PS fluid quieter than ATF in cold temp startup

[crainholio]

Vehicle is a 2007 Toyota 4Runner at 274K miles, bought at 164K miles with negligent maintenance by the original owner. I had initially flushed the black PS with Castrol DEX-MERC High Mileage ATF, temporarily plumbed in a Magnefine filter on the return hose for a few hundred local miles while the crud pushed out, and all seemed fine until temps dropped into the
This summer I saw a video by the Car Care Nut, who appears credible and claims to be a Toyota Master Tech. In the video, he asserted that power steering fluid was to be used rather than ATF (skip to 13:40):



I bought two quarts of Lube Gard "Complete Synthetic Power Steering Fluid Multi-Vehicle Formula" and did another flush. The fluid is clear in color and I didn't get every last drop of the ATF out, as the fluid in the reservoir turned light pink shortly after reconnecting the return hose and starting the engine. Ah well. The good news is the cold start groaning noise is gone, even down to 1degF recently. The steering has always been smooth and this made no noticeable improvement, but it's nice not hearing the "morning sickness".

 

[ka9mnx]

Never had such an issue with Dex ATF in my 4Runner. I don't know what's going on with your 2007. This guy is pure B.S. ATF is a hydraulic fluid just like PS fluid. Your PS system might need a better cleaning. If it's having trouble pushing the fluid through the system is starving for fluid which will cause the groaning when cold.

 

[incognito_2u]

Vehicle is a 2007 Toyota 4Runner at 274K miles, bought at 164K miles with negligent maintenance by the original owner. I had initially flushed the black PS with Castrol DEX-MERC High Mileage ATF, temporarily plumbed in a Magnefine filter on the return hose for a few hundred local miles while the crud pushed out, and all seemed fine until temps dropped into the
This summer I saw a video by the Car Care Nut, who appears credible and claims to be a Toyota Master Tech. In the video, he asserted that power steering fluid was to be used rather than ATF (skip to 13:40):



I bought two quarts of Lube Gard "Complete Synthetic Power Steering Fluid Multi-Vehicle Formula" and did another flush. The fluid is clear in color and I didn't get every last drop of the ATF out, as the fluid in the reservoir turned light pink shortly after reconnecting the return hose and starting the engine. Ah well. The good news is the cold start groaning noise is gone, even down to 1degF recently. The steering has always been smooth and this made no noticeable improvement, but it's nice not hearing the "morning sickness".

Original pump?

 

[SC Maintenance]

There are certainly different viscosities of ATF. Dex/Merc sounds like an old school high viscosity fluid. Maybe something like official Dex VI fluid - which is a lower viscosity ATF - would have the same affect as your PS fluid?

Castrol DEX-MERC High Mileage ATF

I have read not to use high mileage fluid in vehicles with rack & Pinion because the seal conditioners might swell the seals making the rack take more force to move. Not sure if there is truth in that.

 

[crainholio]

Original pump?

Yes.

 

[Egg_Head]

I use this too in my vehicles, does calm down any noise. Popular in the Hyundai crowd b/c of claimed PSF 3 compatibility.

COMPLETE Synthetic Power Steering Fluid - Lubegard

www.lubegard.com

 

[crainholio]

There are certainly different viscosities of ATF. Dex/Merc sounds like an old school high viscosity fluid. Maybe something like official Dex VI fluid - which is a lower viscosity ATF - would have the same affect as your PS fluid?

I looked up the product data sheets for each, and assuming the specs haven't changed since I used Castrol HM and Valvoline, here's how they compare:

40degC 100degC VI​

Castrol HM 36.6 8 200
Valvoline 34.5 7.1 174
LubeGard 36.29 6.64 140

If cold viscosity was causing the groaning noise, Valvoline should have performed better it seems based on the low temp viscosity and viscosity index. I had looked up viscosity data after getting tired of the noise w/ Castrol HM and saw Valvoline DEX-MERC was thinner back then, which compelled the selection.

I have read not to use high mileage fluid in vehicles with rack & Pinion because the seal conditioners might swell the seals making the rack take more force to move. Not sure if there is truth in that.

Whatever. In this case, the groaning noise was not associated w/ rack component movement as the truck was and is stationary during cold startup. No hands on the steering wheel, I'm sipping coffee which is at a much lower viscosity.

 

[Tomioka]

Pentosin CHF11S goes much lower for freezing temps and is recommended in GM vehicles that operate in extreme cold.

 

[Foxtrot08]

I know of an OEM chassis builder that uses Allison 668 ATF in their PS systems…

 

[HyundaiAbuser]

I’ve had better luck with Maxlife in power steering vs regular dex/merc for keeping the pump quiet in the cold

That is from using both in the same vehicles

 

[Egg_Head]

Pentosin CHF11S goes much lower for freezing temps and is recommended in GM vehicles that operate in extreme cold.

... and it's only $26/liter.

 

[Jetronic]

I'm using total fluide DA, pretty similar to pentosin I'm sure.

I also use it in the hydraulic actuators for my automated gearbox.

Volumetric mass at 15°C kg/m3 820
Viscosity at - 40°C mm²/s 1 050
Viscosity at 40°C mm²/s 18
Viscosity at 100°C mm²/s 5.9
Viscosity index - 320
Flash point Cleveland °C 157
Pour point °C -51

low density, high viscosity index, similar viscosity to ATF when hot but relatively thin when cold.

Looks like a PAO fluid with lots of VII

Would be much more fluid than any ATF when it's really cold, nowhere near $26/liter either

 

[JMJNet]

There is also a factor when you changed it to the PS fluid was later than when you changed to ATF so I suspect that the fluid is probably cleaner.

I had to do the same when I bought the Highlander.
I flushed it once but I was not happy with the result so a week later, I took of the reservoir out, soaked and washed it with brake cleaner, solvent, etc. till all the crudz were all cleaned.
Then I installed it and filled it back.
The fluid still not as red but it is already 40K miles later without issues.

 

[dfarr67]

Pentosin CHF11S goes much lower for freezing temps and is recommended in GM vehicles that operate in extreme cold.

GM has their own CC fluid, probably much cheaper than Pentosin.

 

[Greasymechtech]

You went from thick conventional to thin synthetic.... next time don't skimp on the ATF

https://www.lubegard.com/products/psf/ I've used the "complete synthetic Lubegard PSF too. Looks like they changed the marketing and don't mention 'synthetic' much more.

AUTO TRANSMISSION FLUIDS | WELCOME | CASTROL USA

Castrol® auto transmission fluid can restore smooth shifting, even in vehicles with over 75,000 miles on the odometer. Learn about this Liquid Engineering from Castrol® USA.

www.castrol.com

DEX/MERC (ATF) Automatic Transmission Fluid - Valvoline

Valvoline™ DEX/MERC ATF is a high-quality transmission fluid formulated to meet the challenging demands of many automatic transmissions. Its responsive low-temperature fluidity is beneficial in both electronic and hydraulic controlled transmissions and transaxles. Recommended for use in the...

www.valvoline.com

 

[nthach]

I have read not to use high mileage fluid in vehicles with rack & Pinion because the seal conditioners might swell the seals making the rack take more force to move. Not sure if there is truth in that.

I use MaxLife all the time as PSF. No issues yet.

 

[Jetronic]

There are certainly different viscosities of ATF. Dex/Merc sounds like an old school high viscosity fluid. Maybe something like official Dex VI fluid - which is a lower viscosity ATF - would have the same affect as your PS fluid?


I have read not to use high mileage fluid in vehicles with rack & Pinion because the seal conditioners might swell the seals making the rack take more force to move. Not sure if there is truth in that.

Lower vicosity ATF might help, but it's not going to have even close the viscosity index some PSF does so in the extreme cold it's still viscous.

seal swellers are also seal softeners, that should mitigate them pushing too hard on the rack

 

[mrbreezeet1]

Never had such an issue with Dex ATF in my 4Runner. I don't know what's going on with your 2007. This guy is pure B.S. ATF is a hydraulic fluid just like PS fluid. Your PS system might need a better cleaning. If it's having trouble pushing the fluid through the system is starving for fluid which will cause the groaning when cold.

Sounds to me like the proof is in the pudding. It's quiet now when cold. Solution, use the power steering fluid.

 

[BufordTJustice]

My 2011 Subaru Outback 3.6R has always been hard on its PSF. I turkey-bastered the recto reservoir with Subaru ATF-HP every 5k OCI. Fluid stayed bright, translucent, cherry red all the time. Steering whine was ever present when it was hot and cold. Yes, it was bled; both by me and two different ship shops. New hoses/washers/gaskets. Added Lubegard Power Steering Protectant; better... but still very present.

Transitioned to M1 Dex/Merc ATF over 3 quarts of Turkey bastering. Better. But problem not solved.

Then threw my hands up and grabbed a gallon Redline D4 ATF (7.2cst @ 100C) from Summit. Added a bottle of Lubegard PSP to the gallon, agitated thoroughly, and began my ritual.

Huge, enormous improvement as I replaced more old fluid with Redline. Better Steering feel, quieter pump, lower PSF reservoir temperatures, and greatly reduced whine. However, the whine was not completely gone; still there at very cold (19F) and hot (105F) temperatures

Another F-it moment, I ordered a quart of Redline High Temp ATF (9.5Cst @100C). Added a single bottle of Lubegard PSP to the quart, and did two reservoir swaps with the High Temp ATF. This is roughly 8oz. I get about 4oz out of the reservoir with each extraction and the total system capacity is .7qt (not great, TBH).

All whine is gone; at both temperature extremes. Steering is now ultra smooth. Very similar to my Lexus GX460 (which also gets Redline D4 and loves it). The best Steering this old Subie has ever had. Did a 27F start the other Day and the pump was dead silent for the first time since.... ever.

I honestly don't know what is going on inside the pump and rack. This didn't make logical sense to me for the cold improvement (using a much thicker fluid mixture). But the Improvement is just huge.