LIM gasket and DEX info. Tell me what you think: - Page 8 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


General GM Chat When starting new posts, please specify YEAR, MAKE, MODEL, ENGINE type, and whatever modifications you have made. Chat about all things GM (and related cars). Off-topic stuff should be in the Lounge, and all Model specific mechanical problems should be posted in the proper forum.

Reply
 
 
 
Thread Tools Search this Thread
Old 10-30-2007, 11:24 PM   #71
Senior Member
Posts like a Camaro
 
Join Date: Jan 2004
Posts: 1,166
Thanks: 0
Thanked 1 Time in 1 Post
mkaake is on a distinguished road
Default

Yeah, I'd agree on that point. Another quick q though - why don't we see as much damage to the nylon carrier of the UIM gasket as we do to the LIM? I checked this morning, and yes, the UIM gasket carrier is the same material as the LIM gasket.

More food for thought.
mkaake is offline   Reply With Quote
Old 10-30-2007, 11:28 PM   #72
Junior Member
Posts like a Ricer Type-R
Thread Starter
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

The Silicone-rubber inserts are thicker. Are they mounted the same to the carrier? I can dissect both to see the difference. I'd say from EXTERNAL reference, the UIM gasket is manufactured a bit better in terms of sealing. The silicone-rubber portion is beefier, wider, and a cooler color.

You also have to take into account the thermal expansion coefficeints of the adjacent material. LIM gaskets are cast iron/aluminum interface, the UIM gasket is Nylon/Aluminum.

In other words, the UIM gasket thermal expansion coefficient is very closely matched to at least one of it'* adjacent materiels.
willwren is offline   Reply With Quote
Old 10-31-2007, 03:12 AM   #73
Senior Member
Posts like a Camaro
 
Join Date: Jan 2003
Location: Jenison, MI (Near Grand Rapids)
Posts: 1,070
Thanks: 0
Thanked 0 Times in 0 Posts
theJMFC is on a distinguished road
Default

Quote:
Originally Posted by mkaake
... So, I dug up some pics from 2004. Unfortunately, our 2 megapixel cams (near top of the line at the time) didn't have enough resolution for me to put my question to rest ...
Fortunately, I'm an avid packrat. I still have that gasket hanging in my garage. The EGR bore is indeed crumbling. Here'* the pictures I just took 15 minutes ago:









Do you know what else I see in those pictures? A great reason for the UIM gasket redesign! The orange water passage sealing material seems to be pushing back into it'* flow channel over time. There is nylon supporting it all the way around, except for that channel (which is necessary for the material to flow through when it'* molded), and that is where those seals are looking to fail. With the push-in black gaskets on the newer UIM gasket, there is no such weak area. I'll bet that'* why that got changed.

Quote:
Originally Posted by mkaake
As a quick personal thought, I'm leaning towards our biggest issues with the LIM gaskets being the reliefs in the nylon around the ports. Maybe theJMFC can post some thoughts on why they'd put that in the molding (edit: I think I found my answer... but I'd still like some outside feedback)?
Well, there is no reason I can think of that those reliefs would need to be there from a molding standpoint. If anything, it would just be an obstruction to material flow, and hinder the ejection of the part slightly.

Do we know if this gasket was two-shot molded, or if the sealing material was applied in a separate mold? There might be a way to tell by it'* injection point, but I don't deal with two-shot much at all.

Whatever the reason for their existence, I believe it'* an engineered-in feature of some sort. Perhaps it'* for expansion, as Bill suggested. I can't honestly think of any other reason for it.

Actually, expansion could account for the failure there, too. The area "gifted" with the molded in "expansion joint", is allowed to expand with heat, while the material directly next to it is not. That'* a recipe for stress and failure over time, isn't it?

Quote:
Originally Posted by willwren
... However, from what I've seen on multiple DEX gaskets (not just 3800'*), the failures don't start at those 'expansion slots'. The failure starts at the silicone rubber/Nylon interface.
I suspect that the area where the silicone (or whatever that is) overmolds onto the nylon is the thinnest part of the nylon carrier.

If the failure is caused by the "expansion slots" allowing some material to expand while the material next to it can not, then failure could be expected at the thinnest/weakest point. Without having a failed gasket in front of me, that kinda sounds like what we're seeing here.

Not to say that is the root cause of the failures, but it is one possible factor.

I would also be very interested in knowing if there is any difference in the thickness of the nylon carrier where the sealing material is overmolded, between a S1 and S2 nylon gasket. A small difference in thickness there could at least partially account for the different failure rate between S1 and S2 gaskets. Either take a micrometer to them, or look up a part print for each...?
theJMFC is offline   Reply With Quote
Old 10-31-2007, 02:41 PM   #74
Senior Member
Posts like a Camaro
 
Join Date: Jan 2003
Location: Jenison, MI (Near Grand Rapids)
Posts: 1,070
Thanks: 0
Thanked 0 Times in 0 Posts
theJMFC is on a distinguished road
Default

Sorry for the double-post, but the last one was getting a tad long...

I forgot to mention that I picked up some small scrap parts from work. They're about 1" x 2" in size, made of nylon 66 (actually says >PA66< right on the back). It is not glass-filled, but I think that'* irrelevant as far as a reaction to chemicals. SO, if anyone wanted to do some scientific testing, and has the means to... I could pass those along.

I would have no problem doing the testing myself either, if we can agree on a solid, scientific method (and one that I can actually accommodate in my garage or basement).

EDIT: Also, this is interesting...

I think I may have found the company who makes at least a few of the Series II gaskets: http://www.spmgaskets.com/index.php?id=419
theJMFC is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
How can I diagnose a blown head gasket? Maybe LIM gasket? rstrunk 1992-1999 6 03-15-2009 10:24 PM
LIM gasket replace I think !!!!!!! jamesvmvmurray 1992-1999 1 10-27-2008 09:09 AM
GM Settlement for Dex Cool caused gasket failures WalterMitty General GM Chat 1 04-25-2008 02:10 PM
Who can tell me what this is? I'll tell you where I found it 01BonneSC 2000-2005 19 07-19-2007 12:59 PM
CHECK MINE OUT AND TELL ME WHAT YOU THINK vze3r85p Your Ride: GM Pictures & Videos 6 01-30-2003 02:25 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 11:17 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.