What size hose do I need to bypass the heater core?

toddr124

toddr124

Hagerstown, MD
I drove the X1/9 about 250 miles yesterday and as I pulled into my garage the heater core went BOOM. The car filled with steam and the smell of antifreeze. Seems strange since the heater was off at the time.

I want to bypass the heater core. What size hose do I need to this?
 
There was a thread about this a few weeks ago...

I think the conclusion was that blocking off the ports was preferable to looping them....
 
Well... you can also use the existing hose...

... and loop it back in the engine compartment.

I never heard of blocking the ports... but with the core valve in the OFF position, its essentially the same thing... so it wouldn't hurt.

Looping the hose is the simplest and easiest and easy to put back once you replace the valve and or core... There is a "junction" and two clamps on MOST cars near the right side cover next to the cam belt cover... which is a point that is generally easy to get to.

Sorry for your trouble...
 
Just did it

On my '86 1.5 it was 5/8. It was my thread a few weeks back.

I used Dorman/Motormite/HELP! number 02252

dorman02252rw5124261854.jpg


And some Gates Powergrip clamps.

Clamp em here

10063456.jpg


And here

18882648.jpg


And then have a beer :)
 
Last edited:
noobie q

Is the heater core plumbing independant of the rest of the cooling system then? If a guy had a stuck heater control valve, he could do as above until he could get to it, and prolong the work and such while still driving around......yes? I need some of them cap thingys.
 
jvandyke said:
Is the heater core plumbing independant of the rest of the cooling system then? If a guy had a stuck heater control valve, he could do as above until he could get to it, and prolong the work and such while still driving around......yes? I need some of them cap thingys.
Click to expand...
Yes and yes. They are separate from the main coolant hoses/pipes. As suggested by other members in my bypass thread I left my heater hoses in tact and in the car in case I want to fix the heater at some point.
 
Stuck open or closed?

jvandyke said:
Is the heater core plumbing independant of the rest of the cooling system then? If a guy had a stuck heater control valve, he could do as above until he could get to it, and prolong the work and such while still driving around......yes? I need some of them cap thingys.
Click to expand...

Hi Jeff,

Is your valve stuck open (heat all the time) or closed (no heat). If it is stuck open, you could put a ball valve in the input hose back in the engine bay. That would allow you to turn the heat on and off in case you need heat occasionally. It's not convenient to use, since you have to get in the engine bay to open or close the valve.
 
It's stuck open so heat all the time. A valve in the bay isn't too bad. My Midget has that now. I'll likely replace the original valve. They aren't too $$ and seem relatively easy to get at. This is not a priority at the moment (been cool here) but when it gets warm, it could become a priority fast.
 
Thanks for the part #s and pictures.

This is what a poor mechanic like me needs.

Anyone have a step by step (with pictures) instructions to change the heater core? Please?
 
Depends on the year...

And whether your car has A/C.

Keep in mind those caps are not as strong as a heater hose (which is usually braided) and also do not last as long in under-hood conditions. Consider replacing them yearly.

Another stronger option is to run a hose from one location to the other, like a very short heater core circuit.
 
Chances are it's not the heater core

toddr124 said:
This is what a poor mechanic like me needs.

Anyone have a step by step (with pictures) instructions to change the heater core? Please?
Click to expand...

Chances are it's not the heater core that you'll be replacing, because in your original post you say "Seems strange since the heater was off at the time". If I recall correctly (away from the car right now) the valve is right at the inlet to the core, so with the valve shut there's no flow into the core. I'd look for a problem with the valve or the hose right at the valve first.

- Do the blockoff in the engine bay, like the other postings have described. That will give you a drivable car with no heat.

- Then find exactly where the leak is, by inspection and by running cold water from a hose into the inlet hose at the engine bay. If you're lucky it won't be the core.
 
Common failure mode is the valve

As already mentioned. Of course, bypassing the heater core circuit and rinsing out with water, makes for a nicer repair experience. :D
 
tfphoenix said:
On my '86 1.5 it was 5/8. It was my thread a few weeks back.

I used Dorman/Motormite/HELP! number 02252

dorman02252rw5124261854.jpg


And some Gates Powergrip clamps.

Clamp em here

10063456.jpg


And here

18882648.jpg


And then have a beer :)
Click to expand...

DANGER!
In about a year the end will fall out of those plugs.
They are best for emergency repairs, do NOT trust them!
 
don't forget to separate flow and pressure.

If your radiator cap and other pieces are working correctly you should have from 0-gauge to 15 gauge psi in the system. The radiator core is still connected on the return side even if the hot water valve is "closed"...." (closed is in parenthesis because these valves seldomly perfectly close). My point being that even though hot water might not be flowing to the heater, there is still system pressure in the core (maybe slightly lower than system, but still there). That doesn't mean its the core, just something to consider.
 
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