Tank cleaning advice needed

[1976RD400C]

I'm getting this tank ready for a paint job and somewhere in it's life it was sealer treated. I'm not sure why it was done, I don't see any rust on the seams underneath. It seems hard but looks like of funky. Anyone know what kind of sealer it is? Should I get it out of there? How do you do that? Then what, check for leaks and reseal if need and with what product? Thanks.

[Organicjedi]

I would leave it unless it's causing problems.

Always use inline fuel filters for the extra insurance.

[Hawaii-Mike]

I agree, if it's not flaking or peeling, leave the liner in.  If the liner starts to come apart and you have fuel filters, they will catch the junk.

[m in sc]

if you don't trust it, throw a thin layer of caswell on top of it after you rinse it out with acetone. yes, you can actually do that.  but, if its not flaking id leave it alone. 

[klaird]

It looks like cream was used to line the tank.  MEK will dissolve cream, of course it will also dissolve any paint it contacts but since you are getting it repainted no worries.

[pidjones]

If it is Kreame, just acetone will dissolve it. Fill with acetone ans let it set for a couple weeks, pour out mud.

[1976RD400C]

After looking down in there closely I see 1/2" pieces of the liner flaking off so I dumped 1/2 gallon of MEK in and swished it around. Checked it a couple hours later and the MEK was working great. Let the tank lay on one side for a while and then switched to the other. Tilted forward for a while then back. Swished it now and then. One day later and all the liner was broke down. Tomorrow I'll dump out the MEK and pressure wash. I think all the liner will be gone.