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2000 996 Porsche mystery coolant disappearing...............


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This has been a on-going issue where every once in while Ill check the coolant and its low so Ill refill it with distilled water. It was topped off to the full mark and yesterday I took the car out and drove it to work and back home and had it parked in the drive way and later moved it into the garage and noticed that on the drive way there was a good amount of coolant there. I moved it back into the garage and checked the coolant and its still full but the car was also warm. I looked underneth the car and see alot of buildup from Im assuming coolant on the exhaust. Not sure if its been on going or if its just because of the amount that leaked???

What do you all think this could be? Bad coolant cap? Reservoir? Pump?

Any help would be greatly. Thanks in advance.

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Could be all of the above. You'll need to get under the vehicle and have a look around.

I tried looking under the tail section and cant seem to really see to far up there. How hard is it to remove the reservoir and any good places online for a reasonable price? If its cheap enough Ill just buy a new cap and reservior.

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Throwing parts at a vehicle is the wrong way to go about repairing it. Have the system pressure tested to determine the source of the leak.

Yea you may have a point. Should this be done at a Porsche Dealership or any other shop that is able to pressure test the system should be ok?

WVicary is correct, you need to pressure test the system first as it is not uncommon to have more than one leak point. Throwing parts at the car is the wrong way to go................

Thanks for the additional push towards getting that done!

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I wouldn't drive the car anyomore until you have diagnosed the source of the leak. If your water pump fails while driving it can have devastating effects on your engine. Ask me how I know... :cursing:

If you have a good independent have it towed there. If you go to the dealer be prepared to open your wallet twice as wide...

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Any shop with a pressure tester and the correct adaptors can check out your system in about 15 min.; that said, expect the dealer to charge you at least an hour labor. Find a good independant and have them check the system out, it will save you money......

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I wouldn't drive the car anyomore until you have diagnosed the source of the leak. If your water pump fails while driving it can have devastating effects on your engine. Ask me how I know... :cursing:

If you have a good independent have it towed there. If you go to the dealer be prepared to open your wallet twice as wide...

How do you know when a pump or thermostat is going bad on this car? And how hard is it to replace it? Is this something a DIY'er can do or is it pretty complicated? Car has low miles on it as well I believe its at around high 60k to low 70k so would the pump and things start to fail at such low miles?

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Any shop with a pressure tester and the correct adaptors can check out your system in about 15 min.; that said, expect the dealer to charge you at least an hour labor. Find a good independant and have them check the system out, it will save you money......

yea if I can keep it from going to the dealer that would be best. Just got to find a local shop where I live that knows Porsches now.

With that said anyone here in Northern California Eastbay area who is reasonable and know's Porsches?

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There are lot of folks on this site that live around that area.. Be patient and I'm sure someone will give you a lead on a good shop to take it to..

But like I said be very cautious driving the car. A sudden overheating becuase of a failed pump (or loss of coolant) can crack a head and or cause cylnder damage..which equals an engine rebuild...You don't want to go there.... :blush:

Edited by phillipj
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There are lot of folks on this site that live around that area.. Be patient and I'm sure someone will give you a lead on a good shop to take it to..

But like I said be very cautious driving the car. A sudden overheating becuase of a failed pump (or loss of coolant) can crack a head and or cause cylnder damage..which equals an engine rebuild...You don't want to go there.... :blush:

Yea I really dont want to go there! Just looking at the motor seems like its a nightmare to do anything to it.

What type of symthoms would one encounter if the pump was going bad? Cars temp has always been stable and no spikes what so ever.

As for locations if anyone on here is able to refer me to a good place I would greatly appreciate it!

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I had similar symptoms on my 02 and it turned out to be my reservoir. My mechanic guessed at the problem just based on my description and he wasn't surprised at all. I forget the version number on the replacement, but Porsche had definitely changed the design a few times. In my case I had a slow drip from my driver's side exhaust pipe but most was evaporating on the exhaust. The leak was on the bottom of the reservoir but I'm not sure how easy it was to find.

It is probably worth checking if you can get a mirror to see under the reservoir, but I haven't tried it so I'm not sure. There are probably articles here on replacing the reservoir but unfortunately it isn't easy to get out. If I remember right it involves letting the engine drop slightly to make room to extract it.

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I had similar symptoms on my 02 and it turned out to be my reservoir. My mechanic guessed at the problem just based on my description and he wasn't surprised at all. I forget the version number on the replacement, but Porsche had definitely changed the design a few times. In my case I had a slow drip from my driver's side exhaust pipe but most was evaporating on the exhaust. The leak was on the bottom of the reservoir but I'm not sure how easy it was to find.

It is probably worth checking if you can get a mirror to see under the reservoir, but I haven't tried it so I'm not sure. There are probably articles here on replacing the reservoir but unfortunately it isn't easy to get out. If I remember right it involves letting the engine drop slightly to make room to extract it.

I took another look in the engine area and Im seeing alot of what looks like dried coolant underneth the reservoir area. Also as indicated Im seeing alot around the exhaust area right below the reservoir. Ive done some research and it appears that this is a comman issue even with low mileage cars. How many miles did you have on your car? Im just tempted to replace it.

What other common areas are common for leaking? Also Im reading that its recommended to replace with OEM rather than aftermarket? Any suggestions on that? Where's a good place to pick up a new one?

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Does sounds like a leaking coolant tank and/or cap. Yea, these tanks tend to crack in time and the cap is also known to leak. The cap has been redesigned for a few times.

Definitely go with OE parts. You could get good deals from Sunset or Suncoast Porsche.

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Start with the simplest, (and cheapest) route- replace your cap to the newest available. It is only about $16 and the earlier ones do fail- mine did. Then move on to pressure testing the system. The water pump replacement isn't hard to do- I had to replace one with my broken wrist in a cast! There are excellent DIYs here and over on Rennlist. The AOS can also leak a lot of coolant and often drips down near where you are describing. The reservoir can fail and is another possibility. I have 120k on my car and the reservoir is still fine. I am planning on replacing it at some point this summer just to be sure I don't have an issue.

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Does sounds like a leaking coolant tank and/or cap. Yea, these tanks tend to crack in time and the cap is also known to leak. The cap has been redesigned for a few times.

Definitely go with OE parts. You could get good deals from Sunset or Suncoast Porsche.

Its just odd that Im reading even with cars with low miles are having reservoirs crack and leak. Design flaw? Im pushing more towards the reserviour and figured I replace the cap while at it or do it in steps. Yea Ill most definitely go with OE parts.

Start with the simplest, (and cheapest) route- replace your cap to the newest available. It is only about $16 and the earlier ones do fail- mine did. Then move on to pressure testing the system. The water pump replacement isn't hard to do- I had to replace one with my broken wrist in a cast! There are excellent DIYs here and over on Rennlist. The AOS can also leak a lot of coolant and often drips down near where you are describing. The reservoir can fail and is another possibility. I have 120k on my car and the reservoir is still fine. I am planning on replacing it at some point this summer just to be sure I don't have an issue.

Yea Ill probably go with a new cap first and test it. Im still not able to find a shop locally that can do a pressure test on the system so ill probably call around later today. Worst case scenario if its still leaking Ill probably just say hell with it and replace it.

Glad to know that the water pump isnt that hard to do. How would I know if its gone bad? Or is it something I should replace while Im at it?

Also what is a AOS sorry for the newbie questions!

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AOS is the air oil seperator (search).

If the water pump is bad generally it will leak, but it is also possible for the blades to disintegrate, typically either situation will come with other symptoms including leaks, unusual noises, or overheating. None of which are good things.

Be sure to buy the latest cap with the -04 part number.

The cracking tanks is an issue primarily with older cars, the plastic has either worn and is brittle or could be due to a defect.

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Johnny - talk to Eduardo who owns a shop in Fremont called Foreign Auto. He did my IMS and clutch last winter and was very reasonably priced. The guy owns a Porsche himself so he understands our emotions.

If you're still looking for parts like the coolant cap, call Parts Heaven in Hayward. They are the Porsche Gods in East Bay.

Edited by ltumacder
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AOS is the air oil seperator (search).

If the water pump is bad generally it will leak, but it is also possible for the blades to disintegrate, typically either situation will come with other symptoms including leaks, unusual noises, or overheating. None of which are good things.

Be sure to buy the latest cap with the -04 part number.

The cracking tanks is an issue primarily with older cars, the plastic has either worn and is brittle or could be due to a defect.

Car runs fine and dont see much fluctuating in temp so I believe the pump is still in good working order. Ill probably look around still for a place that can do a pressure test on the coolant and try to hit everything out this weekend. Im sure its the tank but figured it would be good to see what else it could be. Hopefully I get lucky and its just the cap. Which I doubt!

Johnny - talk to Eduardo who owns a shop in Fremont called Foreign Auto. He did my IMS and clutch last winter and was very reasonably priced. The guy owns a Porsche himself so he understands our emotions.

If you're still looking for parts like the coolant cap, call Parts Heaven in Hayward. They are the Porsche Gods in East Bay.

Thank you Ill give them all call later today and see what they can do for me. Thank you for giving me the info on the parts place locally. That should help me out with alot of the parts Im needing to order.

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The older caps are known to leak, the -00 part numbers especially. I encountered one of these on a Boxster at an autocross just this last weekend in fact.

You can normally see tell tale evidence of coolant that has leaked out near the cap and has been leaking through the overflow tube and burning off on top of the coolant tank.

It could also be due to improper threading (cross threading) or undertightening of the cap.

Similarly, you can normally see if the tank is leaking, when you shine a good flashlight on it you should be able to see the evidence of coolant leaking out and burning off (you'll see a crusty yellow or brownish fluid from where the fluid is eminating).

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AOS is the air oil seperator (search).

If the water pump is bad generally it will leak, but it is also possible for the blades to disintegrate, typically either situation will come with other symptoms including leaks, unusual noises, or overheating. None of which are good things.

Be sure to buy the latest cap with the -04 part number.

The cracking tanks is an issue primarily with older cars, the plastic has either worn and is brittle or could be due to a defect.

I did a search on AOS and I believe I understand the concept of it. What I cant find is how do you know if one is bad? Ive read at start up if you have a good amount of smoke coming from the exhaust than its a good indication that its bad or going out. Other than that is there any other way?

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The older caps are known to leak, the -00 part numbers especially. I encountered one of these on a Boxster at an autocross just this last weekend in fact.

You can normally see tell tale evidence of coolant that has leaked out near the cap and has been leaking through the overflow tube and burning off on top of the coolant tank.

It could also be due to improper threading (cross threading) or undertightening of the cap.

Similarly, you can normally see if the tank is leaking, when you shine a good flashlight on it you should be able to see the evidence of coolant leaking out and burning off (you'll see a crusty yellow or brownish fluid from where the fluid is eminating).

Ill probably replace the cap this weekend since its cheap anyways and probably drive the car locally. Than Ill come back home and feel around under the tank and see if I can feel anything leaking around the reservoir.

Ive also posted something else above.

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Ok I had a chance to go out and start the car up today and double checked the coolant tank, cap was on tight and was going to take it for a spin and decided to look down near the exhaust and Im currently seeing a little bit of coolant already. Im thinking the coolant tank is my issue as its not coming from the cap. So Im assuming its most likely my tank that is the issue.

Since its a gradual leak do you think it will be ok to drive the car to the parts shop to pick up the tank and back home? Its going to be probably about less than a hour each way for me? Currently my commuter car is currently down due to brakes which the parts wont be here till tomorrow.

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I really would not be driving a car with a coolant leak around; if it totally fails, you are stranded, and you could do some irreparable harm to the engine if it overheats (alloy engines do not like being overheated). Park it until it is fixed.

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