Interior heater pipe in center tunnel - Advice?

[79X19]

By now many of you have already seen my thread about replacing the coolant pipes on my '81 FI car. I've elected to go with the B&W 304SS replacements including the external heater tube. My question is about the internal heater tube that runs in the interior center tunnel from about the emergency brake handle to just past the accelerator pedal. I have replaced the heater hose from the engine to the connection point at the e brake but I am concerned about the condition of this 3-4' interior pipe. The outside looks good and the end that's connected to the heater box looks solid. The end of the pipe by the e brake was corroded at the 6 o'clock position but not bad. How have others dealt with this pipe? Its welded in place so replacement is all but impossible. I was thinking of bypassing the tube altogether and used brass hose menders to complete the connection to the heater box. If I dont have to address it I really dont want to and leave it alone. I've replaced every other pipe and hose other than this one and Id hate to have an interior leak after a complete interior resto. Thoughts?

 

[Dan Sarandrea (Phila)]

By now many of you have already seen my thread about replacing the coolant pipes on my '81 FI car. I've elected to go with the B&W 304SS replacements including the external heater tube. My question is about the internal heater tube that runs in the interior center tunnel from about the emergency brake handle to just past the accelerator pedal. I have replaced the heater hose from the engine to the connection point at the e brake but I am concerned about the condition of this 3-4' interior pipe. The outside looks good and the end that's connected to the heater box looks solid. The end of the pipe by the e brake was corroded at the 6 o'clock position but not bad. How have others dealt with this pipe? Its welded in place so replacement is all but impossible. I was thinking of bypassing the tube altogether and used brass hose menders to complete the connection to the heater box. If I dont have to address it I really dont want to and leave it alone. I've replaced every other pipe and hose other than this one and Id hate to have an interior leak after a complete interior resto. Thoughts?

Have any buddies that are plumbers? They test pipe like that all the time for leaks.

You can also get a cell phone endoscope to do a visual. The better ones are HD and you can get WiFi ones, too.

 

[kmead]

You might run a second pipe in the bottom stacked on top of the normal pipe alongside the coolant pipes. This was done by another member recently.

Alternatively you could run the return line down the outside alongside the tunnel and change the internal line to the supply line.

In either case you could just abandon the original line inside the car.

 

[Dr.Jeff]

On one of my X's that heater pipe started leaking (rotted from the inside). And when that happens it's worse than when the other pipes leak. Because it not only floods the tunnels, but the floor pans on the inside (under the carpet), the seams along the sides, etc. If you have the interior out, and are going through the work to replace the pipes underneath, then I'd also replace/bypass this one. As Karl suggested, either run two heater pipes stacked on top of each other in the lower tunnel, or add the second one alongside the tunnel on the outside. See Darin's thread "Project Overkill" for how the two were stacked in the lower tunnel. I've never quite figured out the logic behind Fiat's routing of the heater lines throughout the car, lots of weirdness going on.

 

[kmead]

Some of the logic is that holding the supply and return tight to each other transfers heat from the one to the other. Meaning the returning cooled heater fluid cools the arriving heater fluid, and vice versa. We can easily argue how much actual transfer happens between two partly contacting pipes in amongst other pipes.

Now the assumption in the schema of the cooling system is that if there is flow through the heater core, then returning fluid from it which is dumped directly into either the water pump (older cars) or farther upstream and mixed with other cooler coolant (later cars) that it is actually cooled coolant by heating your ambient air.

Thanks for finding/remembering the thread, I was at an airport waiting for my next flight and ran out of time.

 

[carl]

I was able to remove that pipe, it's held in place with a few welded on clips and I was able to access them through the various holes in the top of the tunnel (shifter hole, e-brake hole). I seem to recall it was a combination of Dremel cut off wheel and just flexing back and forth to fatigue cracking the clip sheet metal. All very fiddly and your hands look like you will have been playing with a thorny rose bush when you are done. This was my Rat X so the replacement hose was just run along the outside of the tunnel by the passenger seat. Running both lines in the lower tunnel would seem like a very doable repair.

 

[darwoodious]

Some thoughts on easy to hard:

Easiest: get it tested for leaks (you could do a leak-down test yourself or probably find someone that can do it). if it doesn't leak, just hook up the heater tubes and roll with it.
Harder: so if it leaks or you don't trust it, next easiest is to run a hose parallel to the inner heater tube and ignore the corroded hard pipe. two adapters at the both ends and you're good. seems there should be enough room in there
Hardest: pull out the old line and put in a new line. you might want to consider pulling the carpet on the passenger side and drilling out the spot welds for the tube. next hard part is you need to remove it from the car. I *think* you can pull it out thru the back of the tunnel by removing the cover that houses the parking brake rollers. then you can bend the new 5/8" tube and spot weld it back to the brackets, put the brackets back and spot weld them back on. you could also skip the welding and attach the tube to the bracket with clamps and drill thru the brackets and bolt it up. yes, harder to do for sure.

The brackets will slide off the pipe and you could just ignore that it moves in there or use adhesive. I took a couple photos of the pipe I pulled out for reference as well as the side of the tunnel where I drilled out the spot welds.

 

[79X19]

Thanks all for the reply's. I think ill elect to run a hose with hose menders as suggested as the "Harder" option from darwoodious above. Even if the pipe is good now it doesn't mean it will be good 5 years from now. I'll feel better if all the components of the cooling systems are new. This is the last in line. R.I.P. pipe and run rubber heating hose. My B&M cooling pipes arrive next week. Cant wait to get them installed so I can start this thing for the first time in two years.

 

[Dr.Jeff]

The timing of this is almost spooky (Halloween reference).

Today at the SEMA Show I was discussing the making of hardlines for AC installations (to replace long runs of flex line). The engineer I was speaking with does most of the R&D for one of the big aftermarket A/C - Heater companies. In our discussion he mentioned the difference in heat transfer between hose and hard line (much like we've discussed between copper and SS pipes). He went on to tell about a recent event he experienced on one of his builds. When adding a second "rear" heat/ac unit to a vehicle, he discovered the heater was not working well at all. Finally traced it down to the fact he had used hard lines for the heater as well as the AC. There was so much heat transfer with metal lines that the heater had little "heat" output. After switching them to rubber hoses the heater performed excellent. I wonder if the X's heater will be much more efficient with rubber hoses than the stock metal lines?

 

[darwoodious]

I always thought the X had a perfectly suited heater for the interior - even with the top off. While I do live in the very temperate zone of Seattle, it does get hot (over 100˚F) and cold (10˚F), the heater was never substandard. The hardline in question is both inside the vehicle and under 4 foot long, so no worries there.

A/C is a totally different beast I suppose tho. Seems that the valve is very close to the evaporator(?) so no non-interior loss of cooling.

I think your decision is a good one @79X19 . Best of luck.

 

[carl]

My Bertone has 100% rubber heater hose runs for both hoses and my heater is pretty effective, even the rubber hose gets pretty hot. Fiats traditionally have very effective heaters, I remember a track day in my 128 on a 15 degree day with the mandatory windows open policy and the car was quite comfy.

All this heater pipe replacement talk had me in a real panic yesterday when I saw small coolant puddle under the 77 X and thought is was dripping out the coolant pipe box under the car...fortunately it was just a loose radiator pipe drain bolt.

 

[79X19]

I've successfully replaced the internal heater pipe by bypassing it with 5/8" heater hose. Had to navigate a few hurdles but its finished and I'm confident it will be a suitable long term fix. When using a rubber hose and not removing the old heater tube you need to be mindful of the E brake mechanism, the shifter linkage and the accelerator linkage. You need to place the tube in a way to avoid all of these mechanisms to avoid wear on your new rubber hose. Also you need to be mindful of the temp that the hose could get to. With that I choose to use Stainless Steel cable ties purchased at Home Depot to hold it in place. Pics attached explain it all.

 

[darwoodious]

well done and great photos of the work. can't see this not outlasting the life of the car.

 

[Dr.Jeff]

Yes, excellent job and pics.
I like the use of SS ties to secure the hose.
I have not looked to see, but if the new hose was long enough could you go all the way on each end to the related fitting (at the heater and engine) to eliminate the joints/barbs? In other words not use the factory rubber ends, but just bend/curve the new hose to fit in their place - all one piece?

 

[79X19]

Yes, excellent job and pics.
I like the use of SS ties to secure the hose.
I have not looked to see, but if the new hose was long enough could you go all the way on each end to the related fitting (at the heater and engine) to eliminate the joints/barbs? In other words not use the factory rubber ends, but just bend/curve the new hose to fit in their place - all one piece?

Dr Jeff. I thought about connecting the engine directly to the heater box without hose menders. Since I already replaced the hose from the engine to the steel pipe connection under the e brake handle and the formed hose from the center tunnel to the heater box I wasn’t too keen on it for it for a couple reasons. The first is I already wrestled with replacing the aforementioned hoses and they were difficult to do. Second the bends in the formed hose under the heater box wouldn't be easily replicated. Its for those reasons I decided to use the brass hose menders. Now if I was starting this whole process from the get go I would surely have considered the one length of hose fix. I wonder though if wrestling 8-9' of continuous heater hose with a memory curve to it, through all those twists and turns, through tight spots and curves if it would have been too arduous of a task. I'm sure its doable but I would have suffered carpel tunnel, arthritis and a slow death from the 1000 little digs and cuts to my hands and wrists resulting in a severe case of tetanus!

Sorry, got carried away there at the end but we all know working on these little beauties isn't easy.

 

[Dr.Jeff]

I completely agree. I actually had the same thoughts as I typed my earlier statement about it. But I wanted to throw it out as food for thought. I think it wouldn't be too difficult to include the engine end of it as one piece (assuming you are starting from scratch, as you say). But I agree that the heater box end may have too much curve to it to allow for that. Great work.

 

[79X19]

Thanks Dr Jeff. Appreciate your point of view, you always keep us thinking!

 

[dllubin]

I've successfully replaced the internal heater pipe by bypassing it with 5/8" heater hose. Had to navigate a few hurdles but its finished and I'm confident it will be a suitable long term fix. When using a rubber hose and not removing the old heater tube you need to be mindful of the E brake mechanism, the shifter linkage and the accelerator linkage. You need to place the tube in a way to avoid all of these mechanisms to avoid wear on your new rubber hose. Also you need to be mindful of the temp that the hose could get to. With that I choose to use Stainless Steel cable ties purchased at Home Depot to hold it in place. Pics attached explain it all.

Great write up. I plan to do the same thing except with one continuous piece of hose since the existing ones are factory original. My pipe started leaking where the bracket was welded on to it by the e-brake. They must have let the metal get pretty thin there as the rest of the pipe was not too bad. It originally not leaking, but my pressure test seems to have opened it up. Probably would have gone soon on it's own.

 

[Dr.Jeff]

It originally not leaking, but my pressure test seems to have opened it up. Probably would have gone soon on it's own.

Once in awhile when servicing the cooling system on my older cars, it causes a new leak. As you say, it was about to go already and better to find it now than somewhere remote.

 

[dllubin]

Some thoughts on easy to hard:

Easiest: get it tested for leaks (you could do a leak-down test yourself or probably find someone that can do it). if it doesn't leak, just hook up the heater tubes and roll with it.
Harder: so if it leaks or you don't trust it, next easiest is to run a hose parallel to the inner heater tube and ignore the corroded hard pipe. two adapters at the both ends and you're good. seems there should be enough room in there
Hardest: pull out the old line and put in a new line. you might want to consider pulling the carpet on the passenger side and drilling out the spot welds for the tube. next hard part is you need to remove it from the car. I *think* you can pull it out thru the back of the tunnel by removing the cover that houses the parking brake rollers. then you can bend the new 5/8" tube and spot weld it back to the brackets, put the brackets back and spot weld them back on. you could also skip the welding and attach the tube to the bracket with clamps and drill thru the brackets and bolt it up. yes, harder to do for sure.

The brackets will slide off the pipe and you could just ignore that it moves in there or use adhesive. I took a couple photos of the pipe I pulled out for reference as well as the side of the tunnel where I drilled out the spot welds.

View attachment 16422 View attachment 16423 View attachment 16424

Your photo of the spot welds just saved me a bunch of time today. Thanks much! I drilled those locations and pulled the old pipe out through the hand brake opening. This required bending the pipe slightly but it was headed for the recycle bin anyway. I used a continuous piece of 5/8" heater hose from the engine to the heater core. I'll be using some ties and/or clamps to keep the hose attached to the passenger side of the inside of the tunnel wall to keep it away from the shift linkage. There is actually more room on the driver side of the tunnel with the 4 speed as the linkage doesn't move very far in that direction. I'm reserving that space for a rubber return line in case the condition of the one under the car is worse than I thought.