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2002 996 C4S - Coolant loss (AOS, Cracked Head, Gasket???)
I recently traded in my 986 Special Edition for a 2002 C4S with 105k miles on the clock. Car looks great for its mileage and age, it was very well cared for an came with a stack of service receipts. The car even had RMS, LN IMS, Water pump, and new clutch services performed.
Now the car drives great, no obvious faults or concerns - great power and responsive delivery. The problem I do have is the following, coolant loss and a sweet smell emanating from the exhaust, not really coolant sweet but kind of like running rich sweet. I have searched high and low for coolant leaks and cannot find anything, no puddles on the floor and no drips. Considering that the exhaust has a sweet tinge to it I am relatively certain that some foreign fluid or gas is being introduced into the exhaust manifold and possibly the oil system.
Other than those 2 symptoms I have nothing to go off of - no signs of oil in the coolant or coolant in the oil (checked coolant cap, coolant reservoir, dipstick, and oil filter.) I did try the AOS test of removing the oil cap while idling and the cap was kind of difficult to remove, much more so than when engine isnt running, it also sounded like the engine was struggling - RPMs dropped and were hunting to stabilize.
So where does that leave me, I have already mentally prepared myself for a cracked head being the culprit. To give context to "coolant loss" - after filling up reservoir to MAX with distilled water it was a hair below MIN after a 10 mile drive. I know that the next steps are probably pressuring testing cooling system, leak down test, and compression test but is there anything else I can check to put my mind at ease? Can i be losing this much coolant with a bad AOS? Oh and speaking of AOS, when people mention AOS replacement are they talking about this part? http://cdn4.pelicanparts.com/techart...mall/pic01.jpg
Thanks for the help and sorry for a long winded post
Edit: Forgot to mention - no smoke on startup, engine temp is just a hair past the "8" on 180 but doesnt hit the "0", on cold start the rpms jump to about 1050 initially then settle down to 700-750.
The most likely cause is hair line cracks on the coolant reservoir. Usually at the bottom of the reservoir on top of the muffler so coolant just drips down and get burned directly without a trace.
If you want to diagnose it yourself, just get a Stant pressure tester and pressure it to 21 PSIG and wait for at least 1/2 hr. Check for wetness by your hands and also by inspection mirror.
The cap should also be tested or just replaced as a safety measure.
Yes, the AOS is the bigger in the pic. A royal PITA to replace.
The most likely cause is hair line cracks on the coolant reservoir. Usually at the bottom of the reservoir on top of the muffler so coolant just get burned directly without a trace.
If you want to diagnose it yourself, just get a Stant pressure tester and pressure it to 21 PSIG and wait for at least 1/2 hr. Check for wetness by your hands and also by inspection mirror.
The cap should also be tested or just replaced as a safety measure.
Yes, the AOS is the bigger in the pic. A royal PITA to replace.
Thanks Ahsai - the coolant reservoir is revision ending in 03 and the cap is 04, I was unable to find any traces of seepage from the reservoir when checking but I will do a pressure test to make sure!
GT: My 2005 996 C4S was not losing that much water and at the start of smelling exhaust/cooling water after parking in garage no sign of water. However, Ahsai is right many times the leak does not make it to the ground. Also hard to see as the "normal" leak is on the back side of the tank and, of course, is buried in the corner of the engine compartment. Cap must be of proper type and just as important put on tightly repeat tightly. Check around the neck beneath the cap for signs of leakage. Ask me how I know...
This is where mine cracked on the 2003 C2. It is on the back, fender, side. I could smell antifreeze but never saw it. One day after a long drive I heard it sizzle on the muffler, still no drops made it to the floor. I got my bore scope out and snaked it between the tank and fender and then I could see droplets on the tank and residue on the "frame" rail underneath the tank.
Rented the coolant pressure test kit and pumped up to 21 psi, left it on the car for roughly 45 min.
After 45 min the gauge read 19.5 psi, so I lost a total of 1.5 psi over 45 min.
At first, I didn't see any signs of a leak, nothing near the coolant expansion tank, nothing near water pump or any hoses in the engine bay or underneath the car. But then I walked to the front of the car and could smell coolant, sure enough the passenger side radiator was leaking coolant near the top and it was trickling down. So, now that i have identified A leak, what are next steps, is it possible I still could have another leak somewhere or would I have noticed it? Here are some pics of the radiator leak, how bad is it?
Good job diagnosing it! Looks like the radiator is leaking. Looks like time for the front bumper to come off to have a better look. Hopefully just a bad hose??
Good job diagnosing it! Looks like the radiator is leaking. Looks like time for the front bumper to come off to have a better look. Hopefully just a bad hose??
Thanks Ahsai! Once I remove the bumper what am I looking for specifically, do I need to pull the condenser off of the radiator? If the cause of the leak is a hose, will I be able to get to it or will it be behind he radiator...any diagrams of the cooling system that shows hoses? Can this leak be what's causing me to smell coolant near the rear of the car, doesn't seem likely to me
Nice 996! I think the best is to remove the fromt bumper and wheel liner and do the pressure test again so you can see excactly where it's leaking. It's always possible to have a leak at another place but you will just have to fix what you can see first and retest afterwards.
Nice 996! I think the best is to remove the fromt bumper and wheel liner and do the pressure test again so you can see excactly where it's leaking. It's always possible to have a leak at another place but you will just have to fix what you can see first and retest afterwards.
For parts diagram, check autoatlanta porsche. To buy parts, try sunsetporscheparts.com
Thanks Ahsai. I started the car today and let it run for a bit to see if I would be able to detect any more leaks at operating temp. When I was surveying the coolant expansion tank I noticed some fluid around the overflow collection rim of the tank...my cap is the 04 version, could I still be losing fluid via the cap?
GT: ... Cap must be of proper type and just as important put on tightly repeat tightly. Check around the neck beneath the cap for signs of leakage. Ask me how I know...
The most likely cause is hair line cracks on the coolant reservoir. Usually at the bottom of the reservoir on top of the muffler so coolant just drips down and get burned directly without a trace.
If you want to diagnose it yourself, just get a Stant pressure tester and pressure it to 21 PSIG and wait for at least 1/2 hr. Check for wetness by your hands and also by inspection mirror.
The cap should also be tested or just replaced as a safety measure.
Yes, the AOS is the bigger in the pic. A royal PITA to replace.
Originally Posted by wildbilly32
Might make sure it is tight!!!! Repeat TIGHT!
So tight that I need to use both hands to unscrew it?
Yep thats how tight mine is! If it is tight then perhaps try a new one like Ahsai suggests. The drain for this area drips down past the spark plug coil area and may not make it to the ground. Could be your coolant smell in the engine area. P.S. once I got all my leaks corrected it took some time for the smells to completely go away.
11-13-2016, 12:01 PM
2002 996 C4S - Coolant loss (AOS, Cracked Head, Gasket???)
