Possible Coolant Tank Failure

[mnc-i]

Question: If the coolant tank isn't leaking (break or hole in tank) where is the water coming from? My best guess is a bad pressure relief valve on top of the cooolant tank (below the plastic cover with about 10 to 12 screws holding it down)

Here is the background...what do you think?
My local Porsche dealer quoted me $1,000 to replace the tank. A local independent Porsche mechanic quoted me $800 to $850 to replace the tank including new coolant. The independent mechanic told me I should check to see if I had water in the trunk and to check the relief valve. I haven't taken it to be seen by a mechanic yet.

My 1999 Boxster w/193,000 miles gave me the flashing coolant temp light Friday as I left the office for home.
I stopped at Walmart filled the tank with distilled water (approximately 1.5 quarts).
Over the weekend and Monday at lunch I poured the rest of the 1 gallon jug in the coolant tank.
I never had any water on the ground under the rear of the car. I did have condensation in the trunk right over the dip stick, oil filler cap & coolant cap.
This evening after I drove home and parked the car I had coolant running from under the car from below the coolant tank.
I took the carpet & padding out. There was no water on the trunk floor and no signs that there ever was any water in the trunk below the carpet (totally dry).
I also saw no signs of a leak from my coolant tank.

What are your thoughts/recommendations?

MNC-I

[Perfectlap]

water-cooled means water-cooled, if the system is not running 100% do not drive the car again. As Lawrence the cable guy says, git er done.
Make appointment with the independent of your choice and get the Benjamins ready.

when was the water pump last changed?

[ATX_Boxster]

^ agree - if you have a coolant issue, it's not worth it to drive the car...especially with the heat forecast for this week.

sounds to me like you need an accurate diagnosis of the problem.

i recently had my tank done by a small local indy shop here in town. the coolant system was also flushed and they installed a low temp thermostat. they are very enthusiastic about working on p-cars, and they are very reasonably priced.

if you need their contact info - just send me a PM.

[Spinnaker]

Have your system pressure tested to find the leak. Any shop or radiator place can do this. Identify the problem before you start replacing parts.
I just replaced the O-rings on the bleeder valve a couple of days ago. You have to remove the cover flap that surrounds the fill caps to see the bleeder valve and if there are is any leakage there.

[southernstar]

If there are no signs of leaks from the coolant tank and no water on the floor of the garage after driving, and yet water is being lost from the cooling system, have you checked your water pump? A failed pump can have greater leakage when the engine is operating than when parked. Also, you should check your engine oil to ensure water isn't getting into it through a blown head gasket. Admittedly, it does seem like a great deal of coolant to be lost through a head gasket, although I guess the second top up could be due to air locks in the system after loss over a significant period of time. Regardless, if you have been operating the vehicle with with air locks/bubbles in the cooling system, you run the risk of damaging the impellor in your water pump, adding to your misery. Even worse if you are running it with coolant in the oil. I agree with all of those who have suggested that you whatever it may be, you get it towed into a trusted mechanic immediately.

Brad

[Perfectlap]

^ head gasket failure is very unlikely with these cars.

With nearly 200K I'm curious to hear if he's on the original wp.

[southernstar]

Perfectlap, without overheating you are correct, head gasket failures are rare. I too would be interested in hearing about the age of the waterpump. MNC-1, inspect the pump. Particularly if it has been leaking for some time, even if the water leakage from when it was last operated has evaporated, you can expect to see some white residual staining in the area where the shaft for the pulley exits the pump.

Brad

[dbear61]

I had a similar experience last year when I was driving home to Milwaukee after picking up my 01 S in Chico, CA. Flashing coolant light, but no rise in temperature. Reservoir tank was empty, so I added coolant (what else was I going to do in the middle of Wyoming?) and drove on.

A few hours later, the light started flashing again. When I got home, I refilled again. I noticed once that there was a bit of liquid on the ground on the rear passenger side, but never any fluid in the trunk.

The is went on for a week while I waited to get it into the P-Dealer. Cracked reservoir tank. Less than 100K miles at the time. $1,700 to replace and refill.

You should jump with joy that the dealer you have is quoting only $1K. Get it fixed at the dealer or the indie and have peace of mind.

BTW, talking with my neighbor about this, he said BMWs have the same vulnerability with their coolant tanks. His 07 3-series had the same thing happen at 62K miles, and it cost him $1,200 to replace.

DBear

[soucorp]

My 996 had cracks in the coolant tank that leaked slowly drip by drip. Had it replaced by a Porsche specialist @$1400. Should have done it myself but this was 8 years ago. Anyways, if your tank is not leaking, it could be the hoses going bad or waterpump. Lets pray its not a head gasket issue where the coolant is flooding the engine. You do have serious mileage on that car, so I'm not surprised.

Best

[Perfectlap]

I think I paid $700 for the coolant tank from a Porsche specialist with experience on every Porsche ever built.

I have to look into this dealership service dept business some day. 100% mark ups seem like the way to go.

[southernstar]

I know the job is a knuckle-scraper and a pain, but I still can't believe the labour charges being quoted by some. I mean, the original Porsche reservoir sells for $310.00 at Suncoast. Even with new hoses/clamps and antifreeze, total parts should still be under $500.00.

[mnc-i]

As Paul Harvey would say...Now the rest of the story.

It was the water pump. I'm going to invest in the company that makes Porsche OEM water pumps:-)

Since purchasing the car in Sep 09 w/104,000 miles, I have now put three pumps on the car. I had the first pump replaced at approximately 108,000 miles (I could hear it making noise). I replaced the second pump at 168,000 miles because I read in Excellence Magazine the series of articles on Porsche water pumps and their poor reliability (best to change out the pump at every 60,000 miles). This third pump was leaking via the weep-hole (no noise, just water that I thought was coming from the coolant expansion tank).

But it gets better.
After I received the new water pump and thermostat, I lost about two gallons of water between driving from the mechanic's shop to my office parking lot (approximately 3 miles).

I had a bad coolant expansion tank cap.

[CA_Boxster]

I was thinking 1) cracked tank, 2) WP, 3) cap. As I got through reading the posts I though it was kind of funny that with all that use of the car you were the one guy who never had to replace the cap

You drive a LOT...