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REpairing plastics

General Tech Talk

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REpairing plastics

Post by ash_on_mtb »

It would appear that someone has tightened the fittings up on this heat exhanger a bit too much. Which leaves me in a bit of a spot... :?

Image

What do people suggest doing about the crack in the inlets?! Simply silicon it up and hope for the best? Glue in a fitting? Melt it back together with a soldering iron?

I'm not really on top of plastics, so does anyone out there know what can be done to repair or at least get this serviceable!?

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Post by Coogs »

Ask old mate for the plastic repair stuff off the fancy red stand :finger:
It works a treat :D
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Post by Bert-O »

ash, that is the trouble with plastic it is hopeless for female threads (internal), and even then its risky as screwing another fitting into it is forcing the fitting to split exactly as this has done.
chuck it out you wont get it repaired properly, what ever you do to try and fix it will always be in the back of your mind especially if it is on your cooling system and not just the Hotwater side. but if you want to persevere you will need to put, say, a hose clap or a sleeve of some sort, around the fitting to prevent it forcing apart again. really that sort of connection is to be made once and left alone not taken apart and reassembled - it looks a bit second hand can I say.
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Post by ash_on_mtb »

a bit second hand?? You should see the thing! Hell kicked it out, now its back!

I reckon I'll try a combination of all 3. Plastic repair to start with, silicon/PFTE tape on the thread and a hose clamp, and a whole lot of praying!!

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Post by thomo.in.a.gq »

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Post by SWBMQCraig »

Araldite (spelling) and a hose clamp and it will be stronger than new.. if you NEVER ever want to pull it apart cover the thread in araldite too and screw it in.. my 2c

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Post by fester2au »

There is s liquid seal that I think is better than any of the tapes, we used it on stainless fittings in an under car wash with dozens of spray nozzles. Can't think of brand but it's called 567 or something like that from memory, could be a Locktite but don't know, comes in a white tube with read writing I think. I think the idea is that it can seal without relying on excessive pressure from screwing the fittings up as has cracked yours.
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Post by beinthemud »

SWBMQCraig wrote:Araldite (spelling) and a hose clamp and it will be stronger than new.. if you NEVER ever want to pull it apart cover the thread in araldite too and screw it in.. my 2c

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Post by KUSTOMV840 »

Vee the crack out and use some stuff called "Quick Bond" Its like super superglue with a powder you sprinkle on the glue. The two react to go off super hard so you can sand it or what ever you like. Tough as nails. I use the stuff to repair all my plastic stuff. It stronger than origingal. I get it off my snap on dealer or from our local tool place. I'll stick up a pic of the box tomorrow.

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Post by ash_on_mtb »

I'll persevere with this one I reckon, plus I get to learn how to actually fix plastics. If I just bought another one, yeah it might be reliable, but this way I get to learn what does and doesn't work fixing plastics. Plus it saves me 100+ dollars.. :)

So I think I'll v out the joint, try some plastic repair product, then sneak in a fitting with some fine teflon tape, and hose clamp that bad boy up.

thanks to all for the tips,
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Post by PJ.zook »

Im with kustomv840, 'q-bond' is awesome stuff, ive used it to repair broken lugs n retaining bits on dashboards and it worked great. You can get it from Repco and similar.
As he suggested, vee it out only slightly, then use this stuff, but try not to get it in threads. Then i would still put a thin layer of rubber around the outside and use a hoseclamp.
Also use liquid teflon tape in the thread when putting a fitting in, it wont stress the threads as much as it forms and seals with both the threads instead of forcing its way in like with tape, which you dont want with some weak ass plastic.
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Post by chimpboy »

My first thought was also "hoseclamp". Repair with some suitable goop, hoseclamp on the outside... some other part of it will break before your repair does imho.
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Re: REpairing plastics

Post by carrot »

Has anyone tried this q-bond stuff on softer plastics? I haven't found a good way to repair plastic mounting brackets on things like headlights, wheel arch flares, etc, where there is a fair bit of stress on small cross-sections.

The q-bond documentation says "Suitable for use on wood, aluminium, porcelain, ceramics, glass, rubber, ABS, rigid PVC and many more."

I've tried this other 2 part glue that was supossedly good for most plastics (maybe it was Shelly's Plastics glue) where you 'paint' the surfaces to be glued with this highlighter-type thing, wait a few minutes then apply a bit of the other part, but I haven't had any success with that stuff. I've got to admit, the contact areas between the two parts have been really small.

What about adding a bit of fibreglass matt to some suitable adhesive (q-bond, araldite)?
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Re: REpairing plastics

Post by KUSTOMV840 »

Yep, Ive used q-bond on headlights etc. No drama, works a treat. Just remember to vee the joint out well so it has something to stick to. Bigger the V the better it will be.

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Re: REpairing plastics

Post by Clanky »

Dont use a tapered fitting - get a parallel thread one and it wont put outward pressure on your repair
Another thing you can do instead of the thread tape is the loctite pipe sealant (515??). - again wont put outward pressure on your repair and will seal like a beauty.
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Re: REpairing plastics

Post by KUSTOMV840 »

Clanky wrote:Dont use a tapered fitting - get a parallel thread one and it wont put outward pressure on your repair
Another thing you can do instead of the thread tape is the loctite pipe sealant (515??). - again wont put outward pressure on your repair and will seal like a beauty.

Yep, I wish I had of thought of that! :rofl:
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Re: REpairing plastics

Post by Clanky »

KUSTOMV840 wrote:
Clanky wrote:Dont use a tapered fitting - get a parallel thread one and it wont put outward pressure on your repair
Another thing you can do instead of the thread tape is the loctite pipe sealant (515??). - again wont put outward pressure on your repair and will seal like a beauty.

Yep, I wish I had of thought of that! :rofl:
Some if us find out the hard way , myself included :)
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