When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
See small crack below. There is no leakage and it smooth when I run my fingernail over it. Not bad being original. This is the only crack I can see.
So... is there anything I can do to stop the crack from spreading and then failing?
I was thinking of making a patch of flexible plastic and "welding" it down with that PVC cement. That PVC cement really melts down both sides and then fuses them... more than a glue. This is all easy to do no?
BTW, doing some research, I am looking for an all-purpose solvent cement that does PVC and other plastics... any experience with this stuff? On my tank?
Peace
Bruce in Philly (now Atlanta)
Last edited by Bruce In Philly; 02-08-2023 at 02:30 PM.
Your research is best done in obtaining a new tank which will be a 996 part but the latest revision will end in 04. (996 xx....04). The tank is polyethylene or polypropylene , neither of which are "gluable" . The tank is past dead and waiting to let go. Trying to fix it is like trying to patch an old pair of blue jeans when the fabric is not only worn but actually rotten. Same as soldering up a throughly rusted thru gas tank, doesn't work.
Is this your original tank (which will end in 03)?
Remember to lower the engine enough to make this easy. Otherwise it will be a wrestling match which you will not win.
Oh, Floyd, you are such a killjoy. The one in my car is original.
I think this will be a cool experiment. The integrity of the cell wall has not been fully compromised. Seems like a patch would reinforce the pending crack. A simple, few dollar project. Are you sure the tank is polyethylene or polypropylene? Not ABS? Loctite Super Glue All is recommended for the poly-problems.
Does anyone know the difference between the 03 and 04 sequence number?
Killjoy here.
"It's dead Jim" Not sure of the movie or the song, but that is the answer.
PE or PP are very low surface energy. materials, making them difficult to wet and they are just too lazy to want to join in with anyone or anything. The tank is not ABS. The long heat history with water and coolant has degraded the base material.
When I replaced my tank (preventative maintenance) last year I did not see any obvious differences between the rev 03 and the 04 version. All of the new ones are rev 04. That makes it really easy to tell if someone has an original tank or not. With 30 years as a professional plastics engineer and knowing that those materials are not that great in the application, I changed mine out even though there were no cracks. Also the design of the tank could not be worse for a pressure vessel application.
When you get around to replacing the tank, there is nothing needed to be removed except the attaching water hoses on a 997.2 The other bits will move out of the way. The tank will come out easy if you lower the engine enough.
They make a jb weld called plastic weld, I'm not sure of they type of plastic its used on but i got a feeling it would work. I'd at least try it before ripping the thing out. Might last 5 minutes or might last 5 years.
My recommendation for replacement would be because you don’t know what the other side of the tank looks like. Also, as mentioned above I replaced with genuine rather than OEM. I know Raby has mentioned the genuine is better for this part than the OEM. Not sure if that’s true but for the bit of extra cost I figured it was worth it to not have to do the job over again.
Did you feel the crack after driving the car and getting the cooling system hot and up to pressure? If not, I bet you can feel the crack with your fingernail then.
The tank replacement job really isn't that bad. You may have to remove the rear bumper and heat shield, but the goal is to get a floor jack under the lip of the engine cross brace (don't support it from the sump plate), put it under tension, remove the two lower motor mount bolts, then lower the engine using the floor jack until the rear angles down until itnwont angle down any further. This will give you plenty of room to slide the tank out once disconnectws. Might help to have the rear of the car on jackstands too.
If you can get the jack to the engine carrier crossbar without removing the bumper and heat shield then you can skip that. My car, with the through-bumper exhaust doesn't let the engine come down with the bumper installed.
Ah right... ah right... I just ordered a new tank. You guys are tough. Where is your sense of adventure? Discovery? F'n something up beyond repair?
Suncoast again, $140 + $16 ship + 12 Tax = $168.49 FCP Euro was $183 without tax or shipping.
While I am in there... oh oh.... I will pull and examine my engine mounts. I changed my mounts at 96K miles so maybe they are due? At a minimum, I will swap them left for right as it appears one side fails (or compresses) before the other.
One last parting thought confirming you are taking the correct course: Even if still sound and not leaking, even if you successfully repair it, its very presence suggests it is highly likely to be other cracks where you cannot see them that might be closer to total failure.
The best 140 bucks you have ever spent. PP or PE can be "welded" by the traditional welding process of melting the parent material. However you don't have a simple small hole to weld. the parent material has degraded to the point of being useless. The degradation begins on the inside where the hot coolant is in contact. Again trying to fix it is like trying to weld rusty perforated steel. I have a long history as a consultant for spin and ultrasonic welding PP and PE and other resins.
We have two data points here from you and "graufuchs". Both of your cars have approx 6,000 hours at operating temp and pressure at full failure. That falls in line for those knowledgeable in the chemical/ heat compatibility of those resins.
Pete has a 997.1 which is different than your .2 . You don't need to remove the bumper or anything. You have a real metal engine sump to support with a board and floor jack when lowering. A good remote control hose clamp tool is very helpful but not essential.
Remove the coolant sensor, (quarter turn); remove the attaching coolant hoses to the tank,( emptying the tank with a turkey baster makes less mess) ; remove the one screw that attaches the tank to the side wall ; remove motor mount nuts/barrel nuts and lower the engine slowly until it hits on something,( maybe a cross brace) and then give it a small pump back up. This will give you room to slide out the tank. Study the new tank so you can understand how simply it fits into the tray. It is an up and slide out maneuver You can not tilt it ,twist it or fight with it.
Also on your .2, the other hard plastic vac lines that seem to be in the way will move by unclipping them from attaching brackets. You do not have to remove anything. . I have done this on my 2011 .2
Pete: I used the scratch test on a cold engine so you are probably correct about that crack. It looks like replacement is a bit easier for a .2.
Floyd: Thanx for the tips. I find it odd that the stress crack appears to be cracking from the inside, but I guess, to Pete's point, it really is cracking from the outside and I just can't feel it.
Bxtr: You really know how to feed paranoia.
BTW, I lowered my engine to do my water pump and the limit was some lines in the engine bay stretched straight so I know what to watch for.
Full disclosure: Last week, after a hard drive, I smelled some coolant. The coolant was down just maybe 1/2 pint.. very little but definitely a leak.. I thought the smell was coming from the front of the car but I hope now it is from the tank. I could not see any evidence of dried coolant.
So... safe to drive? She is out of town this weekend so I will use Her car.
Peace
Bruce in Philly (now Atlanta)
Last edited by Bruce In Philly; 02-09-2023 at 03:29 PM.
The material begins degrading from the hot side (inside) and loses its strength (tensile strength and flexibility ).and progresses to the outside. It is now no longer strong enough or flexible enough to withstand the internal pressure of the hot coolant inside. It is weak and brittle. The crack can be felt on the outside since it failed in tensile mode from pressure inside, hence the fingernail test. It has fully failed. To feed the paranoia (it gets hungry too) the tank is waiting to be away from home for the gala event of "thar she blows" and the associated festivities.
It is dead Jim (from star trek)
Disconnect the hoses to the tank first before lowering the engine. There should not be any pulling of any lines in the engine room' but is has to be low enough to make it an easy job, not an impossible one. Clearance will be fractions of a millimeter.
Does the new tank come with a new cap? Otherwise you might want to consider replacing that as well, with one of the later revisions, as it's also known to leak under pressure.
02-08-2023, 02:24 PM
Coolant Expansion Tank - Prevent Crack?
