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Model Specific Questions and Info => MK2 Golf/Jetta and Audi 5k => Topic started by: thomas m on October 20, 2016, 03:50:59 pm
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I've looked at nearly 100 threads on heat shields without finding a more detailed how-to on rejuvenating them for reuse.
I get the idea that a nut or collar is used as an anvil so that a ball bearing can be squeezed into the dome to bend them back to some desired shape.
Can I get a more detailed description as to how you do this and what "shape" is the final outcome?????
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The ball-bearing and socket as die/counter, pressed using visegrips* gives fairly consistent results. It just pushes the center opening back where it was before installation.
New ones have a bit of gap when set on the end of an injector, so that is what I'd shoot for when reforming.
(https://dl.dropbox.com/s/q6p8j7mmj6xzbdc/gapAnnotated.png)
The main goal is to get a good seal by "crushing" the interface (red outline) of the shield onto the face of the nozzle, so hot gasses don't leak in and cook the nozzle.
Sometimes you can find the shields (seal 068130219) at a buck a piece or so, not so bad to use new, then. If the old ones have surface damage or corrosion, I'd use new.
*(h/t to Quantum Man)
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I am not specifically recommending reshaping the heat shields. They are not particularly expensive. If you are going to reshape using vice grips, ball bearing, and socket, I would recommend rotating the shield/socket while going through a series of clamps with the vice grips while gradually increasing the pressure. That will reduce the likelihood of warping the cone. I would also recommend carefully inspecting the the sealing surface of the shield for any cracks afterward.
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I would not recommend this kind of practice- it's because it's like the torque-to-yield bolts- they're disposable after using them only once. But I reuse them when trying to work on the injection issues, but once they are in order, I remove the old ones and install new ones in to complete the setup. They are rather inexpensive, and once the shields are "crushed" to spec, they are useless once removed.
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I disagree!
All metals have some amount of flexibility and the method advocated here using small adjustments using a pair of pliers exhibiting an ever increasing force on a ball bearing and turning the force applied several times is ideal for this application. I have over 25 heat shields that I can see in a jar on the workbench. Why would I ever need to buy new ones? It is unnecessary in my opinion. These things do work for a long time and I have not incurred a problem in all the years of re working them. I do check that matting surface because that is the transfer point of heat and protection at the tip.
So I for one will continue to practice what I think is responsible recycling of parts. I don't replace the lug nuts every time I take off a wheel and I won't start replacing injector seals either.
But then I run a 1/6 N\A 1981 in town at roughly a max speed of 45 MPH. Hardly a performance engine now is it?
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I would not recommend this kind of practice- it's because it's like the torque-to-yield bolts- they're disposable after using them only once. But I reuse them when trying to work on the injection issues, but once they are in order, I remove the old ones and install new ones in to complete the setup. They are rather inexpensive, and once the shields are "crushed" to spec, they are useless once removed.
inexpensive, again is one of the key words.
when done right reforming heat shields is not/should not be a problem. key word(s), (when) done right.
i (we, im sure) in one place or another have seen much interest for quite some time on this subject.
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I think the interest stems from the repair of the injectors or the need to repair them at times. Some new owners don't have any idea that there are pieces of metal under the injectors and that they have to have a bit of a curve on them when you return the injector to the hole. It isn't obvious and new owners are the first to admit they "bought this diesel and I really don't know much about them"
That leads to them removing the parts and not having the needed replacements at hand. Who keeps a set of 30 year old parts around for their 30 year old car? So the interest is how do I deal with this situation. They may need the car on a daily basis and so some of us offer advice on how to get over that hump without much of a problem. Reforming the heat shields is one of those humps.