asellus

No. I'm saying that the idea itself is a completely arbitrary grasp at a concept that has absolutely no relevance whatsoever to the situation.

The amount of air movement required to create a significant enough pressure differential to pull vapors from a closed, but not entirely sealed cap will immediately dilute said vapors to the point where you will not be able to detect them by smell. There are many cars out there built with vented expansion tanks, which would be the equivalent of just not installing your coolant cap there. none of those cars have issues of coolant smells from freeway speeds. The blue tubeframe car in my signature rotation runs such a setup for example, and I have never had a coolant smell issue despite my unprotected face being directly downwind from the vented coolant reservoir. In your case you're upwind of any such vapors.

This theory is also making the weird assumption that the reservoir has enough airspace in it for such a pressure differential to extract a meaningful amount of air to begin with, which it does not. the alternative would be the assumption that it is a pressurized system so the pressure differential is helping it escape, but if it's a pressurized system the pressure in the system would overcome the poor seal long, long before your miniscule vacuum effect from airflow would do anything useful.

See above with regards to this idea that pressure differentials are a problem. They aren't. If it's a pressurized system that isn't sealing, you're significantly reducing your boil temperature and are allowing tons of steam to escape the system, completely unrelated to external air pressure. Further, the physical expansion of the fluid is a concern here as it would likely spill out through the bleeder tube, usually onto the ground but sometimes onto the chassis because routing tubes is hard.

With regards to the sound symposer... it is supposed to be a sealed system. If the tube is cracked, then engine bay air could bypass into the cabin, sure. You'd get oil and fuel smell at that point though.

Also, if it's coming from your HVAC vents, that's coming from the wrong side of the car for what you're currently troubleshooting. HVAC air comes from the frunk area. Your potentially leaking reservoir cap is on the other side of the car, behind you. None of that air is being pulled in through the HVAC unless you're driving in reverse. I'd bet you have a pinhole leak in a radiator up front or in the runner tubes somewhere.

I wrote that line on how to determine this so you would be able to figure it out in case you didn't know if it was pressurized or not. Check and report back!

Live Steam

Well today I solved this issue that has plagued my car for a few months. I've been wanting to plug or completely disconnect the sound symposer. Today it was raining on and off, so no golf or back road driving. Thought it was an opportune time to see what difference plugging up the symposer would have. I don't like the boosted exhaust sound when hitting the go pedal hard. RPMs hit 4k and it sounds like the space shuttle taking off. I wouldn't mind if it were natural and gradual, but it just sounds too canned - yeah I know it's somewhat amplifying the natural sounds of the exhaust - but it kicks in abruptly and that doesn't sound natural.

I pulled the fans and a thought suddenly came to me when peering into the engine bay. The source of the odor was coming from the engine bay thru the symposer. I've been monitoring the coolant level and it's hasn't changed one bit, yet the odor has been there for all this time. So if it were a breech in the cooling system somewhere, that wouldn't be the case. I checked everything else too and was still stumped as the odor would return. But it didn't appear unless I was driving hard. Just tooling around and there was no odor. Ha! The symposer opens up at 4k or there about. This thing isn't only pumping sound. It's pumping the odor into the cabin! So I checked the oil filler cap and it was loose by a 1/4 turn or so. Maybe the odor was hot oil? I also remember having my indie install BMC oiled filters a few months back when he did the oil change. So maybe it's the filter oil that gasses off when hot?

So I disconnected the hose from the symposer to the fitting that enters into the back of the cabin and stuck a large rubber stopper inside the hose where it connects to the fitting and then reconnected them so the hose wouldn't just flop around. The fit is very tight and I believe sealed well. I took a nice blast of a drive after the skies cleared this evening and there's no odor at all. The sound is much better too. So it seems that the symposer doesn't only pump sound into the cabin, it pumps odors and gasses into the cabin from the engine bay. Next oil change I'll probably revert to paper filters even though I have no idea if it was them or the loose oil cap that caused the odor. Either way, the symposer was the conduit for the odor and that ain't cool.

asellus

This statement is true only if the symposer diaphragm is broken which, by your updated description, is the case.

Live Steam

Has this been reported to have happened before? I guess I'll have to pull the bumper cover and remove the vile thing and inspect it. However, if the symposer is somehow compromised and pumping fumes into the cabin, it further illustrates that it is a bad idea. But I'm happy I figured this out and don't have to deal with the odor.

IDK if it matters, but my GTS has an aftermarket Akrapovic exhaust. Where does the symposer connect to the exhaust? Or does it? I guess I can look at the diagrams before taking everything apart.

asellus

It connects to the intake, not the exhaust. Where you unplugged it from should have a short tube running downwards towards the intake piping, shouldn't be much longer than 8 or 10 inches.

Someone recently had symptoms of a failed symposer diaphragm here, but it was on a .2 and I don't recall if it was found out to be the symposer for certain. Just "I unplugged the tube and plugged it up and the smells stopped" kind of ordeal, like this.