I have a 94 960 with 226,000 miles.

The engine knocks really bad when it is hot.

What it does:
Doesn't knock and runs like a top when it is cold.
When the engine warms up (after a 10 or 20 mile highway drive) and I come to a stop I can hear excessive knocking in the motor. It is also be drinking coolant.

What I have done so far:
As a precautionary measure I filled up with high quality non ethanol fuel and put in a bottle of high mileage fuel system treatment hoping it would go away. It didn't.
I feel this is a mechanical issue since it only happens when the motor is hot. Are there electrical issues to also look into ?

What I plan to do:
Pull the spark plugs and make sure they look good (there were changed about 10k ago). Inspect in and around spark plugs and coil caps....

Head Gasket ? - no apparent condensation on tail pipe. Exhaust smells normal.

What do I need to do next ?

 

Sounds like it is overheating.
Cooling fan working?
Thermostat good?
If you keep driving it like that the headgasket it going to blow.

 

The temp gauge doesn't indicate an overheat condition. Coolant fan which is electric is working. I will check the thermostat but I don't think it is overheating. Full Water Pump replacement occurred w/ Timing belt 25,000 miles ago.

 

I should add that the motor isn't 'hot' its just up to operating temperature.

 

Only other thing I can think of is a loss of oil pressure causing the knock.
But when a car overheats it knocks as well.