Coolant Leak Boxster '00S

My level looked a bit low this morning to I added coolant and water. I left it below the max line, while the engine was cold

This evening, as I drove into the garage, after a 10 mile drive, the coolant was dripping out onto the floor.

My coolant tank was just replaced 4 years ago.

Any ideas on what happened? Is there an overflow tube, and could I have overfilled it by adding coolant while it was cold?

Thanks for the help.

Sounds like it's not likely to be the tank. The max line on the tank is (I think) the highest it should be with the engine hot so (considering you added fluid the same morning) it is possible you simply overfilled the tank a bit. Another concern may be the water pump. Is the coolant dripping down just ahead (and inside) of the right rear tire? If so, check the water pump and related hoses.



Edited 1 time(s). Last edit at 03/31/2011 03:16AM by Edmond in SoCal. (view changes)

It's possible it is your water pump, but more likely that you overfilled the tank. Coolant expands when hot, and if the tank is at the max line when hot, spirited or heavy driving will result in substantial coolant expansion. When this happens, the system will purge itself of excess coolant through the cap - it then drains out below the rear trunk, as there is a drain tube. If the tank purges itself, the area around the coolant cap, inside the trunk, etc., should be wet.

To be safe you should check the water pump, as you cannot drive the car once the pump fails. The water pump is below the #1 cylinder bank - on the passenger side. If your water pump is leaking, all you need to do is start the car and let it warm up a bit and coolant will leak out of the pump. If the pump is not leaking, if does not mean it is OK - listen for unusual noises - it should be running smoothly - any kind of repetitive rattling, squeaking, etc., and the pump is probably going bad. You can also put your nose about against the passenger side engine vent and smell for coolant.

I don't how many miles you have, but the coolant pumps on these cars usually fail anywhere between 75,000 and 90,000 miles.

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger

In the past I have found if cold level is mid point or higher system purges some coolant- right now my cold coolant level is close to minimum and has been there since I replaced my engine 3 years ago.

Once it settled there I have not touched it.

to actually see where the coolant level was -- I couldn't see it through the side of the coolant tank -- and found the level right at the max. level line.

This was with the engine cold too.

Sincerely,

MarcW.

So, per your post - I recently replaced the water pump in my 1998 986 at 176,000 miles - prior pump had gone in at 90,000 miles. Before the replacement, coolant tank was usually at max and never purged (except for a bad cap I replaced).

Now that I have the new pump in, I need it closer to the min line when cold - if it is at the max line it purges every time.

I don't know what this tells us, but it is interesting. The newer pump may be a Porsche update that allows more coolant back and forth into the expansion tank.

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger

ago this was but I'm sure it has been a couple of years. (Car has 240748 miles as of this AM.)

My Boxster's coolant level has been very stable.

From the time I bought the car until the car lost a radiator from me hitting some road debris and all the coolant was lost I never added any fluid to the cooling system.

After the radiator was replaced and the system refilled with fresh coolant the level remained good for years. I had to replace the water pump but not because of any leak, but due to the noise the pump made, the play at the water pump pulley/shaft, and a tiny hint of anti-freeze residue on the pump's casting.

(BTW, Porsche techs tell me that signs of anti-freeze residue alone is not proof the water pump is bad. They tell me Porsche allows for a tiny bit of leakage from the water pump but there's a callout on this. IIRC no fluid, no moisture is allowed to be seen just a tiny bit of residue and the location and size of this residue stain is specified. If the stain is too big or located in the wrong place, the water pump is bad.)

Anyhow, after the water pump was replaced the coolant level remained ok until the cap went bad. Afterwards, the level remained good right up until the coolant tank split.

Since then -- I can't remember when this happened but my WAG is last summer maybe -- the level has been unchanged and right where the tech had it when I picked up the car.

In fact years ago I bought a jug of Porsche anti-freeze and keep distilled water on hand and I don't think I've even used any anti-freeze from the jug and the distilled water I used (about a gallon?) to bring the level up when the cap was leaking. The rest of the distilled water has gone into my cars' windshield washer reserviors.

So, I don't buy into these cooling systems losing coolant over time, unless perhaps the water pump seepage that is I'm told allowed by Porsche is at the very high end of what's allowed and this accounts for the drop of the coolant level over time. Just a WAG understand. Until I get some hard data on what's allowed or tolerable I'm going to assume any fluid drop is a leak somewhere and needs to be addressed.

Sincerely,

MarcW.