I am constantly adding power steering fluid to a 1994 Lexus LS 400 with what may be a power steering pump or hose problem. How can I find out where the problem is?

Answer 1

Here's the system block diagram: the pump, the hoses and the powersteering ram. It's a closed system. The fluid in there stays in there unless there is a leak. The pump pressurizes the system via power derived from the belt that drives it. A hose and line delivers the fluid to the ram. In the ram, the fluid forces the operating cylinder one way or the other, as directed by the steering wheel. Fluid returns to the pump via another hose and line assembly.

If you are adding fluid, it is getting out of the system. You are looking for a leak. Internal leaks in the pump or the ram will cause the system to work poorly, but won't necessarily cause a loss of fluid. If you are replacing fluid, it's getting out. Look at the fittings and the hoses and the ram itself. Fluid can leak at fittings, out of hoses, or out of the seals in the ram, and that means out along the operating shaft, so look there.

It may help to put a clean piece of cardboard under the car to help spot the leak. Use a large enough piece of the stuff so it is under the pump and the ram and the rest of the delivery system. (Newspaper may not stay put.) Start the car in a safe way and in a safe place, and then just turn the wheel back and forth slowly while sitting there in park or neutral so you don't go anywhere. After a minute or so, shut the car off and have a look at your cardboard. Go for another minute or two if you don't see anything. If you have a leak, it should show up shortly. You may have to clean some or all your hoses and fittings off to find a small one, but with some luck you'll have it spotted in a few minutes.

---------------------------- Following added 12/9/2010----------------------------

I have a first gen. LS400 myself, and here might be a simple fix that could save you alot of money.

Does your car blow a little (or a lot) of white smoke when you start it up cold (first time you start it for the day)?

If the answer is yes, your problem is most likely the exact issue mine had; which is also an extremely common issue with the first generation LS400. It is called an air control valve, and when it fails it will cause Power Steering fluid to be sucked into the intake on start up which creates your powering steering "leak" (Which can be alot of fluid!), and also could account for other problems such as a failing alternator or starter... If any of this rings true read the following taken from clublexus.com where you will find everything you need to know about this issue. Very simple cheap fix.

---------------------------ClubLexus forum post below---------------------------------

The most logical thing to check would be the air control valve. If this valve is leaking, there are no visible signs of fluid because it is being drawn into the engine and burned. A good clue for this being the problem is a white puff of smoke from the exhaust when you crank the car. However, if the volume of fluid being leaked is small, this would not necessarily occur.

Yes, your mechanic can easily remove the air control valve. It screws into the bottom of the power steering pump.

You can check for leakage in this valve by detaching the two hoses that run from the valve at the nipples where they attach to the air intake and manifold. Seal off the ends of the hoses by putting a screw or something similar into them. You would also need to seal off the two points where they attach to the air intake and engine. You will not do any harm by trying this for a few days. You might not even notice a difference in the car's operation.

If the power steering fluid loss stops while you have these hoses disconnected, you have found your problem. The part number for the valve is 17630-16040. It should cost about $70.00 and should be available at any Lexus or Toyota dealer.

This is a very common problem on first and second generation LS models and has been discussed numerous times. Do a "Search" for more discussion.