Greasy brown residue in coolant reservoir - 2001 Pontiac Bonneville

SOURCE: The engine is overheating, the

Hello and welcome to FixYa!

If you have overheating problem, it can lead to multiple issues. You may be running on low coolant that's why the vehicle overheats. If that's the case, please add coolant and make sure that it sits on the right level, too much coolant can cause overheating too for coolant will overflow.

The vehicle may have a faulty or worn out radiator blower motor that's why it overheats. If that's the case then you will need a blower motor replacement to resolve the issue.

If the radiator is clogged with dirt and rusts this issue occurs too. The coolant doesn't flow normally on the cooling system if it's clogged. If that's the case, I strongly suggest that you have the radiator flushed to drain out dirt and rusts. If you think that the radiator served you enough then it's better to have it replaced.

Please do check the radiator hoses, If you have worn out hoses it can cause coolant leakage which can result to overheating. A tiny hole is good enough for the vehicle to overheat.

A faulty thermostat sensor can cause the issue too. If you have worn out thermostat, the fan may not trigger that's why the fan won't work when under stressed conditions. A blown radiator blower fuse can cause this issue too so I suggest that you check the radiator blower fuse and replace it when necessary.

Hope you find this information helpful enough and thank you for using FixYa! Have a good one!