JNC Tip: Never Pull on Heater Core Hoses

heater_core_hose2Last month we found ourselves at the boneyard because of a stupid mistake I declined to mention. I guess it’s about time I swallow my pride. See that pipe above? It was once part of the heater core but in a moment of colossal idiocy I shucked it like an oyster, clean off.

Most old cars have little slider knobs controlling the cabin temperature. When you turn up the heat, they open the diverter valve, a Y-shaped pipe that routes hot coolant from the engine block into the cabin where it enters the heater core, a small radiator-like object. As the coolant snakes through the heater core, it emits the heat it carried from the engine up through the dashboard vents and into your face before flowing back to the cooling radiator at the front of the car.

Time has a way of hardening the sliders, and that usually means corrosion in the diverter valve is making it stick. We’ve known people who’ve endured petrified climate controls for years, but all you really need to do is douse the diverter valve’s insides with WD-40.

heater_core_hose1Unfortunately for us, Toyota uses a ridiculous clamp to attach one of the hoses to the diverter valve. It involves a cotter pin and a tightly wound ribbon of metal and is impossible to re-clamp inside the engine bay. The only option was to disconnect the end of the hose at the heater core, which had a normal clamp, and assemble it outside of the car.

But as you can see from the first photo, some overzealous clampsman on the Toyota assembly line went to freakin’ town on that sucker. The hose was squeezed so tightly that rubber spewed out like Play-Doh from a Fun Factory. And now, 23 years later, hose and pipe had fused into one.

But I had no idea, and the moronic thing was, while I was tugging on the hose I actually felt it starting to give way and thought, “Hey, it’s coming off!” Seconds later, a pop accompanied by a river of coolant. “Ha ha,” said Nelson Muntz.

heater_coreHere’s what an unbroken heater core looks like. The protruding pipe ends are pretty soft and merely brazed on. Sadly, installing this requires taking apart much of the dash. That is no fun. But if there’s a silver lining in any of this, at least it happened while heater cores were still relatively plentiful in junkyards. The hose wouldn’t have been any easier to remove 10 years from now, and by then a move like this would really put me up a creek.

So, um, yeah. Don’t pull on heater core hoses.

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13 Responses to JNC Tip: Never Pull on Heater Core Hoses

  1. Slag said:

    O god. I feel your pain, but at the same time am kinda glad (relieved is a better word maybe?) that other people go through the same sort of things I do.

    I think if this had happened to me I’d have been very close to just blanking off the hose and living without a heater . . .

  2. Sr-FairladyZ said:

    I bypassed mine in the S30. Mainly because when I got the car, the leaking heater core was the culprit to my rust hole in the passenger side floor board. I think the bypass was anger fueled rather then laziness. …6yrs later now with it still bypassed and a new cobwebbed heater core sitting in the shed I’ll have to put a check next to ‘Lazy’.

  3. Ben said:

    Well the new heater core ain’t in there yet… talk to me in 6 yrs. :)

  4. immorality said:

    I wish Cressida’s were plentiful in the junkyards around me!

  5. DIASISS said:

    you what!!!!!!????

  6. i have a bypassed heater core, with a new one in the trunk. maybe before this winter………………………….

  7. Brooks said:

    Couldn’t you just braze it back on? I mean, you’d still have to pull it out of the car, and set up a torch and all, but it seems easier than taking apart _two_ dashboards.

  8. BlownArrow! said:

    Brooks is right! I could have done it for you… duh…

    Oh ya, I was broke down on the side of the road running down the hill to catch my drive shaft
    that very same day….ugh..

    Unlike you I never made it to the yard…. :-(

  9. speedie said:

    I did the same thing while changing the hoses on my 84 supra. I learned my lesson though and cut the hoses off the one I got from the junkyard.

  10. Aaron said:

    Like Brooks says, why not fix it yourself? To my eye that looks soldered rather than brazed, which is why it pulled apart like that. 15 minutes with a propane torch, a roll of solder, and a can of flux would have fixed it. If you don’t feel like doing it yourself, a radiator shop would have been able to fix that easily. Then again, that’s my attitude because I live in MN where junkyards are not vast expanses of barely-rusted vehicles. Here the yards send stuff to the crusher to keep ahead of the rust.

    • Ben said:

      There’s also the danger that perhaps the core itself was in a similarly weakened state. I acttually pulled 2 cores from the jy. It never hurts to have a backup :)

  11. Brooks said:

    Well, if you kept the old one and solder/brazed it back together, you’d have a backup backup!

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