Coolant Change Interval for Hemi Engines

[HEMIMANN]

I see Hemi engines come from the factory with OAT coolant...

COOLANT: 10 Year, 150,000 miles.

Part Numbers: Mopar

68163849AB 50/50 COOLANT
68163848AB Concentrate COOLANT

IAT being the original old time "green" coolant with silicates. (Inorganic Acid Technology)

Reading about these, OAT coolant lasts a long time, but doesn't do a great job on preventing corrosion for a long time, which is why HOAT was developed to do both. Ok, I'm not going to switch form OAT to HOAT as they have chemical compatibility issues, and there's always some residual left in the block.

Do members really think we should wait 10 years or 150,000 miles to change OAT coolant? I'm concerned about corrosion and water pump bearing lubricant additive being used up. I used to change 2-3 years with old time IAT.

When does member ship change Hemi Engine coolant?

 

[Jwithing]

Interested to hear the opinions. I did a full flush at 55k miles or so... because I put windshield wiper fluid in it haha. I realized rather quickly and highly doubt any made it out of the reservoir, but I did a full flush anyway.

 

[kurek]

I just did coolant and transmission fluid change on my 2015 with 41k miles. Both "early" by a long shot. Both fluids when drained were visually indistinguishable from new but six years is a long time for anything exposed to oxygen, multiple metals, heat, etc.

Can't tell anyone else what to do with their truck but that's what I did with mine.

 

[srv1]

I love to change fluids in my truck.It makes me feel warm and fuzzy inside.Just finished up a brake fluid flush.That old fluid looked like straight up doo-doo.

 

[RLJ10X]

I let the dealership change the fluids when the manual says. If anything goes sideways, it's on them. Your truck was designed and built by a team of very smart, experienced engineers. For the most part, they make few mistakes. I recently had the coolant changed by the dealership, for the first time; 10 years.

Don't do big power, don't do big tires, don't do some redonculous lift; Use your truck for what it was designed, and 97% of potential problemswill never materialize.

Put away 15% for retirement, don't buy stuff you don't need, to impress jerks you don't like. You'll be set for life. I'm done.....

 

[HEMIMANN]

I love to change fluids in my truck.It makes me feel warm and fuzzy inside.Just finished up a brake fluid flush.That old fluid looked like straight up doo-doo.

A lifetime of designing, working on, and experience with powertrains and I still see brake fluid (DOT III glycol-based) needs replacement every 2-3 years due to moisture absorption. You can feel brakes getting spongy over time. I did mine @ 3 years (regardless of mileage.....moisture absorption is time-based) and instantly they stiffened up.

 

[Burla]

Why I always say I like my hoat, glad it came with it. I'm not sure if the first run will last ten years or not, I guess a lot of it will be miles, but I seriously doubt any future runs would be ten years. Absent hooking a hose to radiator, there is no way to get a 100% flush without spend series money due to block plugs. So you re-use a large % of coolant, because nobody hooks the hose to radiator anymore. I am on a 3 year interval high my hoat, I wouldn't go much longer then that with oat if it were me.

 

[Jwithing]

Why I always say I like my hoat, glad it came with it. I'm not sure if the first run will last ten years or not, I guess a lot of it will be miles, but I seriously doubt any future runs would be ten years. Absent hooking a hose to radiator, there is no way to get a 100% flush without spend series money due to block plugs. So you re-use a large % of coolant, because nobody hooks the hose to radiator anymore. I am on a 3 year interval high my hoat, I wouldn't go much longer then that with oat if it were me.

I used distilled water to flush it, but no block plugs removed

 

[Burla]

Yes, but how do you flush block with no plugs and no temp as the thermostat will be closed? Even if you fill and flush a bunch of times, you will still have old coolant.

 

[Burla]

Yes if you can figure out the quagmire that is a cooling system to deal with trapped coolant, the best thing you can do is a full flush. However, once you realize the effort versus reward, I think most guys just opt for draining what you can and refreshing what is left.

I tried to see how many flushes it would take to get back to factory color, far left new coolant far right first flush, I friggen gave up at 3. I just say go to a 3 year interval and get 60% out, that is all I got. I gave up because of guys before me I trust on the board had a time and half dealing with drivers side block plug, and my passenger side bold was froze anyhow. Man it would have been nice if oem used anti seize on factory bolts, but instead of opening up a can of worms it is best to make due sometimes.

 

[HEMIMANN]

They used to have coolant drain ports on V8 blocks - we just changed coolant on the 2005 Chevy Big Block 8.1L this way. But I'm gettin' too creaky to keep crawling around these things like that, so 1st coolant change I'm taking to my local shop with Mopar OEM OAT. Wish they'd put in HOAT. Oh, well.

Thinking 5 years is a good limit for corrosion protection / anti-corrosion additive depletion? Flush out any rust scale? Hemi engine blocks are still cast iron, so....

 

[Docwagon1776]

Your truck was designed and built by a team of very smart, experienced engineers.

Under the direction of a team of lawyers and accountants...

 

[Burla]

Don't forget the all important focus groups.

Yeah, they all look like truck drivers to me.

 

[Wild one]

Yes, but how do you flush block with no plugs and no temp as the thermostat will be closed? Even if you fill and flush a bunch of times, you will still have old coolant.

The block has drain plugs,they're just not all that easy to get at Mike.

 

[RLJ10X]

Yeah, Burla, how many times have you read here that some dude will time how long it takes to perform a job by the number of beers consumed?

^ That one of the many reasons why I don't buy anything used anymore. You can have Joe Sixpack.

If I didn't believe Dodge /Chrysler didn't build a good product, I'd quit buying them.

 

[dpinvidic]

How about the Flush and Fill Kit ?
You insert a "TEE" in the heater hose and flush the system with a garden hose letting water come out of the radiator cap.

 

[Bigskyroadglide]

Well I have trucks with both hoat and oat. I just stick to the original stuff. My 5 year, got a flush and fill at about 8 years and tested great down to - 50 with some adjustments to the recommended 50/50 mix on the 5 year variety.

My 10 year is coming up for a recommended change I'll hopefully get to it by at least year 12.

I have been lucky with no water pump issues, no overheating issues and generally a stable environment.

While I can understand the importance of change and agree with it, I just try not to overthink it.

 

[HEMIMANN]

Yeah,

How about the Flush and Fill Kit ?
You insert a "TEE" in the heater hose and flush the system with a garden hose letting water come out of the radiator cap.

I used those in my youth. There's so much a guy is willing to keep doing, though, when the arthritis sets in in earnest.

 

[HEMIMANN]

The block has drain plugs,they're just not all that easy to get at Mike.

Even my RV was difficult to get at the block drain plugs - the steering gear was right in front of the left bank drain plug. Some guys take the stat out before hooking up the heater hose flush so the radiator tubes get flushed too. Most stats have some kind of orifice de-aeration bubble relief, so the lazy way to do "flush" is add chemical flush de-scaler and drive around in summer weather (no antifreeze). The de-scaler has water pump lube. Then drain again, rinse, and re-fill.

That's fine for smaller engines like my tractor, but a royal PITA project on a full size vehicle for us folk getting older.

 

[El Guapo Phil]

I had my coolant flushed not by choice but by stupidity. I had an oil change at the best shop around. I am in Belize and the RAM dealership is at best a hit or miss shop. I did not notice that the tech filled the oil pan with 5 ½ quart of blended synthetic oil, 5 -20 wt.
My 2016 Big Horn had 52k miles on it.

After driving up and down hills and using my 4X4 drive, the engine heated and literally began to huff and puff. Coolant spewed out the pressure release cap and I was perplexed. Must be the stat, so I changed out the thermostat and drained as much coolant as possible since it need coolant. Bled, burped and reburped the Hemi and refilled it with HOAT coolant.

It kept getting hot but not too hot, so I checked the coolant, added some and went on my way. It was time of another oil change and took to the best shop in town. After an hour or so at home, I decided to check the oil. Just a hunch. You bet, it was at just under the safe make. The shop put 5 ½ quarts of oil because the tech thought that what it needed. I added almost a quart of oil. Check it the mark and it read full. Since then, the Hemi stays in acceptable heat range.

Moral to the story, check the oil regardless of who or where you have the oil changed. The engine cooling system need the oil to be in acceptable parameters for it to work properly. Remember the engine systems are interrelated. Best be mindful than stupid.