What to do if debris in coolant reservoir after few weeks after flush

Once you have sludge in a system, it's about impossible to get it all cleaned out. Have it professionally flushed because those tees really don't do much.

Single flush never works as some debris would be knocked loose and it is a matter of time before they surfaces. For badly sludged systems, it might take 3 or 4 flushes over a period before they become really clean. Of course you need to run the vehicle for some time in between flushing.

Note your coolant quality.

I would usually flush and run without any coolant for one or 2 days and reflush until the water becomes clean. RO water would be the best choice to use for this.

Hmm I did not know I could run engine with just water for that long. I will try this method since July 4th i have 5 days off. What is RO water?

As long as you don't have freezing weather, running without coolant for one or 2 days is ok. RO = reverse osmosis.

If the engine is not running at operating temperature, sludge in system would be stuck and won't be cleared by normal flushing.

When flushing, always use clean water to final flush before adding coolant. Mixing of different brands of coolant can result in clogging of the cooling system, especially the radiator core so you have to flush clean and also after using flushing agents.

Back again, I took part of your advice and drove car with just water for a week. I did backflush 3 times during this period. Today I backflushed and put in some prestone radiator cleaner and filled reservoir back up to required level. I drove car around about 2 to 4 hrs. When was about 2 blocks from house my check engine light came on. When at home I let car cool down before checking water color in reservoir. Once cooled I checked and noticed color of water was rusty looking. Is this a bad thing or do I need to reflush and fill water and drive around more until this changes clear? Thanks in advance.

The radiator cleaner should have gone in at the beginning of the process, not the end. The goal here is to use the chemical to loosen things up and backflush to carry them away.

In that case I intend backflush it out and put in just water and drive it around. Then flush again. I just need to know if I am hurting vehicle with just having water in coolant system too long? Thanks.

Short periods of water will not hurt it as long as it is flushed out after. Water is a long period problem. Coolant gets rid of heat better too. Don't leave the chemical in too long (1 day max) as that has a lot of acid in the and will be corrosive if left in.

As of now I had water in there for about a week. Today I backflushed and just put chemical flush with water. I attend to flush it out again tomorrow. Put in more water and drive around for awhile and backflush Then put in 100 percent universal coolant until I hit fill mark since it is hard to remove all diluted water from engine.

Sounds like a good plan.

Oh yeah, I forgot to ask. Does it matter what coolant to use Dexcool or universal coolant for O'reilly's?

Dexcool would be better. The universal is more for topping off.