Air Filter Box

As some of you may know, I just purchased a 99 XJ Sport with 62K last monday. I think it is the coolest Jeep ever (my first Jeep) and I've always wanted a Jeep since I was old enough to know what they could do.

Here's my Question. I pulled the air filter out to see what shape it was in, and was surprised to find it in relatively new condition. But while examining the box, I noticed the air intake hole (in the front of the box) is quite small for an engine of this size. I then went and looked on my neighbors 98 GC 4.0L and their was bigger. Has any body else noticed this? Has anybody made their's bigger? What was the outcome? I'd like to cut mine out to be bigger, in an attempt to maybe squeeze some better milage out of it. Any feedback is apprecitaed.

Yep, that's normal. But that's why there are so many who do (make themselves)/buy custom air intakes. Which allowes more air flow to the engine. Do a search on this site any you will find plenty of idea's that work for different people. Hope this helps ya.......

Yes that helps alot. But I don't have alot of money to play with, so I was thinking about just cutting the opening bigger to allow more air to get in with the stock setup. See any problems in doing that, that i am over looking?

I personally would not do that. Your opening it up to more dirt, bugs, rocks, and water to the stock air filter, not a good thing. You can build yourself one for pretty cheap if you look around a little. Here's a website that help me get a couple of idea's: http://www.madxj.com/
I'm sure some others will chime in her too........

This should help too: http://www.naxja.org/forum/showthread.php?t=31683

I did it, but I've also done several other mods since then including the stroker.
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Dino's "Mean Green Machine"
1992 XJ Laredo 4-dr - 4.6L I6 HO Stroker - 180k miles - AX15, NP231, D35c, D30

263hp@4900/321lbft@3300-3800, 1/4 mile = [email protected], 0-60 = 5.8secs
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I tried that on my 95 just for grins, since I had a spare box anyway. It made no tangible difference as far as I could tell. I think the Jeep engineers probably figured out what was needed and did it.

Thanks for all the responses.


Now I have another problem. I have a random thumping. Yesterday while going out driving I noticed a loud thumping and steering wheel shaking, like the tires were out of balance. On the way home last night it didn't do it untill I got to a right hand curve in the road, and during the curve it started again (while going anywhere from 40-45 mph). Then it did it when I stopped later on (like anti-rattle brake clips). I stumped as to what the problem is. Any input before tomorrow is great cause it's going back tomorrow for a couple of other items that need to be looked at, if I can go in there with some info on the thumping, that would be one less trrip across town.

99XJSPORT06 said:

Thanks for all the responses.


Now I have another problem. I have a random thumping. Yesterday while going out driving I noticed a loud thumping and steering wheel shaking, like the tires were out of balance. On the way home last night it didn't do it untill I got to a right hand curve in the road, and during the curve it started again (while going anywhere from 40-45 mph). Then it did it when I stopped later on (like anti-rattle brake clips). I stumped as to what the problem is. Any input before tomorrow is great cause it's going back tomorrow for a couple of other items that need to be looked at, if I can go in there with some info on the thumping, that would be one less trrip across town.

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Figure out how to duplicate it and take the mech for a quick ride. He'll probably pick it right out.

As for opening up the filter box, you can, use a hole saw to cut with but I would put a PVC 2 or 3 inch pipe in the hole or even find a horn from a TJ and put that in there, that horn will allow you to raise hole into the airbox to a higher angle if you play around water alot.
You can also put a K&N flat filter in there but I noticed no difference in milage or power when I did mine, although it did get noisier and louder. It's main benifit is that it is cleanable and reuseable so I swap mine out with a stock paper filter for a couple of days while the K&N gets cleaned, dried and reoiled then swap it back in. I bought a case of filters when I bought my 98 new plus a couple of frams and purolator AIR filters, not oil, and still have maybe 3 or 4 left so sometimes I leave the paper one in till the next change then put the K&N in. The air box also does a good job of catching bugs, leaves and other debris so it gets vacumed out whenever I open it up...
I and others here will also recommend that you spend the $100 on the Factory Service manual or FSM, it will pay for itself the first time you do a job that would cost over a $100 and you do for say $10.... You can order it from the dealer or from the back page of your owners manual... it is the size of a good sized phone book, about 3 inches thick and covers ONLY your year and model speficically, not like a chiltons or haynes that covers 10 years and 3 different models in an over sized softcover paperback.

When I did my cowl induction modd [do the serch for "another cowl induction adea"]I think it only cost about $10/12 bucks for the pvc, if even that. If you dont have a hole saw that big then you would have a good chunck of change in that. I think the one I bought was about $20/25 dollors. I did notice a small increase in power with my K&N but my paper filter was real dirty. I also noticed an increese with instalation of a high flow muffler. I have a Flowmaster 40, but there are others that are quieter that should work just as good.

RichP said:

Figure out how to duplicate it and take the mech for a quick ride. He'll probably pick it right out.

As for opening up the filter box, you can, use a hole saw to cut with but I would put a PVC 2 or 3 inch pipe in the hole or even find a horn from a TJ and put that in there, that horn will allow you to raise hole into the airbox to a higher angle if you play around water alot.
You can also put a K&N flat filter in there but I noticed no difference in milage or power when I did mine, although it did get noisier and louder. It's main benifit is that it is cleanable and reuseable so I swap mine out with a stock paper filter for a couple of days while the K&N gets cleaned, dried and reoiled then swap it back in. I bought a case of filters when I bought my 98 new plus a couple of frams and purolator AIR filters, not oil, and still have maybe 3 or 4 left so sometimes I leave the paper one in till the next change then put the K&N in. The air box also does a good job of catching bugs, leaves and other debris so it gets vacumed out whenever I open it up...
I and others here will also recommend that you spend the $100 on the Factory Service manual or FSM, it will pay for itself the first time you do a job that would cost over a $100 and you do for say $10.... You can order it from the dealer or from the back page of your owners manual... it is the size of a good sized phone book, about 3 inches thick and covers ONLY your year and model speficically, not like a chiltons or haynes that covers 10 years and 3 different models in an over sized softcover paperback.

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Thats the problem, I can't duplicate it. It comes and goes when ever it wants to. U-joitns maybe?

lol, I almost bought the Haynes manual yesterday, i'll look into the FSM.

Well, now i've sprung a leak! I THINK it's my transfer case leakin. My guess is a seal? But at 62K, anybody else had this problem? I was outside and noticed a little puddle of some sort of fluid. I was lookin under and saw the front drive shaft, and the rear, and it's the silver part in the middle leakin. SOrry for the lack of Terms, this is my first Jeep and i'm not too familiar with what stuff looks like. Is this my transfer case? Any input before tomorrow is great, as it goes to the shop tomorrow (kinda odd things start breaking BEFORE the trip to the shop.....I thought most cars break AFTER the shop....LOL). p.s., the fluid is ordorless, which is why i'm asking.

99XJSPORT06 said:

Well, now i've sprung a leak! I THINK it's my transfer case leakin. My guess is a seal? But at 62K, anybody else had this problem? I was outside and noticed a little puddle of some sort of fluid. I was lookin under and saw the front drive shaft, and the rear, and it's the silver part in the middle leakin. SOrry for the lack of Terms, this is my first Jeep and i'm not too familiar with what stuff looks like. Is this my transfer case? Any input before tomorrow is great, as it goes to the shop tomorrow (kinda odd things start breaking BEFORE the trip to the shop.....I thought most cars break AFTER the shop....LOL). p.s., the fluid is ordorless, which is why i'm asking.

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Stick a piece of cardboard under there to determine where the fluid is leaking from, both the auto tranny and the transfer case take ATF so color won't help much unless it's the rear main seal on the engine...

Just got done looking at it again, i'm pretty sure that it's the t-case. Perhaps if I take a pic and get it up on the net?

well, the leak stopped. I've been checking it on a regular basis tonight and it's completely stopped leaking on the ground. As for the area around the seal, it looks pretty bad, like the seal is spent. Anybody else had this happen at 62K?

TIA

Tim

I can't say I have any t-case problems. But I did cut open my stock air box.

I have a manual tranny so I may get some different feedback than an automatic. But I noticed a pretty huge difference in accelleration. Around 2700 RPM there has always been a surge in power. Before roughly this RPM it's always felt a little sluggish and once I would get to around 2700rpm it felt like the motor just freed up and would rev more easily. Cutting the box completely got rid of this sensation and seemed to allow it to rev a little more freely in the lower RPMs as well.

As far as power and gas mileage. It's only been 2 tanks of gas so far, but I have noticed no differences other than the lack of the surge.

99XJSPORT06 said:

well, the leak stopped. I've been checking it on a regular basis tonight and it's completely stopped leaking on the ground. As for the area around the seal, it looks pretty bad, like the seal is spent. Anybody else had this happen at 62K?

TIA

Tim

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The question is did it stop leaking or run out of stuff to leak out...

99XJSPORT06 said:

Well, now i've sprung a leak! I THINK it's my transfer case leakin. My guess is a seal? But at 62K, anybody else had this problem? I was outside and noticed a little puddle of some sort of fluid. I was lookin under and saw the front drive shaft, and the rear, and it's the silver part in the middle leakin. SOrry for the lack of Terms, this is my first Jeep and i'm not too familiar with what stuff looks like. Is this my transfer case? Any input before tomorrow is great, as it goes to the shop tomorrow (kinda odd things start breaking BEFORE the trip to the shop.....I thought most cars break AFTER the shop....LOL). p.s., the fluid is ordorless, which is why i'm asking.

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Did you have this vehicle inspected before you laid down the cash? Only been a week and you have some big issues come up. :repair:

pancake said:

Did you have this vehicle inspected before you laid down the cash? Only been a week and you have some big issues come up. :repair:

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Thats the EXACT reason why I bought it from Carmax and paid more than I should have. I THOUGHT they checked their cars out good, and everybody i've talked to just raves about them.

Now, I'm no dummy, I had my old man come with me to inspect the Jeep before and after we took it on a test drove, and he's been in the mechanic business for over 35 years, so he know's alot. At the time, the transfer case was not leaking. It's obvious the seals are beginning to get old in the t-case and differentials due to the fact they constantly "look wet". But we both agreed that it ran great and looked great for the age.

Of course, it IS used, and I did expect a few problems to pop up, but at the same time, some of these things I just can't see how Caramx could miss (inless my instincts are correct, and they don't really check them, but rather slap the stickers all over it saying they did). Come on, power steering fluid AND coolant being down at the add marks (I made them put coolant in it before i drove off the first time, didn't know about power steering untill a couple days later)).

Don't get me wrong, the t-case is not gushing, just a few drips here and there. I ran it around the block in 4 full time and it shifted in and out just fine, so I believe it's a leak in it's early stages.

Anyways, it's at the shop right now. I should hopefully have it back sometime tomorrow evening. Meanwhile, in order for me to still get to work, my parents had to take it down there and pick up a loaner, and i'm driving the KJ for the next couple of days so I can still get back and forth to work and school. Hopefully, I'll get a new t-case seal, balanced tires, a full tank of power steering fluid, and my brakes will shut up. (I even went nit picky with them and told them get my light under the hood working again (their fault for saying we'll fix ANYTHING in the next 30 days...LOL))

Atleast she stayed home for a few days this time.....and got a couple baths so it looks real shiney for the mechanics

So the shop called and said the T-case seal WAS bad (no crap) and they are replacing it as soon as the part gets there from the dealer (should be any minute now, as they called about 10 min ago saying that). They said the brakes are fine (now i'll pull the wheels off myself and see if they are), but since it's gone on reccord, somehow that extends my warranty further on the brakes (plus I had them pull what work they did to it before it went up for sale and they said they replaced the drums (I thought they lasted forever???)). They added the power steering fluid and said they found no leaks (i think it just used it over time, and I hope to god they didn't dump ATF in there), balanced my tires, and ordered the light for under the hood and said that i could swing by and pick it up once it came in, in a few days. Hopefully they will have the seal on by tonight (but I know it takes a while to replace the seal most times), as I want my Jeep back, and I know my mom wants her KJ back (they put her in an 2001 Camry 4 cylinder, couldn't even give her a mid size SUV).

Now here's my question. Since they have to pretty much take the t-case apart to get to the seal, doesn't this mean I automatically get a free t-case fluid change? Or would they be daring enough to put the old fluid back in there? How can I check to see if the fluid is new (i remember the color it was before i sent it in, it was dark grey)??