Coolant flush before or after radiator change?

BonesXX

BonesXX

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About to replace the radiator. Flush system before or after radiator change. I’m thinking before so I don’t run the gunk thru the new radiator.

Before anyone ask I went with a Denso. I did find an OEM for $225 at factorymoparparts, however the shipping was $195. Just couldn’t see paying that much.

By the way don’t by a Denso at Napa. They wanted $350. $150 on Amazon
 
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When I have all my new parts I'll be doing the same. If I am replacing the radiator and water pump both, and removing the block plug, will I be able to get a good flush or should I do some flushing before tearing it all down?
 
TheBoogieman said:
Why remove the block plugs, unless they're rusted to crap?
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To get a thorough flush? Maybe not necessary on the 4.0? Pretty much standard procedure on my diesels but never did a Jeep 4.0 before. I'm going from green coolant to G-05 so I want it to be thorough.
 
B1Toad said:
To get a thorough flush? Maybe not necessary on the 4.0? Pretty much standard procedure on my diesels but never did a Jeep 4.0 before. I'm going from green coolant to G-05 so I want it to be thorough.
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Flushing without the draining the block is something that can be done, but if you have the time and resources, the correct flishing is with draining the block. The only way to drain all the fluid from the block is through the drain plug, otherwise you drain from radiator drain petcock, and drains half what is supposed to be.
I drained the every flush, did 3 Preston’s, 3 or 4 evaporusts and it was really shiny and nice from inside.
At least before the final fill with new coolant, drain the block one time. Other wise all tue gunk from the bottom of the block will mix up with new coolant.
 
Sorry for the thread jack, but maybe this will help OP as well. The PO had the radiator replaced before I bought it. I had to remove the grill and left the radiator attached and drained it. When I detached the lower hose, there was brown sludge in the hose at the lowest point. So clearly there was no flush done. At this point I am wondering what to do. I want to flush but have the radiator removed. Ideas?

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NCLife said:
I want to flush but have the radiator removed. Ideas?
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Might have been a hillbilly idea but I did that many years ago. Before installing a new radiator I used a garden hose "sealed" with a rag to flush the block until water ran clean. Dont recall which radiator hose I flushed through or if I restricted the exit hose or not.

Same idea as flushing and back flushing heater cores with a garden hose.
 
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TheBoogieman said:
Why remove the block plugs, unless they're rusted to crap?
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Because the engine has a cast iron head and block, which leads to nasty stuff (flakes of corrosion etc.) settling in at the bottom. After seeing what came out of the bottom of my 4.0L, I highly recommend folks drain the block during a flush (if you can).
 
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