Repairing expansion tank

[75_Steve]

My 75 has a very thin, hairline crack in the expansion tank.

It's not leaking a lot of coolant, but it does, over several weeks, lose enough to drop from max. to min. level.

I'm out on the track next Saturday and want to stop this leak, in case it gets worse under pressure.

Any recommendations of a product I can apply to fix it?

[GavinPearson]

The problem is that joining the plastic will be very difficult - to get the plastic to bond you need to have the area in the crack totally clean and dry. This will be a tall order.

I think there are two routes to fix this, neither of which you will like.

1) Fit a replacement.
2) Encapsulate the entire reservoir save for the openings with Glass mat & Epoxy or less preferably chopped strand mat & polyester resin.

[75_Steve]

Well, I haven't got time to find a replacement - they're not available new and most used ones are as yellowed and brittle as mine.

I've just bought some Plastic Padding 'Leak Stop' - sanded the area around the cracking down and applied a layer of it.

We'll see if it lasts - if nothing else it should stop the cracking spreading and getting worse.....

I've already done a track day with it like this, and didn't lose a lot of coolant, but I'd prefer to do something to try and help things.

[wildoliver]

Second the fibreglass I did it on 924 it worked a treat after I redid it a second time (think it was dirty first time). Also excellent at mending pitted fuel tanks!