Pontiac Grand Prix Forums : Grandprix

Alright guys and gals, here it is, the permanent fix to the chinzy rubber water deflector under the cowl. This new part will completely eliminate the problem once and for all along with the worry of ruining a blower motor or your interior carpet. No more questions like, "Is the rubber seal going to stay on?" or "Is the cowl going to seal against the rubber good enough?". This diverts any water 100% and deletes the rubber bulb seal for good. It is also super easy to remove for cabin air filter installation and replacement.

This installation write up is for the Grand Prix since that is what I own and have readily available.

First off, here is the new part. It is rigid ABS plastic with a soft rubber on the front and rear edges. The rear rubber edge is contoured to fit and seal against the bottom of the metal flange that the factory bulb seal attaches to. Probably not 100% necessary, but it is there just in case any water gets blown backwards under and over the underside lip.

GM part is #15794785 It can be bought at any local gm dealer



Now, my Grand Prix has the 2-piece cowling so I only need to remove the passenger side half. If you have the 1-piece cowling, you will need to remove the wiper arms and remove the entire cowl. Some have also stated that you can pull the 1-piece cowl up far enough on the passenger side to gain access to the area below it without removing the wipers.

The 2-piece cowl has a split in the center and is easily recognizable if your's looks like this in the center.


For the 2-piece cowl, turn on your ignition and then turn on your wipers. When they are in the full up position, turn off your ignition so that they remain up.


Next, remove your rubber hood seal.


Now unclip the windshield washer hose from the two clips on the passenger side. I then just tuck it under the cowl area so that it's out of the way.


Next, there is a large retainer with a slot in it. Remove this. It should simply unscrew with your fingers without much effort.


Now you must remove the two plastic cowl retainers with the phillips heads on them. There is one on the far passenger side and one in the center. You need to pull the center of the plug up first and then remove the lower portion. You can sometimes unscrew the center enough to get it out, but sometimes it just spins. If it just spins, you can pry the center portion up with a small flat screwdriver and then remove the bottom half. A panel tool works very well for these as I have pictured.


Now you can remove the half of the cowl.


Once removed, you can see the factory rubber bulb seal. This is what usually falls off and lets water run right down the windshield, under the cowl and right into the blower fan. Not good. Normally this sets in place and relies on the cowl you just removed to seal against it. The large retainer with the slot in it is supposed to hold the cowl down firmly against it allowing it to divert the water around the blower opening. However, the cowl does not always seal against it 100% even when the seal is in place, thus allowing some water into the fan no matter what.


Now, remove the factory rubber seal. You can toss it in the nearest trash can if you want since it will no longer be used. Mine was glued on (from the old How-To fix) so you can see the black RTV on the metal flange in this picture. If you have never had this apart, there will be no glue and the rubber seal will most likely already be off the flange.


Here's the new piece ready to go in. You will see that it has three "fingers" that go over the metal flange where the old rubber seal used to be. These hold it tight against the flange on the bottom side so that the contoured rubber edge will seal snugly against the metal on the bottom.


The new part is designed with a built in gauge to space it to the correct position. It is just a long finger on the far passenger side of it. When it is slid all the way over to the passenger side against the metal edge, the entire part is correctly positioned.


The rear contoured rubber edge goes under the metal flange and the three "fingers" go over it.


Here it is correctly installed. Once the back edge is on, the front simply lays down where the cowl half normally sits. It has an extended section in the center to fit snugly and keep the whole part from sliding forward and off the flange. There is also a soft rubber edge on the front mainly just so that when the cowl half is placed back over it, it give the part some grip on the metal below it.


This part will divert 100% of the water that gets down here around the blower motor opening. It will not allow for even a drop to get past it since it completely covers the opening. There is still ample space underneath it, so there is no worry of blocking air flow at all. You will even note that the passenger side of the part is even molded to funnel water directly into the factory drain.


Now that it is in place, there is a little bit of work to do to the Grand Prix's cowl half. It has a large rubber flap on the bottom of it that has to be removed. This flap used to keep water that drained through the screen on the cowl from splashing over into the blower inlet. The new part eliminates that possibility also and this will have to be removed for the cowl to fit over the new part.

Here's what the bottom of the cowl looks like


Simply pull off the rubber flap. Then I scored around the plastic flange twice with a razor blade knife.


Once scored, you can simply break the flange right off with a pair of pliers.



Now here's what it looks like when you're finished.


Next step is to replace the cowl half back onto the car. You will see that the cowl will stack on top of the new part on the front edge. The front edge of the cowl is lifted up about 1" in this picture just so you can see the new part below it.


Once the cowl half is on, you will see the alignment guide of the new part fits perfectly into the the factory notch in the hood seal metal flange.


Once the cowl is back in place, you can't even tell the part is there.


Replace all your cowl retainers, your windshield washer hose goes back into it's two clips, and turn on your ignition key to let your wipers park and you are finished. That's it!

Here is a picture of what you removed and is no longer needed.

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Kansas City Pontiac Motorsports Club
Green Bastard Performance

I'll kill two birds with one stone. I have an '04 Impala. I'll take one if you haven't had someone else speak up. I'd also need one for my '00 GP, and I'll keep my self honest and buy one for it as well. So let me know if that works for you.

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2004 Impala SS - ZZP PCM, 3.4" Pulley, K&N CAI, TOG Headers, SLP Cat-Back, 180* thermo, Autolite 605s, PRJ Performance wires, Alternator rewire, GMPP Handling kit
2000 Grand Prix GT, Commuter Car - K&N CAI, GMPP Handling kit, ZZP downpipe w/U-bend delete, ZZP Plog, Alternator rewire

Excellent. Im going to have to get me one of these. Ive never had the leaking issue, but no sense in not taking advantage of something that will keep it from ever happening.

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Scotty Hall
2001 Pontiac Grand Prix GTP
It whines a lot, but I like it.

The only place success comes before work is in the dictionary.

Great spirits have always found violent opposition from mediocre minds.

And just so you know, dealership charges about $10 for the deflector, so this is a GREAT deal compared to buying a new deflector.

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2004 Impala SS - ZZP PCM, 3.4" Pulley, K&N CAI, TOG Headers, SLP Cat-Back, 180* thermo, Autolite 605s, PRJ Performance wires, Alternator rewire, GMPP Handling kit
2000 Grand Prix GT, Commuter Car - K&N CAI, GMPP Handling kit, ZZP downpipe w/U-bend delete, ZZP Plog, Alternator rewire

E-mail me when these are ready Abraisive, i'll take 3 of these...

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Shawn W. Larsen


'07 Chevy Trailblazer SS___'00 Pontiac Grand Prix GTP ___'99 Pontiac Grand Prix GTP

Exactly, last time I bought the rubber deflector for a customer's car at work, it cost me $9 and some change with my company discount.

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Kansas City Pontiac Motorsports Club
Green Bastard Performance

I was about to pick up a new deflector this weekend before reading this. Glad I didn't!

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2004 Impala SS - ZZP PCM, 3.4" Pulley, K&N CAI, TOG Headers, SLP Cat-Back, 180* thermo, Autolite 605s, PRJ Performance wires, Alternator rewire, GMPP Handling kit
2000 Grand Prix GT, Commuter Car - K&N CAI, GMPP Handling kit, ZZP downpipe w/U-bend delete, ZZP Plog, Alternator rewire

I should have 10 ready to go out later this week.

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Kansas City Pontiac Motorsports Club
Green Bastard Performance

oh thank GOD! finally somthing, im just to lazy and have to many projects on my hands to make sumthing right now. ill prolly place a order in for one.

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99 Grand Prix old build- CAI, Custom exhaust, HV3, Stage 2 TB, custom tune, ported heads intense s1x cam, headers.
Nothing great Just a small T66 Turbo with a Hv3 On a stock tranny untill i finish the other one.

i will take one as well. pm me as soon as they are ready!!!! sick of haveing my pass. floor board flooded. thanks

Keep me posted! I need 3 or them for sure....

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Shawn W. Larsen


'07 Chevy Trailblazer SS___'00 Pontiac Grand Prix GTP ___'99 Pontiac Grand Prix GTP

yessssssssss! too bad its too late for my blower motor though. $90 later and a ruined passenger side floor mat to boot. I'll be placing an order as well.

Do these fit the '04+ GTPs?
I'm having the same problem, and if they fit will be ordering 1
PM me with info
Thanks!

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No trees were destroyed for this message.
However, a great number of pixels were extremely inconvenienced.

I can only say 100% for sure on 97-03 GP's.

I will test fit one first chance I get.

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Kansas City Pontiac Motorsports Club
Green Bastard Performance

Mail to me, I'll test and post pix

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No trees were destroyed for this message.
However, a great number of pixels were extremely inconvenienced.

I have one available to test fit it to, I'll get it tested before the next bunch. Looks like the first 10 are spoken for.

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Kansas City Pontiac Motorsports Club
Green Bastard Performance

Am I one of the first 10?? I sure hope so! LMK! (sorry to bug you, i need to fix my dads 00 GT ASAP plus I want them for my cars too)

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Shawn W. Larsen


'07 Chevy Trailblazer SS___'00 Pontiac Grand Prix GTP ___'99 Pontiac Grand Prix GTP

Absolutely Shawn!

I counted three of them for you.

Should hopefully have them ready to ship out by Thursday.

Here's what I have counted for GPF
2 for Deezul_Awt
1 for SyntheticShield
3 for Iron Indian
1 for chrisb
1 for 98gpgtp
1 for hockeymaniak88

9 total for here and I have at least three spoken for on our local boards. So, already short haha. I should have more the first part of next week, so no big deal. If anyone is on this list that doesn't want one, or want it yet, let me know. Once I get eyes on this first batch and make sure they are good to go, I will just PM each of you my PayPal info since this first batch is pretty much gone. Whatever is left out of the next batch, if any, I will post in the for sale section.

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Kansas City Pontiac Motorsports Club
Green Bastard Performance

Looking forward to it. I don't know if you'll get them out in time, but I plan on going to an Impala meet in New Jersey on Oct 25, so I could show it off and maybe get you a few more sales. Any referral bonuses?

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2004 Impala SS - ZZP PCM, 3.4" Pulley, K&N CAI, TOG Headers, SLP Cat-Back, 180* thermo, Autolite 605s, PRJ Performance wires, Alternator rewire, GMPP Handling kit
2000 Grand Prix GT, Commuter Car - K&N CAI, GMPP Handling kit, ZZP downpipe w/U-bend delete, ZZP Plog, Alternator rewire

LOL! Better worry about if it fits your Impala first.

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Kansas City Pontiac Motorsports Club
Green Bastard Performance