Cracked heater box

[rapandi]

Hi all,

 

So I am currently working on my heater box (rebuilding it). I have been using resources available online and on the FAQ. I see people have addressed the broken heater valve bracket issue and have solved it however mine is an interesting one.... not only is the heater valve tab broken but so is the plastic on the right hand side of the box. I am trying to work out how to fix the latter.

 

I don't want to glue it cause I am worried it might break again in the future and I don't want to pull the box out again in the future to fix it. I was thinking of bending a thin flat plate in to like and 'L' or 'U' shape and rivetting to the box. The plate would have two holes to allow the cables to go through. I would have to seal that area well to avoid air leak.

 

Any criticism on my thoughts or has someone solved this problem before?

 

Raj

 

 

 

[SydneyTii]

I had the same problem, eventually I had at least 4 boxes in order to make one good one, that said I've kept as many of the worthwhile bits as I can, there were was a lot of crap! I tried quite a few things similar to your suggestion but in the end the cable mount kept moving, if you have any contacts that could make a corner out of fibre glass that may work? But I'd just keep looking out for a good base.

[rapandi]

1 minute ago, SydneyTii said:

I had the same problem, eventually I had at least 4 boxes in order to make one good one, that said I've kept as many of the worthwhile bits as I can, there were was a lot of crap! I tried quite a few things similar to your suggestion but in the end the cable mount kept moving, if you have any contacts that could make a corner out of fibre glass that may work? But I'd just keep looking out for a good base.

Yeah one of the boxes above I obtained from a fellow 2002 owner and it too had the same issue..... I will keep the fibre glass idea in mind....

[harold]

I have repaired similar breaks and other cracks on plastic items like the Behr AC console, defroster ducts and the heater box.   The plastic in all cases is ABS, I believe.

 

I use two things:  first, use a solvent bond type of adhesive -- this melts the plastic and effects a very strong joint.   Go to your favorite big box or hardware store in the plumbing section and buy pipe adhesive that states it is for ABS in addition to PVC.  It should be stated right on the can.

 

The second item is to get a sheet of 1/8" ABS plastic.  I got some from McMaster-Carr, but there are many online plastic suppliers.

 

I use a combination of bonding the cracked item, or just the crack, and also a reinforcing piece of ABS that can be applied without interfering with the function of the device.    Clamp everything in place and don't touch it for 24 hours.

 

I have found the resulting repairs to be very robust, and nearly as good as new. 

[TobyB]

I was scared to dive as far into the chemistry as harold has-

 

my solution to similar cracks was to use Sydney's fiberglass-

scuff the plastic well on both sides, use very strong tape on the inside

to hold the crack together, then use a thin fabric and thin epoxy (meant for fiberglassing)

to put 2 layers of mat on the outside. 

Let it cure, then take the tape off, and do a single layer

on the inside.

 

My fear about the chemicals was that the plastic's really brittle now, as lots of the

plasticisers (heh) have depositied themselves on the inside of the windshield.

The ABS cement seemed like it'd stress the plastic (maybe I'm just paranoid)

whereas the epoxy makes a physical, not chemical, bond to it.

 

I've fixed laptops, etc that way, and it almost always works.  Don't drill holes-

they create more stress raisers, and be really careful about tightening fasteners much at all.

 

hth

 

t

 

[scanner]

I made up a metal bracket and attached it using the existing rivet holes, crude but effective it's still holding up after a couple of years. Hope the link works, its the second post in my project blog

[Son of Marty]

I just use JB weld and have never had it let me down, as for the bracket if you have the broken piece cut to sheet aluminum bits that just fit the bracket contours then sandwich the broken piece between them with JB weld and pop rivets, let it dry overnight and it will be as good as new.  

[bobthomas]

You may want to consider Bondic for this repair.  I've tried to repair plastic tabs on e36 a pillar trim with it & it almost worked well.  Fixing the tab on the heater box might be a better use for it.

[jerry]

2 hours ago, Son of Marty said:

I just use JB weld and have never had it let me down, as for the bracket if you have the broken piece cut to sheet aluminum bits that just fit the bracket contours then sandwich the broken piece between them with JB weld and pop rivets, let it dry overnight and it will be as good as new.  

i'm a big fan of just using a 2-part epoxy cement and aluminum patches.  avoid rivets as they are only necessary to join the case together and they are merely stress risers on already brittle plastic.

use some 16 to 18 gauge Aluminum stock (around 0.025-0.040in thick), could be thinner.  i've made valve bracket out of this and merely epoxied to the remnants of the plastic attachment feature.  good as new and strong enough; no rivets needed.  as for the missing corner section, make a corner out of aluminum sheet to the contour and epoxy to the box.  use c-clamps to secure overnight.  if your housing is cracked (who's isn't by now?), merely glue an aluminum patch (can be thinner stock, even a beer can gauge thickness) over the crack and clamp overnight.  don't clamp too hard or you'll squeeze out the magic epoxy.  spray paint the whole exterior in satin black and no one will ever know the difference.

[Scott Sislane]

I made up a metal bracket and attached it using the existing rivet holes, crude but effective it's still holding up after a couple of years. Hope the link works, its the second post in my project blog

I can't see a picture but sounds the same that I did. Making a second layer that supports the broken layer. Mine's held up for 10 years now.

Scott


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[pehlivanov_tii]

I used thin aluminium grill for support of the 3M A+B glue. Seems pretty strong to me and also i put the aluminium grill in the inner side. On the outer side i have put only A+B glue, then put a bondo for plastic, sanded and sprayed the heater box black again. And you can't tell that anything is repaired on the box. No matter that this is not visible part, i wanted to look perfect and as new as possible.

 

About the bracket - i had a spare heater box. And if you see from what car i took it off, you will never say that there is any bracket left on the heater box. But luckily the bracket was there. Ok, when i removed the heater valve i saw that the bracket was cracked before and only the valve hold it somehow. And because as i said i wanted original look as much as possible I wanted to use these broken pieces of the original bracket. So i put a metal bracket as a base and on that bracket i glued the broken plastic pieces of the original bracket. See the pictures in the next post. 

[pehlivanov_tii]

[pehlivanov_tii]

Also the following photos are not related to your problem but i am very happy how my heater box rebuild turned out so i wanted to share the result. All metal parts were sandblasted and zinc plated.

Edited December 25, 2016 by pehlivanov_tii

[Driv3r]

Also the following photos are not related to your problem but i am very happy how my heater box rebuild turned out so i wanted to share the result. All metal parts were sandblasted and zinc plated.

What did you use for grommets that support the flap rods?

[pehlivanov_tii]

I got the grommets from one of the 3 spare boxes. They doesnt look some generic grommets they look OEM, but they were missing on one of the spare boxes. They are plastic but they should be installed carefully because as you ser the flap rod is very curvy and i broke one of the grommets. I was lucky to find a spare one and used a WD40 then. If you miss those grommets you can use some generic wiring grommets. They are rubber not plastic, but there are also other rubber details in our heater boxes si it shoukd not be a problem. Few months ago i bought from autosparks.co.uk grommets that i have found to be with the same hole size like the rods in the heater box.

Edited December 25, 2016 by pehlivanov_tii