Might you be thinking of shrink tubing/shrink wrap? I believe you
slide it over the wiring and apply a heat gun to shrink the material.
It is commercially available. I believe I saw some at Autozone in
their electrical department.

F

I don't know the name offhand, but the type we get looks like a roll
of electrical tape.  It is (was) from Wurth and the label was written
at least partly in German.  There are no unopened rolls left to look
at and my existing roll has nothing stamped on it.  Apparently the
only wording was on the discarded paper label under the plastic shrink
wrap.  Anyway, this stuff forms a cohesive bond, particularly when it
is stretched first.  It is kind of a PITA to work with in cramped
quarters.  There is a plasticy fabric release strip rolled up with the
tape since the tape material sticks equally on both sides.

I have two viable suggestions.

1) Clean the harness and wrap in regular electrical tape, then use two
small wireties, one at each end of the tape, to keep it from
unravelling.

2) My choice: remove the wires from the harness connector, then apply
shrink tubing, then replace the wires.  There should be plastic tabs
retaining the metal terminals, you need to pry on those tabs in the
correct direction and lightly pull the wires out one at a time.
Sometimes there is an added retainer mechanism, kind of like a tiny
comb, that needs to be pulled partially out of the connector body
before performing the above step.  You're smart, you'll figure it out
in no time (assuming you don't already know).  Just have a small thin
pick handy.

Toyota MDT in MO

PS  if you can find small diameter corrugated plastic tubing, that
would make a really durable jacket.

Rubber electrical tape will do this, its quite a bit thicker than
standard electrical tape.

I want to say self-vulcanizing tape / self-vulcanizing electrical
tape? Googling that looks promising.

Dave

3M splicing tape is the good stuff.  The local auto parts stores sell
some thin junk that sort of welds to itself, no it sticks to itself, the
3M stuff welds solid...

http://products3.3m.com/catalog/us/en001/utilities_telecom/electrical_contractor
s/node_GSG9JNTVZCbe/root_GST1T4S9TCgv/vroot_GSBCDFDZ1Zge/gvel_LJLFLP2Q4Dgl/theme
_us_electricalcontractors_3_0/command_AbcPageHandler/output_html

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08

Self-amalgamating tape.

Useful stuff, buy it from a car electrics specialist  (RS components or
Vehicle Wiring Products in the UK).

Be warned that there are several different rubbers that will do this.
Some work better than others for different purposes - for car work, you
probably want one that remains flexible afterwards, rather than ultimate
sealing. The car electrics place will probably have something suitable.

I know it as stretch tape. Go here http://www.mcmaster.com/ and use their
search engine. You'll probably find just what you are looking for. I use it
for supplies for work and I think that will sell to the general public. It
is a well done website that any gearhead will like.

You can get liquid electrical tape where you brush it on and let it dry. It
is not real pretty but it works.

You may be able to remove the metal connectors from the plastic housing so
that you can get shrink tubing on to the wires. All the ones that I needed
to work on have a tab that can be deflected with a wire, pin or other tool
then pull the connector out of the housing.

3M Rubber Splicing Tape. AKA "Self-vulcanizing tape." Also available
from other brands.

Great stuff, but be prepared to have to CUT it off. Also, it is a great
weather seal, but for long-term exposure you really should put it on,
then wrap the whole affair in regular electrical tape or something to
provide abrasion and UV/ozone resistance.