How to Make Custom Coolant Lines Using Exhaust Tubing

We take a couple of mandrel bent U-bends and get to work making our very own radiator coolant metal tubes

The only time a lowrider should sport a standard black rubber coolant hose is if you’re going for a full factory spec resto. Other than that, we don’t want to see one amidst a sea of chrome. It’s just not right.

That said, an aftermarket coolant hose is one of the first things you should add. It’s a simple detail that goes a long away so that’s what we’ll be talking about in this issue. For our LS, we decided to visit Summit Racing to see what they had and we then decided that making our own would be the best bet. To do that, we ordered a couple of 16-gauge, 1 1/2-inch-diameter mild-steel, mandrel-bent U-bend pieces. In addition, we picked up a 7 1/2-foot, 16-gauge, 1 1/2-inch-diameter piece of straight tube.

Once they arrived we got to work, and thanks to a bit of past welding experience—and a whole lot of patience and measuring—we made moves and finished off our custom coolant pipe in just about three hours.

Of course, buying an aftermarket stainless steel coolant pipe would be much easier and cost effective but you can’t beat the look of a well-crafted mandrel bent unit like the one we just built.

1. After browsing online, we wound up ordering two 16-gauge, 1 1/2-inch mild-steel U-bends (PN SCH-015016U) and one straight length (PN WLK-47980) of the same gauge and diameter exhaust piping from Summit Racing. All three pieces only set us back about $40.

2. Using a Sharpie, we marked the dead center of our first U-bend in order to create our first 90-degree turn.

3. To cut the U-bend you can use a hacksaw or a cutoff wheel but the best results come from using a bandsaw.

4. Clean whatever burrs may be left after the cut. You can use a wire wheel, deburring tool, or whatever’s handy.

5. Using hose clamps and a bit of 1 1/2-inch id hose, we then mocked in the first cut coming off of the water pump’s outlet to get an idea of where to cut the second piece going into our AutoRad radiator.

6. Using the other half of the U-bend tubing we cut earlier, a mark was made indicating where to cut the second piece of our hardline.

7. Using Eastwood’s Benchtop bandsaw made cutting the tubing quick and easy.

8. We mocked in both pieces of tubing and then marked a straight line from one to the other to ensure the correct orientation once we started welding.

9. Using our Miller Diversion 180 welder loaded with 1/16-inch tungsten, we used 1/16-inch rod and welded the ends together, making sure to get a good bead all the way around the tubing.

10. You can see the nice thick bead all the way around the tube. We weren’t concerned about aesthetics at this point.

11. We then smoothed the welds down by using an angle grinder topped with a 36-grit Rolox disc.

12. From there, we hit the welded area with a DA topped with 80-grit sandpaper to knock down the deeper scratches. Next, we went with 220-grit paper to get a smooth, uniform surface.

13. Even though there is a little more work to do here, you can see the weld beginning to smooth out. We eventually performed the same process on the entire piece to get a uniform look.

14. We did one last mockup before metal-finishing the entire tube.

15. For the lower hard line, we used the second U-bend and went through the same basic mockup and marking process as we did for the top hard line.

16. The space is a little more confined coming from the bottom of the radiator to the thermostat housing, so we needed to make the angled cuts a little more precise than we did up top.

17. Just like up top, we mocked in the bends and marked an orienting line where the two ends need to be welded.

18. The welding process is the same for the bottom hard line as it was for the top.

19. Here’s the bottom line all finished and looking sweet.

20. After about 3 hours and around $40 later, we were all done fabricating our coolant lines.