Recall on Coolant caps

[Burg Boxster]

Joji-

First off, the coolant comes rushing back up when you remove the cap b/c you are releasing the pressure in the system. When the pressure is released, you are also decreasing the boiling point of the fluid in the system. Not a good idea to do.... especially quickly. Anyhow, sounds like you definitely have air trapped in the system. You might also have an issue w/ t-stat or water pump.

You can try either the short cut bleed method or the long one. Either way, w/o proper coolant or coolant flow, you're running the risk of creating hot spots in your motor - definitely not good!

Short cut method of bleeding the system of air:
Not 100% guaranteed effective but...
Open the bleeder valve (and leave open). Drive around w/ some random accelerations, upto 5K RPM, for about 15min. Close valve and test - make sure both radiator fans are working when at operating temp.

Prescribed method of bleeding the system of air: (from Bentley)
- For tiptronic, remove fuse B1 in fuse panel to disable ATF cooler shut-off valve)
- remove filler neck trim cover
- open up bleeder valve locking clip
- fill w/ coolant to bottom edge of filler neck
- run engine at idle. Top off w/ coolant until no more can be added when engine idle is raised sharply
- replace coolant cap and tighten. Warm up engine for about 10 min at approx 2500 rpm until coolant thermostat opens. To be sure engine is fully warmed up, check to see that radiator cooling fans in front wheel wells are on.
- allow engine to run addl 5 minutes at 2500 rpm. Every 30 seconds briefly rev engine to 5000 rpm
- open reservoir cap, relieving coolant pressure w/ extreme care. Top off coolant, close cap and repeat process of intermittently revving to 5000K rpm for 5 minutes
- allow engine to idle until radiator cooling fans cycle on and off once. Shut off engine and open reservoir cap, relieving coolant pressure w/ care
- top off coolant until level reaches max
- flip down bleeder valve locking clip
-replace filler neck trim cover and cap.
- If tiptronic, replace fuse B1

The cooling system is pressurized to 19psi and has a total capacity of 18 liters (~ 4.5 gal) so don't be afraid of adding just distilled water (entire system ratio s/b 50/50 water:approved coolant).

Good luck!

[Sputter]

joji,
Go back and read your Bleeder Tab thread.

[Joji]

All right I am making some progress. I finally have the coolant level right below the max line when the car is cool. The Temperature light above 250 is off now. The new cap I ordered from Sunset works with no hissing and leaks. The only thing I notice now is when I open the trunk after a drive it sounds like the coolant is boiling. Far as I know coolant can't boil. Is it the water mixture boiling? do you think it is boiling at all.

Also if it is wouldn't the coolant tank melt since it is plastic

I also smell a slight burning smell now. not sure if it is related

thanks

[Jaxonalden]

Joji,

Quote;
Q-"Far as I know coolant can't boil." A-Yes it can, adding anti-freeze raises the boil point of water (212 degrees). The radiator cap is set at a certain pressure (8-15 psi) this pressurization of the coolant system also raises the boiling point.
Q-"Is it the water mixture boiling? do you think it is boiling at all." A- Not possible, the water and anti-freeze is a mixture. If it was the engine would be so hot that you would be getting an idiot light and the temp gauge would be well above 230 degrees.
Q-"Also if it is wouldn't the coolant tank melt since it is plastic." A-The melting point of the tank is well above the boiling point of the coolant. If the tank ever melted, you would have bigger problems on your hands than the tank.

[roadracer311]

Are your cooling fans coming on? Boiling suggests something is really wrong with your cooling system, like a stuck thermostat or cooling fans that fail to come on.

[Joji]

I checked the 2 in the front. I hear them come on. But the wierd thing is that 6 months ago I heard the left fan in the front sound like it was miss aligned. it was making a bizare noise. I was just about to bring it in but it went away. I did have the thermestat chaned recently when the water pump when out. but maybe it is a bad one or not instaled right. How do I check that?

How do I check the fans if they are spinning the rigth amount. Any type of tool or way of testing it
thanks

[turbo23dog]

I think that if you are hearing a boiling sound then your cooling system is not holding pressure or air tight. Since you've been through a couple of coolant caps, this leads me to believe the cap is not the problem but likely the tank or a hose at fault and the reason the system is not holding pressure.

BTW, the pressure is what keeps the coolant from boiling. Going too far back on my chemistry lessons to explain better but temp and pressure are related...