Faulty Bleeding Valve

[Shred]

Hi,

I have googled this but seems to be a number of different answer if the Bleeding Valve would open by it self or not.

In my logic, the valve should never open in order to keep the pressure. But I thought of asking before going out and order a new part.

 

For a while I've been losing coolant after driving. The coolant is going through the tank overflow tube which drips down under the car on the passenger side. (left hand drive)

 

I just had installed, new water pump + LN Eng. low temp. thermostat, full coolant flush, along with a new 04 coolant cap. (My last pump was a Lasso and only lasted 30k miles. The whole pulley of the pump broke off!)

 

Still getting condensation and drips of coolant under the car after driving.

 

After examination, I can see that my Bleeding Valve pop up by itself when the coolant is hot and it can't hold the pressure along with coolant leaking out of it through the top. I hear it losing pressure. SEE ATTACHED PIC.

I have no coolant under the carpet in the trunk, my tank is version 07. Not pressure tested in but everywhere else looks dry.

 

Does it look like I need a new Bleeding Valve put in part 996-106-347-02?

 

 

Any advice would be appreciated.

 

 

[Ahsai]

That bleeder valve has a diaphragm inside that prevents venting to the atmosphere (to keep the pressure inside like you imagined). All it does is when the coolant is hot, it connects the internal venting of the system so that any trapped air bubbles inside the system could escape to the coolant tank. Basically a self-bleed system. When hot, the stem will come up and when cold it will drop back.

 

Your valve is leaking (likely the diaphragm has cracks). The best bet is to replace the whole tank. Don't bother trying to replace that valve and the screws, which are like one-time use.

[Ahsai]

More details here http://rennlist.com/forums/996-forum/849714-how-the-coolant-bleeder-valve-works.html

[Shred]

Thanks for the reply. I was hoping I don't need to replace the tank because it is a total pain, especially getting to those clips.

[kbrandsma]

I've have replaced the valve without an issue.  I also replaced the screws as they are typically for one time use as Ahsai suggests.  Don't over tighten the new screws as they can strip easy.  I figured if that didn't work I could always replace the tank. A new tank comes with a new valve already installed.

Edited February 16, 2016 by kbrandsma

[Hilux2400]

This was also the cause of one of my pressure leaks.  I also replaced the tank.

[JFP in PA]

Thanks for the reply. I was hoping I don't need to replace the tank because it is a total pain, especially getting to those clips.

 

When we get one in the shop with a bad bleeder assembly, the car gets an entirely new tank; you can sometimes replace just the valve itself, but repeat failures are far too common.  Get a new tank, you will save yourself grief in the long run, and do not buy an aftermarket tank, get a Porsche unit.  We have seen way too many aftermarket tanks fail after short periods to ever consider using one.

[Shred]

Thank you to everyone for their knowledge and ideas.

This is the car's second tank, I am going to try my luck with just changing the Bleed Valve, o-rings + screws and hope it will work.

 

It's such a pain to change the tank, maybe I can wait until the next clutch job to make it easier.

Anyone on their 3rd tank already?

[Ahsai]

I am ('03 996 70k miles).

[JFP in PA]

Anyone on their 3rd tank already?

 Many.

[Shred]

Thank for everyone's help. By changing the part 996-106-347-02, it has solved the problem. No more leaks :) ... for now haha