Get one of those flush kits from an auto parts store.
You can use plain water to get sludge out of your car radiator. You can use Marvel Mystery oil to remove sludge from the oil pan.
Car radiator flush sold as most automotive shops
Mineral sludge from tap water. A good radiator flushing will help and then use proper coolant to help keep the sludge building up and blocking the radiator.
Time to replace the head gasket.
the so called sludge is most likely some sort of cooling system sealant.
Time to replace the head gasket.
I don't know for sure, but can't you just get a radiator flush kit to get out the sludge? It's worth asking the guy at the parts house about. In such extreme cases of cooling system sludge build up, I would take it to a shop for a professional flushing and cleansing. I would suggest a car radiator specialist type shop - they'll know how to NOT cause more damage to the system. See "Related Questions" below for more about flushing it yourself
Thick gray sludge in the radiator can be caused by a buildup of corrosion, oil contamination, or a coolant leak mixing with debris. This sludge can block the radiator channels, leading to overheating and potential damage to the cooling system. It's important to flush the radiator and identify the root cause to prevent further issues.
Drain the water from your Corvette radiator. Remove the radiator hoses. Remove the radiator stabilizing arm bolt. Remove the radiator retaining bolts. The radiator will come off.
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It's best to remove the radiator and take it to a shop to have them do it professionally. It usually doesn't cost too much and they can make any minor leak repairs while they're at it. When they're done your radiator will be as good as new. Chemicals and power flushing of radiators will only remove loose material. If you have any compacted sludge in the radiator tubes you will not be able to flush them out without having the professional take care of it for you.
Remove the water from the radiator. Remove the radiator hoses. Remove the stabilizing arm from the top of the radiator. Remove the radiator retaining bolts. Reverse the process to install the new radiator.