Neto

So, I have to travel 3.5 hrs today with my 996 and I opened the trunk to ensure coolant level was ok and check the condition of the oil & belt. I noticed my coolant cap had some coolant around the reservoir and a slight drop of coolant on the upper bleeder valve. I replaced the reservoir and cap like 5 months ago and they where from pelican parts..

Question is, where do you think is leaking, at the cap or at the bleeder valve? See attachments.

DBJoe996

I vote for the bleeder valve from the pictures.

5CHN3LL

Could be the coolant cap - when it does vent coolant, it can do so vigorously enough to wet nearby components. Since the cap was the most recently tinkered-with component, it would be my suspect. I think there's a rebuild kit available for the bleeder...

I'd replace the cap and clean everything up. If it reappears: new bleeder. If it doesn't: done.

Hurdigurdiman

The bleeder valve opens up to release over pressure if you over filled the system when cold. I suspect if a bleeder valve sticks in the closed shut position, that could cause the coolant tank to split. In your case the bleeder valve lifted and released the over fill and that's where the green coolant shows in the photos. It's always good policy to manually lift and release that valve when checking oil fills or anything else when you have the engine compartment open.

I suspect that you see the remaining coolant left from the last time you ran the car to top temperature. You may have over filled the level before the run. Clean it off, run it again up to top temps and I think you should be clear.

RollingArt

The o-ring in your bleeder valve has gone bad. You need to purchase the whole bleeder valve to get that o-ring.

Just had the same problem on my '04 Boxster S. New bleeder valve fixed it right up.

fpb111

Get the correct blue colored coolant cap from Porsche, 996 106 447 04, to be sure that you have the right # pressure relief valve. The pressure relief is in the cap.

The black unit, air bleeder valve?, is not a pressure relief. It is a vacuum break that allows air to equalize tank/atmospheric pressure (burping the system) as the engine cools when the bail is snapped up.

Neto

I thought the black cap was the "new" suggested replacement cap.. at least thats what I read on the forums.. The cap is brand new, only 5 months old and so is the tank!. I will monitor it, I did top off recently so thats maybe what happened.

fpb111

The black cap is an aftermarket cap. No Porsche number on it.

CDLVancouver

I bought the new updated cap from the dealership this summer and it was blue.

Hurdigurdiman

If you topped off recently as you said, then there is nothing wrong with anything. The coolant expanded as it heated up and found a way out of the system via the lift up valve. Don't buy anything.

fpb111

If it is leaking out of the "lift up valve" you have a problem with the *cap. The correct cap has a pressure relief (~18 lbs.) built in. That is why the cap has a trough around/below it with a drain.

The "lift up valve" only leaks if there is something wrong as mentioned by RollingArt in post 5 above

*Edit:
This should have been "valve".

fpb111

When you "top off" with a cold engine don't fill more then 1/2 way between min & max. Typically the level will be very close to "min" when cold and right at "max" when hot.

joe-1972

Do not fill the F-ing tank to the top! That coolant is not cheap, stinks up the whole car, and scares the hell out of you when you open the trunk lid and see it dripping everywhere! I changed out my old water pump because it failed, and put in a low temp T-stat, flushed out the system many times with water and compressed air to fish out some impeller pieces and then refilled it with the good Petro something coolant... everything went perfect till I went to fill and cycle the cooling system... for a week I would warm up the car and drive her around checking the coolant level and temp with an ODB dongle. And every time I would over fill the tank and every morning I would find the damn coolant dripping down the tank and onto my floor!
Fill it to the top of the low line and leave it alone. If your paranoid like I am just plug in the ODB dongle and keep an eye on the temp and make sure that the cooling system fans come on at the right temp!

Hurdigurdiman

So you are saying that the lift up relief valve only opens at a higher pressure than the blue cap? Or ONLY opens under high water pressure? Can you tell us the exact pressure when each component opens? That's if there is a relief at all on the actual blue cap. To have two pressure relief valves on the same system standing next to each other, makes no logical sense to me what so ever. Does one open under water pressure and the other under steam pressure? I am baffled. I see a green liquid which to me says coolant and not steam pressure which would dissipate on hitting the atmosphere.

fpb111

Hurdi,
The blue cap, 996 106 447 04= latest rev #, has the pressure relief built in to it. (take one apart you will see)

The black unit with the bail is a spring loaded diaphragm 'vacuum break' valve, not pressure relief.. When you have the bail up it holds the diaphragm up as the engine cools this forces the valve to open.
When the valve is open the system can vent to the atmosphere allowing air bubbles to escape. On a cold start,with the bail up, as the coolant warms up it pushes out air pockets.

That is why you should start with a cold engine, bail up, when you are using the start it, rev it to various RPMs, method of bleeding the system.

Look at the valve when your engine is hot. The square peg that the bail mounts on is up, hard against the top of the unit without the bail up. With no coolant venting.

Take one apart. You will get a better idea how it works.