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Discussion Starter #1
I have a 08 9-5 that seems do have a VERY slow coolant leak. I just added about 8 oz after 5 months and that seems to be about the same rate for about the past 9 months. The coolant bypass is disabled by unplugging the vacuum line and I also wrapped the area with a large paper towel and have seen ZERO evidence of it leaking after inspecting it on a monthly basis. I will run a pressure test and look for something easy but my gut tells me it might be the o-ring at the water pump that was replaced about 3 years ago by a very reputable Saab shop. Will a pressure test show the o-ring leak ?
Any advice on particular ares to look other than the water pump o-ring and coolant bypass valve ?
 

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Discussion Starter #3
My reservoir has a line toward the top that I assume is the full line. I check it when it's cold.
 

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I had a similar leak. It was the O-ring on the extension pipe that snugs into the block onto which the water pump housing slides onto. Specifically, that extension pipe or adapter has two o-rings, one on each end of it - one side fits into the block and one fits into the water pump. I had replaced my pump about a year ago and had only ordered one o-ring which I used on the outer, water pump side. Rather than wait for the additional inner o-ring to be delivered, I went ahead and sealed everything up as I was in a hurry to get this done before a big road trip. No leaks for a year, then it started to drip. Went in and disassembled everything recently and found the inner o-ring had pretty much degraded to where it broke apart when I slipped it off. I put on a new one and all is well again. Sounds to me like the Saab shop that replaced your water pump maybe left out replacing the inner o-ring. Sometimes that extension/adapter is hard to pry out from the block. It gets snugged in there pretty good and there is very little room to work with in trying to get it out. Maybe your repair guy just skipped it. My bet is on that inner o-ring.
 

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Discussion Starter #5
Would a pressure test show that leak ? I have a 4 yr/48k warranty on the repair but don't really want to take it in unless I can pinpoint it. I would hope a Saab specialty shop with a great reputation wouldn't take that sort of short cut.
 

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Discussion Starter #6
I have been filling it close to the full level while cold and check periodically and for about 2 years there has been VERY slow loss that I see the overflow closer to the minimum line(I check every 3-4 months since it's my wife's car), never enough to trigger low coolant message.
 

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Pressure test might register the leak. On mine I could visually see the tiny leak. Of course I had to remove a bunch of stuff like the heat shield, the cobra pipe, and such. You have to have a clear view of where the water pump goes into the block. Shining a flashlight on that area I could see the glint of coolant sweating from the junction.
 

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Discussion Starter #9 (Edited)
Maybe I. causing my own confusion. The coolant reservoir has a "cold" stamp right above a large line and a much smaller line about 3" below connected by a vertical line. Is the lower line the proper level ? I have been using the upper line as long as I have owned the car. Would filling it to the upper line cause some overpressure evaporation through the cap ?
 

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Correct level is 15-20 mm above low level line when cold. Lower line is correct line.

Exceed fluid will overflow from thin line just under cap.
 

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Discussion Starter #11
Can having coolant at the high line cause enough excess pressure to release through the cap until it reaches proper coolant volume ? I don't know where the extra coolant has been disappearing from my previous overfilling. I don't see any signs of coolant residue.. How long should pressure test hold to prove no leak ?
 

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Maybe I. causing my own confusion. The coolant reservoir has a "cold" stamp right above a large line and a much smaller line about 3" below connected by a vertical line. Is the lower line the proper level ? I have been using the upper line as long as I have owned the car. Would filling it to the upper line cause some overpressure evaporation through the cap ?
I agree, you are. If you look closely what MIMI and I have been suggesting is correct!
 

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Can having coolant at the high line cause enough excess pressure to release through the cap until it reaches proper coolant volume ? I don't know where the extra coolant has been disappearing from my previous overfilling. I don't see any signs of coolant residue.. How long should pressure test hold to prove no leak ?
Did you read what I just said?
 

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Discussion Starter #14
Did you read what I just said?
I did read your previous remark about the line below the cap. Just wanted to confirm that the excess probably has been venting out. I don't doubt you at all, just wanted to confirm that's probably what I have been experiencing with the mystery coolant loss. I assumed that as the venting occurs at the reservoir I would see some evidence of it escaping. It's VERY clean there with no coolant residue. I just wanted confirmation from people with more knowledge than me.
 

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if it is very slow leakage you might not see any residue.
fill it to the lower line and observe it further, if water still disappears coolant level low will pop up in the sid. Then you should investigate other aspects.
 

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Overflow will occur only when you drive with warm engine. So if you want to find drops, you have to follow your drive path again.
 

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I think what dho was looking for was some white or red-ish debris what you normally could find on slowly but constant leaking hose.
As I said, try with lower coolant level, just to exclude this option.
 

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I use a pressure tester to pressurize the system to like 20 psi. Don't go higher than that.

I have found leaks in the reservoir return hose, radiator tank seam, and of course the stupid coolant by-pass valve.
 

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Hi DHO -

Glad your leak is slow. I would recommend a pressure test - and you can do it simply. I use the "UncleMiltie" method of removing the small diameter return hose from the coolant reservoir. I plug that hose (use a 1/4" extension and clamp), then I attach a clean piece of 1/4" ID rubber fuel hose. Use whatever LOW PRESSURE source you like to carefully apply pressure - but don't exceed about 10 to 11 PSI (the cap is rated for about 15 PSI). See post #11 in this thread.

Just weeks ago one of my daughters experienced coolant loss - in two stages. First off, I pressure tested and the leak turned out to be the O-ring for the radiator drain plug (petcock). I installed that radiator as a replacement a while back, and until now, I had never touched the drain plug. The O-ring was pinched, but it had taken over a year to leak noticeably. The second stage was that she was still losing coolant slowly (over a week, low coolant light came on). I had her drive back and pressure tested - no leaks at 10 PSI for hours. I had a new coolant tank cap, so I installed that, and I told her to check the coolant level cold every morning before her regular >70 mile round trip commute. It's been holding steady for about 4 weeks.

Hope this gives you ideas.
 

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I also have a a very small coolant leak that requires a top up once a year. I was checking out my subframe bushings the other day and I think I unintentionally found the coolant leak. I'm getting a small leak where the coolant crosses the firewall to get to the heater core. Spring clamp around one of the hoses is pretty rusty, probably cant put down enough clamping force.
 
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