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Coolant leak from cap???

 
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Old 06-12-2011, 11:48 PM
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Coolant leak from cap???

Yesterday i drove about 15 min and stopped at a stop light to only see a whole bunch of smoke (steam) from the engine area. i pulled over, opened the hood and saw lots of antifreeze coolant pouring out from the expansion tank cap. The car was not overheating when i was driving. I poured water in it and drove it home and it seemed fine? has anybody had this happen to them? what could be the problem? i did some research on it and people say it could be the expansion tank or cap? can it be true? the car only has 35k miles
 

Last edited by turbo_secret; 04-15-2012 at 09:15 PM.
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Old 06-13-2011, 12:40 AM
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I would begin here: http://www.pelicanparts.com/catalog/..._pg2.htm#item8

My 99 C2 had a minor leak at 41K. The OEM radiator (expansion tank) cap has been since redesigned:996-106-447-04-M100. $25.00 + shipping. Super fast delivery. OEM from factory I believe was: 996-106-447-01-M100. Good luck.
 

Last edited by rrrruben; 06-13-2011 at 12:42 AM.
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Old 06-13-2011, 06:02 AM
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Yep......try a new cap.

Just replaced mine when it did the same thing.
 
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Old 06-13-2011, 10:40 PM
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I just had a conversation with a service manager Saturday, he told me that was a common problem for the 996, so yes I'd start there.
 
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Old 06-20-2011, 12:23 AM
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ok yea bought a newer cap from the dealership and i guess it fixed the problem
 
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Old 06-20-2011, 01:39 AM
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Originally Posted by turbo_secret View Post
ok yea bought a newer cap from the dealership and i guess it fixed the problem
Just a heads-up.

Keep an eye on any small drips coming from connectors.
I replaced my cap and stated getting a small drip from the front connector at radiator.

When I took it in they performed a pressure test and no leaks...
Tested the new cap and it wasn't venting.
Insisted on testing the new cap they where about to put on and the following 3 caps where also not venting at properly!

Go figure...

Cheers!

Sid.
 
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Old 06-20-2011, 10:00 PM
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yea, replacing the cap should help....if your tanks have a yellowish in color, then you might want to keep an eye on it cause they are known to have small crack underneath which will also leaks under pressure
 

Last edited by MkC2S; 06-20-2011 at 10:08 PM.
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Old 06-22-2011, 07:47 AM
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Hopefully u added mineral free water
 
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Old 06-23-2011, 10:28 PM
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The caps do not vent unless they are bad. The vent is the black plastic thing, with a metal bale, on the expansion tank behind the cap.
 
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Old 06-24-2011, 06:25 AM
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Originally Posted by fpb111 View Post
The caps do not vent unless they are bad. The vent is the black plastic thing, with a metal bale, on the expansion tank behind the cap.
OK....
Not for nothing but hmmmm I think you should check your facts.
The the "bale is part of the cap.
 
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Old 06-27-2011, 04:47 PM
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Psyco
I learned something today.

Dissected my old blue '01 cap, it has a pressure release and a vacuum break built into it. Pressure release in case of boil over and vacuum break to allow air into the expansion tank as it cools. (plus a nice little round screen for your hash pipe)
The burp vent to get air out of the system is in the black plastic "cap" with a metal bale on it mounted on the expansion tank behind the blue cap.
 

Last edited by fpb111; 06-27-2011 at 04:49 PM. Reason: spelin
  #12  
Old 06-27-2011, 11:15 PM
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Originally Posted by fpb111 View Post
Psyco
I learned something today.

Dissected my old blue '01 cap, it has a pressure release and a vacuum break built into it. Pressure release in case of boil over and vacuum break to allow air into the expansion tank as it cools. (plus a nice little round screen for your hash pipe)
The burp vent to get air out of the system is in the black plastic "cap" with a metal bale on it mounted on the expansion tank behind the blue cap.
It's all good, no worries .
That's the beauty of 6speed everyone can learn something new (including or especially myself ).

Bottom line is that a defective cap will either cause increased pressure on the system and you'll get a leak at a weak point (crack in tank, hose connectors etc.) or the opposite and hot coolant will start coming from the cap it self.

Cheers!

Sid.
 
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Old 07-21-2018, 12:07 PM
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I know this thread is over 6 years old, but I have the proverbial new 996 owner question. I bought a 2001 911 Carrera 2 Cabriolet in Feb with 81K on it. I made note of the smell of antifreeze in my original test drive, plus subsequent trips and in the instructions to the local Porsche dealer who did a PPI. The dealer claimed no leaks under the pressure test. Yet I have lost 2 gals of coolant in 500 miles. (1/2 oz per mile). Yet all seem to say the car is ok.
Now it notice the car runs hot, with gauge showing over 180 degrees and sometimes shooting up toward the 230 degree mark especially if I sit in traffic.
Yet there had been no evidence of a drip leak, just the low coolant warning light on the dash when the level fell below minimum. I've already cleaned out the debris in the radiators and pressure-washed them, so that wouldn't seem to be a factor.
Yesterday, I did get a steady drip when I accidently overfilled the expansion tank and the blue cap leaked quite a bit. Haven't driven yet with the level back down where it is supposed to be. That would point to maybe a defective cap.
So the question is, with theses snippets of info, is it a stuck thermostat? low coolant flow due to a broken composite impeller on the water pump (no leaks around the pump however)? Too much distilled water and not enough antifreeze? I'm starting to go insane ...
 
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Old 07-22-2018, 12:23 PM
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Originally Posted by Jglowien View Post
I know this thread is over 6 years old, but I have the proverbial new 996 owner question. I bought a 2001 911 Carrera 2 Cabriolet in Feb with 81K on it. I made note of the smell of antifreeze in my original test drive, plus subsequent trips and in the instructions to the local Porsche dealer who did a PPI. The dealer claimed no leaks under the pressure test. Yet I have lost 2 gals of coolant in 500 miles. (1/2 oz per mile). Yet all seem to say the car is ok.
Now it notice the car runs hot, with gauge showing over 180 degrees and sometimes shooting up toward the 230 degree mark especially if I sit in traffic.
Yet there had been no evidence of a drip leak, just the low coolant warning light on the dash when the level fell below minimum. I've already cleaned out the debris in the radiators and pressure-washed them, so that wouldn't seem to be a factor.
Yesterday, I did get a steady drip when I accidently overfilled the expansion tank and the blue cap leaked quite a bit. Haven't driven yet with the level back down where it is supposed to be. That would point to maybe a defective cap.
So the question is, with theses snippets of info, is it a stuck thermostat? low coolant flow due to a broken composite impeller on the water pump (no leaks around the pump however)? Too much distilled water and not enough antifreeze? I'm starting to go insane ...

first things first...

1. When you start the car with AC on full blast, do the front fans come on?
2. Do you know if the water pump has been changed out in the last few years?
3. Was the thermostat tested? Have you thought about changing out the thermostat with a low temp version?
 
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Old 07-22-2018, 04:21 PM
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Thanks for your thoughts.
1. When you start the car with AC on full blast, do the front fans come on?
Yes, now they do. Before I washed out the AC and coolant radiators, the left hand side fan did not come on when the AC was on. Now they both run.
2. Do you know if the water pump has been changed out in the last few years?
I have the most sketchy historical service records, only what the Carfax listed, when I bought the car this past Feb. Not even the most recent owner, who traded it in, provided any documentation ... no owners manual, maintenance records, parts replacement, etc. In the Carfax report, there is no listing of the water pump and/or the thermostat ever being changed. At 81K, it is starting to look like the next thing to do
3. Was the thermostat tested? Have you thought about changing out the thermostat with a low temp version?
Per #2 above, I have not tested it. If it is the original 17 year old factory thermostat, it has lived a long life but needs to be shot. I was also considering the low temp thermostat when I was considering the pump change-out.
I do wonder what I'll find out about the pump vanes. If OEM was a composite impeller, I am expecting to find the vanes in iffy shape anyway. The failure scenario I am piecing together says that the pump impeller has lost some vanes and the thermostat has lost its full range of motion to fully open. Why else would it seem like the cooling system is not up to the task of keeping the engine cool, even at idle?
 

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