OK, so the truck I just bought has I think some major issues, mostly lack of maintenance, but I think they're fixable. In the past, I've (a couple times) filled the crankcase full of diesel fuel and ran the engine at idle until it was up to temp with an oil pressure gauge installed to monitor pressure to ensure no damage.

On this truck, I'm considering half and half. half full of oil, half full of diesel. Run it, dump it, change filters. Run it with a cheap <$10 per jug oil, dump it and change filter again. Replace oil, install new filter, and go. This truck is a '97 Chevy 2500HD with an unknown mileage Vortec 350 in it. Compression numbers are all over the place, and the top end is full of carbon as well, which I plan to attack with seafoam. I think a majority of the problem is just stuck rings, and I'd like to attack it well now and be done with it. I figure a strong attack to the crankcase while monitoring pressure for a short period of time should do no damage to anything. Thoughts?

Don't do anything too drastic - fresh fill of oil with a quart of MMO in it to start, run that 1-2k, and then do it again, and then go to whatever oil you want to use.

As for the carbon, don't waste $$$ with Seafoam - take off the air cleaner, and 'mist' hot wanter into the intake while revving the engine gently. Feed about a quart throught the engine, it will steam-clean it.

Diesel although oily is not a lubricant. It won't hold up well when the engine is up to temp, and although it may have worked for you in the past I would be worried about unnecessary wear.

I'd take off the valve covers and take a look. Clean up what I could, do a piston soak while you are at it, and after letting the pistons sit a few days. Then go get a 10w40 High Mileage oil and run it for 500 miles. I'm starting to like the 10w40 High Mileage oils out there due to their abundance of additives compared to their 10w30 brethren.
Then another 500 mile OCI. Then go to 1000 miles, another 100 mile OCI.
What you want is SLOW. If a big piece breaks off and clogs an oil passage the engine will be a goner.

It would be best to drop the oil pan and clean it out and the oil pick up, but I have no idea what that entails and it could be a MAJOR project.

It would be 4 or 5 oil changes into the short OCI routine before I even thought of MMO in the oil.

If you want to go FAST. Look into Kreen in the Additives section. A bunch of people are having good results from it.

The idea of putting diesel in a gasoline engine scares me. Much less putting it in the crank case.

I vote too for 20% MMO and your favorite brand of oil. Do this a couple of times.

Sounds like a good candidate for Kreen.

+1 Water is the old school way of doing it. Still works now and is a great candidate for your 350

As the sludge/deposits dissolve the oil gets ruined with contaminates.

Buy cheap oil and change often through out this cleaner additive process.

Yes, but get the engine good and hot, a 20 mile highway trip would work, then when you pour in the water keep the rpms up high like 4000 or more and pour slowly so you dont hydrolock a piston and destroy the engine. I did this on a '92 Aerostar 3.0 once and after I got done pouring a pint or two of water through, the whole area around the van smelt like spent firecrackers. Oh, and after the water treatment, why not do an Italian Tuneup, which is simply to run it on the freeway in a lower gear so it is turning 4000 or more rpm for 5 or 10 miles.

As for the crankcase, MMO 20% with low cost oil, maybe several changes. Just how bad is the crankcase anyway? Did you drip hot oil on a file card to see what the soaked in blot looks like? Photos please.

You do the water trick with a mister, like an old (clean) Windex bottle.


And this is the condition of the motor. The plugs are [censored], carbon and blowbye contaminated. Combine that with the goofy compression numbers, my bet is the rings are just stuck as [censored] from lack of maintenance. It was about 2 quarts low on oil when I got it.

http://www.fullsizechevy.com/forum/gener...elp-needed.html

Diesel may lower the flash point enough for the engine to catch fire in a worst case scenario. After cleaning the top, drop the oil pan and clean what you can there. It's impossible to manually clean all of the little oil passages inside the engine. The crank, cam shafts, pistons just to name a few all have oil passages too. You'll need a good oil additive and high detergent oil or maybe even an HDEO for that.

I also don't think that 100% Diesel fiel was a good idea.why did you buy the truck in this condition?

Kreen or MMO, I'd pass on the diesel fuel.

Yes it does.

Listen to this guy.

Another option is 30% LC20 and 70% PYB.

But don't loose sight of the fact that none of these options will bring it back to factory specs; you may still have to re-ring and re-bearing the short block, and have the heads reworked.

I would do this, and will if I ever get my hands on a sludgy beater. It's cheaper and quicker than playing around with different oils and fancy additives.

I would just drive the thing.

I perfectly clean worn out engine is still a worn out engine.

If you do "clean" it, go aggressive, if it goes, it goes.

If it were me, I'd change the oil and drive it. There are plenty of people who drive plenty of miles on cars they had no idea required periodic maintenance. If the motor is on its last leg, doing something as drastic as you plan may be enough to put it over the edge. I'd rather have an ok-running engine than an engine with a spun bearing and sparklies on my dipstick.

If you can, please post up your results. I'm very interested in seeing some before/after pics. Speaking of before pics...

If you're pulling plugs you might as well do a piston soak. Kreen works really well, a couple ounces per cylinder should work good on a 350, add some Kroil for good measure as they have a deal going on right now for both. Soak for a few days if you can, turning the crankshaft clockwise a quarter turn every twelve hours or whenever you feel like it. Don't go too crazy with the amount of liquid and hydro lock the engine. Cranking with the plugs out works with rags to catch the solvent. After soaking get the engine up to temperature and dump the oil.

Advance has 10w30 Rotella Diesel on sale this month as well as Pure One oil filters. Buy a few jugs and filters and have at it with the Kreen.

From my experience after cutting open filters from high mileage vehicles with unknown maintenance, while initially dosing with Kreen in the oil at 3 Oz per quart; change out the first filter at 250 miles the second at 750 then back to normal.

Always keep an eye on things and when in doubt change it out.

If you're willing to try one of my Crazy Ideas(TM) you could try this:

Change the oil, then fill up the gas tank. Crush up two napthalene type moth balls and wrap them up but good in coffee filter paper. Let the engine cool for a couple of hours. Get some wire or what ever and attach the package of moth balls in coffee filter paper to the bottom of the oil fill cap or any place you can be sure it will be exposed to the air inside the crankcase. Start the engine and let it idle for a good 12 hours or so. This truck is new-to-you, so check the temperature gauge frequently during the first hour. Remove the package and then change the oil again. Even if I really am as crazy as I know I am, all you really lost was a little fuel, an oil change, two moth balls, and a coffee filter. Oh yeah, do this outdoors.

Here is what NOT TO DO.

Rofl!!!

FYI, Gunk Motor Flush and K&W Motor Flush are composed of 60% - 100% diesel fuel per the MSDSs, so there's plenty of precedent for using diesel "safely" in crankcases for cleaning purposes. But that's as a temporary oil ADDITIVE, rather than as a 100% lube itself! Diesel is also used in at least a few "fuel system/injector cleaners," including CRC Fuel Injector Cleaner (>95% diesel), so it's also "safe" to add to gasoline tanks, but perhaps at 12 oz at a time. I'm not judging the effectiveness of either application, but simply mentioning that diesel in limited quantities is "safe" for both crankcases and gas tanks. (There's no absolute safety when using such chemicals...hence the quotes.)

Use kreen, idle it for a bit, change that oil filter often. don't use an idle flush until a few OCIs of maintenance cleansing/shorter intervals with something like kreen.

should have run it on dish soap and water to make it slippery.

Frequent oil changes with 5w40 or 15w40 HDEO with MMO, bottle of redline fuel cleaner and clean the throttle body with some intake cleaner would be my suggestions.

^This COA would also do some good, true.

THAT........WAS...........AWESOME...........