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Oh man, was hoping you’d ride it out and see how long it would last without doing anything. I knew a guy who wanted to test how long his polyrib engine belt would last in his Boxster without ever changing it out and it ended up lasting over 100K miles before it snapped on him. LOL.
It's my understanding that the coolant expansion tanks with small cracks, while compromised, won't just burst. So you have a little time. I've heard that when a light pink curst starts to develop outside the tank on the crack (meaning that it is now allowing coolant to escape slowly), that you definitely need to expedite its replacement.
I noticed my 997.1 had a crack with some pink crust on it not long after I bought the car in '19. What's crazy is that the previous owner had it replaced at around 35k miles. I had to replace it at 50k. The car lived in Vegas so I'm assuming the additional heat may have compromised the coolant tank faster than it would have in cooler climates.
I have a buddy with a 997.2 with a cracked coolant expansion tank that isn't as meticulous with maintenance as I am. He's been monitoring the crack for over a year and 5k miles and it is still holding up. He knows he's on borrowed time and I keep reminding him to monitor the crack, but so far he hasn't had any problems with it.
Oh man, was hoping you’d ride it out and see how long it would last without doing anything. I knew a guy who wanted to test how long his polyrib engine belt would last in his Boxster without ever changing it out and it ended up lasting over 100K miles before it snapped on him. LOL.
Ha! I sure was considering running this tank until it burst, but I learned my lesson the hard way. I wanted to see how long my ignition coils would last... I do my own spark plugs so I could have done it many times but I didn't. So one finally failed at 174K miles... and I was in a situation during my move to Atlanta where I didn't have my tools... The indy I went to tried to rip me off by installing new spark plugs I specifically said I didn't want (I had just replaced them 14K miles prior). Anywho... that work cost me $510 for the coils (Suncoast had them for $310) and $560 for the labor!!! I could not sit down for 3 months. Given my experience I recommend replacing the coils on .2 at 120K miles or 80K if you are conservative. Granted this is from a sample size on one... but it was my experience.
Besides, Floyd expressed some wisdom given his engineering experience with a super technical explanation: "It's dead Jim". With such well-informed advice as this, well... a new on is one order.
So... no, I am not going all the way with this tank. And, as I noted above, I smelled some coolant the other week and am hoping it is coming from the tank.
Peace
Bruce in Philly (now Atlanta)
Last edited by Bruce In Philly; 02-10-2023 at 01:11 PM.
To "nerdnic" above, The design of the tank is OK for a container but horroble for a pressure vessel. There are many creases and corners in the design to provide some rigidity to tank when pressurized but at the same time they present stress risers in the material which is where it will always fail first. For all you other pressure vessel design engineers out there , the well known tried and true shape for pressure is a sphere. Maximum strength , no stress risers (except at required openings) minimal material use, flexural strength easily calculated, etc.
Any shape that moves away from a sphere is a compromise or worse a horrible design. For an ideal design for an expansion tank look at VW and Audi's tank used on many models including the Lemans prototype race cars. It is a simple sphere. I have one on my Eurovan. It has 260,000 miles on it and it will probably be good forever given the shape and the coolant temp being probably 15 degrees cooler.
Coolant system failures on the road are not what I call a good day. Coolant system failures in your own driveway makes for an opportunity to have fun with tools.
Overall, this is very dooable for any DIYr but cripes... I want to meet the engineer who designed this thing. I am not sure if I should punch him/her in the nose or give them a reward for making an impossible situation doable.
Question: How long does it take for the splashed coolant on the engine and exhaust to fully burn off and not smell?
Some notes FWIW:
- The small crack in my old tank was all the way through... I could grab it with my nail... I don't know why I didn't pick this up before as it felt smooth. Yep, the tank was leaking.
- I removed the fluid from the tank using a thin vinyl tube... it has to be small to snake between the chambers. Took probably 10-15 mnts to siphon into a bucket... coolant initially tastes super sweet then you get a blast of awful chemical taste that sticks with you.
- Floyd is correct that everything pushes out of the way on a .2... I only disconnected the piping at the tank and no where else. That fuel line... I unclipped it from the engine compartment ceiling both near the tank and deeper near the fire wall... real simple. Everything pushed out of the way.
- How that tank clips and comes out is still a mystery to me. To get it out, I had to slide it all the way out. Then, after feeling the underside of the clip realized that you only have to slide it out until the "teeth" line up. So going in was easier, but then the bolt pin didn't line up. A good deal of cussing and then pop... in it went. Why? I have no clue how I got it out and back in. Cussing is required and, frankly, the only way to do this project.
- Suncoast's part number when I ordered was the old sequence number 03, but they ship the new 04.
- I recommend replacing the blue cap with a new one as they will fail... I didn't because I replaced my cap a few years ago.
- I did not drain the engine, I just disonnected the lines from the tank. The lowest hose, the one that feeds the engine will drip out some fluid... after re-connection and fill, I gave this hose a few squeezes and burped out the remaining air bubble. I don't believe I have any air in the system.
- You need a hose clamp removal tool. I own this one, about $10:
Regarding my Porsche-labeled engine mounts... I replace them at 96K miles and one was sagging. So now with the same miles on the new set, I suspected to see the same but the mounts were equal and appeared fine... this is odd. Anyway, I switched left for right.
Again, thanx all.
Peace
Bruce in Philly (now Atlanta)
Last edited by Bruce In Philly; 02-15-2023 at 09:32 AM.
I am sure you are satisfied and sleeping happily now. Yes, this job is awful and the design of that tank is pathetic.
Thank you for all the hints and for the specific list of cursings that needs to be used to turn this daunting work into a walk in the park.
Another good job and reporting. Cursing is always helpful and little to no blood loss is a successful day. The one big deal you did not mention was the all important "lowering of the engine." Siphoning out the tank first and only removing the necessary hoses makes for a no mess project. The coolant tank fit into the tray is only learned AFTER you do it. After removing the 10 mm bolt, slide the tank partway out (towards the engine) and lift straight up when the keystone shaped shoulders clear the slots and then slide completely out. the fact that keystone (trapezoidal ) shoulders cannot be seen does not make it easier . Study the new tank when you buy it and that helps on figuring out how it is mounted. Installing it requires getting the keystones lined up and then it literary falls into place, slide toward the left (outside) and install the bolt.
Be amazed. then connect hoses, level sensor, raise engine and bolt up motor mounts and refill with coolant and burp the air as you did. By this time you have thrown the old tank so far away that you don't want to go get it and study how it fits in the tray. Therefore the magic lives on.
To "docdrs" above; the life of the tank is like other plastic engine/cooling system parts. It is a function of heat history which is hours at operating temperature. Milage is a convenient measure. 100,000 miles and some will be ready to go, 150,000 miles and most of them will be failed and the last of the 3 sigma group will fail by 200,000 miles. I replaced mine at 100,000 miles Not an expensive part and they will fail.
Thanks for sharing everyone.
My 997.2 is at 43k miles and hairline cracks are developing on the coolant tank. You guys getting 100k miles plus should be happy it lasted so long. My Indy said I should replace it. I am going to replace my engine mounts soon so I might as well change the tank myself at the same time. Glad you swapped yours out successfully Bruce. It gives me the encouragement to do the work myself instead of paying the Indy shop. I was quoted $900. Glad the 997s are so easy to wrench on at home.
To Fatsix, 43 K miles is statistically low but still in the 3 sigma limits. If the car has been a daily driver in city traffic then the hours are greater than the rule of thumb of average speed driven of 35 MPH. In any event a crack is a failure and needs to be addressed. Since they will all fail, anyway replacing them now since they are 12 years old or more does not leave much money on the table. A good hose clamp tool made for the modern style spring clamps is the best advice you can get. The old days of "waterpump pliers" and the associated pinched fingers is a thing of the past. The remote control ones with a cable are great and since they rachet and hold the clamp open until released is worth the price of admission. DIY and be amazed at how the tank just sits in the tray after removing one 10 mm bolt. Brute force never works on this job.
The design of the 997 coolant expansion tank is not terrible. It's very similar to other Porsche/VW/Audi models I have seen. Some of the older Audi models I have seen use a spherical design but most do not. You should replace the expansion tank as soon as you see any signs of cracking, which is due to the heat cycling of the polymer. For this reason the life of the tank will depend on several factors like how the car is driven, what geographic location you live in (hot or cold), etc, etc. Some models also utilize a heat shield which can help.
This is what mine looked like when I replaced it on my 2014 Audi Q5 2.0T -- different model but FWIW exact same issue as you see on the 997 and other model expansion tanks and shows what it looks like:
This is what it looks like if you continue to ignore it and you will start to notice your coolant level drop:
Make me wonder why not use a different material (or just more material?) in the design.
02-10-2023, 12:23 PM
