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Old 05-25-2011, 12:22 PM   #1
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Question Constant Coolant Top up Needed - Why?

Hello fellow forum members. I have a problem I was hoping you gurus may have an idea on.

I have a '99 Boxster 2.5 58K miles. About 6 months ago I had the water pump fail. I took it in to be looked at (not a genuine Porsche dealer), and they replaced the pump. I was told that they were having a hard time 'burping' the system and that there were air pockets that needed to flush out and it would happen in time. They told me to top it up with water and after a while it would be fine.
6 Months later and I'm still topping up coolant with about a pint every 100 miles or so.
I know what you're all thinking. There's a leak. Well that's what I thought, so when I took it back to be looked at again (after about 1500 miles), they told me they put pressure on the system and there are no leaks. I have never noticed any leaks on the garage floor either.

So anyone have any idea as to what may be happening? Where is the coolant going? Any help or advice would be most appreciated.

Thanks for looking

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Old 05-25-2011, 12:32 PM   #2
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This isn't normal. Take it back to the shop and have it checked again.

If its not leaking outside the engine and evaporating (most likely), its leaking inside the engine (not likely but really not good). Also, check for coolant in the oil.
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Old 05-25-2011, 01:06 PM   #3
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if they pressure tested the system, then the system is fine (sans cap unless they also tested) and more than likely it's not disappearing into the motor.

Remember, the cooling system on the M96 is ~ 5gal (varies slightly depending on motor but w/ a '99 IIRC it just about 5gal). So, how much are you always adding to it? I'd say if it's been more than 3qts (cumulative), you might have an issue someplace...

Otherwise, have you tried burping the system yourself? Here's the procedure courtesy of Pedro:

• Start with a cold engine.
• Remove both caps (oil and coolant).
• Pull bottom plastic cover out (using a spatula lift one edge and pull out).
• Lift bow on bleeder valve. Screw oil cap on again.
On Tiptronic vehicles, the pneumatically operated coolant shutoff valve (flat-seat-valve) must be opened for the bleeding process. The electric switch-over valve must be switched off for this purpose.
Triggering can be performed with the PST-2 or PIWIS, or by pulling out the Tiptronic control module fuse B1 with the ignition switched off.
• Check whether coolant shutoff valve is open.
• Fill reservoir with coolant up to the bottom edge of the filler neck.
• Run the engine at idle and top off with coolant until no more coolant flows into the cooling system when the engine is revved moderately. (Coolant level now at the lower edge of the filler neck) The coolant temperature must not exceed 80 degrees Celsius; proceed directly to the next step if necessary.
• Close the reservoir and warm the engine up to operating temperature at an engine speed of 2,500 rpm until the thermostat opens (approximately after 10 minutes). Coolant temperature should now be 90 degrees Celsius.
• Check: The radiator supply lines and return lines in the front wheel housings must be hot.
• Allow the engine to run another 5 minutes at 2,500 rpm. Every 30 seconds, briefly rev the engine to 5,000 rpm. This is important for proper bleeding.
The level warning light can light up during the bleeding process (reset by restarting the engine). Interrupt the procedure if the coolant level is below the "MIN" mark. Open the reservoir with extreme caution and allow overpressure to escapeuntil the coolant level reaches the lower edge of the filler neck; top off with coolant if necessary. Again, intermitently rev the engine for 5 minutes.
• Allow engine to run at idle speed until any activated radiator fans switch off again. Then switch off the engine. Open reservoir cap with extreme caution until the reservoir is depressurized (danger of scalding!).
• Top up coolant expansion tank until level reaches lower edge of filler neck (cold, this corresponds to = "MAX").
• Reposition bow on bleeder shutoff valve. Unscrew cap.
• Put on cover and body seal. Screw on both caps.
• Reactivate ATF shut-off valve on Tiptronic vehicles.

Also, when you remove the caps and find the bleeder valve, is there any white residue residue around it?

What are the last 2 digits on your coolant tank cap?

Good luck

PS - the cheater method to burping the system is to pull up the bleeder valve and drive around for 20-30 min with it up. Not as effective but can work in a pinch.

Last edited by Burg Boxster; 05-25-2011 at 01:11 PM.
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Old 05-25-2011, 10:16 PM   #4
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I didn't have good luck using the burping method.. As per Loren on renntech I drove around for about a week with the bleeder valve in the up and open position. After about two or three days of driving and adding coolant when cold it leveled off.
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Old 05-26-2011, 03:57 AM   #5
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If you lost the water pump, a piece of the impeller may be stuck way up in a coolant passage and caused a crack in the head. Under driving conditions, it may be enough to allow coolant to be burned, hence the disappearing liquid. I'm certainly not an expert, but have read similar tails from Jake Raby's postings.

When I replaced my coolant 1 1/2 years ago, I used the burping method and was fine after three days of driving in various conditions.
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Old 05-26-2011, 05:59 AM   #6
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Thanks all for your comments. I'm adding about a pint of coolant every 100 miles or so, and that's definitely more than 3 quarts over the last six months.

I was afraid of the possibility of a piece of the impeller causing problems in the system. I'm going to look into that a bit more.

I will also try burping the system.

If I don't get anywhere, I'll just suck it up and take it to one of the mechanics in the Atlanta area that has been recommended elsewhere on this site, rather than the one down the road that don't impress me that much.

Thanks again!
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Old 05-26-2011, 07:03 AM   #7
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I actually just got off the phone with Jake Raby, he says the most likely thing here is that when the water pump failed a piece of the plastic impeller probably lodged in a capillary in the head, causing a blockage, causing a hot spot, causing a crack, most likely to the exhaust system, causing the burning of coolant.
Repair will be about $12K, which is the value of the car.

I now have to consider my options.

If there is one thing I can tell all Boxster owners: Change your water pump every 3 years no matter what!!!
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Old 05-26-2011, 09:47 AM   #8
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I hear you...my car is nine years old with 19k miles and the original pump...it's on the "to do" list. I just fixed my ailing alternator and probably just should have done the job since the whole thing was already ripped apart, but I don't have the time right now. Sure hope this doesn't come back to bite me...
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Old 05-26-2011, 01:07 PM   #9
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If I lived in Atlanta, I know where I'd be taking my Boxster for stuff like this...


[QUOTE=jmatta] I'm certainly not an expert, but have read similar tails from Jake Raby's postings.[QUOTE]

another hint, click on the ad to the right for "Flat 6 Innovations". I don't live in Atlanta and I've never used Jake, but if I did -- no question I'd take a short drive north toward the mountains and give him a try for stuff like this.

Hope you work it out...
SOLD - 2002 Boxster S - PSM, Litronics, De-ambered, Bird Bike Rack, Hardtop, RMS leak...
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Old 05-26-2011, 11:54 PM   #10
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Find myself everyday wishing I had bought a NissanGTR instead of this piece of crap. More bang for the buck and none of these problems.
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Old 05-27-2011, 05:35 AM   #11
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Don’t look at the Nissan GT-R as perfect, they are anything but…………and if you think Porsche means expensive, just wait till something major craps out on a GT-R……….
“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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Old 05-27-2011, 08:13 AM   #12
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I just changed out my 10-year old water pump (myself). Feeling real good about it right about now. And not too bad a job, especially as I was doing the motor mount at the same time which gave more working room. The impeller on the old unit didn't look too bad, but it's still 10 year old plastic...

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