstick.

My 2 _Maz

Hang on to your hat.
To be timed with a change of oil. Drop oil level by two quarts. Add any trany fluid or heavy fuel to it's full, install a cheap filter. Run engine until normal operating temp or 10 min. Drain refill oil, replace filter. Unless it's so bad it's hopeless this will do the trick.
(IMO) It's an engine not a diner plate. A little build up will do no harm

badron said:

Hang on to your hat.
To be timed with a change of oil. Drop oil level by two quarts. Add any trany fluid or heavy fuel to it's full, install a cheap filter. Run engine until normal operating temp or 10 min. Drain refill oil, replace filter. Unless it's so bad it's hopeless this will do the trick.
(IMO) It's an engine not a diner plate. A little build up will do no harm

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I agree with that last statement and my only 'but' is that you are trying to avoid a mass breakdown of sludge. I've lost an engine, main and rod bearings, to a plugged up oil sump that flatout plugged up when a mass quantiy of sludge worked it's way down thru the return galleries. By using a synthetic you will break those sludge dams down a bit more gradually so that both the pickup and the filter can handle it and you can keep an eye on the oil.
Once you can't read the hash marks and lettering on the dip stick it is time to change the filter/add a quart, not the oil, not until you reach the normal oil interval time unless you are a type A and have deep pockets . For that I would use a good quality filter, Mopar, Purolator, Wix, Hastings, the K&N and Mobil-1 filters are too expensive to use for this purpose because you wll be changing the filter at around 500mi intervals during the clean up, the more sludge you have the faster it will break down. hasta

Maz said:

4. MMO in the crankcase, drive 20-40 miles, and change oil.

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OK .... whats this? (mmo)

I just got this Jeep 2 weeks (?) ago and just wanted to clean it out before I started my maint schedule on it. I plan on running the same thing in it that I have been running in my ' 99 ... Castrol 20/50.
What about the bottles of stuff that you just dump in with the oil that say it will clean it out? Will they dump too much sludge into the pan at once? Eat gaskets and seals?

No deep pockets here. Guess you can so "no pockets at all".

drifto77 said:

OK .... whats this? (mmo)

I just got this Jeep 2 weeks (?) ago and just wanted to clean it out before I started my maint schedule on it. I plan on running the same thing in it that I have been running in my ' 99 ... Castrol 20/50.
What about the bottles of stuff that you just dump in with the oil that say it will clean it out? Will they dump too much sludge into the pan at once? Eat gaskets and seals?

No deep pockets here. Guess you can so "no pockets at all".

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MMO is Marvel Mystery Oil, your choice, fast cleaning with a motor flush or additive or slower cleaning with a synthetic oil.

What do you call "HEAVY FUEL"?I have heard of old timers (old man may know about this ) used to drain the engine and literally fill it up with say 1 or 2 GALLONS of diesel fuel and run the crazy thing that way for 15 minutes and then drain the engine.

They say that it gets all sorts of crud out of it. I would think that is might work to some degree as diesel has some lubricating qualities in it but wouldn't it also score the bearings and rings due to a lack of proper lubrication - even if just a short interval?

I was also thinking that it is still fuel! what is the flash point of diesel? I know it takes compression in a diesel motor to make it work but wouldn't a spark plug also ignite it until it fouled due to the oil in the fuel?


just some "redneck folklore" to be proven or disproven.


JC95.

drifto77 said:

What about the bottles of stuff that you just dump in with the oil that say it will clean it out? Will they dump too much sludge into the pan at once?(

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For the 91, with unknown history (you didn't mention mileage), IMHO, I wouldn't use "those bottles of stuff", as there is a good chance breaking too much sludge too quickly.

RichP said:

your choice, fast cleaning with a motor flush or additive or slower cleaning with a synthetic oil.?

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Like Rich mentioned, it's your choice and you've been told the how2's and the risks associated with each.

hasta


I put in synthetic in my truck with a fresh brand new overhaul and I hated it...after the initial break in oil change I changed to the synthetic. About a month later I started getting oil leaks! I would fix one leak and another would appear as fast as I got the last one fixed.
I changed back to the valvoline 10/40 and have run it since and there is 21k on the ticker now with no more leaks.

I will say I noticed a performance increase as the motor seemed to rev easier to the 7k limit, that was nice!

JC95

RichP said:

MMO is Marvel Mystery Oil, your choice, fast cleaning with a motor flush or additive or slower cleaning with a synthetic oil.

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Sure dont want to take the chance of clogging the pick up, is that CD-2 stuff the same way? (fast)
BTW .... this motor has 183,000 on the clock.

drifto77 said:

Sure dont want to take the chance of clogging the pick up, is that CD-2 stuff the same way? (fast)
BTW .... this motor has 183,000 on the clock.

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I don't have a lot of choices of what I can do with limited funds, so what I've been doing is putting in CD2, running it for a week, then doing an oil and filter change. Have had no problems at all, and I find the oil seems cleaner when I do a change now.

I've thought of going synthetic, but I've already got a small leak somewhere, and seems that with synthetic, it will just get worse, which I don't want to have happen, as I can't afford to have a major oil leak fixed at the present time. Down the road maybe.