Engine problems when warmed up?

[a3ternus]

Hm,I m not sure how to put this... :-/
My car behaves in a different manner when fully warm up.
The engine gets somehow slower to react to the gas pedal from idle.
There s a small but noticable lag when revving it.
When the car is cold this doesnt happen.
Also when warm,there s a bigger chance I ll hear petrol knocks
at around 3000rpm,something that never happens when the engine is cold.
So,apart from changing petrol station what else shοuld I check?
Apart from that I think my clutch fan needs to be replaced.
It may be hot here,but I ve never again seen my temp gauge go over
to the third mark(line) before in 4 years.Now it sometimes gets there,
even though it goes back in the middle soon after that...still,I wonder.
The noise the fan makes is also louder than before,so what do you think?
Thanks for all you comments/suggestions,tips... :-)
N.

PS.Apart from all these,the car is fine...Acceleration is fine and there s no throttle lag in higher rpms!
PS2.Does the thermostat or fan clutch have to do anything with the whole situation...?

[dlmpsy]

I am not very familiar with the mid '80's 4 cylinder cars, but if your car is running hotter, it could be related to the engine knock. Low octane fuel can also cause knocking. If your clutch fan is bad, definately replace it. While the fan is off, you may want to use a water hose to clean the cooling fins of the radiator.

[thejimlab]

There are 3 different temp sensors screwed into the thermostat housing. They go bad and cause you car to run lik shit depending on how warm it is. One may be going bad. I have no idea how to test them.

[a3ternus]

There are 3 different temp sensors screwed into the thermostat housing. They go bad and cause you car to run lik shit depending on how warm it is. One may be going bad. I have no idea how to test them.

Can someone please explain what Jim said above?
I m getting desperate with the whole knocking issue here...:(
N.

[Jean]

See items 4,6 and 8.

http://www.realoem.com/bmw/showparts.do?model=1031&mospid=47252&btnr=11_0681&hg=11&fg=35

Have you already checked condition of your fan clutch, tried to stop it with a rolled newspaper ? How about thermostat, when was it changed and coolant flush ?

[a3ternus]

See items 4,6 and 8.

http://www.realoem.com/bmw/showparts.do?model=1031&mospid=47252&btnr=11_0681&hg=11&fg=35

Have you already checked condition of your fan clutch, tried to stop it with a rolled newspaper ? How about thermostat, when was it changed and coolant flush ?

You re talking about these three,huh?
Item4:TEMPERATURE-TIME SWITCH.
Item6:ENGINE COOLANT TEMP SENSOR
Item8:TEMPERATURE SWITCH
Wow,we re talking about 180$ (130€) here? :roll:
(I guess the LSD I had in mind is out of the question for me...)
How do they operate? Does any damage to either
of these parts cause ping/knocks when the engine is warm?
What does the fan clutch got to do with these?
I mean,the newspaper trick worked ok and it didnt stop.
The problem is that the temp goes all the way to the third mark
when uphill using second gear and around 3-4k rpm...but it
goes down to the middle again very quickly...
Thermostat is ok I guess.Never been changed though...
And the Radiator was flashed some year ago...No probs there...
N.