My 2005 Stype R is overheating when driving at highway speed or idle. changed thermostat flushed system. Engine gets hot still and is overpressureizing the plastic tank. What could it be? Please help

 

If the engine has been overheated, it may now have a warped head(s) leading to head gasket failure.

 

Is the fan operating correctly, when it's hot is the fan on?

 

Also, over pressure in the coolant can be a blown head gasket. Blown head gaskets and overheat go hand in hand.Sometimes with a blown head gasket you can see bubbles in the coolant resevore . Do not continue to overheat or you will have deeper issues.

 

Make certain your thermostat is not installed backwards. I'm speaking from experience...it will fit just fine backwards but it caused my STR to over heat.

 

I found out that the coolant system has to be bled I did not know this and had never heard of it before. I did that and it seemed to be ok will double check everything thanks everyone

 

I never bleed my 2005 STR. Just operate it thru several heat and cool cycles and then keep topping up the coolant level.

Seems to take a couple of days before it stops changing and all the air is out.
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So what has probably happened, there was no hot coolant against the sensor,(level too low) so sensor didn't read properly. Burp the system and get the air bubbles out and the sensor reads coolant as it should, not air.

 

some systems do not automatically add coolant as needed,start a string as to why. But now you know your's doesn't so besides adding coolant as needed make sure you system is burped regularly. Make sure any time you see heat your fans are working correctly and NEVER EVER overheat again.