Is My Ps Pump On The Way Out?

[K9crew]

I recently bought a '95 SC400 with 46K on the odometer. A couple of weeks ago I began to notice a humming/vibration coming and going that I can "feel" in the brake pedal. It comes and goes with the trans in D, N or P and with my foot on or off the brake pedal. With my foot on the brake it's more noticeable. When the humming/vibration occurs it seems to go away or diminish if I turn the steering wheel to the left ... or at least it did initially. I checked the PS fluid and it's an odd brownish color and not the ATF red that I'm used to. I've read that PS pump failures are common on the SC400. Any thoughts or suggestions?

While I'm here I was wondering if the reddish coolant in my cooling system is the right stuff for this car. It came that way so I have no idea if it's normal.

Thanks for any help.

:)

[AWJ]

Heh - those damn low mileage 95's weren't driven enough to keep the seals wet I think. Go figure. My steering pump is doing the same - or it was. It went away. I don't know why you would feel it through the brake pedal though unless it is just vibrations. The pump does make that kind of cavitation noise or whirring, soft whiney sound that will change tone louder or quiter when turning the wheel. My pump is leaking. Kind of bad. I need a rebuild or a new one. I thought ps fluid should be more clear. Try flushing it first. Make sure your reservoir strainer is not plugged. You could refill it with toyota ps fluid and a seal wetter. That just might help you out. As long as that reservior strainer is not clogged. If you still have noise - you need a new one or rebuild too.

PS - the antifreeze is that red toyota stuff. I'd recommend draining it and using the normal green stuff. I've only heard stories but they weren't good about the red stuff. I just don't like it. The previous owner of my car mixed the red and green <!--emo&--><!--endemo--> I need to flush that crap ASAP. Any way, yea - the red stuff is normal.

[K9crew]

AWJ,

Thanks for the help. I think you're right about the brake pedal merely transferring the vibration from the engine compartment since there's a direct metallic pathway from my foot to the engine. The vibration/humming can be felt without depressing the brake ... but it's less obvious. I'll try to drain/suck the fluid out of the PS pump and replace it with fresh fluid to see if that helps or eliminates the problem. At this point I don't know if it is the PS pump ... perhaps someone else has experienced the same symptoms prior to a PS pump failure.

Thanks for the confirmation regarding the coolant. I plan on draining/flushing the system in a few weeks and refilling it with Sierra propylene glycol coolant.

:)

[AWJ]

No problem man - I should have given you the old listen test - but I wasn't thinking of it at the time ;)

Have someone work the steering wheel with the engine running while you get ear on the pump. Best way to know. If it makes noise - that's the culprit. Could just be a plugged strainer in the resrvoir. The strainer can't be replaced though. It is molded into the plastic reservior. Some guys have pulled it out. Others have bought new strainers, replaced the fluid and had no more noise or issue. Others have had to rebuild or replace the pump because of fluid leak. The latter is my condition, although it did quit making noise <_< .

Anyways, maybe someone else has dealt with it as well. Feel free to jump in.

[K9crew]

AWJ,

I decided to replace the PS fluid this morning before I went to work. I disconnected the return hose (at the reservoir) and drained the reservoir. Next, I used a short section of 3/8" hose with a plug to cap the return "nipple" on the reservoir. I extended the return hose by about 10" and ran the line into an empty 1QT container. I filled the reservoir with Amsoil ATF and ran the engine for about a second. The empty container now contained about 1/3 QT. I repeated the process two more times until red ATF came out of the return line. I ended up with just over a QT of black/brown PS fluid in the container and nice red ATF in the rack, pump and reservoir. After driving about 20 miles to work I thought that the steering was quicker and more precise (placebo effect?) but the vibration/humming was still there. I'm now convinced that it's something to do with the brake system ... possibly the ABS pump (if there is one). The vibration/noise is definitely more obvious with my foot on the brake but that could be due to an increase in the load on the engine and electrical system .... I'm going to flush and bleed the brake lines and ABS modules over the weekend to see if it helps.

Thanks for the help though .... I appreciate it. Oh, my reservoir is a metal canister and the screen looks very clean.

:)

[AWJ]

Cool. I've been wrong before. I'm getting used to it. Thanks for the clarification on the ps reservoir. At least that can be eliminated as the issue then. Nice job.

Brakes eh? I haven't done much with those yet. Keep us posted please. I may be able to get some info for ya when I get a chance. This helps me learn as much as I can as well - and I like that.

[K9crew]

Well,

I think the noise that I'm hearing/feeling is the hydraulic fan coming on. I doubt that what I'm feeling is normal so either the hydraulic pump is getting ready to quit or the fan bearing is in bad shape. With my hand holding the hydraulic line from the pump to the fan I can feel the fluid flowing in the hose almost like there's air in the line. As the fan cycles on/off I can feel the change in the hose and a change in the vibration. I need to read the repair manual to see if there are any diagnosis/repair procedures for the hydraulic fan.

[AWJ]

Perhaps, I may assist there. I just got back. Your fan, or pulley may have gone out of balance as well. Perhaps the thermostatic clutch assy. Or the water pump itself. Stay tuned. I'll try to have some info tonight if I may find some time.

Regarding the cooling system, there is no documented trouble shooting other than the thermostat. Removal and dropping in water heated to opening temperature. It is possible your water pump is cavitating, or you thermostat is acting up as well as the other items, perhaps a loose bolt or damaged pulley or something throwing things out of whack. Let me know if you want the schematics or removal items procedure - I'll try to get it up.

[K9crew]

AWJ,

At this point I don't think the cooling system is the problem, well at least I don't think it's anything that has coolant flowing through it. I've been reading up on the hydraulic fan arrangement including the hydraulic pump, hydraulic motor on the fan, the fluid reservoir, ECU etc. I was pleased to learn that the hydraulic assembly uses plain old Dexron II ATF which is a good thing. I wasn't happy to learn that the hydraulic fan, pump, ECU etc comprise a relatively complex system. What was Lexus thinking? I don't see the benefit of an hydraulic fan vs. an electric one at all. The system is CONSIDERABLY more complex and WAY more expensive in addition to not being able to run unless the engine is running. I'd be interested in hearing the reasons for the hydraulic set up if anyone is privy to that information. Anyway, I digress ... I plan on flushing the ATF out of the lines, pump, reservoir, cooler etc and refilling the system with Mobil 1 synthetic ATF. The manual lists a procedure for "bleeding" the system so I'll do that to make sure there's no air in the lines. After that I'll have to follow the manual's numerous inspection/repair procedures.

I think you may be right about the fan being out of balance since it appears to oscillate in and out of the plane of rotation ... not by much but enough to be noticeable.

Thanks for your help and your willingness to bounce ideas around.

:)

[AWJ]

Good luck friend.

[slidermike]

I think i am having a similar problem with my clutch fan.

We replaced the radiator and now a high pitched squeeling noise comes from that area.

Does any one know how to "balance" the fan? I checked the fluid levels and they seem fine.

If any one knows how to bleed the clutch fan fluid, then i could try that too!

Thanks

[UCF3]

I think i am having a similar problem with my clutch fan.

We replaced the radiator and now a high pitched squeeling noise comes from that area.

Does any one know how to "balance" the fan? I checked the fluid levels and they seem fine.

If any one knows how to bleed the clutch fan fluid, then i could try that too!

Thanks

There's no fluid for the Engine Fan. See if the fan moves/wobbles. If it does, it's your fan bracket, not your Fan Clutch. I replaced mine two months ago, and man it was a pain.

[slidermike]

Can we replace the fan with an electric one?

I wonder how hard that is?

[K9crew]

UCF3,

SC400's have an hydraulic fan. There's a reservoir containing ATF along with a pump on the block, a hydraulic motor to drive the fan, hoses to connect everything etc. I've never been able to find out why Toyota chose that set up.

slidermike,

I flushed the old ATF out of the reservoir, lines etc and bled the system following the directions in the factory repair manual. I had to use a wire to short two pins under the hood then run the engine for about a minute until no bubbles appeared in the reservoir. I can give you more details when I get to work since I left the factory manual there. As for installing an electric fan .... I don't think that it'd be too hard.

:)

[K9crew]

slidermike,

Here's a link to a pdf file on my server. There are fourteen pages in the manual dedicated to the hydraulic cooling fan. The bleeding procedure is described in full ... I hope it helps.

:)

Hydraulic Cooling Fan information from factory repair manual

[AWJ]

That's nice K9. I linked that up in the faq. Thanks.