When I got my LS it had aftermarket cap. So after replacing bad radiator why not go oem with rad cap? So I did, paid $27 for one. Ever sine then I noticed coolant level is always low but not empty, leaks started at radiator hoses. When I squeeze the coolant hose it's very FIRM. So yesterday I switched back to aftermarket one and noticed that hoses weren't as firm and coolant level didn't change much after driving 20 mi. I'm a little lost... Did dealer give me wrong cap? Aftermarket one is rated at 13 kPA I think.

 

Not sure what 13kPA is, but it is possible that the after market cap isn't rated for the same pressure that the OE cap is. You should have your cooling system pressure tested, and at the same time test both the caps. Good luck.

 

My bad it's 13 lbs or 0.9 kg/cm2 for aftermarket. Part no for oem is 16401-50071.

 

thanks I thought I was off on the .9 lbs/kg - I just remember seeing .9 on the OEM cap

 

Looks like my cooling system happier with aftermarket unit. OEM one appear to overpressurize the system. With aftermarket level goes up a little when engine's running and goes down a little after it cools down. Maybe I'll go back to dealer and ask for a different unit?

 

have you checked/replaced your coolant temp sensor? just a thought

 

I haven't but maybe previous owner did. So my car was underheating now, seiches back to oem and now it's good. Just need to replace leaking upper rad hose.

 

If the pipes are firm it is normal , if you have a leak , you have a leak . The cap is working normally temp fluctuations are when a cap is not working .