So I'm having a strange issue... any coolant that I put into my overflow bottle will disappear within a day or two.
Only thing I have noticed is a small coolant leak at the hose going into the engine - could this be the issue? Will try replacing it this week!

At the same time, my 1999 AP1 s2k runs 2 bars for a good 20 minutes until it gets to 3 bars if the ambient temperature is 12-14 degrees Celsius (Aussie winter)
It will drop from 3 bars to 2 bars when the car is moving (cooling the car down)
My friends s2k in contrast will get to 3 bars in a mere <5 minutes and stay there. Which is normal??

Any help would be much appreciated as I am preparing the car for its first track day

 

Solve your coolant leak first. The engine thermostat should keep the coolant in the 195°F (90°C) to 220°F (105°C) range range for proper operation. According to the top section of this graphic (below) "2 bars" is somewhere between 131°F (55°C) and 160°F (71°C). Not warm enough for efficient operation. But your missing coolant isn't giving you good data on the dashboard.



-- Chuck

 

Scary thought. What if the coolant isn't disappearing, but is filling up the radiator that is too low?

If not enough coolant, engine will run hotter than its supposed to. But if its really low, there won't be enough coolant to reach the temp sensor, and the gauge will read cool when engine is actually dangerously hot!

When engine is cold, remove radiator cap and make sure its full. If its not, DO NOT drove car. Fill with Honda coolant, and very, very carefully do the bleed procedure.

And yes, fix the leaking hose! Actually I suggest doing that second (First is check coolant level!)

 

i had a leak on my radiator for a solid 3 weeks before i noticed it and not once did my temp went above 3 bars... couldn't change my radiator same time so i topped off the reservoir with type 2 blue. but it was rather strange that when i checked i lost a lot of fluid.. but didn't go above 3 bars.

 

Obviously fix the leak first

Any sign of bubbles in the coolant if running with the radiator cap off ? Obviously, do not take the cap off WHILE it is running, take it off first and start and let it warm up. These very symptoms can occur if a head or head gasket is cracked and combustion pressure is making its way into the cooling system. I had a truck once that would overheat very soon after warming up. Coolant was cold. Head was cracked, and the pressure in the system was preventing the coolant from circulating properly. Bubbles coming up in the radiator and if you ran it for a bit and shut it off (Even before it started getting warm) and removed the cap it would spew cold coolant.

If coolant is being lost into combustion (another head gasket or head symptom potentially) then if bad enough, you can many times smell an odd sweet smell in the exhaust (burnt coolant).

 

I'm pretty sure your thermostat is sticking open, even in frigid Canadian winters (-20 degs C) with a huge aftermarket radiator our cars will never go from 3 to 2 bars when moving unless the thermostat is stuck. You will eventually get a CEL if it runs too cool for too long, and the car actually runs worse cold compared to 3 bars.

Not sure about you loss of coolant, lots of potential sources of leaks in the engine bay. If you are going in there to change the hose check the thermostat.