2000 c4 with approx 65k on engine... I have had the car since it had about 40k (on engine) ...oil change every 5k , does not burn an ounce of oils, no contaminants in the oil or colant, runs great and is a DD.
Last april i had to replace water pump and radiator, i used my indy (very reputable in hampton roads and known via PCA).. Once the work was done no problems... This summer i had to add 1 litre to the resevoire, since i check it once every 2 week and around the cap there was resedue coolant, my indy said it was probably just the cap not properly fastened.. (cap is the older part). drove it 2k miles, no loss, 3 weeks ago i checked the coolant and was fine..... The last few days i drove very spirited for about 50 miles, checked the coolant today.... 1 litre of coolant low (no light)... when i remove the cap pressure is heard every time. Car souds like a sewing machine, dose not burn any smoke of any kind.... My indy sais that they start smoking when cracks develop in the heads... Im changing plugs and oil this week-end... If i had a crack in the heads would i be able to tell from the plugs?

 

btw my cap # is 996-106-447-00, i understand the new one is 996-106-447-04-M100... But could that much coolant evaporate via the cap?

 

On vehicles with coolant loss and no plumbing leaks you could have cracks in the head or a blown head gasket. No water in the oil and no/little smoke. Whent the car runs compression gases force themselves into the water jacket raising the pressure and the water runs outthe overflow. May not leak under a leak tester because they normally go to pressure 12 - 20 pounds.
This is just one possibility but I
have seen this on more than one car.

 

I have read about that, but those cases also had oxidation and residue on the exhaust ... would i find the plugs fawled if that was the case?

 

It would depend on how quickly you lost that litre of coolant. I'm not sure if a the stainless exhaust or the plugs would show much because if this is like the other cases I have seen most of the water went out of the overflow while driving down the road.

 

1 litre in just under 2k miles... but 2 liters in the last 5k (summer)... if that was the case, when the car is running at reg temp (BTW has never overheated) i would be able to see boubles in the res tank right? i just ordered the new cap....

 

I believe you would only see bubbles under load, probably not at idle. I'm not sure if there is a way to attach another jug to the overflow to determine if this is actually the problem. There is not a lot of space to work with.
As with any on-line diagnosis take them with a grain of salt. Things break in a myriad of ways, your mileage may vary.

 

Well, we looked every where (with out lifting), the only time you can smell is from top left of engine, i can see some dry glycon in the back. Indy is pretty sure its the cap or the res tank... I will bring it in next few weeks for a pressure test (after replacing the cap, if it did not fix it). BTW no bubles at 5k rpm for over 1 min... You cannot smell glycol from exhaust in any way.... No smoke what so ever even after hard driving and then sitting for some time.... Will keep posted/

 

It was my cap leaking while pressurized when driving.

 

I just checked the expansion tank on my 2000 Carrera 2. It has a hairline crack on the underside. Any recommendation for a stronger tank design. This is the second tank within a year. She only has 70k on the clock.

 

Have you changed the waterpump recently? Install the new coolant cap but keep the old 1 you may need it if the added pressure is a problem. Get a oil sample & have it analized for excessive sodium from coolant in the oil. You could have a crack in the coolant reservior or heads that leaks only when hot. It's a good idea to check the plugs but just because they look good doesn't mean you are crack free.

 

If i had coolant in the oil, would it not show, it has been 2 liters of coolant loss over 5 k miles.... i'm doing oil change tomorrow with plugs, but from the stick it looks as new

 

If 2 liters went into the oil it would & your oil level would be over full, but you don't know where it's leaking & it never hurts to get a oil sample tested.

 

I replaced the cap and and so far no apparent loss of liquid, i took the expansion tank tube and placed upward (to ensure if it dose come out i will know it)... BTW where did it originally go down to, over the exhaust? or do i have to take the air pump out to fit it right (otherwise seems to leak above cats of exhaust)

 

You can also have your coolant system pressure tested for not a lot of money...