Replacement cowl screws - 99 tahoe

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99tahoemomma

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Before you respond, yes, I have read the 1,758 other posts on passenger side leaks and re-sealing the cowl screws. :)

My question is on the actual screw. We had our Tahoe repainted by a local community college, who did a pretty good job I'd like to add. Anyway, one area they need to work on is putting the right screws back in place. That being said, I don't think any screw in the cowl right now is original because everyone one we took out was different. Has anyone gone to tractor supply or advance auto and gotten the M4.2x1.41x20 screws and used those? I see there are M4.2x1.41x16 and M4.2x1.41x25 on the post below.


Just wanted to get other opinions before I order screws and wait another couple days to get this project done, or hoping I can just head down the street and finish up tomorrow!

Thanks!!!
 

east302

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Here are the sizes/part numbers that GM used, maybe it will help. It looks like #4 in the center piece, #6 on the end pieces.

Edit: sorry, reread your post and see that you already have this info.

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someotherguy

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Length shouldn't be much of an issue because they simply go through the plastic, then sheetmetal, down into a large open cavity where the wiper linkage lives.

The bigger concern is using the correct type of screws so that you don't break the plastic. IIRC they're countersunk style, with an integral washer, to match the conical hole in the plastic.

Richard
 

someotherguy

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Here are the 3 screw types used on the cowl -

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Long w/countersunk style head and integral washer goes across most of the large middle plastic

Short w/countersunk style head and integral washer goes at the ends of the large middle plastic, IIRC just one at each end near the corner pieces

Long w/flat style head and integral washer are what hold down the corner pieces only since the holes are molded in flat areas

Is it critical to use these types of screws? No, but if you use the wrong style you must be super careful tightening them because the risk of splitting the plastic is increased. You have to be careful even with the correct style.

Richard
 

99tahoemomma

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Wanted to give an update on this project. I appreciate someotherguy showing a pic of those three screws. Luckily, I did have the two long flat head ones. I ordered the other two from LMC truck. The only difference between what I ordered from LMC and the two in the photo is that the long screw did not have the integral washer. We found the video below on youtube and picked up some silicone from HD.... covered all the areas he noted, and used silicone on all the screws we replaced. This was almost two weeks ago... it has rained a couple times.... haven't felt any wet carpet so far. That's a win! Thanks to everyone for the advice and help!
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someotherguy

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Wanted to give an update on this project. I appreciate someotherguy showing a pic of those three screws. Luckily, I did have the two long flat head ones. I ordered the other two from LMC truck. The only difference between what I ordered from LMC and the two in the photo is that the long screw did not have the integral washer. We found the video below on youtube and picked up some silicone from HD.... covered all the areas he noted, and used silicone on all the screws we replaced. This was almost two weeks ago... it has rained a couple times.... haven't felt any wet carpet so far. That's a win! Thanks to everyone for the advice and help!
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I've had those screws on my mind because they've been out of my '93 several times over the past couple weeks messing with wiper linkage adjustment, sprayer function, and windshield replacement!! And of course at least one of those times I made the mistake of turning the cowl plastic over and dropping one of the screws which immediately disappeared in my garage. Fortunately I've got a ziploc of "special" screws stashed so I had an extra.

Richard
 
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