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Old 11-09-2010, 01:13 AM   #1
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sudden coolant leak right rear wheel area, and now stopped

I was idling my car today for about 30 minutes when working on something.

Suddenly the car started dumping coolant from around right rear wheel area. It was quite quick and sounded like a steady hose leak. Initially I actually thought it was the neighbour using the garden hose.

The leak then stopped after about losing 1L of coolant. No oil in the mix.

I then topped up the coolant, it required about 4L, so it was low on coolant already. Although I haven't noticed any obvious leak before.

I then ran the car down the street, sat it idling for a while, the problem hasn't occurred again.

This is strange because the speed of the leak when it happened, and the fact it just stopped leaking straight away. One would think if the leak comes from a broken hose it would constantly leak once the flood gate is open.

Does the Boxster have some sort of "over pressure" coolant dump mechanism? I theorize that if I was low on coolant already, the idling made the remaining coolant boil (it's mostly water, not much of the green stuff in there), and then some sort of pressure valve opened to dump the coolant? I didn't think this existed on the Boxster.

I replaced the water pump 3 years ago, so hopefully it's not that.

What could it be?

--1989 Mazda MX6 GT
--1997 Porsche Boxster
--2005 Lexus RX330
--2007 Maserati Quattroporte Sport GT
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Old 11-09-2010, 04:22 AM   #2
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are all of the cooling fans working ? do you have the latest coolant cap ?
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Old 11-09-2010, 04:48 AM   #3
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Thats the area where the overflow exits the car. You probably had an air pocket that created a belch out the overflow.. Top off the coolant and you should be good to go.. Just keep an eye on it.
BTW- Water pumps need to be changed every 3 years to resist issues stemming from cracked heads due to broken impeller blades.

Just keep an eye on this, lots of very early intermix issues begin with a symptom like this, especially if the car is a '99
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Last edited by Jake Raby; 11-09-2010 at 04:53 AM.
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Old 11-09-2010, 09:43 AM   #4
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same thing happened to me last month. i checked my coolant and it appeared topped up. went to get gas at the station a mile from the house. as i was filling up i looked down and realized it was dumping coolant. when my heart stopped racing i thought to check the cap. l looked and sure enough it was slightly crooked meaning i'd skipped a thread. took it off, topped it off with a little distilled water and put the cap back on and it's been fine ever since. *phew*
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Old 11-10-2010, 12:41 AM   #5
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Thanks for the replies, guys.

I drove the car out with trepidation this morning and so far, all is well. So a gas bubble pressure overflow sounds like what caused it. I bled the cooling system last night and heard some bubbling noise when I opened the valve.

My coolant cap ends in 01.and there were a lot of condensed steam on the rear trunk lid, so I guess that cap is no good. Getting a replacement today.
--1989 Mazda MX6 GT
--1997 Porsche Boxster
--2005 Lexus RX330
--2007 Maserati Quattroporte Sport GT
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Old 11-10-2010, 06:35 AM   #6
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In order to make sure all the air is bled, follow the instructions found here:
http://www.pedrosgarage.com/Site_3/Install_3rd_Radiator_%26_Coolant_System_Bleeding_I nstructions.html
Scroll down half way and you'll see the bleeding instructions.
Also, check your coolant cap and/or any cracks on the reservoir.
That bubble of air got into the system because of a leak.
The most common is the coolant cap.
Happy Boxstering,
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Old 11-11-2010, 06:58 PM   #7
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Just went thru this. Newest model for cap ends in -04. Get the latest cap. Clean out the trunk.bleed the reservoir. While ur cleaning out trunk , pull back carpet and inspect the reservoir. They say it may possibly leak from then level sensor also. Yes some of them crack. After reading most of the threads on this very imformative forum....I was glad mine was just the cap. No problems since I put the new cap on last sat. Btw if u pull up the black plastic under the oil cap and antifreeze reservoir cap u'll notice a hole for fluid drainage. This is also where the pressure bleed valve is. It promptly pours out in front of the passenger rear tire . Found this out by pouring water too quickly into reservoir. Now I know. Now so do u. Hope this helps. Cheers.
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Old 11-12-2010, 07:48 AM   #8
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I have the same problem. Where is the best place to order the new cap and part #?

Last edited by cbarnes; 11-12-2010 at 07:51 AM.
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Old 11-12-2010, 05:15 PM   #9
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996 105 447 04

Got mine on eBay. You lucky Americans can get them on Suncoast or Pelicanparts. Everything in Australia is expensive, and postage is prohibitive at times.

Chris, luckily no obvious signs of crack/leak around reservoir.

Pedro, I did all this when I last changed coolant 3 years ago. Completely forgot about the whole bleeding thing when I topped up coolant a few weeks back. Maybe that's what led to all this.

Bled the system, no more problems so far.

--1989 Mazda MX6 GT
--1997 Porsche Boxster
--2005 Lexus RX330
--2007 Maserati Quattroporte Sport GT
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