In article . com,
"Joseph" wrote:

....... I want to tidy up the wirings in the engine compartment
of a car to isolate grounding problems. I am hoping to use shrink wrap
tubings to insulate all the lose electrical signal wires.

Joseph-

I believe the normal temperature in an engine compartment would not hurt
heat-shrink tubing. Perhaps it would be damaged if it touched an
exhaust manifold, but otherwise not likely.

That said, there is a flexible tubing for sale at auto parts stores,
that may be better (easier) for your application. It has a slit along
its length so wires can be easily inserted, removed or brought out at
intermediate locations.

Fred