Yes, stop leak turns into a thick substance to plug any leaks, when it ends up in the overflow bottle it turns into sludge there.
broken radiator
The radiator cap could be the cause of coolant reservoir overflow or backup. Have the cap checked to see if it is bad.
The most likely cause of this is a blown head gasket dumping oil back into the coolant passages. The oil will mix with the glycol in the antifreeze and make a thick yellow paste. It is very important to flush the cooling system after the repair or this sludge will cause heating problems.
Only if the coolant is leaking from the heater core, but you will see this.
degradation of the coolant. flush the system and refill it, and all should be well.
If you have the pink Dexcool antifreeze in it then that is the reason. You can go on the web and there are several class action lawsuits against General Motors concerning the issue.
Engine coolant temperature is cooled by the radiator, moved by a water pump and controlled by a thermostat. If there are troubles with any of those components the coolant will boil Also if the head gasket goes bad gasses from combustion inside the engine will get into the coolant and cause it to boil.
There could be several reasons. Under normal operation, the vehicle will experience this as the coolant heats up and expands into the over flow. A bad water pump, low level of coolant, as well as a clogged radiator could also cause this problem.
If the radiator is cracked then the vehicle has ran dry on coolant. This would cause the radiator to crack if there wasn't any coolant.
Could be a leak in a radiator hose, or radiator. ==Answer 2, Another Possibility== It could also be the radiator cap pressure relief valve action which vents coolant and/or coolant vapor to the coolant overflow reservoir/tank when steam is created in the coolant passages in the engine block. When the engine is shut off, the residual heat in the block can cause the additional pressure and/or steam.j3h.
Low coolant or an inoperative radiator fan.Low coolant or an inoperative radiator fan.
Often the cause for loss of heat in a vehicle is low coolant levels. Double check the coolant levels in your radiator overflow tank (unless it is a system flush never add fluid directly to your radiator) and refill it if neccessary. Do this while the engine is running for best results.