I got sick and tired of getting coolant spew everytime I went to the track. Two new OEM reservoirs and caps still didn't help. Canton with the 30 lb. cap to the rescue! No more mess!

 

It may have sounded like I was joking but the reason I asked is there seemed to be an escalation in cap pressure in the thread. I can hear my stock cap hissing away after shutdown.

A an issue resulting from this is the steam and residue gets in the bonnet liner and makes it stick to the top of my strut brace. Now I've got this funky mess of matted hair stuck to it. Not that big of a deal but to clean it up I'll probably have to strip the paint off of it. I guess that's my fault for getting the painted brace.

 

R53 coolant caps are rated 1.1bar(16psi). If temp rises & causes pressure to exceed the rating, cap will relieve the pressure. Ever since I restored my 1st stage fan by bypassing the burnt resistor, haven't had coolant overflow from the cap. Check if you still have your 1st stage fans.

 

I was in traffic today and could smell the sweet sweet smell of coolant -- checked under the hood and there was a bit of coolant around the cap and also spattered on the coolant tank.

So I went out for a few minutes at lunch - got a some coolant (probably filled no more than 2-3 ounces) and filled to the max line and re-tightened the cap.

The tank I have is a dark orange-ish brown color, which from reading these posts seems to the upgraded one.

I have ordered a coolant cap from Moss MINI, should I be checking for anything else?

 

After replacing my expansion tank with the Canton I noticed my radiator fan was not working properly. Listen to see if the low speed fan is working properly. If you do not have the updated wiring harness, check your power steering fan which can cause the radiator fan to fail if it's siezed up with grit. You might want to see if your thermostat is leaking too. There are lots of threads on these issues that will explain them much better than I.