Cooling system upgrades

I need to replace both cooling fans. I'd like to upgrade the system, can anyone recommend a good aftermarket solution? Also, I'm getting a lot of rust in the coolant. I've tried various rust inhibitors but still need to flush the system every 6 months. Has anyone tried a filtration system? Does that work?

You need to fix where the rust is coming from before you go any further. The Hesco water pump and ZJ fan clutch are about the top, you also didn't say what year your XJ is?

I have replaced engines and radiators several times and throughly cleaned the system everytime, yet every 6 months it's full of dirt again. I firmly believe it's being introduced through the air hole in the overflow bottle. One day I'll get around to putting an airfilter on it. Unless you are doing something above and beyond engine wise, stock cooling works fine.

Unless you live and drive in Death Valley, stock cooling fans are all that should ever be required.

A coolant filter might be helpful. There is no way coolant contamination is entering from the overflow bottle.

A coolant filter helped my Jeep a lot.

If you are replacing the electric fan, go with the late model design. It flows a lot more air than the early model design.

As far as rust accumulation goes, be sure to use distilled water or deionized water. A filter will only serve to catch debris. It won't stop further accumulation.

I would flush the coolant system with a cleaner until it is clean it may take a week or two and maybe a lot of flushes . I got a power flush gun from Ebay and it does work good . I got my system clean and now I watch the cooling system and change the coolant often or use a coolant the last a long time . I do use distilled water only with the coolant .

Be careful using any of the harsh flush kits, they can do damage to other parts including the freeze plugs. I would recommend at constant water flush followed by a full refill with white vinegar and let stand for at least 2 hours. When refilling buy only the pre-mix anti-freeze, distilled water can be a problem also.

Tim_MN said:

There is no way coolant contamination is entering from the overflow bottle.

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There is something to air getting in the system causing rust. I recently had a slow coolant leak that was hard to diagnose (at first), ended up being the heater core, but it was only leaking from the drain at the firewall (nothing in the interior). I eventually found it as it worsened but the air introduced into the system caused rust really quick.

The lore associated with using distilled water stems from a real phenomenon, but it doesn't apply to iron or steel to any significant degree. The solubility of elemental iron in pure water is very low. Anion additions to water such as chlorides or allowing the pH of the coolant to drop will increase iron solubility, corrosion, and loss of iron from the engine.

Using premixed antifreeze negates any need to try to prove that distilled water is not bad, so its the easy answer, but distilled water is the right choice when using concentrated antifreeze. Its certainly a better choice than tap water, bottled drinking water, or softened water, all of which can have significant anion content.

For those people having rust build-up issues, it might be informative to monitor water pH. The target pH range should be around 8.0. There will be a tendency for the pH to drop over time. If it drops below 7.0, then change out the coolant. If freshly changed engine coolant starts out at 7 or below, then there is some issue with the coolant and/or water that is being used. The upper end of the acceptable pH range is a little fuzzy, although I think its safe to say that its better if the coolant pH stays below pH 9.0.

Probably overkill for most, off the shelf/ebay aftermarket beef up i did:

3 row all aluminum rad (must cut out rad support for fill neck)

https://www.ebay.com/itm/Full-Alumi...p2349624.m46890.l6249&mkrid=711-127632-2357-0

While in there, its a good time for new hoses

https://www.ebay.com/itm/Fit-For-19...p2349624.m46890.l6249&mkrid=711-127632-2357-0

Fan Clutch from Rockauto was a Hayden 2737. Water pump i went with the GMB high flow. E-fan was a stock 99 style from Amazon, dorman iirc. OEM 195* thermostat, gates housing (NOT high flow as listed) from rockauto round it out.

I have yet to break the 210 mark on the stock gauge, usually hovers around 195-205. On triple digit days this fall it got a hair away from 210 with AC on full blast at idle.


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boncrshr said:

There is something to air getting in the system causing rust. I recently had a slow coolant leak that was hard to diagnose (at first), ended up being the heater core, but it was only leaking from the drain at the firewall (nothing in the interior). I eventually found it as it worsened but the air introduced into the system caused rust really quick.

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If the leak is large, there's a reason for that. Oxygen dissolved in the water enhances corrosion. The water in the cooling system is mostly oxygen free by virtue of the fact that it's a nearly sealed system where the initial available air is consumed by corrosion. Once the oxygen is consumed, the corrosion rate will drop.

The water in the reservoir is in contact with outside air, so it absorbs oxygen in the air. Small amounts of dissolved oxygen enter the cooling system when water in the reservoir is pulled into the cooling system as the engine cools. However, if there is a substantial coolant leak, then a lot more water with dissolved oxygen enters the system because the water is more frequently replaced. In addition, if an air pocket is allowed to form in the cooling system, that will greatly increase the amount of dissolved oxygen.

And if the user is pouring tap water or bottled drinking water in the cooling system, the anion content of the coolant is going to be continuously increased.

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boncrshr said:

There is something to air getting in the system causing rust. ..... the air introduced into the system caused rust really quick.

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Cooling system rust is caused by owner neglect of maintenance, not by air. By definition, an open cooling system is not sealed from the atmosphere,

Green ethylene glycol coolant should be changed every 2 years or 30,000 miles to replenish the rust inhibiting additives.

Tim_MN said:

Cooling system rust is caused by owner neglect of maintenance, not by air. By definition, an open cooling system is not sealed from the atmosphere,

Green ethylene glycol coolant should be changed every 2 years or 30,000 miles to replenish the rust inhibiting additives.

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Here's the thing though, this happened in my new to me XJ and I had flushed cooling system, new water pump, new radiator, radiator cap, thermostat and hoses when I got it, which was only about 6 months prior to the heater core incident.

It seems like there should be very little air in the cooling system, or am I missing something? After filling your system, the air bleeds into the overflow tank as the motor heats up, and then coolant mix is sucked back in as it cools, so eventually there shouldn't be much air? It did seem like it got rusty awful quick as it got worse and lost coolant faster.

By definition, an open cooling system is self bleeding. There will be only the smallest measure of air (essentially none), in the coolant.

Rusty coolant is from lack of maintenance. Loss of coolant is from leakage or head gasket issues.

I have owned 7 XJ Cherokees over the last 19 years. One for all 19 of those years, and several for 4-6 years each. I have replaced several radiators, a couple heater cores, and lots and lots of coolant.


No rust in my cooling systems.








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My xj was doing something similar... rusty clumpy coolant every 6 ish months... turned out to be a blown head gasket. Exhaust gasses were getting in the coolant. Was like that for 50k miles before someone hit it and totalled it.

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Tim_MN said:

By definition, an open cooling system is self bleeding.

...

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It is open in the sense that it has the coolant reservoir that is exposed to atmosphere, but by virtue of its design, only the small amount of the cooling water in the reservoir is exposed to the outside world at any given time, so there should be very little dissolved oxygen in the cooling water circulating in the motor.

SlowXj said:

My xj was doing something similar... rusty clumpy coolant every 6 ish months... turned out to be a blown head gasket. Exhaust gasses were getting in the coolant. Was like that for 50k miles before someone hit it and totalled it.

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Before i did my upgrade, my flush and fill came out looking like this. I dont think it was ever backflushed, or if it was someone dumped stop leak in it for the leaking heater core.

Fwiw, drain and fill with a quart of CLR in a “dry” system before upgrading (backlfush all coolant out with water until clear, then fill). Make sure to thoroughly backflush the CLR out (i did a couple rounds of this, finishing off with a distilled water flush twice and refill with 50/50 zerex g05 and distilled water). When you stop seeing soapy bubbles in the fill neck its done. When the flush water comes out clean, you are done.

Before all this, the gauge sat halfway between 210 and the next hash mark on the gauge (~225*F est. temp). Now around 200-205.


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Woodswanderer said:

Before i did my upgrade, my flush and fill came out looking like this. I dont think it was ever backflushed, or if it was someone dumped stop leak in it for the leaking heater core.

Fwiw, drain and fill with a quart of CLR in a “dry” system before upgrading (backlfush all coolant out with water until clear, then fill). Make sure to thoroughly backflush the CLR out (i did a couple rounds of this, finishing off with a distilled water flush twice and refill with 50/50 zerex g05 and distilled water). When you stop seeing soapy bubbles in the fill neck its done. When the flush water comes out clean, you are done.

Before all this, the gauge sat halfway between 210 and the next hash mark on the gauge (~225*F est. temp). Now around 200-205.


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Click to expand...

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You could always run a glycol-free coolant........
https://www.naxja.org/forum/showthread.php?t=1156848