How do I clean out the coolant/oil sludge properly?

Okay, so here it is, I bought a 2001 Cherokee with a "blown head gasket" about 2 yrs ago, actually it was a cracked head. I knew this and knew they were notorious for this. I had a mechanic weld it for me which lasted almost 2 yrs. Now it has cracked again so I am intending on changing it out with a cylinder head off a '97/'98,(having it checked over at a machine shop first). What I am needing to know is how do I effectively clean all the sludge out of the engine? It has been sitting for 4 days since I discover the actual problem. I have read everything from trans fluid to diesel fuel in other forums but I figure I would ask other enthusiasts, thoughts?


PS: I will probably have other questions to come, first time doing something of this caliber on my own.

A short run with diesel fuel is a common one for that. It is actually a light oil. Trans fluid is good too, very high detergent and will help a lot on the shot run.

If you have the head off I would just flush it out well with a garden hose. I had a old 50's (AC) diesel tractor that looked like the coolant was mud. Quick flushed it, as much as I could, to get the crap (slug/mud) out. Then added a bit of dish washing soap and continued flushing until it was clear.

If your concerned about more than just the block; like heater, rad, water pump; then of course you will either do more extensive part removal and/or flushing.

I've never done the diesel fuel flush but typical engine flush is with engine running. I don't however believe that this would have been sufficient with the situation I had in the tractor.

I always use distilled water when refilling the coolant. But that my just be my idiosyncrasy. :crazy:

Diesel. Personally wouldn't use water but to each their own.

OK. I was thinking sludge in the cooling system not sludge in the oil passages. That's what the problems seemed to be on my initial read. I don't think the soap and water would hurt anything, but would not be real aggressive in cleaning the oil sludge. I've used brake cleaner or carb cleaner for that, in the past. Or if you have a parts cleaner just use that. I usually do a final wash of the cylinders and of the bearing surfaces with kerosene or other solvent that retains a bit of lubricity. I suppose diesel would fall into that category although it is actually more waxy than having lubricity.

my use of water would depend on how long it took to the the engine back together and cranked. If its a day or two then water wouldn't hurt as you would fresh oil back in it then fire it to get the engine heated up. of course, I'd run that oil or oil/diesel mix for a few hours then drain oil and refill with fresh oil.

For coolant sludge water obviously wouldn't hurt anything.

To OP I'd get diesel in the crankcase ASAP. Water will get in between your crank bearings and you'll spin one for sure. then your looking at pulling the block and starting from scratch.

hmm... stroker time if you get to that point.

Thanks all for the tips. After finally removing the cylinder head another question developed. 4 of the 6 piston heads are coated with significant carbon build up. Carbon cleaner/brake clean is not getting it all off. Would the careful use of a gasket scrapper and or some 100/200 grit sandpaper work to clean it up? (it was interesting that the two cylinders that were occasionally misfiring were the two that were clean from carbon build up.)

I'd put a sanding wheel on something and go to town. You're not going to hurt anything.

I forgot to add you can spin the oil pump to get diesel in all the engine passages, rocker arms lubed etc.