Updated LIM gaskets for S1? - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 04-25-2006, 12:14 PM   #11
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Many cars here that have NEVER had an UIM failure or gasket failure get the buildup. It'* a chemical breakdown with the DEX itself. There are numerous TSB'* and other communications within GM about it.

We used to have a couple Techinfo articles regarding DEX, but since nothing 'official' has ever come out of GM regarding it, jr's3800 felt it best to try to include a little information and some suggestions in the UIM failure article instead.

Some cars do fine with it, some don't. Dex may simply react differently to different types of water, sealants, and other things like chinese tea. It'* just not as stable in the long-term as standard Glycol-based coolants.
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Old 04-25-2006, 12:15 PM   #12
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Just to weigh in on this one a minute...

I have no specific beef with Dexcool having had it only in the Bonneville so far, personally. However, here are some interesting tidbits I've picked up over the years...

After, my UIM and LIM gasket replacement, the dealer (pre-BC) replaced my Dexcool with regular green coolant. At the time, I considered it odd, what with the dealer being a GM rep and all. I would have expected that they would have refilled with the same Dexcool. Since my wife picked up the car, I never did go back and ask why. Still... interesting.

I do know that Dexcool requires a closed pressurized system or it will tend to do more internal damage. While I was involved in the development of a coolant hose system for the Delta program (Cavalier, Grand Am, etc.) we held many discussions and testing sessions to measure (what was considered to be) the increased cavitation of tees and elbows caused by Dexcool under pressure at higher flow rates. In addition, steel was no longer allowed in the coolant lines or sensors.

Therefore, my personal opinion is that Dexcool systems must be more closely watched/maintained. This is fine for those who are religious about their car maintenance and upkeep. These folks are, however, a minority of car owners...

IMO then, Dexcool falls into a higher risk catagory than the green coolant.
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Old 04-25-2006, 12:16 PM   #13
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On a side note I have had nothing but good luck with the Prestone Longlife Dex Compatible coolant... Whne we put a water pump on the 92 Mitsubishi 5 years ago I used the new Prestone Longlife coolant in it... Been great stuff and resides in the 95 as well.. This is the stuff that will reside in the 91 LE and 91 SSE in the near future

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Old 04-25-2006, 12:26 PM   #14
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Quote:
Originally Posted by willwren
Many cars here that have NEVER had an UIM failure or gasket failure get the buildup.
Just to clarify, I was referencing the LIM and not the UIM... and not a complete failure either, but gaskets that just leak period.
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Old 04-25-2006, 12:32 PM   #15
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The dexcool seems to evaporate and sludge up when it has airflow and is not pressurized.

Thinking about the vacuum theory, if a leak exisited some coolant would get into the oil. When running there is constant heated pressure when this occurred it would destroy the bearings quickly.

Maybe you could perform a test for us CS.

Fill a glass w/green coolant and one with GM Dexcool.. leave them open to the air and see if over time Dexcool doesn't evaporate and sludge a little while the green stays consistent.
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Old 04-25-2006, 12:32 PM   #16
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Quote:
Originally Posted by CSFiend
Quote:
Originally Posted by willwren
Many cars here that have NEVER had an UIM failure or gasket failure get the buildup.
Just to clarify, I was referencing the LIM and not the UIM... and not a complete failure either, but gaskets that just leak period.
I've been thinking about this....

The residue rings COULD be related to the cavitation and POSSIBLY actual wear of the rubber hoses. Dexcool required a ton more complicated rubber compounding and reinforcement for the coolant hoses, as it tended to attack the hose lining. But that'* just speculation at this point. A lot of chemical and compound testing would have to be done before a real determination could be made, IMO.
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Old 04-25-2006, 01:52 PM   #17
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I think for saftey sake, im going to swap to the green when I can. My GF used to have a 99 Lumina in which the intake failed. We didnt have the money to repair it at the time and so we drove it for a long period of time adding more coolant as the level dropped. When you looked at the oil filler cap, it was full of sludge but that didnt make a difference, we kept on driving it.

Finally the engine started to misfire and the lower end went out, we still drove it a little here and there, it was our only car at the time and finally got rid of it a little over a year ago and got her into a 04 Grand Am.

Now I have Dexcool in my 94 Bonne and I dont notice any sludging in the resevoir tank at all. The lower intake is leaking though and will be confirmed the next time I get the car up on a lift.

I will be doing the gasket soon, but not if the Dexcool will eat at it and force me to do the gasket again.

When my brother ran the vehicle info at his work, it came up that the lower intake was done a few times all within a couple of months. Now I dont know why it went back for the same problem so many times, but now that I have learned about the Dexcool, I think that might have something to do with it.
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Old 04-25-2006, 02:18 PM   #18
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As Lash mentioned to me off line, the dexcool system needed to be different than the previous ones with sensor that didn't contain steel etc. I'd flush and change back when you do the gaskets.
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Old 04-25-2006, 03:15 PM   #19
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Yes, do a VERY thorough flush whenever you change. I'd be tempted to entirely replace the capacity with water first. Then switch coolants. Don't allow the smallest chance of a mix.

Consider the dex-compatible stuff Bill and Don are running.
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Old 04-25-2006, 03:30 PM   #20
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This was never meant to turn into an informational session on the pros and cons of using dex-cool versus green, but i'm really pleased it'* gone that way. i'm glad we can all learn so much from this forum; it beats the pants off of the DSM forum I used to frequent when i had my 95 TSi AWD.

Regarding Black94SSEi'* comments about his 94 running Dexcool, if it were my personal choice, i'd switch back to green when you can. All of the comments that have been made regarding the corrosive properties of Dexcool on rubber hoses as well as the sensors being made out of incompatible materials sound like they have a lot of technical aspects to base their opinions on.
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