Infiniti FX50 PSF Foaming, overflowing and making noise.

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2,040
Location
Jupiter, Fl
I bought a used FX50s in June of last year. When I bought it, the power steering was loud in the morning and got worse as it got hot, but it was otherwise OK. I tracked the noise to the pump and swapped it out for a new one. I also swapped the PSF to Dex VI as it was a recommended 'upgrade' over the nissan PSF. It was nice and silent until a few thousand miles later when I stared doing some serious mountain driving. After it got hotter than normal, it would start to whine loudly. No performance issues, and when it cooled back down it would be quiet again. Initially I though the fluid level might be a little low and the G force from going around the sharp corners as fast as possible might have it sucking air. After adding a little more fluid and bringing it up to the hot line, the oil was starting to leak out of the cap. When I checked it while it was still hot, it was obviously aerated and expanding. I don't know how air could be getting into the system. The low pressure side is a straight line from the bottom of the bottle into the pump. I don't know if there is a different PSF that is less likely to foam, or if I need a larger PSF reservoir to allow the oil to settle. An additional cooler PSF cooler? It is totally fine until I am in really tight mountain roads and mid to high RPM. I suspect having aerated PSF is not ideal for any component in the system. I'm getting ready to head back into the mountains in a couple of weeks and am curious if there is anything I should do, aside from staying in a higher gear and or cornering less agressively.

A minor point is that this vehicle has electric rear wheel steering as well, and all the tires are a bit wider and stickier than stock - so steering gear load could be higher.

Is there a non-foaming additive? The oil I used was Mobil Dexron VI that was left over from the Buick.

Thanks!
 
Messages
9,014
Location
Virginia
^^^^^^^

I believe that this is correct by 2eha.... Pump is done.

A new better pump and new Dexron VI fluid and you will be good to go.

I have used Dexron VI in my 08 Nissan Altima VQ power steering pump system.... And it has been perfect. 321,000+ miles still on original power steering pump.
 

CBR.worm

Thread starter
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2,040
Location
Jupiter, Fl
The pump was replaced 6 months ago w/ a new OEM pump, as mentioned in the second line of my post.

I also have a VQ powered infiniti that is close to 200K on the original pump. The FX50 pump looks and sounds nothing like the VQ pump.
 

Astro14

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Virginia Beach
I’m curious what you mean by “new”. I read your post, but many people use that word to mean, “a rebuild that I just purchased” and not, “new manufacture from the OEM supplier”.

A new pump for my Mercedes retails at $1,724. Even that is a remanufactured pump, but that’s at the MB dealer parts counter. You’ll read a lot of posts on the MB forum about “new” pumps, that aren’t actually new...

So, forgive me for asking, I just want to understand the source for this pump that’s giving you trouble...
 
Messages
9,014
Location
Virginia
The pump was replaced 6 months ago w/ a new OEM pump, as mentioned in the second line of my post.

I also have a VQ powered infiniti that is close to 200K on the original pump. The FX50 pump looks and sounds nothing like the VQ pump.

I honestly feel bad for you and that this circumstance is not right or the way it should be.

Sure sounds like you got a dud... A bad one.... Obviously...

If it's jacked up already.... Which is sure seems to be....


It is a bad pump.

Bad parts happen... OEM included at times...
 
Messages
3,271
Location
Outer Banks, NC
If the PS pump is not covered by a parts warranty, I'd suck it up and shop for a Nissan/Infiniti pump and go back to using Nissan PS fluid. I hope you didn't have a remanufactured pump from an outfit like Cardone or A1. If so, that likely would explain your problem. An option would be a brand new pump, Hitachi PSP0031, for $255 in stock at Rock Auto. Also, I wonder if the foaming was caused by not properly bleeding the system during the last repair, which could have prematurely killed the replacement pump.
 
Last edited:

CBR.worm

Thread starter
Messages
2,040
Location
Jupiter, Fl
It is a new OEM Nissan/Infiniti pump (made by Hitachi maybe?). It might be covered under a parts warranty - I'll have to check.

Is it likely though that the replacement pump would have the same issue as the factory pump? It is totally fine for around town or highway driving, it only gets loud after being on twisty roads for more than a few minutes - which is pretty common for me. The transmission temp at that point is typically 210-220 degrees, not that they are related, but I think possibly all the fluids are run hot in this car. The factory pump was like this for as long as I've had the car. Again, I don't know if having rear-wheel steering has any impact on the pump. I wouldn't think so.

Before this, I had an FX45 which had a totally different power steering setup which never made any noise under the same conditions.

Going back to Nissan PSF is probably worth a shot, it's easy. The fluid seems to be getting foamy and aerated.
 
Messages
9,014
Location
Virginia
You know that is worth a shot like you said...

Change the fluid. . .

Hopefully the part is still under warranty. .

Feel bad for you here.

I have been there. And it sucks big-time.
 

Astro14

$100 Site Donor
Staff member
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Since the previous pump failed, I’m wondering how much debris (metal shavings, junk, etc.) got into the system as a result of that failure.

In other hydraulic systems, like my Mercedes suspension, a pump failure can flood the system with debris, causing a rapid failure of new components, particularly new pumps.

When you fit a new pump, and it sounds like that’s your only option, I would do a thorough flush of the system and seriously consider installing a filter in the return line from rack to reservoir.
 

CBR.worm

Thread starter
Messages
2,040
Location
Jupiter, Fl
Sorry to revive this oldish thread, I'm still driving it as is. One point I forgot to mention is that the tires were changed from all-season 265/45/21 to UHP Summer 295/40/21s. I don't know how much more stress that would put on the hydraulic components, but I imagine it could add some heat on twisty roads at high rpm.
 
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