> The plastic cooling lines are leaking at the ends, and as hard as I try I
> can't seem to get the clamps tight on the tubes.

Might be you have a classic case of "stiffener slip". The plastic pipes have
a metal stiffener molded into the last couple inches. The stiffener keeps
the clamps from collapsing the pipe. Over time the raised rib section at the
end of the pipe can separate from the pipe body, allowing the stiffener to
sloooooowlyget "squeezed out" of the pipe. After a while you end up with
pipes that look like this:
<http://raq.foodhammer.net/pics/pipes1.jpg>
No amount of tightening the clamps is gonna get a good seal on that exposed
metal stiffener.

I've been looking around the internet for replacement lines, and have
> stumbled upon an E-Bay listing for a set of stainless steel replacement
> coolant lines.
>

From what I hear, Terry makes good replacements. Pricey, but very good. If
you don't want to lay out all that cash, you can go the alternate route (as
I did). Get a propane torch and very slowly bring the end of the plastic
pipe up to temperature and, when the plastic gets soft, push the stiffener
back in:
<http://raq.foodhammer.net/pics/pipes2.jpg>
Good as new (almost). GoWesty sells a kit to keep them from extruding again.
It consists of brass inserts than clamp into the hoses and block the steel
stiffeners from coming out. They explain it better than I can:
<
http://www.gowesty.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=251-121-399KIT&Category_Code=mp-h20
>

FWIW, my pipes were only extruded in the front.

--
John Bange
'90 Vanagon - "Geldsauger"