Beating a dead windshield (1 Viewer)

[leonard_nemoy]

I had a guy replace my windshield gasket last year. He said he would follow the fsm pages that I printed for him but of course it still leaks.

After talking with him some more he told me that he used polyurethane between the body and the gasket but used silicone between the glass and gasket.

From reading the fsm it sounds like he should have used polyurethane between the glass and gasket instead of silicone.

Question #1: If the shop replaces the gasket again but uses polyurethane instead of silicone in-between the gasket and glass do you guys think it will fix the leak?

Question #2: If I have him redo the gasket should I source the Sitka flex urethane and primer listed in the FSM or let the shop use his own urethane and primer? The shop owner says all urethane is the same and the brand doesn't matter. He says he uses dow urethane and primer.

Thanks

 

[bhsdriller]

#1) Maybe

#2) Can't say to that I used a sealant I got from Lowes on mine ~6 years ago and it's still holding

 

[gummycarbs]

The windshield TSB in my '94 LC folder says:

In order to comply with FMVSS 212 – Windshield Retention and FMVSS 216 – Roof Crush
Resistance, the factory uses a urethane adhesive sealant with bonded strength of not less
than 40 kilograms per square centimeter or 569 pounds per square inch for certain bonded
windshields and rear windows on Toyota vehicles.

A Urethane adhesive sealant of at least equivalent strength must be used to maintain
these retention and roof crush standards when windshield glass replacements are
performed by either the dealer or an outside glass shop.

Since the adhesive kits listed in Toyota Repair Manuals are not available in the U.S.A., a
listing of some locally available equivalent materials is provided below. Be sure to follow
the sealant manufacturer’s instructions for best results.

• CVS Urethane Auto Glass Sealer by American Sure Seal
  Bonding strength = 600 pounds per square in. (approximate)
• Super Fast Urethane by 3M
  Bonding strength = 1000 pounds per square in. (approximate)
• Unrest 212 by Kent Industries
  Bonding strength = 600 pounds per square in. (approximate)
• Urethane E Auto Glass Sealer by Protective Treatment Inc.
  Bonding strength = 600 pounds per square in. (approximate)

The first result for Dow windshield urethane is Betaseal One. Its specs are:

Cured Physical Properties
• Shore A hardness – Approximately 70
• Elongation – >250 percent
• Tensile strength – >700 psi
• G-Modulus – >2.0 MPa at 10 percent strain after seven days at 72 ˚F (22 ˚C) and 50-percent relative humidity
• Specifi c electrical volume resistivity – >5 x 1010 ohm cm

Sounds like it meets the requirements to me.

 

[mudgudgeon]

After talking with him some more he told me that he used polyurethane between the body and the gasket but used silicone between the glass and gasket.

From reading the fsm it sounds like he should have used polyurethane between the glass and gasket instead of silicone.

Silicone and rubber are chemically incompatible (at least to some extent. There are different silicone polymer blends).
In construction, I've repaired hundreds of rubber roof penetration gaskets/boots what pipes pass through a metal roof.
Typical practice is to seal these with silicone. The bond fails surprisingly quickly (months), and silicone goes kind of hard and bond fails as a result of chemical incompatibility.
The same install completed with polyurethane will last decades.

Silicone and polyurethane are also incompatible with each other.
You'll never adequately clean silicone off the rubber gasket to get a reliable bond between polyurethane and the rubber windshield gasket.

In some ways, silicone is easier to work with. Cleaning up excess is easier. Black polyurethane makes one hell of a mess fast if the installer is not really meticulous and careful.


Every sealant has it's purpose, and limitations

 

[Rusty Marlin]

Silicone and rubber are chemically incompatible (at least to some extent. There are different silicone polymer blends).
In construction, I've repaired hundreds of rubber roof penetration gaskets/boots what pipes pass through a metal roof.
Typical practice is to seal these with silicone. The bond fails surprisingly quickly (months), and silicone goes kind of hard and bond fails as a result of chemical incompatibility.
The same install completed with polyurethane will last decades.

Silicone and polyurethane are also incompatible with each other.
You'll never adequately clean silicone off the rubber gasket to get a reliable bond between polyurethane and the rubber windshield gasket.

In some ways, silicone is easier to work with. Cleaning up excess is easier. Black polyurethane makes one hell of a mess fast if the installer is not really meticulous and careful.


Every sealant has it's purpose, and limitations

Good explanation! thank you.

 

[leonard_nemoy]

Silicone and rubber are chemically incompatible (at least to some extent. There are different silicone polymer blends).
In construction, I've repaired hundreds of rubber roof penetration gaskets/boots what pipes pass through a metal roof.
Typical practice is to seal these with silicone. The bond fails surprisingly quickly (months), and silicone goes kind of hard and bond fails as a result of chemical incompatibility.
The same install completed with polyurethane will last decades.

Silicone and polyurethane are also incompatible with each other.
You'll never adequately clean silicone off the rubber gasket to get a reliable bond between polyurethane and the rubber windshield gasket.

In some ways, silicone is easier to work with. Cleaning up excess is easier. Black polyurethane makes one hell of a mess fast if the installer is not really meticulous and careful.


Every sealant has it's purpose, and limitations

Thats whatI wanted to hear. The repair guy says he is an expert and been doing it for 30+ years and silicone always goes between the glass and gasket.

But he can't tell me why it leaks lol

He also wanted to re use the year old Gasket but I insisted he use a new one that I ordered. I am glad because it sounds like the silicone on the old Gasket would cause problems.

I am going to let the same guy re do the windshield but I have his word he is going to use polyurethane on both the glass and body. I will also let him use his dow polyurethane and primer.

 

[Mat Jadamec]

All polyurethanes are not the same....I can see someone saying that they are for a particular grade applicable to this kind of joint, but just because it's poly doesn't mean it will work

 

[Kernal]

It's been discussed many many times in the forum.

Whichever brand is used it must be an ADHESIVE-SEALANT (having both properties) that is designed/approved specifically for use in automotive windshields.

Rubber to glass and rubber to body.

KEY words: ADHESIVE (so it doesn't go flying out in an accident) and SEALANT (so it doesn't leak), all in the same product.


Here's one example:

https://www.3m.com/3M/en_US/p/d/b40066982/

 

[leonard_nemoy]

Yeah, I think the dow polyurethane for windshields will be a good enough product. Or maybe I will change my mind and order the Sitka flex. Idk

 

[mudgudgeon]

The repair guy says he is an expert and been doing it for 30+ years

I get paid a lot in my job to prevent and undo the issues caused by "experts" who've being "doing it for 30 years".
The number of "experts" who have never taken the time to read and understand manufacturers instructions or product data sheets is astounding. Most tradies do what they do, because that's what someone showed them to do 30 years ago. This does not equate to expertise

A few minutes reading product data sheets should give a good idea if a product is suitable. Data sheets are usually easy enough to find online

 

[baldilocks]

I had a windshield installed in 2016. I stood there to make sure they did it correctly. In 2019 it started leaking. Gentle lifting if the gasket from the glass revealed what looked like a very thin black layer of the sealant that was used. It had lost its adherence. My solution was to use Permatex silicone windshield sealant from NAPA. It’s clear and runny which allows it to creep down into deep, narrow crevice's. 2.5 years later it was still waterproof when the windshield got broken and replaced again last spring.

Do it yourself unless the job is being redone for free.

 

[leonard_nemoy]

Well the fsm calls for sikaflex 256 urethane and sunstar 9002 primer. I can find th3 sikaflex on Amazon but I can't find the sunstar primer stuff.

I am going to let the glass guy use his own dow polyurethane and primer.

 

[mudgudgeon]

Well the fsm calls for sikaflex 256 urethane and sunstar 9002 primer. I can find th3 sikaflex on Amazon but I can't find the sunstar primer stuff.

I am going to let the glass guy use his own dow polyurethane and primer.

In Australia, some of the sika primers (and other products) seem to be restricted to sales within the relevant industry due to being nasty stuff.

Might have to go to a specialist automotive paint supplier of similar

 

[Kernal]

Be a good idea to inspect the sheet metal once the glass is out, there's often rust that needs to be fixed before the new windshield is installed. Or, if there's no rust now there very likely will be cuts down to bare metal from the installer's blade caused from cutting out the old adhesive/sealant. You'll want to repair those also, otherwise you'll have rust popping out some years later.

 

[MtnAddict]

Well the fsm calls for sikaflex 256 urethane and sunstar 9002 primer. I can find th3 sikaflex on Amazon but I can't find the sunstar primer stuff.

I am going to let the glass guy use his own dow polyurethane and primer.

Let us know how it works out.