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A few weeks back my car displayed the Cooling System Fault, Visit a Workshop. I was also getting a coolant smell in the cabin. Car was running fine and temps remained normal. I brought it to my local indie who is gold certified. He found that the COV for PSE was not operating and replaced it. That cleared the code. He told me my car, a '16 GTS, had the F type CoVs and they were not installed with adapters, but rather the harness was correct for the F CoVs and believed it was factory installed. The rest of the CoVs were fine. At the time of service, he pressured tested the cooling system and gave everything a good look over. No issues were found. He also checked the water pump and didn't see any signs of a leak.

Since receiving the car back, I still get the coolant odor in the cabin, but it seems only when the AC is in operation. Car is not throwing a code and it's running normal temps. Coolant level is fine.

Any ideas?

koala

I'm not trying to be argumentative, but are you sure it's a coolant odour? Water pump failure on a 991.1 would be pretty uncommon, and it stands to reason if your indy didn't find any other leaks that it's possibly not actually coolant you're smelling?

My money is on the funky smell that HVAC systems can develop over time. It's usually most noticeable in high humidity situations with AC running or when you manually turn off the AC, but the blower fan keeps operating - that few minutes after switching off the AC compressor can cause a very noticeable odour in the cabin.

If it does turn out to be the HVAC causing the odour, you can try cleaning the system out with something like nextzett Klima-Cleaner. I have to treat my wife's minivan with this stuff every couple of years as she never turns off her AC. I've shown her how it can be helpful to get in the habit of switching off the AC 2-3 mins before getting home (while leaving the blower fan operating!) so that the system has a chance to dry out before the vehicle is switched off.

ddolbi

I agree with koala it could be HVAC odor.

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Thank you both. I'll give that a try. After speaking with him last night at a car show event, he did suggest it could be just as you both suggested, but man it does smell like coolant. Being the odor comes about when the AC/fan is running, the only other issue he could think of is a cracked heat exchanger which is behind the dash. He said he's never seen one fail.

desking101

I've had this happen in a car in the past, and it was a bad heater core. I'm not sure if this is an issue in these cars, but always a possibility

Live Steam

Thanks. How was this determined? Physical inspection?

Edit: Did you get an odor when not running AC/heat/fan?

barncobob

if the heater core was leaking i would suspect a leak somewhere evidenced by lowcoolant level

Live Steam

Would there be signs of that inside the cabin under the dash? I don't smell anything when the HVAC isn't running.

barncobob

feel for a wet spot i guess,,,no wet spot, no leak?

cpbmd

How would you do this on a Porsche 911. Do you spray it inside the central vents or do you have to find the evaporator and do it that way.

koala

The way I did it, and I have no idea if this is the correct way: I removed the pre-filter in the front trunk and sprayed the cleaner into the cavity below there, as you can see the blower fan from there. Then, when all done, I replaced both filters

The instructions say not to spray into the vents, but on my Kia minivan I have done a little bit of that as it's really difficult to get to blower fan on that vehicle

cpbmd

Awesome. Thank you.

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So I'm hoping I solved the mystery of the coolant odor in the cabin. It does not appear to be an issue with the heater core as I have not found any dampness in the carpet. That doesn't mean it's not the core as the leak could be slight. However I've been checking the coolant level on a regular basis and it does not seem to have changed much if at all - that little red thingy isn't a great gauge for this. I did this on a regular basis prior to my indie testing the system and subsequent to it, just to be sure there isn't a significant leak somewhere. There are no signs of that on the undercarriage or on the garage floor.

While performing the visual checks on the coolant level, I was somewhat surprised by how easily the filler cap was to turn and lock. It never seemed to provide any resistance prior to the final click. So I changed the O ring and now when tightening the cap, it feels as if the O ring is providing a better seal. My thinking is, if the O ring was not providing enough of a seal, some steam was escaping and the coolant odor was being pulling into the cabin via the sound symposer? or via some other avenue into the cabin. The odor seemed to only appear on longer drives at highway speeds and not when tooling around town. Highway speeds could cause negative pressure outside the cap and pull coolant or steam if the O ring was faulty. Keeping my fingers crossed this was a simple fix.

asellus

you're overthinking it. highway speeds causing a negative pressure situation in that area to pull vapors out of the cap but not pull them out of the engine bay? doesn't work like that.

if the reservoir is supposed to be part of the pressurized system, then if that didn't seal you'd be boiling over much easier, which will cause coolant to go everywhere and smell and that smell permeates everything. the sound symposer is a sealed system and it being broken would be the least of your worries at this point. besides, if it were cracked, you'd get fuel/oil smells in the cabin.

if the reservoir is not part of the sealed system (or in other words, it's a vented reservoir) then that O ring not making a perfect seal will change absolutely nothing.

I don't immediately recall if the reservoir is pressurized on the 991, but you can tell by removing the cap and looking at the diaphragm setup. if the neck has a stepped entry with a bleeder hole above the diaphgram, then it's a pressurized system. if no such hole or diaphragm exists, it's a vented system.

Live Steam

you're overthinking it. highway speeds causing a negative pressure situation in that area to pull vapors out of the cap but not pull them out of the engine bay? doesn't work like that.

Not sure what you mean by this. Are you suggesting there should be signs of coolant on the outside of the car around the deck louvers?

if the reservoir is supposed to be part of the pressurized system, then if that didn't seal you'd be boiling over much easier, which will cause coolant to go everywhere and smell and that smell permeates everything. the sound symposer is a sealed system and it being broken would be the least of your worries at this point. besides, if it were cracked, you'd get fuel/oil smells in the cabin.

Again, my thinking is the O ring was not providing an adequate seal, allowing just some gasses to escape when the seal was overcome by high speeds and negative pressure on the outside of the cap. I placed a question mark after the symposer because it utilizes a penetration into the cabin to allow the sound in. At least I believe that is how it works. Are there other penetrations into the cabin on the 911 from the rear? But maybe you can clarify what you mean.

if the reservoir is not part of the sealed system (or in other words, it's a vented reservoir) then that O ring not making a perfect seal will change absolutely nothing.

I don't immediately recall if the reservoir is pressurized on the 991, but you can tell by removing the cap and looking at the diaphragm setup. if the neck has a stepped entry with a bleeder hole above the diaphgram, then it's a pressurized system. if no such hole or diaphragm exists, it's a vented system.

I don't know the answer to this either.