I noticed a very small coolant leak coming from overflow area. It would drip down onto the frame, then onto sway bar, then onto ground. I could never find where it was coming from. When I replaced the front shocks and springs, the plastic tube from radiator to overflow resevoir snapped in half. Damn. I ordered a replacement, and the leak has disappeared . So I was wondering if anyone has replaced the "fragile black plastic " return line with something more solid, and resistant to heat??

 

I used a long piece of fuel injection hose. You can use any rubber fuel/coolant hose of the correct diameter, I just happened to have injection hose on hand.

 

I used rubber fuel line.

 

Rubber fuel line is a bad idea, it is not rated for the temperature. SAE J30 hose is only rated for 212 F, You need to use SAE J1532 transmission cooler hose, rated for 302 degrees F. Double check what they hand you at the parts store because they almost always hand you fuel hose. The fuel hose gets soft at high temperature and will rupture, bad voodoo.

 

You want 5/16" or 8mm ID for the replacement hose.

 

There are different types of fuel hose. Extinct is spot on that NBR is only rated for 100°C, and while good for most of us that have addressed our inadequate cooling systems, FKM grade (which is BMW spec) is good to 200°C. Unlikely you'll get handed that at a parts counter without requesting it however.

Additionally, if you're consistently going over 100° then you should get the inline thermo mod anyway and then you can use either.