changing coolant on 2007 2500HD

jus2shy wrote:

#1Flyboy wrote:
. . .Silica fallout is usually found in OLD antifreeze( REALLY OLD!!! ) & usually in Diesel engines IF not keeping up with their nitrate levels/ coolant filters. . . NOT an issue with todays coolants as they are formulated (When is last time in last 10 years anyone saw silicate fallout?). . .I worked a successful automotive cooling system shop (33 years) & yes, actually purchased FULL trailer loads (20 pallets) of coolant at a time. . .Only took a few classes on coolants & such but had 43 years in cooling systems industry addressing & solving problems with cooling systems. . .Also talked to several AC Delco guys(at trade shows) about their Dex-Cool problems & every one of them had a different answer. . .By the way your link did not work.. . .YMMV. . .

Well, silica fallout still happens today and forms goo. Here's what happen when you take the coolant from a 2012 chrysler vehicle using a HOAT and mix it with 5% or more of the new OAT (AKA Grapejuice) that chrysler is using in a 2013 vehicle: http://starparts.chrysler.com/newsletters/newsletter_Oct_2012.pdf It's a PDF, so you need to have a PDF viewer to see this as with my last link. Seems to work fine for me anyways. On page 4 of the print, you can see the results of the mixing. This alone disproves that all coolants are compatible with one another.

Some coolants do have wide compatibility, but when you mix coolants, you are always diluting their additive package and I am not a chemist, so I can't tell you what would happen if you mix brand x with brand y. That's why I personally believe in following the manufacturer specs.

Also, Japanese auto makers tend to use a phosphated anti-freeze, primarily because of the intense use in aluminum and such, along with the quick development of that "film" that protects and coats all the parts quicker than a normal OAT. Then Daimler still uses a Silicated anti-freeze. Mix that Silicated with certain OAT anti-freeze and you can run into more of the gelling issues. Another reason why I'm really careful about anti-freeze selection.

However to the OP, I reviewed my coolant notes while at work today. If you did have a full flush in the system and have less than 5% of the old anti-freeze mixed with the new antifreeze and what they used is a universal coolant. You may be able to get away with it. However, you'd still want to flush fairly early compared to the normal 5yr/150k miles that I believe GM recommends for Coolant replacement.

Really the issue is mixing of coolants. However, even though people call it "Deathcool", I think it earned that name due to its early implementation and not understanding the full properties of OAT coolants, especially the 2-eha that's in DEXCOOL. That tends to soften certain seals and types of plastics overtime. Personally, I like that Chrysler's new OAT doesn't use 2-EHA so I'm hoping I don't have the issue with my motor in the future but I will still watch it.

If you're bored, here's a good article on Coolant in general, it goes through why certain packages are in certain coolants and such and may open your eyes to who uses what (and yes, this is a professional rag) (although it's titled to talk about Chrysler's coolant switch): SAE Coolant Article

Thanks for this information and I was unaware that both Ford and Chrysler (I guess MB/Daimler has decided to stay with the HOAT coolant) had switched from their HOAT coolants to the more traditional OAT type coolants so the information in my prior post is somewhat dated. That SAE link was especially enlightening and informative. I can understand the reasoning for the switch since the OAT type coolants as I previously stated do have a longer change interval than the HOAT coolants. I have two vehicles, a 2001 Sebring with the 3.0 Mitsibushi engine and a 2001 Ford 7.3L diesel both of which use G-05 and have been using that coolant in them for some years (I switched the 7.3L from the old IAT green with SCAs to the G-05 back in around 2004). I also have a 2013 Hyundai Sonata LTD. that I don't have a clue on what type of coolant it has so I guess I need to do a little more homework to learn about that one since there is now a plethra of coolants used across the vehicle spectrum which tells me it's even more important to pay attention to where and how you have your coolant system serviced since even the slightest inattention to the details can result in HUGE PROBLEMS.

Larry