The previous owner of my car cut two large holes in the hood where he attached some household ac vents.

the vents worked well in the sense that they lowered my underhood temps quite a bit but it looked like complete ****.

the hood is aluminum so simply welding in some new steel and adding body filler wasnt going to work. instead (bare in mind that i have never done any bodywork prior to this) i used some universal high temp adhesive to secure a piece of steel plating under the hood. this blocked the hole and left a gap that was the thickness of the aluminum of the hood that needed to be filled. i filled this in with body filler and sanded., when it was all said in done it looked good. damn good. like the hole had never been cut in the first place.

the only problem is that the holes were right above my turbo manifold. now i have a piece of sheet metal sitting right above the manifold and it is absorbing a ton of heat.

as a result the body filler on top is getting heated up and cracking as it tries to expand.

i am planning on redoing this and i am in dire need of suggestions. yes of course i could simply get a new hood but i would rather not when i can likely fix it for 20 bucks.

do you guys think i should simply add a barrier between the turbo manifold and the hood to keep the sheet metal from getting so hot and that will keep the body filler from cracking, or do you think i need to use something other than the sheet metal altogether?

here is an example of the awesome "speed holes" as installed by the previous owner:







here you can see that i glued the sheet of steel under the factory skeleton:




which looked like this from the top:



i then added some additional metal to fill the gap. i didnt want the body filler to be too thick:




then i added the body filler:




then once it was sanded i painted it:




it was good as new for the first month and a half. then it started cracking.

i had no idea what i was doing. i just thought i'd try some body work and this is the solution i came up with. please offer some suggestions on how i should do it differently this time. thanks.

 

you gotta weld the piece in, the hood vibrates around alot so if its not welded, and you try to put alot of filler- it will crack

so either you weld it, or get a body shop to, and then you do the rest of the smoothing process. As long as you get it welded in, then using filler ontop will work fine.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by spray2020 &raquo;</TD></TR><TR><TD CLASS="quote">you gotta weld the piece in, the hood vibrates around alot so if its not welded, and you try to put alot of filler- it will crack

so either you weld it, or get a body shop to, and then you do the rest of the smoothing process. As long as you get it welded in, then using filler on top will work fine.</TD></TR></TABLE>

i'm naive about this stuff but i have to disagree. the metal piece isnt going anywhere. it is firmly attached to the hood and i put in additional bracing under it. i marked the outline around the metal to use a reference point and it is all still lining up exactly as it did in the beginning. i can put my hand on a stack of bibles and swear that the metal isn t moving around other than heat expansion.

the body work is only cracking around the very edges of the body work. also, the body work is extremely thin. i built filled the gap with additional pieces of metal to minimize the amount of body filler needed.

 

well, just like the guy before said. youre going to need to weld it. No matter how firmly attached it is. your hood flexes, and it needs to be welded to the rest of the hood, so the metal can uniformly expand and contract, due to vibrations/heat/etc. So weld it and then fill in the imperfections and youll be fine.

the filler is brittle, and wont expand and contract at the same rate as the hood, so its going to keep cracking.

spray2020 is right.

 

OR get a new bonnet .... junk yard

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by db8SI &raquo;</TD></TR><TR><TD CLASS="quote">OR get a new bonnet .... junk yard </TD></TR></TABLE>

yeah i guess i will have to do this. the hood is aluminum and im sure it will cost more have it welded than to get one from a junk yard.

 

The 2 different metals are more likely your problem. 2 different expansion rates. Aluminum gets hotter faster than steel. Thus expanding faster. So you have the whole hood expanding before your piece of metal you glued in and it cracks your work. No matter how thin your body work is, the 2 different expansion rates will crack it. Even more when above your manifold.
The other problem is the weight of the steel in comparison to the aluminum. Every time you take a bump that one spot flexes more than the rest of the hood causing more cracks.

 

so what if the hood is aluminum? get it welded....
how do you know its aluminum?
i find it "annoying" how you ask for help, because your a novice in body work, then disagree when told it has to be welded.....

its not the fact that its aluminum that made it crack....weld it, or throw it away

 

You can check for aluminum by using a magnet. If it is magnetized, it is not aluminum and can be easily welded by anyone. If it is aluminum you are going to have to find someone that can do that job. Not alot of people will weld aluminum. Or work with it. You are going to have to find a large body shop. Most small shops will not have the equipment to do aluminum repair. All the stuff you use to fix steel can not be used on aluminum. You need seperate tools that are only and specificly used for aluminum repair.
Seeing as you don't want to spend alot of money, the best solution is to buy another hood or find a vent that you like better.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hootiehoo &raquo;</TD></TR><TR><TD CLASS="quote">so what if the hood is aluminum? get it welded....
how do you know its aluminum?
i find it "annoying" how you ask for help, because your a novice in body work, then disagree when told it has to be welded.....

its not the fact that its aluminum that made it crack....weld it, or throw it away</TD></TR></TABLE>

i know it's aluminum because that's the only way they come.

i dont recal disagreeing with welding being a better idea than not. welding aluminum isnt as cheap as welding steel (which i could do for free) in most cases and since the hood is curved it will require more than simple technique which will cost more money.

i didnt say that the hood being aluminum is why it cracked. i said it was because the bondo expanded. the only thing i argued about was that the bondo is not subjected to any more vibrations than you would expect if it were on a welded surface. the steel is held firmly in place and is reinforced with bracing from below. it isnt going anywhere.

it is however unpainted stainless steel and it is several inches above a hot *** turbo manifold and therefore it is getting stupidly hot and as such is making the bondo stupidly hot and it is cracking.

i think you are misinterpreting or altogether not reading a lot of what i wrote.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Disease &raquo;</TD></TR><TR><TD CLASS="quote"> You can check for aluminum by using a magnet. If it is magnetized, it is not aluminum and can be easily welded by anyone. If it is aluminum you are going to have to find someone that can do that job. Not alot of people will weld aluminum. Or work with it. You are going to have to find a large body shop. Most small shops will not have the equipment to do aluminum repair. All the stuff you use to fix steel can not be used on aluminum. You need seperate tools that are only and specificly used for aluminum repair.
Seeing as you don't want to spend alot of money, the best solution is to buy another hood or find a vent that you like better.</TD></TR></TABLE>

well is you ask hootie anybody can weld aluminum. i wouldnt have bothered to mention it was aluminum in the first place if i didnt think it was an issue.

i suppose i will just trash it or find a way to make the vents look better... ehh... i suppose i'll trash it. lol.

 

Have you considered picking up a cheap EG hood off craiglist for 50-100$?

It could be cheaper than welding/ smoothing a new pice of metal in.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Leo C &raquo;</TD></TR><TR><TD CLASS="quote">Have you considered picking up a cheap EG hood off craiglist for 50-100$?

It could be cheaper than welding/ smoothing a new pice of metal in. </TD></TR></TABLE>

i dont think an eg hood would fit on my miata.

seriously it just occured i havnt even said what kind of car i have. sorry for the confusion. im sure i can find one for cheap. maybe get lucky at pick and pull or something. i was really trying to avoid buying a new hood because i plan on converting my front end to the second gen in the not so distant future. maybe i'll just drive with the slightly cracked paint until i can do the front end conversion.

 

you can pretty much tig weld aluminum very cheap and very easy

i have the same hood, they tense to get flowy around highway speed.

you might just want to get a used hood, it would sucks ball to have crack on the hood once you laid down paint and all

 

since when is welding aluminum so expensive?

if thig guy has a welder, and can weld steel, then all he has to do is buy some aluminum, and weld it up.

also, how are the body tools so different for aluminum? is sand paper different? are sanding blocks different? are cut off wheels different? is the body filler different? is the paint different? is the DA sander different? he has a clean hole with no dents. all he needs is a patch panel.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by iam7head &raquo;</TD></TR><TR><TD CLASS="quote">you can pretty much tig weld aluminum very cheap and very easy

i have the same hood, they tense to get flowy around highway speed.

you might just want to get a used hood, it would sucks ball to have crack on the hood once you laid down paint and all </TD></TR></TABLE>

that's the problem. i dont have a tig. i have access to mig but i would have to pay someone to weld aluminum. not to mention that it;s a complex shape blah blah blah. im sure it would cost a fair amount of money.

i have already painted it and it has already cracked but that's not too big of an issue since i use the 50 dollar paint method. lol. but still, i see what you mean.

 

might wanna try welding grinding then metal glaze...sand smooth...just an idea but it might be cheaper if you went and found a used hood...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hootiehoo &raquo;</TD></TR><TR><TD CLASS="quote">since when is welding aluminum so expensive?

if thig guy has a welder, and can weld steel, then all he has to do is buy some aluminum, and weld it up.

also, how are the body tools so different for aluminum? is sand paper different? are sanding blocks different? are cut off wheels different? is the body filler different? is the paint different? is the DA sander different? he has a clean hole with no dents. all he needs is a patch panel.

</TD></TR></TABLE>


I should have explained my self more. Most body shops don't tig. Atleast not at the moment. With more and more cars coming in aluminum, it is only a matter of time.
Tools are all the same. As long as you clean all the steel particles off of them. You do not want to contaminate aluminum with steel particles. This is how aluminum rusts. Metal forming hammers and dollies need to be cleaned and preped before being used on aluminum.
This is why most places that work on aluminum panels have seperate tools wich are kept in cabinets to keep steel particles off of them.

And here is some really good info. Most manufacturers don't want you to tig aluminum car parts.

Here is a really good article on how to repair aluminum. Applies to most all body parts of a car made of aluminum. Mainly how to weld it.
http://abrn.search-autoparts.c...d=948

Now I don't want to get into a pissing match here. The best thing for the op to do is to just live with it for now cause you said you wanted to change the front end anyways. Or get a new hood. Will be cheaper in the long run to just get a new one.

 

what exactly is metal glaze? i have heard how it is supposedly better than bondo but what makes it so special? lol.

 

It's a 2 part epoxy. Has virtually no shrinkage. Great bonding to all sheet metals even with paint on it but it is only used for small dings and scratches. Hence the term glaze. I would not use it to fill stuff.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr.E.G. &raquo;</TD></TR><TR><TD CLASS="quote">what exactly is metal glaze? i have heard how it is supposedly better than bondo but what makes it so special? lol.</TD></TR></TABLE>

it doesn't matter what you use, you could use lead on it and make no diffrerent

you see, the primary structure is not securely fastener(or fused with the hood), all the body filler will just crack and breaks with the main structure rattle.

it's like building a perfect castle upon sand foundation, give it some shaking and time, something will happen.

get it welded or buy a used hood, i think you are right, i checked my hood and there's a curve to it, you might end up spending more time bondo'ing crap than just get a used one

you can find a used MIata hood for 100-175 locally.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by iam7head &raquo;</TD></TR><TR><TD CLASS="quote">

it doesn't matter what you use, you could use lead on it and make no diffrerent

you see, the primary structure is not securely fastener(or fused with the hood), all the body filler will just crack and breaks with the main structure rattle.

it's like building a perfect castle upon sand foundation, give it some shaking and time, something will happen.

get it welded or buy a used hood, i think you are right, i checked my hood and there's a curve to it, you might end up spending more time bondo'ing crap than just get a used one

you can find a used MIata hood for 100-175 locally.

</TD></TR></TABLE>

yeah. that's the problem. lol. i dont want to spend 100 bucks. lol. i think i'll hit pick and pull on half price day.