I put brake fluid in the steering rack!

I did a stupid thing. I drove around for a few hundred miles before the power steering failed. Only then did I realize my mistake.

I can get the bad fluid out and put in new, but I’m wondering why the power steering was working on the incorrect fluid and then suddenly stopped working — no more power assistance. Have I destroyed something expensive? There’s no puddle of fluid on my driveway.

I will investigate later, but in the meantime I wonder if you could tell me: how likely is it that I have broken something expensive vs. simply needing to replace the correct fluid?

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This mistake is likely to cost you. Brake fluid lacks the lubricant that the steering rack needs to operate properly. In addition, brake fluid is caustic and will not play nice with the seals in the rack. If the rack will no longer move, or move with difficulty, then the brake fluid has already attacked the moving parts of the steering rack. You could pull the rack and attempt to remove all traces of the brake fluid, but I fear it would be an exercise is futility. Sorry for the bad news.



What about your Ferrari? Is it holding well with the same setup?

Give us more details about this experiment - what failed? Any grinding noises? Is it pumping anything when you’ll try to spin the wheel?

This could be the thing for the MythBusters, but apart from pump being unable to pump anything you may be fine once power steering system will be well flushed with fresh ATF… The fact that you’ve just pushed 200k miles into your steering rack is another thing…

By “no more power assistance” I assume you mean the rack still functions, but with no boost. If there is still fluid in it and you are truly getting zero boost, the pump is probably toast. You could try draining and flushing, maybe fill it half way or more with lucas stop leak and the rest with ATF. That’s a $100 experiment that might save you some time while you save up for replacing the rack, pump and lines. If you choose to drive it this way be prepared for a PS hose to rupture as the hoses will be weak. Only hoses specifically rated for brake fluid would tolerate this, and I am 98% sure that PS hoses are not compatible with brake fluid.

You need to replace pump, rack, everything. Brake fluid will have attacked the rubber lines, they will be getting soft and weak. You need to flush out the hard lines and the cooler while the system is open.

Tough mistake, but others have done worse!


The seals are swollen and must be now three times their size, jammed or torn to pieces.
Lucas stop leak won’t do anything, even aggravate the situation.
Flush the system, fill with ATF and see what the story is.


Aristides is right I didn’t think about the brake fluid swelling the seals…

Thank you for the replies. Here’s some more information that may be relevant.

I bought this car two months ago. About two weeks ago, the steering started groaning. I checked the fluid level and there was no detectable fluid in the reservoir. That’s when I filled it with brake fluid.

I just checked the level in the reservoir now, and it is empty. I was mistaken when I said there was no puddle. There is in fact fluid on my driveway.

So now I’m wondering … is it empty now because it was leaky before, and now the new (incorrect) fluid has leaked out just like the old (correct) fluid did? Or did the new fluid leak out because I ruined the seals with the incorrect fluid?

I don’t know. I’m going to fill up with ATF and see what happens.

@XjsBanger My Testarossa doesn’t have power steering.

@XjsBanger and @BobPhx The power assistance failed. The rack still works, but there’s no assistance.

So my next step is to fill with ATF and see. I will report back. Many thanks again for your help!

You may be lucky then - just purge whatever is inside of your PAS system. Easy to do, however may get messy.
Best way forward is to drain current content and refill with fresh ATF, but that’s just a precaution (undo one of the fittings/pipes in the turret area, gravity will do the rest). The main operation will require full fluid exchange.

  1. Unplug both hoses from expansion tank - you will need to identify ehich one is return.
  2. You will need 10l of ATF and a bucket
  3. Stick inlet hose into the fresh ATF canister (5l pref)
  4. Drop the return into bucket
  5. Disconnect fuel pump with help of inertia switch.
  6. Run on starter motor several times for 10 sec max and eith 2min break between cycles
  7. Start the engine.
  8. Make sure you have fresh ATF in the canister all the time / swap canisters when going low.

There is a big chance that your pump is mincing foamed goo rather than liquid and it may simply have no compression on lowered viscosity. After 10l flushed through PAS the outcome should be clear. If positive - flush another 10l and you’re all set.

Thank you so much @XjsBanger!! I will try that.

Start the engine (fo a short while at current conditon…), take the cap off your expansion tank off and squeeze one of the hoses with your hand to seal it shut (if you’re strong enough…). It will either burst some fluid into the tank on release or suck some of it in. You can see the flow clearly while lighting the torch into the tank normally, however at churrent dluid condition it may be useless.There may be limited flow as well… If you’ll struggle - I’ll have a look at mine tomorrow and update you as I simply don’t rememeber…

The low pressure return hose should be the one connected to the reservoir with a hose clamp. The others will be high-pressure tube fittings if memory serves.

I think both hoses are low pressure in this area :wink:

quote=“XjsBanger, post:12, topic:414512”]
I think both hoses are low pressure in this area :wink:

Probably true only if there is no steering input.

Fill it with Lucas Power Steering Stop Leak in. You never know your luck.