Project Diplomat – Power steering leak and hose replacement



Leak stuff


M30s are old cars and so with that, I’ve decided that if I have to touch something, I should replace it with something new.

After I got my blue M30 sorted over the past few months, I was happy that my oil, transmission and rear main seal hasn’t leaked. But I started to have some decent leaking from something else. After looking closely, it looks like the high pressure PS hose. I was hoping that if I use some kind of PS fluid with stop leak, I can reduce the leaking and hold off until I was over the shows I entered (JCCS, Nissfest and HIN).

That didn’t happen. I’d have to fill it frequently. So a few days ago, I decided to pull it off.


I started to unplug a lot of stuff to get access to the right side of the engine. Hoses, screws, nuts and clamps being 30+ yrs old, it was more of a pain. Then I had to go underneath and continue to the left side and undo the PS hardlines from the PS rack.

While I was trying to figure it out, I ended up pulling my intake system.


I pulled out the High pressure PS hose, but also the right side part of the reservior return system.


The 2 hoses that come off the reservior I really want to replace. They are hard and difficult. Also the hose clamps were a pain to get off as well, so I want to replace those.

I stopped by the Autozone near me (which is the worst) and the guy wasn’t sure what he had and let me go look in the back. The store is like a warzone, tons of depleted stuff, yet plastic containers on the ground with product in them.

Stopped by a few places, and struck out. This will be a “to be continued”.


For the High Pressure Power steering hose, I found a hydraulic shop near me with good reviews. I know friend’s in LA who have had a high pressure PS hose made between $80-$100, so I was hoping for the same range and I would have asked to make 2 just to have an extra.

* Quick note: My RB25det High pressure PS hose was $80.

I go there and the owner runs the place, has no customer service. Monotone, looks bored and even looks like he just doesn’t want to work. Doesn’t acknowledge a customer walking in… I was put off by him.

But his turn around is quick and within an hour, it was taken cared of. The cost was $160, which I felt was high. So no repeat business for him.


Edrik also mentioned he used a heat sheath, and sent me a link.


I was hoping to do a quick turn around on these. Once I get those 2 reservior hoses, I’ll starting putting it all together.


But I also have to do a few things while my car is lifted.

– Clean throttle body

Last year before JCCS 2022, Malik’s shop was suppose to swap out my old steering rack (nothing wrong with it, but I have a new one I wanted to swap out) and also change the bushings with an Energy Suspension set. That’ didn’t happen. At least I can change out the bushings right now *if* it isn’t do difficult.

Steering shaft bushing, I didn’t realize I needed one until Malik demonstrated how the bushing is garbage. Fortunately, I had an aluminum one from Project Leopard (I couldn’t find this original one, so I got another aluminium replacement) and recently found it in a pile of stuff. So I will replace this while everything is out.


With Project Leopard, I did a lot!

  • Rebuilt Power Steering rack
  • New PS rack bushings
  • New aluminium steering shaft bushings
  • RB25det PS pump brackets and adjustment key
  • RB25det PS pump rebuild
  • PS Bracket
  • Nubis PS mount bolt kit, PS bolt kit and
  • High Pressure PS line



Following up on getting the High Pressure PS hose done, I needed to replace a couple other hoses since they weren’t looking too good.

The 2 hoses come off the PS reservior, one to the pump and one a return line, were looking like they need to be changed. When I picked up the High Pressure hose, I asked the guy working (owner) if he could get me 2 hoses that were similar and he said he couldn’t get me one that was molded, which would cause a kink. Again, this guy didn’t seem he wanted to be there, so I didn’t even want to question him as he looked unmotivated.

The following couple of days, I tried 2 Napa, 1 Advance Auto, 3 O’Reily’s and 3 Autozones and nobody could help me. I went to a local parts shop, Monument Car Parts (here in Pacheco) and they guy put effort into finding a hose that was close.


Everything is discontinued

The return line was pretty straight forward, so that wasn’t a big deal.

Part number 49725-F6602




The suction hose, a bit more complex as it was molded. This hose is connected to the reservior and the PS pump.

Part number 49717-F6601





The guy gave me Gates 19425 – heater hose. When I asked if this was okay, the guy told me it was “fine”. From what Gates’ own website said is that this is not suitable for oil transfer. Just checking some forums, they talk about swelling and the rubber breaking down.

This is the bigger hose and is 5/8ths internal diameter.


After convincing myself, I decided to get properly rated hoses. Napa PS lines. While the hose might not be molded, I figured I can make it work still.

For the suction hose: NPS 76077

For the return hose: NPS 73303

The next day, I get the proper hoses.


I never really took the time to understand hoses until recently. This started with Project Leopard. Hung would tell me specfiics on what to get.

Prior to that,  when I was younger and limited on money, we didn’t pay attention to the ratings, just as long as it worked. I honestly never had issues afterwards (my 240sx my fc rx7, my cressida and my eg civic). But I am in a different mindset now and I want to do things properly and with the right stuff.

The return hose I had Gates wasn’t the right hose, but this hose I got had the rating of SAE J2076

“This SAE Standard covers hose fabricated from textile reinforcement and synthetic rubber, assembled with clamps and/or end fittings for use in high-temperature automotive power steering applications as flexible connections within the temperature range of −40 to +150 °C (−40 to +302 °F) maximum and 1.21 MPa (175 psi) maximum working pressure. This specification defines the minimum performance levels of a flexible connector in the hydraulic steering system to convey power steering fluid from the steering gear back to the pump/reservoir.”

*SAE website


400 series hose

“400 Series Rubber Hose has an inner liner of Nitrile which is reinforced with braid made from high tensile synthetic textile cord to give it extra strength. Raceworks 400 Series rubber hose is safe for use with E85, methanol, oils, lubricants and coolant. Recommended for use on low pressure systems/temperature applications. If using in high pressure or temperature above 70°C we recommend securing hose ends with a clamp.”

After finally feeling I used

I finally put these on last night and will fill up the reservior and do my checks to make sure it is all good.