Coolant leak from channel under floor

Todd968

Todd968

Daily Driver
I noticed a coolant leak the other day after a drive. It was coming from the engine-end of the boxed section of the floor that houses the coolant and heater tubes, on the heater side (passenger side) of the box. I had recently got my coolant hoses replaced and noticed a gurgling sound coming from the heater core behind the dash, since. Haven't noticed any coolant inside the car on the floor but smell it a little.

Is this leak more likely to be coming from the hidden boxed section of the pipes or could it be from the heater core and migrating to that area? I really don't want to have to fix that channel. The car has 27k miles and has VERY little rust. The pipe section that is visible is rust free as is the floor section.

Any thoughts or advice?
 
There are heater hose connections inside the tunnel, maybe one of them is loose/leaking.

Most of the major auto parts stores have loaner cooling system pressure testers, pick one up and try to reproduce the flow.

If it still looks like it's coming from within the tunnel, with the aid of a flashlight and inspection mirror, you can see the feed/hotside heater hose to metal pipe connection if you remove the rubber tunnel cover inside the spare tire well. You can see the front heater hose to metal pipe connections under the heater core by removing the sheet metal cover and peeling back the carpet Velcro joint and then use the flashlight and inspection mirror.

Much better to be a hose or connection failure than an issue with one of the metal pipes springing a leak!
 
coolant leak

three tubes run under the car in the tunnel. two for the radiator and one for the heater. knowing the fact that fiats are notorious for crappy steel, one might have a pinhole that can't be seen, but heard with a pressure tester.
best of luck finding the source. on one of mine, I had stainless tubes bent to replace them. and on closer inspection, they had all kinds if pin holes that leaked under pressure.
mikemo
 
Checked the rubber hose to metal hose connection under heater core and it looked fine. The rubber /metal hose connections for the three hoses to the engine side of the channel under the car are all "outside" of the channel box, leaving me to believe there is a hole in one of the pipes inside the channel.

I haven't pressure tested but not quite sure the benefit that will bring me. Unless there is another rubber hose to metal connection within the channel, logic says it's a hole in the metal pipe(s). Right?
 





I pried the edge of the tunnel and looked inside but could see much other than wetness. As you can see on the other photo, the hose to pipe connections are outside of the tunnel.
 
What about the one that comes off the head, goes thru the firewall, snakes around the FI control box, thru the spare tire compartment, and goes down thru the rubberized cover into the center tunnel. I'm 99.99% sure that hose connects to a metal pipe inside the tunnel. Did you check that one, too?

175499a3-6776-43e2-8993-b66b210c9b13_zpsjmr7chtr.jpg
[/URL][/IMG]
 
Yes, looked down there with a camera and didn't see anything leaking. That access panel is a good 10 inches to the rear of the back end of the tunnel so access and visual would be next to impossible I think.
 
Todd, the cost of a FREE loan of a pressure tester...

is "nothing" and you can PROVE conclusively where the problem is. Why would you not move away from assumption and "logic"?

Secondly... as Mikey stated, you can open up the trough and replace the pipes with SS custom bent ($550+) or you can saw off the ends and slide in 1 inch copper house pipe, sweat on some 45 degree fittings and be all in for about $100 bucks.

Generally, those new copper pipes will last forever. HTH.
 
water pipes

I thought about going copper too. but having a bumper fall of the front my first 74 and the damage it caused to the tunnel and to the pipes and my monkey motion to fix it, on my other two went stainless. I was lucky that I had a friend who had access to stainless, but also a friend at a muffler shop the did the bending for free. the only thing about using copper is the fragility of the substrate. copper is mostly meant for houses, and not meant for under a car and road hazards.
mikemo
 
You might also consider opening up the access points in the spare tire compartment/under the dash to make running wires/replaceing throttle cable, etc, etc easier in the future.
 
coolant leak

Been there, mine was the small tube that connects the heater core back to the engine. multiple rust pin holes and one split. PITA. the small tube has 3 tabs spot welded to the side inside the tunnel. Luckily I had a spare x for parts and got a good one. If you have a lot of time you can use a spot weld cutter (harbor freight) and remove the entire tunnel.. there are a lot of spot welds. I ended up using a fine tooth air metal cutter down one side on the bottom. all in all a very time consuming job. I may have some pictures.
 
Copper pipes

mikemo90 said:
I thought about going copper too. but having a bumper fall of the front my first 74 and the damage it caused to the tunnel and to the pipes and my monkey motion to fix it, on my other two went stainless. I was lucky that I had a friend who had access to stainless, but also a friend at a muffler shop the did the bending for free. the only thing about using copper is the fragility of the substrate. copper is mostly meant for houses, and not meant for under a car and road hazards.
mikemo
Click to expand...

Hi Mike,

I replaced my old pipes for copper pipes around 10 years ago and they're still on good shape, no leaks no rust, no reactions for copper chemical issues (radiator is made on copper too :tomato:).

here is the link from my webpage
http://trazia.com/x19/coolant.html

pipe-master.jpg


Regards.
 
copper pipes

yes, that is the easy and the fastest way to fix the problem with copper, but it is not bullet proof. if you take a body hammer to copper ,you will have a hole... SS or regular muffler piping you have a dent. glad that has lasted so long for you Ricardo, but here on the west coast sometimes you feel like your riding off road with all the crap on the freeways and it will take it's toll eventually.
mikemo
 
Same symptom, overkill on my solution.

I had a coolant leak coming from below the spot welded flange below at the edge of the tunnel below the heater core. I could not find any loose hose clamps or signs of pinholes, so I looped the heater hose inside the engine compartment, and it still leaked in the same place.

After purchasing the stainless replacement tubing for the tunnel, and drilling out all of the spot welds on its cover under the car, I found the original tubes to all be perfect.

In renewing the heater controls, I had used the hose clamps which have an inner band of stainless to keep the gear clamp from cutting up the hose. On one of them, the ends of that inner band had tightened in on themselves, not the heater tube. Enough antifreeze had leaked into the tunnel to continue to seep out once I had removed the heater from the circuit.

I renewed all of the bits, and put the stainless tubes in. I used pop rivets and epoxy to reconnect the tunnel cover. If I were to do it now I would use the panel fusing epoxies available.

A lot of work to fix a badly tightened clamp.

Paul
 
Dan Sarandrea (Phila) said:
What about the one that comes off the head, goes thru the firewall, snakes around the FI control box, thru the spare tire compartment, and goes down thru the rubberized cover into the center tunnel. I'm 99.99% sure that hose connects to a metal pipe inside the tunnel. Did you check that one, too?

175499a3-6776-43e2-8993-b66b210c9b13_zpsjmr7chtr.jpg
[/URL][/IMG]
Click to expand...


Update, I think Dan might be on to something here. I cut a "flap" into the lower channel to inspect the 3 pipes and it was dry with zero signs of rust or wet. I drove the car around and determined that it was coming from ABOVE that channel, somewhere in the "transmission hump". Coolant was even seeping through the sealant/weld an onto the rear floor pan under the passenger seat.

I previously inspected the pipe to hose connection off the rear firewall as it goes into the transmission tunnel and it did not appear to be leaking. Does is go from metal to rubber hose, then back to metal as it goes through the tunnel , then back to rubber as it goes up to the hearer core? Im guessing there must be a connection deeper in the tunnel that you can't see from the firewall access point.

Is it best to bypass the transmission tunnel and run a rubber hose in the interior along the passenger seat under the carpet, outside of the tunnel?

The floor looks perfect with no rust so this is a new issue I believe.
Any advice?
 
Update, I think Dan might be on to something here. I cut a "flap" into the lower channel to inspect the 3 pipes and it was dry with zero signs of rust or wet. I drove the car around and determined that it was coming from ABOVE that channel, somewhere in the "transmission hump". Coolant was even seeping through the sealant/weld an onto the rear floor pan under the passenger seat.

I previously inspected the pipe to hose connection off the rear firewall as it goes into the transmission tunnel and it did not appear to be leaking. Does is go from metal to rubber hose, then back to metal as it goes through the tunnel , then back to rubber as it goes up to the hearer core? Im guessing there must be a connection deeper in the tunnel that you can't see from the firewall access point.

Is it best to bypass the transmission tunnel and run a rubber hose in the interior along the passenger seat under the carpet, outside of the tunnel?

The floor looks perfect with no rust so this is a new issue I believe.
Any advice?
__________________
 
yep, it's a shorter metal heater tube

There is a metal tube there. Mine is a 1976, but probably didn't change. You can see the tubes emerge under the heater core up front, one runs thru the "inside" of the car and one pops down into the under-car tunnel area. The inside one might be the hot/source run for the heater (seems logical the return would be below/outside the interior).

Anyways, it is rubber hose in the tunnel and connects to a metal pipe just under where the parking brake is bolted to the tunnel. That runs up the right side of the tunnel to the heater core.

Here's some older pics, the first is looking from drivers side at where the handbrake would bolt:
IMG_20151011_185354_zps3ih2myzo.jpg


Here's looking up thru where the shifter bolts:
IMG_20151011_185345_zpsx2oig473.jpg


and of course where the two pop up.
IMG_20151031_154444_zpsympz3gbw.jpg



I'm doing a resto-mod on mine and when I ran a hose thru the tubes to clean them they had SOOOO many pinholes in them, I just ripped the old tubes out. Turns out this had obviously happened before on my car - there was brazing done previously on the tubes and even some silicon there.

My solution is to replace both the heater tubes as well as the coolant tubes with stainless steel, but that isn't a great solution for everyone. Hopefully you have a leak near where the hose attaches to the tube - that should be easily repairable.

Good luck!
 
Thanks for the fast response and pics! Its great to have a view under the E-brake. My leak is showing up just to the rear of the emergency brake area on the passenger side floor and underneath the car.

I wonder if replacing with rubber heater hose would work? Instead of metal piping.
 
Todd968 said:
Im guessing there must be a connection deeper in the tunnel that you can't see from the firewall access point.
Click to expand...
Yes, all the way to the front. Not easy to reach :mad:

Is it best to bypass the transmission tunnel and run a rubber hose in the interior along the passenger seat under the carpet, outside of the tunnel?
Click to expand...
It's awkward because the hose is much thicker than any of the other things routed under the carpet and there's no graceful way of getting throught the firewall into the passenger compartment.
 
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