I've had two Aero air filter boxes that were bowed out in the center, making it difficult to install an air filter and have the rubber edges of the filter provide an adequate seal. I've done this repair on three boxes now.

(click on any image for larger)


A bit of 1/4" all-thread, a few acorn nuts & washers. Now I have parallel box sides again, and fitting the air filter is a breeze.

One tip: make sure you position the rod low enough in the box so that the filter media clears it. I drilled one too high once a couple of years ago.

Another hurdle is that the 11mm nuts that retain the box to the chassis sometimes do not let loose. It is sometimes easier to remove the lower nuts from the tire side of the fenderwell than to try to remove the upper ones inside the box. If you have a nut that's rusted badly and try to overpower it, the rubber mount under the box breaks

 

I haven't had that happen on my '87 Aerostar XLT 3.0V6, but if it does, that is an EXCELLENT repair idea. (Maybe even a preventative maintenance idea?!!) Thanks for submitting the pictures. I love photos. The photos save a 1,000 words in descriptions!!

Nice work, AL! Thanks for telling us about this. Ed

 

I did the same repair on a Taurus air box for a customer, about three years ago.

My biggest beef with the Ford air boxes of this era are that if you cross-thread the upper's hold-down bolts into the lower's nuts, the nuts strip out of the lower's housing. Never "force" the air filter bolt when tightening. If it won't thread in nicely, it's cross-threaded (why is is so easy to cross-thread these particular bolts?).

I think I've replaced about eight Ford air filter boxes due to the metal nut no longer being attached to the lower housing. With the nut stripped out of the housing, it's very difficult to get good sealing of the filter's edges. In some cases, you can use a longer bolt and nut and washer arrangement, but it's a PITA to access it. The box above is a JY unit that I was prepping to replace my bad one.

 

good air box repair info asavage

a leaking air filter seal will kill the best engine slowly
turns the 300k mile Aero V6 into a 100k mile dead dog
that fine grit that leaks in grinds the rings and cyl walls, the rod and main bearings and the timing gears/chain into a worthless pile of scrap iron

 

Here's a pic of the steel captive nut that comes out of the lower housing if you even think about reefing on one of the upper screws and the threads aren't lubed and aren't aligned right. I must have replaced a dozen air filter housings on various Fords with these nuts loose in the housing.

I'm holding one that's stripped out of the housing and fallen out, and in the background is one still in good shape and holding OK in the housing.



You can just use a longer bolt and nut and washers, but on some rigs (F-series PUs) it's a major PITA to get your hand down there to hold the nut.

 

Nice job Al!

I've had the same bowing problem and did almost an equivalent fix although not quite as elegant as yours. I simply drilled a pair of opposing holes near the top (low enough to not interfere with the filter element) and used stiff coat hanger wire between the holes with a bend at each end.

 

I used epoxy to hold one of my stripped nuts in place. Seems to work.

 

I just found an "as installed" pic that I forgot I'd taken. This is in the '93 3.0l:

(click on image for larger)

 

Nice fix, I dont have the bowed box, but do have the lost captive nuts. I've got longer 1/4 dia stainless bolts to install (nuts will go on top). I intend to captivate the bolts by some method, & the upper nuts will be wing (eared) nuts if they will fit. Since it's a 12 month service interval, maybe I'll epoxy the bolts in place...... or even a dab of silicone rubber might work.....

 

Some more pics of what a box with a missing captive nut looks like (since I just had to do this again on my "new" '97 4.0l).

First, a bowed box. This is the old one with a missing nut. As these things go, this one is not too bad; given proper lid clamping, it would probably seal OK. If I was fixing this one (gluing in a captive nut, for example), I'd fix the bow too. Today, I was just replacing the whole shebang with a JY box (and I fixed the bow in that one, too!).

(click on any image for larger)



Here's a good nut:


Here's a missing nut:

 

I would not have thought of all these repair techniques that I see in these comments for the factory air box/filter assembly, I will have to look back at them at some point. When I had my 1991 F250, I had discovered this problem with the air box that was on the truck initially, only two of the six bolts were joining the top and bottom of the assembly. I was able to find a replacement at a Pick-N-Pull junkyard that when the bolts were installed, they didn't spin and the air box was snug.