Changing the coolant breather valve - 986 Forum - The Community for Porsche Boxster & Cayman Owners

shlim8 · 02-10-2011, 04:31 AM

I've been losing coolant... by not much, but still at a consistent rate....

After further investigation, I discovered that the rear boot lid above the coolant cap, is wet from condensation. After taking off the flat plastic piece, I noticed that the 3 of the 8 bolts that lock down the breather valve seem to have whiteish sediments and looked like it might be leaking from there. The is almost no sediment from the top of the valve.

When I used a hex bolt to check the bolts, they were only hand tight.....

As the bolts are probably screwed into plastic, I refrain from tightening them...

QUestion is, how tight should those bolts be ?? Any reason there should be some leakage from the bolts ? Or is it a sign that the 2 O-rings are deteriorating ??

JFP in PA · 02-10-2011, 10:18 AM

More likely would be that you simply have a bad cap on the tank. If your number ends in anything other than "-04", your cap has been superseded and needs to be replaced. Bad caps cause the condensation you describe, which seeps down and corrodes the bolt heads on the system bleeder valve assembly. Change the cap first, and then clean up the area, most likely the problem will not reoccur.

You are correct, the bolts thread into plastic, so be very careful about tightening them, they snap off easily.

insite · 02-10-2011, 11:27 AM

i noticed the other day when i put the car up that the pressure release was up, like it would be if i pulled the bleed tab. is this normal? i would think it should stay down in all but the most 'heated' situations.

JFP in PA · 02-10-2011, 12:27 PM

You referring to the small rectangular metal wire "handle" on the vent?

insite · 02-10-2011, 12:35 PM

no, the handle actuates the part i'm talking about. i know you know this, but for others reading who may not: this entire apparatus is a pressure bleed valve, much like a conventional radiator cap.

when there is too much pressure in the system, a spring loaded valve will open and allow pressure to bleed out through a tube that exits under the right side of the car. the system is supposed to hold some predetermined amount of pressure, but to relieve that pressure if it gets too high.

the bleed valve is ALSO used to 'burp' the system, and this is done by actuating the wire handle JFP is referring to.

in my situation, the valve is actually opening under normal operating temperatures & relieving pressure when it shouldn't be. i suspect the valve is bad & needs to be replaced.

JFP in PA · 02-10-2011, 12:42 PM

No, it should not be “open” all on its own. Either the part is acting up, or you may have air in the system and are seeing the results of a “hot spot” somewhere in the system. Do you have access to a vacuum filling tool? If you do, pull a quick vacuum on the system when it cools down, if air comes out the coolant level in the tank will drop, and you can top the system off using the tool while under vacuum. If you pull a vacuum, and nothing comes out, you should look at replacing/rebuilding the bleeder assembly.

shlim8 · 02-10-2011, 09:23 PM

I've got a 04 radiator cap. Just bought about 3 weeks ago but am still getting condensation and losing coolant. It does look like the water is seeping pass the3 of the bolts.

Is the bleeder valve a simple unbolt and replace part ? How tight should the bolts be ? Depending on the parts availability I might have to change just the 2 O-rings. I presume that should do it. The bleeder valve is in the closed position when I looked at it with the coolant cold.

JFP in PA · 02-11-2011, 05:08 AM

Yes, you can easily "rebuild" the bleeder assembly, there is a step by step in the Boxster Wiki:

Boxster Wiki

Be careful, if you snap off the bolts, you may end up replacing the entire tank assembly.........

sasha055 · 02-11-2011, 01:20 PM

I have same problem, I replaced the o-rings and I still have condensation going.
Same symptoms as you, condensation and white powder on the bleeder valve bolts.

Does anyone know part nr for the whole valve assembly? maybe changing it will solve the problem.

Sasha

schoir · 02-11-2011, 09:00 PM

Quote:

Originally Posted by sasha055

I have same problem, I replaced the o-rings and I still have condensation going.
Same symptoms as you, condensation and white powder on the bleeder valve bolts.

Does anyone know part nr for the whole valve assembly? maybe changing it will solve the problem.

Sasha

Sasha:

The part number for the complete assembly is 996.106.347.02. It supersedes two earlier part numbers and lists for about $33.

Aside from the O-rings, the rubber gasket/diaphragm sometimes gets torn or distorted. If replacing the O-rings did not solve the problem, check the diaphragm or just replace the entire assembly.

Here is a photo showing a distorted gasket/diaphragm. You can see old coolant residue in a number of places on the underside of the hard plastic piece that is showing, and you can see residue around one of the holes through which one of those fragile bolts passes.

Regards, Maurice.

shlim8 · 02-13-2011, 02:57 AM

schoir, ah.... a bleeder valve like the one in your picture would certainly explain my situation... I think I'll refrain from opening up the valve until I get my replacement valve.... Opening up the valve now might make the leak worse and I still need to use the car

shlim8 · 02-20-2011, 06:42 AM

After a run up a mountain road, I popped the rear boot open and guess what ? I found steam escaping from underneath the flat plastic plate that goes above the breather valve.... guess it should be from the breather valve. Definitely not from the coolant cap.

I'm now waiting for my new breather valve. Hopefully that cures the coolant loss.

schoir · 02-20-2011, 07:49 PM

Quote:

Originally Posted by shlim8

After a run up a mountain road, I popped the rear boot open and guess what ? I found steam escaping from underneath the flat plastic plate that goes above the breather valve.... guess it should be from the breather valve. Definitely not from the coolant cap.

I'm now waiting for my new breather valve. Hopefully that cures the coolant loss.

Shlim:

When you get your new breather valve and go to install it, remember the caution about the fragile bolts. DO NOT over-torque them!

Regards, Maurice.

shlim8 · 02-20-2011, 11:44 PM

Quote:

Originally Posted by schoir

Shlim:

When you get your new breather valve and go to install it, remember the caution about the fragile bolts. DO NOT over-torque them!

Regards, Maurice.

Thanks for the advice. After I saw pictures of the broken bolts, I understand why ! I didn't even try to tighten the bolts on my current breather valve any more than a millimetre...

I had thought of changing the entire coolant expansion tank, it's still good but has yellowed to the point that I can't see the coolant level. But after reading the instructions on the replacement of the tank, I decided not to...

Dale_K · 02-21-2011, 05:10 AM

Please post the results of your bleeder valve replacement. My 2000 S also has some condensation in the same area. I have a new cap on order but suspect the bleeder valve may be at fault. I'm afraid to touch it for fear the tank will crack/break when I attempt to loosen the perimeter bolts. I'm interested to see how your repair turns out.

schoir · 02-21-2011, 09:05 AM

Quote:

Originally Posted by shlim8

Thanks for the advice. After I saw pictures of the broken bolts, I understand why ! I didn't even try to tighten the bolts on my current breather valve any more than a millimetre...

I had thought of changing the entire coolant expansion tank, it's still good but has yellowed to the point that I can't see the coolant level. But after reading the instructions on the replacement of the tank, I decided not to...

A wise idea not to replace the coolant tank unless it's leaking.

To get a better view of the coolant level through a somewhat opaque, yellowed tank, you can take the coolant cap off and put a flashlight vertically on the opening. That usually "clears things up".

Regards, Maurice.

sasha055 · 02-21-2011, 11:45 AM

Maurice, where did you see the valve for 33$?
Pelican parts has it for 80$

Do you know of a secret place thet sells these parts cheap?

Thanks
Sasha

schoir · 02-21-2011, 01:31 PM

Quote:

Originally Posted by sasha055

Maurice, where did you see the valve for 33$?
Pelican parts has it for 80$

Do you know of a secret place thet sells these parts cheap?

Thanks
Sasha

Sasha:

I replaced mine about three years ago, and I think I bought it from either Sunset or Suncoast.

Here it is from another source, apparently available for $32.68, but with an .01 ending on the part number. (Same part, but an earlier version, according to Porsche nomenclature scheme): http://dcauto.gotdns.com/illustration/index/471829446

Let us know if you are able to get it, etc...

Regards, Maurice.

shlim8 · 02-21-2011, 10:18 PM

I ordered my breather valve from the OPC in Malaysia and it cost about US$49. Which was surprising as the OPC in Singapore wanted more than twice that.

Anyway, I tried keying the part no into Pelican Parts and I think the price that came back was about US$80 if I wasn't mistaken.

It's a long wait for the part though.... up to 3 weeks was what they said.

Dale, I'll keep you updated once I get the breather valve.... it's no fun listening to the hissing sound from the area of the valve every time I do a spirited run. At least the coolant loss is quite small (fingers crossed !!!).

shlim8 · 03-07-2011, 05:46 PM

Finally got the breather valve installed this morning. The hardest part of the whole install was only the removal of the old breather valve housing. There is just no space to get a good grip of it. I used 2 allen keys (for the ikea furniture) and stuck them through the holes in the housing and yanked the housing out.

My old breather valve diaphram was in pretty good shape but the bolts were totally rusty and the O rings were slightly deformed. I found that everywhere the coolant came into contact with the plastic, the plastic looks different - you can actually see the fibres, whereas the dry parts were smooth. Does it mean I have corrosive coolant ??

Went for a 15min drive and after letting it idle for another 5 mins, the breather valve went to work and vented. Is it supposed to vent so quickly ? The housing was just somewhere between hot and warm and I could still touch it (water temp was around 85 degrees C, I have the low temp thermostat). This is a brand new breather valve that I just bought from the OPC. If it still vents so quickly, I presume I'll still get condensation on the trunk lid ??

The breather valve looks like an over-engineered item, on my E36 BMW, it's just a screw like thing on the radiator... (I know as it broke once !)