Coolant leak sealer worth trying?

Just took my recently acquired 996.2 C4S with 44k into my Indy for sorting the typical PM items out. Drove it back after purchasing in TX after an oil change and dealer look over to NJ. Ran strong and quiet the ride back. Recently noticed coolant smell and minor loss in the expansion tank. Included in the work just done here - drop and inspect sump, bore scope (looked pretty clean), water pump, low temp thermo, plugs, bosch injectors, and looked for any sign of leaks at radiators, lines and tank, cap, nothing found. AOS, belt, IMSB done by PO in last 2 years. Possible head or gasket? Only less than a pint down in 1k miles since home. Smell coolant after a full warm up drive. Anyone try or have thoughts about trying a little leak sealer to hold me for awhile if it's a small head leak? Hate to pull the motor after dropping so much already, and doing heads for another 7k.

Its your car and you can do what you please with it, however, I would NEVER put leak sealer in any engine I cared about. It will clog up passages, hoses and radiators throughout your cooling system. Take a real hard look at your coolant reservoir tank as these have been known to develop fine cracks that only leak when the coolant is hot, and drip directly onto your muffler so that you never see a puddle but you can smell the coolant. You don't mention the year, but if its the original coolant reservoir its well past due for a change and you don't even have to remove the engine! BTW, the head gaskets in these engines are metallic and rarely ever fail. Best of luck.

My understanding (just regurgitating forum information here), is that the M96 head gaskets almost never, if at all, leak. Frequent discussion points of coolant leaks are that it could be internal to the Oil/Coolant heat exchanger, or the above described leak in the coolant tank. If I remember reading correctly, the earlier pre-2001 engines are more likely to get cylinder cracks, so I think your 3.6 C4S is less likely. Again, these aren't facts coming from me. Consider them starting points for forum searching/reading. Leak sealer is pretty nasty gummy stuff. I used it once in an older car that just wasn't worth doing anything else to. Either that was going to fix it and get me another couple of months out of that car before I sold it, or I would sell the car for a few hundred less with a leak. It worked, got me a few months of use, and I ended up selling the car for $650 (in 2010), which I considered a good deal. I would never put it in my 996.

Forget about using any " fix it in a can" on a Porsche......Use a methodical plan to find/fix the leak....

Hard to follow the timeline. Did it not lose any coolant on he drive from TX to NJ? Did it only start losing coolant after the work was done? I would expect your indy pressure tested the cooling system after the work that was done. Take it back and have them diagnose.

Thanks for the input. Years ago, I used bars leak a few times on one or two of my many brit sports cars and domestics. It is an '05 and I didn't notice any coolant smell until a month or so after the 1,500 mile trip east. My indy, a well known guy who does most of the track car work for the PCA region members and worked my Boxster prior, pretty trusted; told me he had the tank out when he did the water pump and checked it as well as all the hoses and both radiators. I noticed it holds some pressure overnight, no drips ever noticed. Said he thinks he smelled it in the exhaust, which I also think is noticable. His suggestion was keep an eye on it and see how much it loses after a little while. I guess I'll take the advice on not using any additives and drive it a month or so and monitor loss, keep it topped up. My indy suggests next step would be pulling it and checking the heads. I am a geezer without the facility to do an engine pull DIY. t's a tip also, which is tougher. Would he have been actually able to see the oil cooler without the engine out? There was definitely no intermix and the oil in the sump was clean and showed no milk. Thanks for the good opinions! Just hate the thought of the expense of a pull and head work. Just paid over 4k on the work done. I'll report back after a month with status. As mentioned, I might do the expansion tank any way as i understand it's a maintenance item on these cars. He said he looked at it and it looked good but I am not sure he pressure tested.

These cars also suffer heater valve leakage which causes smell of coolant inside the cabin. Is that where you smell it?

Thanks. Actually no noticable smell inside the car. I thought I was initially smelling it around the front because I would get out in the garage and walk past the front end and suspected the radiators, but came to realize it was noticable anywhere including rear.

Quotes source post: 18598341

As Skip said, no stop leak. Anything else is a band aid that is going to end up causing a bigger problem in the long run.

Thanks, I definitely will follow the consensus opinion on this and no additive band aids! Just hope it's not a small head crack.

Quotes source post: 18599788

Be sure to use a Porsche specific machine shop that is knowledgeable on M96 engines and these heads specifically. Some cracks are repairable, some are not. To be perfectly honest, although some claim to be able to fix cracked heads, we won't even make an attempt and advise replacement.

Quotes source post: 18598341

Word. As observed here earlier by smarter folks then me, 996 and 986 were so unloved for so long, they were owned by people with no business taking on that responsibility. I'm not dissing anyone. I understand all about want vs. need, budgeting, and getting in over my head. Been there done that. Respect the 996😎. I was at my local PCA meeting Saturday, and when my 996.1 is lined up in a row with the air cooled generations, appearance wise, it holds it's own. That's subjective of course, but what's not subjective is the driving experience. 996s have more power, better chassis rigidity, more comfort and great AC. I don't consider the 991+ gen cars to be direct comparisons to 997 and older, they're just so different in size and intent. Plus I can't afford them. I should get a "don't laugh it's paid for" bumper sticker.😙 Anyway, if you are lucky to own a 911 of any year, take care of it, for pride and the next caretaker. Cause there will be one. Or several. And they're not making any more of these old beauties. I'm putting my money where my mouth is, and doing all the service that's not documented, bringing her up to date, and eventually, I might even have the bumper, frunk lid, and wings resprayed, someday. For now, I embrace the patina, and doing the important stuff. This spring it's time for a complete fuel system refresh. I've no idea when the injectors were changed, but I've replaced the fuel filter recently, so the timing is right. The cooling system is going to get the treatment as well. When the maintenance stuff is done, then I'll do some OEM+ stuff. For sure an UAOS and something to protect our improve oil pickup. An add on baffle or a sump with better designed pickup management, just in case I want to track her, which is likely. I'm hearing that my son's chosen UNC as his first choice. If he makes it, and I've no reason to think otherwise, I'll be moving to northern NC, close to VIR. Then I can spend my retirement on track time. Haha. Can you tell I'm just back from my Sunday drive? Everytime I get behind the wheel, I'm reminded how great the driving experience is in any 911, especially the one with my name on the title. OP, I hope you're able to get to the bottom of the issue and get it repaired. Fingers crossed.

There are a TON of hoses , the AOS line, the Oil cooler, that are way more likely your problem on the 993, if its . If you let it sit overnight, and scope the cylinders, if there is antifreeze you have a cracked cylinder or cylinder head is possible most likely NOT a head gasket. If its internal to the engine anywhere you should be seeing white vapor out of the exhaust,, especially on startup. The coolant tank is a maintenance item that fails if ignored. Use factory Porsche tank only, the other knock offs will only cause you pain. The cap on the tank should be BLUE not black. They went to a slightly lower pressure cap on these with a better internal design.

Is there any chance the coolant tank was overfilled and it just pukes out the excess when hot? I know it was driven 1500 miles home, but did anyone check the cold level on that journey? Skip and others, can the OP put a dye in the coolant to see where it's leaking by using an ultraviolet light? As mentioned before, there are a ton of hoses and hose connections that could be the culprit. Final point on radiator sealers: Many decades ago I worked in an auto parts store. We used to sell Porter Seal radiator sealer, which looked like a bunch of flakes (sand like) that came in a tin can. Customers who were desperate to save money would ask if this would clog anything. I'd reply, "Yep, it'll clog your heater core right up." They'd buy the $1.50 can (hey, I did say it was a long time ago!) thinking at least they didn't have to buy a radiator (yet).

Thanks for the info. Yes, I worked in a Sunoco "service station" in the early 70s in PA, when it was standard to wash the front and back glass, check oil AND battery levels, maybe air in tires if asked with a fill up! I put a few cans of bars leak in radiators back then to patch a leak in request. I know this M96 is a way much more complicated and copiously plumbed beast than those old carburetored V8s and straight six bangers and I have gotten the message loud and clear on avoiding putting any gunk in there, lol! This morning, I went out and saw a small 3" wet spot of coolant under the driver side exhaust. Called my indy who just did the water pump, etc.. after reading Jake's write up on the expansion tank. Mine has a black cap and per service records, may very well be the original from '05. He suggested I took it out for a good hard ride and park it tonight and look again tomorrow. I just cranked it up to some high speed highway time and just parked it. I smell coolant walking all around the vehicle. My guy suggested he looked it over when he had it up and didn't see any sign of seepage. Wants me to look again tomorrow after that 45 minute ride today for any repeat of the puddle. Did suggest it could have been overflow, but it was down a little after I drove home from his shop the other day. Of course changing the pump and thermo, he drained and refilled. Tomorrow might tell the tale. I told him that I probably will want to bring it back in to replace the tank with a new Porsche blue capped tank either way. Hoping it is that, and not the head, that he suspects could be the issue of the fluid loss and smell around the exhaust, since he couldn't find a leak. I'll update!

The cap is separate from the coolant tank (which does not come with a cap). So buy the blue cap first and see if this fixes the issue. Start simple. You would probably see white residue on top of the coolant tank if the cap was leaking under pressure.

I have an 03 C2. Since I have had the car, I would notice that the coolant would never stay at the full cold line. I had the waterpump replace in '18. That being said, I have never had a car that didn't need a top up of coolant through the years. My brand new 2015 jeep, I always top it up in spring with a cup, since new. This past July, wife and I were out for a drive and we were in an area of town that we rarely get to. We decided to go drive by Drake's house since we had seen write ups about it. It was a really hot day, well into the 90s. Driving through residential neighbourhoods, hammering it medium hard lol. We stopped at a market and when I came out, there was a puddle of coolant under the left tail pipe. My car is parked on a lift, I had never seen any coolant leaks. I drove the car home, parked it at home and it didn't loose any more coolant. Was really wondering if it indeed was the coolant tank, which was original and 19 years old. Picked up an expansion tank at the local dealer, with a purchased separately, coolant tank cap. I changed it all out. A couple weeks later, I was bored and decided to clean the old tank and look for the crack. No crack was evident. Using soapy water and 20psi of air, I finally found a minute crack, no more than 1/8 of an inch long. So, I would not be surprised if you loose coolant intermittently through the expansion tank when there is significant pressure build up related to heat and how the car is being driven.

Thanks for the info. After a good drive yesterday I looked under this morning again and see some wet up under the tank area and wet / drip hanging on the hose to the thermo housing, dried white powder lines on the header. I'm going back to my shop and having a new Porsche tank and blue cap installed, since I'm betting this is the original tank. Hope that does it!

Just circling back on my coolant leak and worry about a head crack... I had a new OE expansion tank put in as a suspect, due to some wet under the bottom hose, not for certain it was leaking, could have been from the overflow. However, did find a leak in the right front radiator and replaced. Looks like there was some scrape, impact in that under bumper area. No longer smelling antifreeze after a good ride! Breathing easier! Glad I didn't try any sealant; folks were clear on that being a mistake. Cheaper than dealing with dropping the engine and pulling heads to inspect!

Glad you found/fixed your leaks without using any "magic in a can"....Pressurizing the system to 20psi and leaving it pressurized overnite will usually show/find those small persistent leaks if they are external...