hairline headgasket leak? or something less serious

[uisim]

So it started when I noticed the coolant was a bit low. I was just looking over things I didn't have issues with the car. It was a bit low so I I added a bit (like a drinking glass amount) and a few months later it was down again. I would top it off and notice it was overflowing from that little port on the side of the expansion tank, the channel its supposed to flow out of if the cap builds up too much pressure. I did once overfill it to the second bubble when the car was cold so at first I assumed that it was the lill bit of extra coolant but way more came out by now. I changed the radiator tank cap and had noticed a sporadic 2b59 code but no CEL light. Today I opened the bleeder screw incase there was air in the system and will properly top it off when cold.

Any ideas on what this could be. should I try changing the tank maybe? I dont know how the tank can be at fault, the coolant is simply evacuating from the tank from pressure or air. All i can do is check compression unless you guys got anything.

[Solo_M_Tech]

check for leaks around the thermostat housing and radiator hose connections. It may be seeping coolant and not a full blown leak just yet. hence the slow leak. I've never seen head gaskets fail on the S65. x

[uisim]

Originally Posted by Adenau

check for leaks around the thermostat housing and radiator hose connections. It may be seeping coolant and not a full blown leak just yet. hence the slow leak. I've never seen head gaskets fail on the S65. x

I know where the leaks at. It's the reservoir channel that's designed to expel coolant. It's that channel right off of the reservoir cap neck. It's working as intended. It's there to aim the coolant overflowing from the tank downward so it doesn't spray the engine when there's a small overflow situation. My problem is finding the reason for excess pressure in my cooling system. Can the coolant overflow due to a sticking thermostat maybe? I do have the fault for a thermostat being thrown. It's been Coming and going for a year. Never threw a cel light I always found it once in a while when playing around with the diagnostic software. The fault just says "thermostat monitoring" I don't know if it's going off cause the temps are rising slightly but not enough to throw a check engine light soon. Coolant is overflowing very slowly. I can go months withought adding antifreeze and I never even had a coolant light come on yet.... that's why I'm maybe suspecting a hairline crack in the head gasket. unless maybe the coolant tank is slightly worn and even a new cap is just a tad too loose. I'm at 60k miles on the car btw

[Solo_M_Tech]

Originally Posted by uisim

I know where the leaks at. It's the reservoir channel that's designed to expel coolant. It's that channel right off of the reservoir cap neck. It's working as intended. It's there to aim the coolant overflowing from the tank downward so it doesn't spray the engine when there's a small overflow situation. My problem is finding the reason for excess pressure in my cooling system. Can the coolant overflow due to a sticking thermostat maybe? I do have the fault for a thermostat being thrown. It's been Coming and going for a year. Never threw a cel light I always found it once in a while when playing around with the diagnostic software. The fault just says "thermostat monitoring" I don't know if it's going off cause the temps are rising slightly but not enough to throw a check engine light soon. Coolant is overflowing very slowly. I can go months withought adding antifreeze and I never even had a coolant light come on yet.... that's why I'm maybe suspecting a hairline crack in the head gasket. unless maybe the coolant tank is slightly worn and even a new cap is just a tad too loose. I'm at 60k miles on the car btw

First change your thermostat. It's defective, that's what that code indicates. The code is set when the engine takes too long to warm up, due to the thermostat being stuck open.

Secondly, the coolant system on these cars are not designed to bleed of coolant in anyway. The reservoir cap is designed to maintain 16 psi of pressure in the system, and in the even of overpressure, bleed of vapor. If you are leaking coolant from anywhere, that part or connection is defective.

How do you know there is excessive pressure? Have you tested the coolant system with a pressure test with a
gauge? What, other than speculation, have you done to diagnosed the condition?

Again, I've never seen a head gasket fail in any way on an S65. You would have to MASSIVELY overheat the engine to do so. The engine would suffer way more damage from an overheating situation than just a bad head gasket.

My advice to you, stop speculating what the problem is, and take the car to your favorite dealer or indy shop and let them diagnose it.

[uisim]

Originally Posted by Adenau

First change your thermostat. It's defective, that's what that code indicates. The code is set when the engine takes too long to warm up, due to the thermostat being stuck open.

Secondly, the coolant system on these cars are not designed to bleed of coolant in anyway. The reservoir cap is designed to maintain 16 psi of pressure in the system, and in the even of overpressure, bleed of vapor. If you are leaking coolant from anywhere, that part or connection is defective.

How do you know there is excessive pressure? Have you tested the coolant system with a pressure test with a
gauge? What, other than speculation, have you done to diagnosed the condition?

Again, I've never seen a head gasket fail in any way on an S65. You would have to MASSIVELY overheat the engine to do so. The engine would suffer way more damage from an overheating situation than just a bad head gasket.

My advice to you, stop speculating what the problem is, and take the car to your favorite dealer or indy shop and let them diagnose it.

I'm testing it now. I'm just looking for opinions in case someone had this Issue before. Not everyone goes to the dealer at the first sign of trouble. I can change the head gasket If I really needed to myself. I feel like it's the coolant tank tho. When I line up the cap with the arrow on the tank it feels more loose than it did before. I also noticed that the coolant tank filler neck has a little groove where the caps o ring sits. Maybe it's blowing past that due to wear somehow and it's expelling coolant. Just ordered a tank and thermostat. Will report Monday on what's going on. Leakdown test found nothing. Compression was the same on all cylinders so already head gasket is out of the question . I keep hearing im crazy on that idea and the tests seem to confirm it.