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Thread: Broken Radiator Barb, Coolant Leaks, & Small Coolant Hose Diameter?

  1. #1
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    Broken Radiator Barb, Coolant Leaks, & Small Coolant Hose Diameter?

    I'm gearing up to do some more work on the delorean this summer, since I wasn't able to get it back to running last fall. My last thread was here: https://dmctalk.org/showthread.php?1...-Turbo-Edition

    I finished off the season by breaking the small, upper plastic barb on the OEM radiator that everyone says to be careful not to break! It's completely my fault for rushing things last fall when it was too cold to be doing any work. I tried to epoxy it, but just couldn't get it to set and hold (again, the cold probably didn't help).

    I figure I have two options. One is replacing the radiator + fans with shiny new ones. The other is trying to patch up my mistake. On one hand, the original fans are pretty ratty (the battery voltage dips when the radiator comes on - maybe lower amperage fans might help), and it would be nice to have a new radiator. However, doing some research it seems like quite the pain and I need to plan on getting a new rock guard and some other replacement parts... Really, I'm trying to converge and get this thing running since it's been down for over a year now, so I'm leaning towards a patch job.

    I'm thinking I can find the correct size barb I can drill, tap, and epoxy a new barb fitting in: https://www.mcmaster.com/barbed-fitt...for-chemicals/

    Can someone help me find the ID for the small small hose? Has anyone tried a patch job like this?

    Further, I'm struggling to get the new silicon coolant hoses not to leak, even with new hose clamps. I think the OEM aluminum hoses are a bit pitted and coolant is finding a path out, even with the hoses clamped. My current plan is to smear some JB weld on the ends of the pipes and then sand them down smooth. Thoughts on this? Maybe there is a sealant I should use for the silicone coolant hoses?

  2. #2
    Senior Member Rich's Avatar
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    Quote Originally Posted by kdumont View Post
    Further, I'm struggling to get the new silicon coolant hoses not to leak, even with new hose clamps. I think the OEM aluminum hoses are a bit pitted and coolant is finding a path out, even with the hoses clamped. My current plan is to smear some JB weld on the ends of the pipes and then sand them down smooth. Thoughts on this? Maybe there is a sealant I should use for the silicone coolant hoses?
    I had a similar issue after an all silicone hose upgrade. Plus one issue not with pitting but with silicone hoses. First was a leak at the end of the lower right rad pipe next to the radiator. I had correct silicone clamps but the pipe was slightly pitted. Several things to look at to fix this.

    a. Be sure you have clamps designed specifically for silicone hoses, not just any new hose clamps. Just google "silicone hose clamp" or buy them from a D vendor. Do not us a traditional clamp like this one.
    b. The pitting near the end of the pipe is very likely part of the problem, as you suspect. My solution was to buy a replacement pipe. No pits. You might try putting the hose onto a portion of the pipe that isn't pitted. See if your hose will go on further than normal.
    c. Go back to a rubber hose. I had silicone hoses leak on all 3 ports of the bleed adapter tee (next to hot water valve). New metal tee, new silicone hoses, correct clamps. Leaks. Went back to rubber hoses for those 3 short hose sections. Same clamps and tee. No leaks.

    About (b), I first tried sanding and filing the pipe at its end to eliminate the pits. I then decided going deep enough to get to good metal would leave the pipe without enough strength such that the hose clamp might crush the pipe.

    I considered the glue-and-sand solution for the pipe pitting. I doubted it would work. Glue isn't a great barrier material and the bond may not be great, long term. One last idea - a good welder could weld over the pits, then grind or file the high spots down til it's smooth enough but with original OD? A new pipe was easier for me.
    Last edited by Rich; 05-21-2022 at 06:39 PM.
    March '81, 5-speed, black interior

  3. #3
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    I recommend the new radiator and fans. I went with the DMCH radiator and it fit right in. I used Toby's fans and they have worked well. Like you, I was concerned about removing the rock guard and AC condenser. Folks on this forum assured me I could fit in the new radiator without removing them. They were right. Radiator slipped right in. I did put some nutserts in the top of the radiator connections for the fan shroud. Those nuts and bolts are hard to get to otherwise.

    There are a couple of reasons I would suggest the new radiator: First, repairing the plastic barb is near impossible long term. Given the heating and cooling cycles of the coolant system combined with the pressurization and depressurization, epoxy will likely not hold up over time. Second, plastic end caps of the OEM unit will eventually leak. I performed a pressure test to 15 psi and observed the weeping at the seams of these plastic endcaps. Convinced me to change out the radiator. This is a common failure of the original units.

    I certainly don't want to stifle innovation here. I've made some incredible repairs with JB-Weld. I tend to only remember the success stories.

    Ron
    Last edited by DMC-Ron; 05-22-2022 at 08:47 AM.

  4. #4
    Senior Member AugustneverEnds's Avatar
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    Quote Originally Posted by DMC-Ron View Post

    I certainly don't want to stifle innovation here. I've made some incredible repairs with JB-Weld. I tend to only remember the success stories.

    Ron
    Truth!!
    Nick A.

    1988 BMW 325is
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  5. #5
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    I agree with not stifling innovation but the best thing to do is replace at least, the radiator. You can do the fans later if you feel it is necessary. Silicone hoses are nice but the rubber ones do seem to last a long time.
    David Teitelbaum

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