dexcool in rusty engine

[mbaker]

I have a 1995 Chevy 1/2 ton that my son and I picked up cheap knowing it had overheated and needed some work. It had blown a head gasket and the cooling system was contaminated with oily residue and combustion gases. We had the heads done and while apart I tried to flush and clean the heater core, the radiator, and the somewhat the block even thought the short block stayed together. Unfortunately the heads took longer that expected and I am sure I ended up with some rusting inside the block as it sat partially filled and open for almost 3 months.

After getting everything up and running I ran a blue devil flush to try and get the rest of the oil and any rust or buildup out of the system and got it to a point where the water running out seemed to be clear with no oily film and inside the radiator looked clean. Here is the big question, 1995 was a transition year between green and dexcool coolant. While the owners manual states to use green, the underhood sticker says Dexcool. I have no idea what was in it previously as it was a complete mess, but I almost feel like it at least had some of the old green in it because the intake was stained but it also had orange muddy look to it. Considering its pretty old school iron block and heads but with aluminum radiator what would be the best option, with the caveat that it may not get driven that much in the coming year as it still needs other work... if that matters.

option 1, refill with Dexcool as stated on the sticker just to be 'correct' to the truck. Considering the flush water is clear would this cause any issue even if there is rust inside the block that the flush may not have completely cleaned up? Or since its been contaminated at some point will I see problems with Dexcool in this situation? I have dexcool in other vehicles and haven't really had problems except late 90's intake gaskets but I haven't had one thie messed up and neglected before.

option 2, fill with conventional green. Would this be safer if there is left over rust or particulate in the block? I'm sure in 1995 GM didn't suddenly change production of the engines and just switched coolant types so this is probably ok even with the aluminum radiator. I guess I could pull the sticker off the underhood and noone would be the wiser.

option 3, fill with Prestone or similar AMAM. I'm not really sure what to expect with these as I have always run the specific manufacturer coolants.

 

[V70tdi]

Run Evaporust Thermocure or equal product in it and then reflush and fill with Dexcool when you seems to run it in your other vehicles.

 

[Snagglefoot]

Both Dexcool and Prestone AMAM have 2EHA as the main inhibitor, so that decision is really just a consumer preference based on advertising. I have been running Dexcool for in my 2008 Suburban for 18 years, changing every 5 years. It has the original water pump, radiator and heater core. My other vehicle is a Ford with Prestone AMAM.

Conventional green is for your Grandfather. It’s totally obsolete. That owners manual is over 30 years old. As for the “gasket” issues with 2EHA, that didn’t occur with the truck engines.

Prestone’s MAX AMAM is good for 15 years.
I’d use that one. Fresh water left in a cast iron block will rust overnight. I think one of the cleaners mentioned or else the Preston cleaner would be a good idea, followed by the Prestone Max.

 

[Kira]

Keep in mind that the "First Commandment" of Dex-Cool is "It has to be used in an airtight cooling system".

Does your 1995 have a tightly sealed coolant reservoir?

 

[mbaker]

I understand the green coolant is outdated, I just didn’t know if it would be more tolerant of less than ideal conditions. Or if I’d have the sludgine issues with Dexcool because of the dirty system.

I guess maybe I will run the flush again and go with either Preston’s AMAM or Dexcool if they are basically the same. The green coolant was in the conversation just because I thought once it had been used then it would cause issues with OAT later if switched back.

 

[SC Maintenance]

Dexcool was designed to last a long time. As such the corrosion protection takes a long time to start acting - like thousands of miles. Since your engine is already rusty I would not use Dexcool. A HOAT is much, much faster acting than a OAT like Dexcool.

I will add that even the early engines GM made that were officially designed for Dexcool - were not - and had gasket problems. Your call on that and on 2EHA in general - there are plenty enough threads here discussing that for you to decide. I personally don't think its worth the risk but others disagree.

So I would use a HOAT or I think Valvoline still makes a IAT for older cars.

 

[mbaker]

So is the AMAM the same as dexcool in that it is slow acting?

This doesn’t have the plastic intake gaskets these are old school metal frame composite type gaskrts similar to head gasket so I’m not really concerned about the coolant affecting them , more how it acts with the rest of the system if it’s not 100% clean. I’m not sure a person could get it that way without completely disassembling and cleaning the block during a rebuild.

When we used to circle track we ran straight water in those cars with similar engines and aluminum radiators and never had issues with rusting or corrosion. Those engines sat for 6-8 months at a time before being drained for winter and never saw anti freeze in their life.

 

[SC Maintenance]

So is the AMAM the same as dexcool in that it is slow acting?

This doesn’t have the plastic intake gaskets these are old school metal frame composite type gaskrts similar to head gasket so I’m not really concerned about the coolant affecting them , more how it acts with the rest of the system if it’s not 100% clean. I’m not sure a person could get it that way without completely disassembling and cleaning the block during a rebuild.

When we used to circle track we ran straight water in those cars with similar engines and aluminum radiators and never had issues with rusting or corrosion. Those engines sat for 6-8 months at a time before being drained for winter and never saw anti freeze in their life.

I believe AMAM is a HOAT, but I haven't looked at it since the last time it popped up here. You have a link to the SDS?

 

[ka9mnx]

option 2, fill with conventional green. Would this be safer if there is left over rust or particulate in the block? I'm sure in 1995 GM didn't suddenly change production of the engines and just switched coolant types so this is probably ok even with the aluminum radiator. I guess I could pull the sticker off the underhood and noone would be the wiser.

This...
Conventional green is no longer available but the replacement is much better.
SuperTech is your friend.

 

[Snagglefoot]

Here is a Prestone chart. Chevrolet 1995 onwards. Dexcool.

 

[Snagglefoot]

Dexcool was designed to last a long time. As such the corrosion protection takes a long time to start acting - like thousands of miles. Since your engine is already rusty I would not use Dexcool. A HOAT is much, much faster acting than a OAT like Dexcool.

I will add that even the early engines GM made that were officially designed for Dexcool - were not - and had gasket problems. Your call on that and on 2EHA in general - there are plenty enough threads here discussing that for you to decide. I personally don't think its worth the risk but others disagree.

So I would use a HOAT or I think Valvoline still makes a IAT for older cars.

There are plenty of threads that are totally out to lunch including 30 year old issues that are discussed like they are current.

 

[Saturnguy]

I run Zerex G-05 in my Saturn instead of Dexcool.
https://www.rockauto.com/en/parts/valvoline,ZXG051,coolant+/+antifreeze,11393

Two Bars leak tablets, crushed, added after flush.
These also have an AC Delco part number
https://www.rockauto.com/en/parts/acdelco,10108,radiator+leak+sealant,17603

Wix 24019 Coolant filter base installed on the feed line to the cabin heater core,
( not the return line)
and Wix 24069 (short) or 24070 (long) filter

 

[SC Maintenance]

There are plenty of threads that are totally out to lunch including 30 year old issues that are discussed like they are current.

And there are plenty of threads saying dumping Dexcool and 2EHA into something not designed for it is fine.

So back at ya.

 

[Snagglefoot]

And there are plenty of threads saying dumping Dexcool and 2EHA into something not designed for it is fine.

So back at ya.

Here you go. I’ve done all I can. Moving on. Mods, here is a screenshot to demonstrate Prestone’s opinion on mixing Prestone Max with other coolants.

 

[RooflessVW]

If I've got an honest-to-Hephaestus empty cooling system, it gets John Deere Cool-Gard II.

 

[mbaker]

Well, I have gone back and forth convincing myself from green to dex, back to green, then yellow then back to orange but in the end it seems like they are all similar anymore so maybe it does not really matter. If they are all newer formulations and the green really isn't the old IAT green then choosing seems more of a color decision than anything.

 

[Trav]

Quick rule of thumb I use is if it has a wet intake no Dexcool, dry manifold is no problem. +1 on JD Coolguard II.

 

[SC Maintenance]

Here you go. I’ve done all I can. Moving on. Mods, here is a screenshot to demonstrate Prestone’s opinion on mixing Prestone Max with other coolants.

View attachment 331821

2EHA is a well documented plasticizer that can soften silicon and certain plastics over time. How do you know if it will soften yours if it wasn't spec'd for it - you do not. If you want to take the risk feel free, it is maybe small. But there is really no benefit either. No reward for even some risk is silly.

GM settled a class action based on this. Even stuff they said was designed for it was not.

Private equity owned Prestone / Recochem that profit from it can promise whatever they want. Its not a real source. If you pour it in your 10 year old car and it starts leaking 40K miles later, they just say its an old car. There OGC is ready for your lawsuit.

All 2EHA advocates always play the drama / exhaustion meme that there somehow above the discussion, but provide no actual data - because they can not.

Use what you like

 

[martinq]

Here you go. I’ve done all I can. Moving on. Mods, here is a screenshot to demonstrate Prestone’s opinion on mixing Prestone Max with other coolants.

View attachment 331821

If I was buying coolant for a Dexcool application and I read this, I would not buy. No mention of Dexcool or GM anywhere but they insist, "... All Vehicle Makes, Models & Years...". Confusing. Why do they do this?

 

[Snagglefoot]

If I was buying coolant for a Dexcool application and I read this, I would not buy. No mention of Dexcool or GM anywhere but they insist, "... All Vehicle Makes, Models & Years...". Confusing. Why do they do this?

Because all AMAM is nature’s perfect coolant. Prestone hit it out of the park. I’m not going to argue about it.

Others can discuss oat, poat, zoat, moat, groat all they want. I not going to participate.They can do their own research. As for Prestone colored coolants: The are all 2EHA. The funniest thing in marketing EVER! So long and have fun. Over and out. Snag.