Sump glue

I’m Curious as to why we want to replace a standard sump gasket with a sealant? And is this standard practice for the rear and timing cover also?

Good question.

I suspect there are two main reasons, the first is there may not be a gasket actually used and the OEM uses a sealant goop, the second is the builders may have had problems with gasket leakage in the past - this is usually down to overtightening the fasteners and forcing the gasket out from between the surfaces, and it may be worsened by failure to check the sump face is flat.

The first is what it is, and the biggest problem is idiots people using WAY too much gloop and having it squeeze into the sump area of the engine, where it can break off and clog pump pickups. Eg. -

The second comes down to care when fitting - not over torqing the fasteners - some of the better gaskets will actually have steel inserts around the fastener holes, so it's impossible to overtighten it down. Eg. - https://www.moroso.com/catalog/product/view/id/8156/s/oil-pan-gasket93162/

Personally, I would normally use gloop on one side of the gasket to hold it in place during assembly, with a dab if there is a cover with a different height to assist sealing the transition. If the engine has to be split, the gasket will normally just stick to it, making clean-up easier and, if required, it to be re-used as it is unlikely to be damaged. However, others may have different practices.