Which component provided the pressure relief valve function?

[Dale_K]

Today I drove my 2000 S in the warmest conditions since I bought the car in December. It was mid to upper 70's in Hot Springs, Arkansas today and I drove the car in some typical small town traffic. I noticed coolant on the ground next to the right rear wheel. This is probably the first time since I've owned the car that it's been hot enough to pressurize the cooling system.

Either the bleeder valve or the tank cap is leaking but I'm not sure which. I removed the cap (seemed tight) and lifted the handle of the bleeder valve and added a small amount of distilled water (maybe a pint) to restore the coolant level. I can't recreate the streaming leak. I let the car sit idling and the fans operate and the car does not overheat. After driving a while I notice some condensation on the bottom of the trunk lid where it seals against multi-fill housing, so there's still some leaking going on.

So I'm looking for some advice and knowledge. It seems to my non-mechanic brain that the component that provides the pressure relief valve function is the one most likely to be leaking. I guess the easiest part would be the cap, then if that didn't fix it, replace the bleeder valve. But the bleeder valve sounds like it might be hissing a tiny little bit so I don't know.

[very~worn~944]

The cap is the component that releases excess pressure. Over time these can bleed pressure prematurely or stick. Also it's very common to be crossthreaded on, never sealing properly but weaning pretty straight. The originals with the part number ending in 00 are almost always leaky, and the 01 caps are known to as well. The other valve on the top of the bottle can seap pressure, and is usually evident by the crusty buildup around the seam. Sometimes snugging up the bolts can delay this failure- but CAREFUL: the plastic can strip VERY easily. Lastly, if you bottle is older and yellowy, chances are it's starting to crack underneath. You can pull back the vertical trunk carpet starting from the right side of the bottle being careful not to damage the dipstick tube. With a mirror check the bottom of the bottle for crusty drips, or check the trunk floor for wet coolant. Chances are you cap is just failing- but you want to be sure. Also, are you sure the vehicle wasn't getting overly hot from a sticky thermostat? Not very common, but keep your eyes on the gauge for abnormally high peak temperatures. A previous grenaded waterpump can leave plastic Impeller blades in the circuit to clog up flow and create excess temps too. Good luck!

[Dale_K]

Thanks. My cap has a part number ending in 00 and there is no corrosion around the edge of the bleeder valve. I'll buy a new cap and then watch it closely.

[BYprodriver]

Originally Posted by Dale_K

Thanks. My cap has a part number ending in 00 and there is no corrosion around the edge of the bleeder valve. I'll buy a new cap and then watch it closely.

Original cap is blue & replacement is black

[Wayne 962]

There's an overflow hose that dumps excess coolant on the ground. This is located right near where you saw the coolant "leak". If the system is overfilled or has excess coolant in it, then it will dump it out there. The fact that it is dumping excess coolant out may signal a problem, but I'm not sure. I would keep a close eye on the levels, and also on the temperature gauge, but in general, I wouldn't do anything about it at this very moment in time.

-Wayne

[very~worn~944]

Just to clarify, the latest and greatest cap from PORSCHE ends in 04 and is Still BLUE. The black caps are aftermarket or a VW/AUDI part. They probably work just the same, but are not the most updated Porsche part.

Quote de Dale_K

Thanks. My cap has a part number ending in 00 and there is no corrosion around the edge of the bleeder valve. I'll buy a new cap and then watch it closely.

Original cap is blue & replacement is black

[Wayne 962]

The part number is 996-106-447-04-M100, and is a Genuine Porsche cap. This one is blue.

The prior number, which was 996-106-447-00, 996-106-447-01, 996-106-447-03 all were black according to the notes from my supplier. Porsche had a bunch of quality control issues associated with this part (sorry, I don't have a tech bulletin number handy), and according to my supplier's notes, Porsche came out with the blue cap to distinguish the blue ones from the quality-control problems of the previous black caps. Not all black caps are "defective", but there's no way to tell.

So, Porsche recommends that black caps no longer be used - only the blue ones. I'm trying to track down the tech bulletin on this right now.

-Wayne

[Wayne 962]

I stand slightly corrected on this, there is no Technical Service Bulletin. Here's the note from my supplier:

There is no TSB on the radiator cap issue. I did learn that according to the supplier of the black cap that we are the only one *not* buying them. Even if the Black ones are 100% equal to the Blue (and that’s the claim) in this case Ken only recommends the Blue since Porsche changed the color to eliminate any questions as to what version cap you have. The part number ending in 04 in blue is how this should be supplied.

Seems pretty clear to me, I'm going to order four blue caps for the two Boxsters and the two 996s tomorrow!

-Wayne

[Dale_K]

996-106-447-04-M100 has been shipped per the Pelican website. I'll post up the results after I receive it and screw it on the car.

[superglide]

Originally Posted by Wayne at Pelican Parts

There's an overflow hose that dumps excess coolant on the ground. This is located right near where you saw the coolant "leak". If the system is overfilled or has excess coolant in it, then it will dump it out there. The fact that it is dumping excess coolant out may signal a problem, but I'm not sure. I would keep a close eye on the levels, and also on the temperature gauge, but in general, I wouldn't do anything about it at this very moment in time.

-Wayne

Thanks for that, Wayne. I just r&r'd the coolant prior to my trip to San Diego, and per the instructions in your Fine New Book. Should I top off the lost coolant (2+qts) and repeat the bleeding process? BTW; mine's a Tip; and I neglected to pull fuse B-1, prior to the operation.
Semper Fi,
Andy