Plastic undertrays

Changed the oil in the WRX today. The good news is the plastic undertray comes off with only 3 bolts, 2 plastic locking clips, and 2 of those pushlok plastic fasteners. The bad news is that the goriilla that torqued on the oil filter at the factory had a lot higher hand strength than I do. Getting the filter off was a struggle.

Why does something like a routine oil change require removing a giant plastic undertray? How many times will I be able to get that thing off before the plastic clips or pushlok things break? I thought trying to bend my arm in 6 places to remove the filter on the MSM was a trick, but at least it can be done without disassembling the undertray.

I suppose these undertrays must be important. Would I get 20 mpg instead of 21 mpg if I removed the thing?

Could you cut an access hole in the belly pan with a holesaw?

Also, buy a filter wrench

or use a piece of sandpaper...

In reply to T.J.:

I currently have the plastic under tray on my SVX sitting in the garage. I haven't noticed any fuel mileage difference with it on or off. Mine comes off with a bit more effort; 6 propitiatory Subaru bolts that can't be ordered without buying the complete tray assembly.

My car had been serviced its whole life by the dealer in Tucson prior to me acquiring it from my in-laws. All of the bolts had been stripped by some ham-fisted mechanic. Some 'field expedience' and a trip to my local Ace Hardware store solved the issue.

In many cases that plastic undertray is the difference between over heating and not in the middle of the summer.

The undertray on my wife's old Audi TT was a huge pain in the ass. It was broken when we got it and only got worse with time. I still had to take out 11 screws to get it off and by the end I also had to cut and re-install 5 zip ties to get the level of support that I wanted as cracks propagated and clips rattled off. On top of that, the tray caught any oil that was leaking out of the engine (and there was a fair bit by the end) and mixed it with sand that blew up on it to make a mess that looked like a Louisiana beach after the Deepwater Horizon blow out. Frankly, it was a car fire waiting to happen. I have no comforting words for you about undertrays.
On the subject of over tightened oil filters, I distinctly remember hammering a screwdriver through the filter on my 6 week old Ford Focus in 2001 to get it off. I have seldom been more freaked out while performing an oil change, wondering if I was killing my brand new car. This was all despite the fact that I'd used the screwdriver trick before so I knew it would work, the car was just so new.........

In reply to carguy123:

Mine's gone through two Phoenix summers and a July trip to Texas without it and I haven't had any overheating issues...

And yet the Camaro wouldn't go through an 80 degree day without overheating with the tray off but had zero issues in 100+ days with it on.

The Mazda 6 had some issues too.

I now leave them on.

The undertray in my WRX once DID catch on fire.

Pulled up after a hard run and there was smoke coming out of the hood. Cue me quoting Jeremy Clarkson: "my car's on fire, my car's on fire!".

Anyway, I guess there was some oil or something down in there, and when the exhaust manifold and turbo got hot enough, it lit up. No damage or anything, and it went out pretty quickly (I think we poured a bottle of water on it), but was pretty freaky at the time.

I guess the moral of the story is to not let any crap collect on the undertray...

carguy123 wrote: In many cases that plastic undertray is the difference between over heating and not in the middle of the summer.

Beat me to it!

A lot of those trays work in concert w/ the front valance and fan shroud to create a low pressure zone behind your radiator to ensure good airflow through it. Other under-car trays are important to reducing lift, a big deal if you track the car.

Of course, just because you probably ought to leave is in place doesn't mean you have to continue to use the same crappy plastic clips and such that came with the car. Nylon zip-ties and whatever the guy at fastenal can come up with often work just as well.

I know the kind that BMW used on the E36 were aerodynamic.. actually shaped like an upside down wing under the M-sport bumpers... unfortunately the first parking stop would usually rip them right off of the car

mad_machine wrote: I know the kind that BMW used on the E36 were aerodynamic.. actually shaped like an upside down wing under the M-sport bumpers... unfortunately the first parking stop would usually rip them right off of the car

And that's why I put one of these:

http://motionmotorsport.net/products/product_info.php?cPath=22&products_id=28&osCsid=20db10422855f92eb48ec3072a149108

on my wife's '98 E36 M3/4/5. It works great.

I have one on the TDI and it's a pain and starting to fall apart after 282K miles and a few bottom-out hits from when the shocks were blown. Fortunately, it's held on with about a dozen torx screws, so they zip off reasonably quick with a cordless driver. On a TDI it's important as the belly pan helps the engine hold heat as well as keeping road grime at bay. It also helps a lot with engine noise (an unshrouded TDI is not quiet). However, the soft stock suspension and low clearance means it and the side-skirts it attaches to take a beating over the years. Fortunately, the aftermarket has stepped in an sells aluminum versions that are more durable and offer some oil pan protection. I'm planning to install one this year sometime although I plan to add some sound deadening as well as painting it black to look more stock.

We actually added a pan of sorts to the MINI's in the form of a Moss skid plate. An original stainless steel version on the MCS and the current aluminum one on the MC 'vert.

A couple of years ago, I saw a front valance under-tray set-up on eBay for an E30 that went back to the front edge of the fender liners. I had never seen one on a car but it did remind me of the panels previously mentioend for the E36 M3. Maybe it was a Euro-only thing? The entire set sold for well over $400.

In reply to Flogger00:

What's an "E36 M3/4/5"?

ShadowSix wrote: In reply to Flogger00: What's an "E36 M3/4/5"?

I'm gonna guess: M3 4-dr, 5 spd? I've often seen the sedan versions called a "M3/4".

I lost the undertray in my Corolla when I hit some ice and got a little slideways...caught on a hunk of ice and bye bye...

the thing would run cool as a cucumber in even the hottest of summer days because of all the airflow through the rad without the tray there to block it., and also the negative pressure under the car.

In the winter though, I got absolutely NO warmth from the heater if I was going over 35 mph...sucked balls.

Noticed a slight hit in fuel economy too. ~3mpg

My Miata's undertray is held on by three screws and a fist full of zip ties.

24K miles on my 2011 WRX. Plastic tray removed every 3K for an oil change, and at least once more for a sway bar change. Shows no signs of giving up yet, but I'm careful (unless I'm auto crossing).

T.J. wrote: Changed the oil in the WRX today. The good news is the plastic undertray comes off with only 3 bolts, 2 plastic locking clips, and 2 of those pushlok plastic fasteners. The bad news is that the goriilla that torqued on the oil filter at the factory had a lot higher hand strength than I do. Getting the filter off was a struggle. Why does something like a routine oil change require removing a giant plastic undertray? How many times will I be able to get that thing off before the plastic clips or pushlok things break? I thought trying to bend my arm in 6 places to remove the filter on the MSM was a trick, but at least it can be done without disassembling the undertray. I suppose these undertrays must be important. Would I get 20 mpg instead of 21 mpg if I removed the thing?

Feel lucky you HAVE an undertray on the MSM. Mine seems to be MIA. New ones cost more than i've paid for cars.

I chased a braking issue on the lowered Hardbody pickup for a while - heavy braking ~only,~ there was a scraping sound coming from the front. Couldn't find ~anything~ wrong with the brakes at all.

Turned out the plastic undertray was dragging on the ground when the weight transfered forward.

It's slowly clearancing itself.

I tore the plastic undertray on my Forester off during a rallycross. I now have a thick aluminum skid plate on there.

I sourced it from a GRM advertiser who knows their stuff about Foresters, yet another reason to love the magazine.

92CelicaHalfTrac wrote:

T.J. wrote: Changed the oil in the WRX today. The good news is the plastic undertray comes off with only 3 bolts, 2 plastic locking clips, and 2 of those pushlok plastic fasteners. The bad news is that the goriilla that torqued on the oil filter at the factory had a lot higher hand strength than I do. Getting the filter off was a struggle. Why does something like a routine oil change require removing a giant plastic undertray? How many times will I be able to get that thing off before the plastic clips or pushlok things break? I thought trying to bend my arm in 6 places to remove the filter on the MSM was a trick, but at least it can be done without disassembling the undertray. I suppose these undertrays must be important. Would I get 20 mpg instead of 21 mpg if I removed the thing?

Feel lucky you HAVE an undertray on the MSM. Mine seems to be MIA. New ones cost more than i've paid for cars.

I've apparently had lunch for more than you've paid for cars - a non-MSM one is nearly $42 from Mazda Motorsports. Can't find the MSM version, but I'll bet they're close enough that you could make it work.

Ian F wrote:

ShadowSix wrote: In reply to Flogger00: What's an "E36 M3/4/5"?

I'm gonna guess: M3 4-dr, 5 spd? I've often seen the sedan versions called a "M3/4".

Exactly. What can I say. My wife picked out a "guy" car for herself. I just filled the order.

Keith wrote:

92CelicaHalfTrac wrote:

T.J. wrote: Changed the oil in the WRX today. The good news is the plastic undertray comes off with only 3 bolts, 2 plastic locking clips, and 2 of those pushlok plastic fasteners. The bad news is that the goriilla that torqued on the oil filter at the factory had a lot higher hand strength than I do. Getting the filter off was a struggle. Why does something like a routine oil change require removing a giant plastic undertray? How many times will I be able to get that thing off before the plastic clips or pushlok things break? I thought trying to bend my arm in 6 places to remove the filter on the MSM was a trick, but at least it can be done without disassembling the undertray. I suppose these undertrays must be important. Would I get 20 mpg instead of 21 mpg if I removed the thing?

Feel lucky you HAVE an undertray on the MSM. Mine seems to be MIA. New ones cost more than i've paid for cars.

I've apparently had lunch for more than you've paid for cars - a non-MSM one is nearly $42 from Mazda Motorsports. Can't find the MSM version, but I'll bet they're close enough that you could make it work.

Local dealer wants $343 for one, not including all the hardware, and i'm not a member of Mazda Motorsports, and likely won't be anytime soon.

I'm just going to go with an aftermarket unit i guess.

yea.. sometimes the BMW shorthand can get a bit weird.. especially with the E36