Used wrong power steering fluid

[Jeepfan123]

Hi everyone,

I have a 2019 JL Wrangler and I thought it would be a good idea to remove the old power steering fluid and add in some fresh. Just as some basic upkeep. I searched for the correct power steering fluid on multiple mopar parts websites and these parts websites with my VIN number kept saying my 2019 takes the ATF +4 fluid in my 2019 JL. So I bought some and drained and filled the power steering reservoir and turned the wheel a many times.

After I finished I watched a YouTube video of someone doing this to make sure I did it correctly and found a video of someone saying the JLs take a special Mopar electric power steering fluid (NOT ATF). I immediately got a ride to the closet dealer and got the correct fluid. I then siphoned out as much of the ATF fluid I could and replaced it with the correct electric power steering fluid instead. Did the drain and fill several times turning the wheels many times again.

After all this everything seemed okay for a few days but lately it feels like my steering is very very heavy and stiff now. Uncomfortably stiff to the point it's tiring to drive my jeep. My wheel barely wants to return to center on turns anymore. My steering was fine before this.

I had an alignment done today at the dealer hoping that would maybe help the issue somehow but no luck.

Does anyone think I could've damaged my power steering pump or something with that brief time I had ATF fluid in it instead of the electric power steering fluid? Should I keep flushing with more electric power steering fluid?

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[2019 JLUR]

I would doubt that you hurt anything. I have run ATF +4 with my ram assist since 2019.

 

[limeade]

It's possible you have air trapped in the system (best case scenario). Try bleeding the system and see if it improves your steering.

 

[BDinTX]

I questioned one of our new AI overlords about this:

If you mix ATF+4 into a system filled with Mopar EHPS fluid, you are setting up a chemical and mechanical conflict that will eventually ruin the steering system. They are completely different types of oil that do not play well together.
Here is exactly what happens inside the system if they get mixed:
1. The Fluid Chemical Conflict (Viscosity & Additives)

• Immediate Thinning/Thickening Misbalance: Mopar EHPS fluid (similar to Pentosin CHF 11S) is an ultra-low viscosity, dedicated synthetic hydraulic fluid designed to flow smoothly in tight electronic tolerances even at extreme sub-zero temperatures. ATF+4 is a much thicker, high-friction automatic transmission fluid.
• Additive Clash: The anti-foaming agents, detergents, and friction modifiers in ATF+4 are chemically incompatible with the base oils in EHPS fluid. When they mix, they can cause the fluid to break down, lose its shear stability, and fail to protect moving parts.

2. Pump Foaming and Cavitation
Because the chemistry is compromised, the fluid will begin to foam under pressure.

• The electric pump spins at incredibly high RPMs to generate steering assist.
• Air bubbles caught in the foamed fluid cause cavitation (where tiny air pockets collapse violently under immense pressure). This strips away the protective fluid barrier, leading to metal-on-metal wear inside the pump gears. You will likely hear a distinct whining or buzzing noise when turning the wheel.

3. Seal Degradation
The rubber seals, O-rings, and internal components of an EHPS system are explicitly engineered to resist the specific synthetic compounds of MS-11655 fluid. ATF+4 uses a different chemical base that can cause these specific seals to swell, soften, or prematurely harden and crack, leading to stubborn fluid leaks along the rack and pinion or at the pump connections.
4. Electric Motor Overheating and Failure
Because ATF+4 is thicker and more viscous than EHPS fluid, the electric motor driving the pump has to work significantly harder to push the fluid through the steering gear.

• This extra resistance causes a sharp spike in amperage draw.
• The increased electrical load generates massive internal heat. Over time, this thermal stress will trigger the system to either drop into a protective "limp mode" (reducing steering assist) or simply fry the electric control module built into the pump assembly.

What to do if they already got mixed
If even a small amount of ATF+4 was accidentally added to the reservoir, do not turn on the ignition or drive the vehicle if you can avoid it. Keeping the engine off prevents the electric pump from cycling and drawing the contaminated mixture deep into the steering rack.

1. Suck it out: Use a fluid transfer pump or a turkey baster to completely empty the reservoir.
2. Flush the lines: If the vehicle has already been driven, you will need to perform a full system flush. Disconnect the return line, drain the old fluid into a container while turning the steering wheel lock-to-lock (with the front wheels jacked up off the ground and engine off) to push the contaminated fluid out of the rack, and continuously replenish the reservoir with fresh Mopar EHPS or Pentosin CHF 11S until only clean, green hydraulic fluid runs out.

 

[Jeepfan123]

I questioned one of our new AI overlords about this:

If you mix ATF+4 into a system filled with Mopar EHPS fluid, you are setting up a chemical and mechanical conflict that will eventually ruin the steering system. They are completely different types of oil that do not play well together.
Here is exactly what happens inside the system if they get mixed:
1. The Fluid Chemical Conflict (Viscosity & Additives)

• Immediate Thinning/Thickening Misbalance: Mopar EHPS fluid (similar to Pentosin CHF 11S) is an ultra-low viscosity, dedicated synthetic hydraulic fluid designed to flow smoothly in tight electronic tolerances even at extreme sub-zero temperatures. ATF+4 is a much thicker, high-friction automatic transmission fluid.
• Additive Clash: The anti-foaming agents, detergents, and friction modifiers in ATF+4 are chemically incompatible with the base oils in EHPS fluid. When they mix, they can cause the fluid to break down, lose its shear stability, and fail to protect moving parts.

2. Pump Foaming and Cavitation
Because the chemistry is compromised, the fluid will begin to foam under pressure.

• The electric pump spins at incredibly high RPMs to generate steering assist.
• Air bubbles caught in the foamed fluid cause cavitation (where tiny air pockets collapse violently under immense pressure). This strips away the protective fluid barrier, leading to metal-on-metal wear inside the pump gears. You will likely hear a distinct whining or buzzing noise when turning the wheel.

3. Seal Degradation
The rubber seals, O-rings, and internal components of an EHPS system are explicitly engineered to resist the specific synthetic compounds of MS-11655 fluid. ATF+4 uses a different chemical base that can cause these specific seals to swell, soften, or prematurely harden and crack, leading to stubborn fluid leaks along the rack and pinion or at the pump connections.
4. Electric Motor Overheating and Failure
Because ATF+4 is thicker and more viscous than EHPS fluid, the electric motor driving the pump has to work significantly harder to push the fluid through the steering gear.

• This extra resistance causes a sharp spike in amperage draw.
• The increased electrical load generates massive internal heat. Over time, this thermal stress will trigger the system to either drop into a protective "limp mode" (reducing steering assist) or simply fry the electric control module built into the pump assembly.

What to do if they already got mixed
If even a small amount of ATF+4 was accidentally added to the reservoir, do not turn on the ignition or drive the vehicle if you can avoid it. Keeping the engine off prevents the electric pump from cycling and drawing the contaminated mixture deep into the steering rack.

1. Suck it out: Use a fluid transfer pump or a turkey baster to completely empty the reservoir.
2. Flush the lines: If the vehicle has already been driven, you will need to perform a full system flush. Disconnect the return line, drain the old fluid into a container while turning the steering wheel lock-to-lock (with the front wheels jacked up off the ground and engine off) to push the contaminated fluid out of the rack, and continuously replenish the reservoir with fresh Mopar EHPS or Pentosin CHF 11S until only clean, green hydraulic fluid runs out.

Well that doesn't sound good. Geez. This is crazy how these Mopar parts websites keep recommending ATF fluid for my 2019.

As for flushing all I can do is drain the reservoir and add electric power steering fluid and turn the wheel and repeat. There isn't a return line on these new ehps reservoirs so regular flushing doesn't work it seems. There's just one on the bottom of the reservoir. I even called a dealer and asked for a power steering flush and they said the ehps in the jeeps doesn't need a flush because there is so little fluid in them.

I have an appointment at a jeep dealer next week for them to take a look closer and see what they can do. I hoping this doesn't turn into an expensive mistake.

 

[Nokones]

Most, if not all of the vehicle manufacturers, stopped using ATF for power steering systems many decades ago and have their own formulated power steering fluid.

It is always best to check with the Dealer's Service/Parts to ensure you are buying the correct product.

 

[BDinTX]

Unfortunately, I agree. Even if they'll try to salvage it, the material and labor costs, and lack of warranty will probably make replacing the pump the better choice.

I do miss the days of going to any auto parts store and grabbing whatever brand I preferred. Everything was compatible, easy to find, and fairly cheap. Not so much anymore.

Good luck

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