Need coolant help! - S-10 Forum
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post #1 of 12 Old 04-23-2019, 11:28 PM Thread Starter
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Need coolant help!

I've got a 1995 4.3L TBI with 166k miles. I need to do a radiator flush and I need new coolant. I haven't done a flush since a got the truck and I don't know what was in it before. I don't know the condition of the gaskets and such around the engine. It has not had a rebuild. I'm planning on flushing it with water twice before I put new coolant in. I don't want to dissolve anything with harsh flush solvents. Any advice on types of coolants?


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post #2 of 12 Old 04-24-2019, 12:19 AM
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Re: Need coolant help!

Even if it originally had the green stuff, your ok to use dexcool but it is important to flush ALL the old coolant out of the system. The green stuff and dexcool don't play nice with eachother so it is important that all the old green stuff is removed before making the change to dexcool. GM actually recommends the change to dexcool for it's mid 90's cars and trucks that had the green stuff from the factory. As for what brands to use, chevron, prestone, shell, valvoline, ac delco and GM (obviously) are the only GM approved manufactures of dexcool coolant so use one of those.

It's also a good time to pressure test the system and repair any leaks you may find
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post #3 of 12 Old 04-24-2019, 12:59 AM Thread Starter
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Re: Need coolant help!

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Originally Posted by thebadwrench View Post
Even if it originally had the green stuff, your ok to use dexcool but it is important to flush ALL the old coolant out of the system. The green stuff and dexcool don't play nice with eachother so it is important that all the old green stuff is removed before making the change to dexcool. GM actually recommends the change to dexcool for it's mid 90's cars and trucks that had the green stuff from the factory. As for what brands to use, chevron, prestone, shell, valvoline, ac delco and GM (obviously) are the only GM approved manufactures of dexcool coolant so use one of those.

It's also a good time to pressure test the system and repair any leaks you may find
Thanks for the quick response! I did quite a bit of research before posting this and what you stated is basically the agreed on stance. I'm just not sure enough to choose. I really like my truck and I want to keep it running forever. I want to take care of it and keep things tip top. Any coolants you would recommend? I've heard OAT coolants are more corrosive than IAT (over time at least). Thanks again!

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post #4 of 12 Old 04-24-2019, 02:28 AM
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Re: Need coolant help!

Dexcool OAT coolant is a good coolant when the cooling system is sealed like it is supposed to be. Where OAT coolant becomes more corrosive is when a small leak is present in the cooling system and allows air to mix with the coolant. Dexcool and air aren't good bedfellows and when they mix, the dexcool becomes acidic which leads to corrosion. As long as the system remains leak free, dexcool works very well for a long time. If a leak in the system develops, repairing it in a timely manner is in your best interests.

I don't see one as being better over the other when it comes to corrosion inhibiting. The service life of OAT coolant is much longer than IAT though. IAT needs serviced every 30,000 miles because it's corrosion inhibitors begin to break down at that point. With dexcool the corrosion inhibitors are good for 100,000 miles, assuming the system remains sealed.

That said, if the truck had green coolant in it from the factory and the change to dexcool is made, GM recommends that the coolant still be flushed every 30,000 for the next 2 to 3 flush cycles (60-90,000 miles) then the dexcools full 100,000 mile service life can be followed. This is because if any IAT coolant remains in the systems when the change to dexcool is made, the dexcools corrosion inhibitors begin breaking down sooner. Essentially, it's just a precaution.

Unfortunately 1995 was the year when GM was transitioning to dexcool. So some 1995 model year GMs came with green coolant while others came with dexcool. The later the production date the more likely it had dexcool but its hard to say which it actually had in it from the factory. The first full production year of all GMs having dexcool was 1996. Personally, I would give it a hell of a flush and use dexcool. Pressure test the system and fix any leaks before doing so though.

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post #5 of 12 Old 04-24-2019, 04:47 AM
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Re: Need coolant help!

I'd have to disagree due to the trucks mileage. You'll need to change either at 196k and again at 226k. Think the engine will last that long? Maybe, maybe not. And since dexcool doesn't like leaks you'd be pushing your luck because of the mileage on the whole system.Most trucks need all new hoses and some a heater core by 200k. J/S

I bought a 98 with 198k for a base for a swap and every hose except the top rad leaked. Which was fine since I was planning to trash them all anyway.
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post #6 of 12 Old 04-24-2019, 08:43 AM
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Re: Need coolant help!

Quote:
Originally Posted by thebadwrench View Post
<snip>
That said, if the truck had green coolant in it from the factory and the change to dexcool is made, GM recommends that the coolant still be flushed every 30,000 for the next 2 to 3 flush cycles (60-90,000 miles) then the dexcools full 100,000 mile service life can be followed. This is because if any IAT coolant remains in the systems when the change to dexcool is made, the dexcools corrosion inhibitors begin breaking down sooner. Essentially, it's just a precaution.
<snip>
Everything I snipped is good information as well, but I wanted to focus on the highlighted section.

Dexcool® coolant is rated for a service life of 5 years or 150,000 miles, whichever comes first. Unless you're driving the thing commercially, 5 years almost always comes first.

The older IAT coolants are good for 2 to 3 years or about 30,000 miles.

For GM Vehicles, my personal preference is Prestone Extended Life Antifreeze/Coolant (part number AF2000 possibly followed with some letter[s]). It's an OAT coolant that isn't as finicky as Dexcool®, mixes with almost any other coolant without any serious adverse effects, and has the same 5 year/150,000 mile service life as Dexcool®. It also seems to have good corrosion protection as far as I can tell. It's more than "good enough" even if it's technically "not as good" as Dexcool®.

Peak has a similar "universal long life" coolant that is probably "good enough" and most of the FLAPSs offer a house brand "universal long life" coolant which is probably also "good enough." All of the universal long life coolants seem to offer the same claims for service life and the ability to mix with other coolants without negative reactions.

Another thing, I tend to replace all the hoses (including all the heater hoses and the bypass hose and any other small hoses in the system) on the 2nd or 3rd coolant change (10 to 15 years out), and I tend to just replace the water pump at that point as well (they also have a limited service life, and rarely make it to 20 years without wearing out and failing).

I always replace the pressure cap when I do a coolant change (every 5 years), and on GM engines with the thermostat at the top, front, I replace the thermostat as preventive maintenance at every coolant change as well. The springs fatigue and weaken on the cap and old caps tend to let coolant boil off, resulting in "mysterious coolant loss" which is often misdiagnosed as a more serious problem. Caps are cheap. And if there's any air in the system at all, the thermostat usually gets air exposure and can corrode and get sticky. Again, cheap part, not worth the risk. If you don't change it, at least inspect it and if you see any corrosion at all, replace it.

Final tip, bleed the air out of the block when you fill it. If your thermostat has a "jiggle pin," you might be able to fill without opening a bleed point to let the air out, but it won't hurt to give it an open port to let the air out. On most S10 engines, the coolant temperature sensor is near the highest point on the engine, right by the thermostat outlet and that makes a great bleed point. The heater hose connected to the manifold port is also a good bleed point and if you're changing that hose anyway, just leave it loose at the manifold until you've filled the system to the point where coolant comes out there. Then connect it, tighten it and top up the rest of the way. Same thing if you use the coolant temperature sensor port to bleed the air out. Remove the sensor, fill until coolant starts to flow out that port, reinstall the sensor and top up.
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post #7 of 12 Old 04-24-2019, 09:13 AM
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Re: Need coolant help!

last 15 yrs or so Ive been using Cascade as a flush
can fill with regular water after a serious power flush,drive it for a while,
flush with distilled water 2x then do a refill with your choice of 50/50
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post #8 of 12 Old 04-24-2019, 01:15 PM Thread Starter
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Re: Need coolant help!

Wow. A lot to take in here. I really appreciate all your help. My plan was to rebuild the engine at 200k. I’m replacing the radiator sometime soon so maybe doing new hoses, thermostat, water pump, and such would be a good idea later on. But for right now I just need em to last until then. My main concern is my head gaskets. My hoses are fairly new already.

So from what you guys have told me.
1. Flush the system really really well.
2. Dexcool should be fine. Can use other OAT coolants designed for older engines.
3. Watch for leaks and make sure to bleed the system of air when refilling.
4. Replace the thermostat along with the coolant change.

Let me know if I missed anything.

Thanks!

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post #9 of 12 Old 04-24-2019, 10:41 PM
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Re: Need coolant help!

Don't forget a fresh radiator cap.

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post #10 of 12 Old 04-24-2019, 10:58 PM
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Re: Need coolant help!

Speaking of radiator caps, it might be just in my head but I've had better luck with the original equipment 15psi cap than the 16psi caps that all of the aftermarket ones seem to be.




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post #11 of 12 Old 04-25-2019, 12:19 AM
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Re: Need coolant help!

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Originally Posted by manbearpig View Post
Speaking of radiator caps, it might be just in my head but I've had better luck with the original equipment 15psi cap than the 16psi caps that all of the aftermarket ones seem to be.
I've had a couple of Spectra radiators in both vehicles. I've used the OEM cap and couldn't get them off no matter what I tried. I finally used a Dremel to cut the wings off of the cap. Stant caps work great.

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post #12 of 12 Old 04-25-2019, 08:16 PM Thread Starter
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Re: Need coolant help!

Thanks everyone! I'll be sure to get the flush done soon. Good luck all!

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