These are more like craftsman’s projects than a mechanical fix.
After getting a messy leak there, I wanted to do away with the junction and all 8 of its o-rings and go all the way through the firewall with standard heater hoses.
I wanted to do the mod in a way that prevents kinking the hoses at the firewall and without stressing the pipes out of square where the o-rings seat at the lower end into the core manifold.
Eliminating the junction, of course, means you need a way to secure the face plate for the hose pass-through on the engine side of the firewall, tightly against the firewall. For that, I made a plywood backing plate that you’ll see below.
Getting started
1. Drain coolant.
2. Move front seats back (suggested: remove footwell carpet, driver’s side).
3. Pry out the pin that secures the gas pedal. The plastic pin is strong, so you probably don’t need to worry about breaking it. If the cruise control link is attached to the pedal, leave it for now, it will pull the pedal out to the left and up to clear the workspace. If the cruise link isn’t connected, like rspi suggests, use a small zip tie or bungee to tie the pedal out the way. For reassembly, I disconnected the cruise link to make it easier to replace the gas pedal.
4. Remove the gas pedal mount (2 10 mm screws).
5. Remove the 4 screws of the heater core box (T-25 for uppers, T-15 on sides), and what I call the T-25 yoke screw that secures the lower pipes into the core sockets. So 5 screws out.
6. Diaper the heater core box with a plastic shopping bag and pull the base of the heater core box loose from the pipes.
7. Remove the heater core pipes from the firewall junction. You won’t be reusing their plastic fittings or the junction, so no need to be gentle. Just yank out the pipes and remove the rings and all plastic parts. Likewise, on the engine side—I just grabbed the metal crimp collars with Channel Lock pliers and gently rotated them and worked them out. If you plan to reuse the hoses, like I did, be gentle with this step.
8. Reconnect the heater core box, replacing the 2 T-15 and 2 T-25 screws. The T-25 yoke screw will be the last step. Don’t lose that yoke screw!
(If you plan to reuse the hoses, like I did, be gentle with this step. If the crimp connector on the engine side is damaged and leaks, you can just cut the connector off the hose and use a barb (as shown) to connect it to your new hose from the firewall.)
Tools and Materials. See pictures below.
Hose. I used the Gates Safety Stripe heater hose. Buy 3 feet in case you want to do the extended hose hack, which I’ll describe later. You’ll have some extra.
Alert: I bought 3 feet of Safety Stripe from one auto supply store; I.D. was a bit bigger than 5/8”, so it might be hard to get a leak-proof seal with that hose. NAPA had the same branded Safety Stripe hose that snugly fits the 5/8” pipes, so I used that. Since exact inside diameter seems to vary a bit, it would be best to take your pipes to NAPA for hose sizing. If their Safety Stripe isn’t a tight fit, try other brands, it probably wouldn’t make a difference. For sizing of hose, you can also use a short piece of ½” copper household plumbing pipe—outside diameter is 5/8”. Some hardware stores have a foot long piece. 1/2” soft copper tubing also has 5/8” O.D.
Sharpie marker and ball point pen stem for marking through small holes.
T-15 and T-25 Torx bits and driver.
Medium size Channel Lock pliers, or similar tool (to remove engine side hoses from junction.)
Small pliers to pop off cruise control link while reinstalling gas pedal.
Sharp long knife for clean hose cuts.
Vise to hold pipes for cutting and backing plate for drilling (see picture).
Cutoff tool to shorten aluminum pipes (or fine tooth hack saw).
File to smooth off burrs around pipe cut edges.
Jig saw for cutting out a blank for your cabin side backing plate.
Drill
1 inch and 1 ¼” wood bits.
O-rings: pipes to heater core connection ( NAPA 727-2114 from their 727-2502 kit)
Silicone spray for o-rings.
Hose cutter
Hose clamps. I use the narrow ones; I think they surround the hose more uniformly..
Permatex 2 sealant (non-hardening) for sealing hoses to metal pipes/fittings.
Duct Seal (or plumbers putty) to seal around firewall hose pass-throughs.
Scissors, cardboard to make template for backing plate.
Small piece of ½” plywood (I just had ¼” so laminated 2 thicknesses).
Hose cutter
- 1. hose cutter.png (156.39 KiB) Viewed 1471 times
Very handy for this project.
Home Depot sells one for less than $15.00.
Menards offers one for around $11.00.
This will be my next tool purchase.
- 2. new hoses installed through plywood no sealant.jpg (217.96 KiB) Viewed 1471 times
This is what your re-plumbed pipes will look like when installed with the plywood backing plate.
- 3. Save your ribs.png (534.61 KiB) Viewed 1469 times
Save your ribs
You’ll be in there on your side. I’ve used a couple of wheels stacked flat. You can top the wheels with a cushion. Your ribs will thank you.
I pulled the footwell carpet (and scrubbed and hosed it down while I had it out). To do that, loosen the 2 seat mount bolts at the back and remove the front bolts (14 mm).
I found that after getting into position on your launch pad, planting a hand on the roof, I could swing my bod into the workspace, then reverse to swing back out.
Set up your work area with:
your vise
cutoff saw (electric or hack saw)
file
jig saw
plywood scrap—big enough that you can hold it down while you cut out the blank for your backing plate.
Drill and 1” and 1 1/4” wood bits.
Backing plate
Since you won’t be using the plastic junction, you need a backing plate for the hoses to rest on and to hold the engine side face plate in place. If you remove the protruding tabs from junction, it will lay flat for tracing.
Template for your backing plate.
On your bench: trace the bulk part of the junction that nests into the firewall cavity (not the flange) that you removed onto a piece of thin cardboard, or heavy paper, as shown. Make your template a ¼” bigger all around than the junction tracing. Cut out your cardboard template, fit it into the cavity. Trim it if necessary, but make sure it’s wide enough to accept the screws from the engine side face plate. Now you have a template for your plywood cutout. Trace it around the outside of your template onto the plywood.
Note: When I traced it onto the plywood, cutting on the trace line, I could be confident that the plywood would be a perfect fit.
If you’re not comfortable cutting it that close, better to make it slightly smaller, then wedge a stick of something across the cavity to hold it in place while you trace the holes onto your plywood blank from the engine side.
- 4. paper tracing of junction for template.png (190.89 KiB) Viewed 1469 times
Black trace line is the junction
Actual cavity width is 1/4” larger than the junction.
On the engine side, position the face plate how you want it, then with your Sharpie marker, trace the large holes onto your blank backing plate.
Next, using your ballpoint pen stem, with the large hole traces aligned, make dots on your backing plate where your fastening screws will go. On the bench, I drilled a very small pilot hole for those 2 T-15 self-threading screws. If you don’t have a small drill bit, use a small finish nail or an awl to make a pilot hole for the screws.
Start the screws into your backing plate on your bench, so you can finger start them when installing them with the face plate in place.
- 5. cardboard template, screw holes marked.png (225.48 KiB) Viewed 1469 times
Cardboard template shows what plywood blank will look like.
Note that the larger hole is at the bottom.
- 6. plywood backing plate w holes in vise.png (317.2 KiB) Viewed 1469 times
Bore holes for the hoses. Top hole is 1”; lower hole is 1 ¼”, it’s larger to allow for smooth curve of hose.
To install your backing plate, you’ll need starter holes for the self-threading screws.
- 7. backing plate in place, OEM nipple showing.png (171.02 KiB) Viewed 1469 times
Backing plate secured in cavity
Rope caulk initially tried, though sealant isn’t necessary around the edge.
New hose from lower aluminum pipe will be fitted to OEM engine side hose.
Shorten the pipes.
Make the pipes different lengths, so the clamps have their own space. In the first picture, above, you can see how they align.
In the picture below, note the shiny stubs where the hoses will connect. Use a fine grit emery cloth (or something like a Scotchbrite) to clean them up for a good seal with the Permatex 2.
- 8. cut pipes with marked hose limits.png (320.34 KiB) Viewed 1469 times
Since you’ll need to remove the hoses from the pipes to smear on some Permatex 2, mark your pipes and hoses for how far they’ll go on the pipes and the right curvature.
For test fitting, install the hoses on the shortened pipes, but leave them slightly longer than they’ll need to be so you can be sure you have enough for connecting on the engine side.
- 9. new hoses show marked pipes.png (440.22 KiB) Viewed 1469 times
Pipes set into heater core (not secured) for sizing hose lengths.
Pipes marked for hose limits and rotation of hoses on pipes so they can be assembled on the bench with sealant.
Connect the new hoses to the pipes so that their natural curvature comfortably arcs upward to curve through the firewall—so they won’t stress the pipe connections at the core. I set up everything without sealant or clamps to get the curvature right. Then marked the hoses at the firewall and pipes and hoses for curvature, as shown.
Cut the new hoses to length by firewall.
- 10. new hoses assembled on table with cut pipes.png (365.56 KiB) Viewed 1469 times
Assembly: Apply Permatex 2 sealant to hoses and pipes (see instructions) and secure them to the pipes with clamps, like in the picture below.
Hoses shown have been fitted through the firewall, marked and cut to size to meet up with the OEM engine side hoses, as shown in the next photo.
Assemble pipes to heater core.
O-rings. Clean up the o-ring seats on the pipes with a mild abrasive, such as a Scotchbrite scrubbing pad.
Use new nitrile o-rings: NAPA 727-2114 from their 727-2502 kit.
Spray o-rings with a light mist of silicone before installing the pipe yoke in the core manifold.
Ensure that inner part of the ring that contacts the pipe is also coated—so coated all around.
Install pipes into core and tighten screw #5 securely. While that screw must be tight, it is fine threaded so I wouldn’t force it too hard. I’ve changed several heater cores and haven’t had a leak there; I use moderate but firm torque.
Sealing out fumes.
- 11. hoses thru plywood plate, not sealed.png (383.54 KiB) Viewed 1469 times
Hoses before sealing
- 12. hoses through plywood plate, w Duct Seal.png (485.46 KiB) Viewed 1469 times
Brand name: Duct Seal
- 13. new hoses connected to OEM's w Duct Seal.png (446.59 KiB) Viewed 1469 times
I also applied Duct Seal around the face plate, as in this pic (it’s sort of like sticky chewing gum mixed with modeling clay). The face plate, itself, has an embossed rubber seal against the firewall. No engine fumes will get past that or the Duct Seal.
Not fancy, but they don’t leak. Definitely use the Permatex 2 sealant. The lower OEM hose nipple isn’t long enough for two clamps, but it seems fine. One caution re the clamps. I chose the narrow ones for sealing because they seem to conform to the contours of the hose better than the beefier clamp. Where the pipe or nipple was long enough, I used a heavier clamp for holding strength, but the second one probably isn’t necessary. No leaks, anyway.
After the clamps were tightened and allowed to set up for a day, I checked them for tightness the next day. The screws did turn slightly with moderate force.
Some readers might be thinking that at least one of those OEM hoses will need to be replaced. I assumed that both will be replaced, but this was a hurried project so I went with the expedient solution. With the shortened pipes and the firewall mod already in place, replacing them will be an easy fix.
The following variation describes how I will do it. I’ll call this:
Mod #2
Replace OEM engine-side hoses with preformed hoses.
Everything is the same getting through the firewall, except that your new lower hose from its aluminum pipe will be longer to connect with an “L” hose, shown below.
The 80401 preformed hose is from Advance Auto; NAPA clerk told me they have a similar one.
For reference, consider this hose has the long “leg” and a short “foot” to connect to the engine nipple.
Supplies
- 14. 80401 hose w. Duct Seal & P-tex 2.png (481.41 KiB) Viewed 1469 times
After removing the OEM engine side hoses, use an abrasive cleaning pad (such as Scotchbrite) to clean up the engine nipples. Some build up there can be crusty and could leak if they’re not smooth (and, of course, prepped with the Permatex 2).
Leave extra hose length while making up the ends to connect to the aluminum pipes.
Start with the lower hose.
The distance from firewall to lower engine nipple is about 14 inches.
The long leg of the 80401 is about 11 inches.
So the lower hose will need to be long enough to extend from the aluminum pipe to the 80401’s long leg.
Dry fit the foot part of your 80401 to the lower engine nipple. You might need to trim its length a bit for alignment of the 80401’s long leg with your new hose from the firewall. Don’t seal and clamp it yet at the engine.
With the 80401 dry fit, you can get a sense of how how long the new lower hose needs to be.
NOTE: Before cutting hoses and connecting things in the engine bay, apply sealant and assemble hoses to pipes and clamp them. With hoses and pipes marked for proper curvature through the firewall, you can assemble the hoses to pipes on the bench, as in Mod #1. Set the pipe ends into heater core for measuring hose lengths.
Hose barbs
The Permatex 2 instructions say to apply a thin coat of sealant to each part you’re going to join and let the sealant “tack up” for a few minutes before assembling.
I suggest applying sealant and making up the barb connections one at a time; let one tack up, assemble and clamp it. Then do the other end.
Connect the foot end of your 80401 to the engine so you have it positioned how you want it to meet up with the long hose. If necessary, trim your new hose for length, and finish connecting the two hoses. Slightly rotate the barb as you insert it to the hose.
Upper hose
You can trim another 80401 and use the same assembly procedure as with lower hose.
The run for this one is only about 8 inches from the firewall to the engine nipple.
Size the upper hose from its aluminum pipe a couple inches beyond the firewall to allow enough space for the hose barb. Again, size and dry fit the foot of the 80401 to the engine nipple, and size the long leg of the 80401 to meet with the new hose from the firewall.
Mod #3
Replace OEM hoses with standard hose and copper fitting.
Those 80401’s are a bit pricey @ around $19.00.
A more economical way to do the engine side mod is with either a copper plumbing fitting, or a right angle hose barb. Parts for the copper pieces shown would run less than $3.00 (assming you have tools, tubing cutter, solder and heat on hand).
- 15. copper 90 degree el with stub.png (410.71 KiB) Viewed 1469 times
Standard 1/2” x 90 degree copper elbow plus tubing stub
Outside diameter of tube is 5/8”
If you’re handy with household plumbing fittings, you’ll find that ½” copper tubing has O.D. exactly 5/8”; so it will mate perfectly with 5/8” I.D. hose and is great for turning corners. Shown above is a longish stub to go with an el that I had handy; you could cut a stub like that in half and use each piece in one side of the fitting. You’d need to sweat solder it all together (after properly preparing joints).
To complete these runs, you’d need: longer hoses, reaching from the aluminum pipes through the firewall to near the engine nipples so all you need at the end of the hose is the right turn to the engine and short piece of hose to connect it.
I didn’t measure hoses for this run, but you’ll probably need less than 3 feet for the lower hose; less than 2 feet for the upper run.
Before cutting, fit a short piece of hose to the engine nipple, connected to the copper fitting—then size the end of the new hose to connect with the other stub of the copper fitting.
Mod #4
Same as #3, except for use of 90 degree 5/8” hose barbs
- 16. right 90 hose barbs.png (212.3 KiB) Viewed 1469 times
If you can find these handy right 90 barbs, you’d also go with the long hoses all the way from the aluminum pipes through the firewall and about 14 inches (for the lower hose) into the engine bay. Then use a right 90 hose barb, as shown, with a short length of hose to connect with the engine nipple. The upper hose will extend about 8 inches into the engine bay. Measure them to be sure. As with the others, be sure to use Permatex 2 sealant—and, again, I’ll recommend the narrow band clamps.
I couldn’t find these right angle barbs locally but Amazon has them, which is where I bought them (about $10.00 for the pair + shipping).
Mod #4
Use of soft copper tubing and choice of right angle fittings.
If you’d like to spend less time and effort on this project and reuse the OEM junction box, read on.
Those right 90 barbs (or the copper 90 degree elbows with stubs) will still be handy; depending on how you configure it, you might need 4 feet of new heater hose—less, if you use the preformed 80401, as shown.
You’ll still have to cut back your aluminum pipes, as pictured above. I’m emphasizing the shorter pipes to minimize stress on the heater core (manifold) where the pipes connect.
This mod avoids all the fussy work involved with eliminating the junction and making a backing plate. Though you’ll still need to remove the junction to take out the plastic locking sleeves and saw off the tabs for a flush fit of sealant—a hacksaw will do the job. Just hold the junction in your vise by its flange.
For this mod, ½” soft copper tubing will go through the firewall. NOTE: it’s not that soft. I devised a simple jig to bend it (picture below).
- 17. mock up of complete lower pipe w 80401.png (432.81 KiB) Viewed 1469 times
This mock up (for the lower, longer hose) is basically what your configuration will look like (if you use the 80401). The lower right end will link with the shortened aluminum pipe. I’d prefer a straight link of hose (and it wouldn’t need to be that long) on that end to minimize stress on the aluminum pipe connection to the core. The curvature of the tubing works well at the other end where it goes through the firewall.
If you look closely, you’ll see that I straightened the right end of the copper tubing.
In the next picture, you can see the bushings revealed that make it easier to seal the openings on either side of the junction.
After installation, they’ll be pushed into the junction to take up most of the space in the original holes. Then, the duct sealant around the pipes at the face plate will complete the seal.
If you do this mod, when you purchase the hose, ask the clerk to cut off 4 1-inch pieces to use as bushings.
- 18. mock up of copper tubing with bushings.png (524.05 KiB) Viewed 1469 times
While I had the junction out, I used a hack saw to trim off the protruding tabs on either side. The flange, where it tucks behind the HVAC duct can also be trimmed back.
- 19. 2x4 copper tubing bending jig.png (466.64 KiB) Viewed 1469 times
Soft copper tubing bending jig
Simple jig to control your bend (or straighten it). I started with a 5/8” inch hole. Then enlarged that with ¾” bit, gouging out the hole at an angle. This provides a sort of rounded backing for the tubing so it won’t dent or kink as easily.
Supplies
The coil of soft copper tubing costs less than $20.00 at Menards; about $25 at Home Depot.
You’ll need a tubing cutter. There’s a very small version for cutting in tight places.
You have to tighten the cutter wheel slowly to avoid collapsing the tubing or getting it out of round.
For my first attempt to bend a length of the tubing, I slipped it into a 3/4” pipe. You can get needed leverage that way, but the hard edge of the pipe will flatten and dent the copper. Better to use a jig like in the previous picture.
I wouldn’t recommend running the copper all the way into the engine bay with a right 90 fitting and hose link to the engine nipples. Why? too much vibration transmitting toward the heater core. Better to use it to get through the OEM junction and then link to the 80401 to the engine.
- 20. Coil of soft copper tubing .png (632.77 KiB) Viewed 1469 times
Coil of ½” soft copper tubing
Some hardware stores sell it by the foot.
So depending on skill level and tools and materials readily available, you have some options for simplifying the p80 heater hoses.
