Why not just fix seal on expansion coolant tank?

[Spdu4ia]

This might be a dumb question but why replace the expansion coolant tank everytime it seems to seperate at the seam? why not put some sealant on it, rtv , etc? Is there a reason I am not seeing that this wouldn't work. It can seal fluids into the engine why not that too , its just plastic.

[FSETH]

You can give it a shot, but at $80 and as easy as it is to DIY, I would just replace it. You will probably only have to do it once over average ownership. Maybe twice if you keep cars for a long time. The cooling system is pressureized, so I would trust the new part more than a sealant.

[Spdu4ia]

I think i'll go ahead and order a new one and put some sealant on the one I have that way I can test my theory and have a back-up plan. Thanks.

[CharlieHustleX5]

Silicone wont seal plastic. Plus with the fluid and temperatures exposed to the sealant, its bound to fail. Silicone is more of a liquid forming gasket as opposed to a seam sealer. It lacks the adhesive to seal a plastic seam. Plus, the expansion tank plastic is too smooth, there's nothing for the silicone to grab a hold onto and seal. Silicone will not seal a splitting plastic seam. Even with it plugging the seam, there is nothing closing that seam up or holding it together. the pressure of the cooling system will blow the silicone out.

[Weasel]

Also don't forget, this isn't the overflow tank in an old american vehicle that just holds water... This tank is in the pressurized cooling system and gets the full pressure of the cooling system at operating temperature. I have seen many of failed attempts to repair, but not a one yet held for more than one or two rides, much less a normal days driving.

[flatlander]

Originally Posted by Weasel

Also don't forget, this isn't the overflow tank in an old american vehicle that just holds water... This tank is in the pressurized cooling system and gets the full pressure of the cooling system at operating temperature. I have seen many of failed attempts to repair, but not a one yet held for more than one or two rides, much less a normal days driving.

You can try to seal it while you are waiting for your replacement tank to arrive, but I've never been able to get it to seal. This coolant system is not forgiving at all.

[Spdu4ia]

ordered a new tank last night then went outside and put some RTV sealant on it and let it sit overnight. Even if it doesn't work i'll be replacing it soon. I'll be out $3 for the sealant