Anyone know what the part number or size of the o ring for the plastic tube running into the top left(drivers) side of the radiator? Thanks.

 

I used one from this box when one of my small coolant line o-rings finally totally decayed. Don't recall which one exactly, but it fit and consequently works

225 Piece Nitrile O-Ring Assortment

and yes, nitrile is compatible with ethylene glycol

http://www.documentation.emersonproc...798x012_06.pdf

 

I noticed Harbor freight had a box of assorted O Rings for automotive use. Would these work as well any reason to spend the extra 4 bucks?

180 Piece Viton O-Ring Kit

 

Viton is also safe with coolant
Viton Chemical Compatibility Results

 

Is it for the s/c radiator or main radiator? I found these for the s/c rad when i was looking for a bleed hose recently, the main radiator may use different o-rings though.

Part no. KSR605001 | O-ring parts from Jaguar Classic Parts UK

EDIT: noticed you have an xj8. same still applies, I'm not sure if the O-ring i have here is the one you need.