Odd problem with PS/alt on 93 Corolla

Look at the number of accessory drive belts on the front of the engine (the front of the engine is on the right hand side of the car from the passenger compartment perspective). If there is only 1 accessory drive belt, then it is driving the alternator, power steering pump, and AC compressor. If there are 2 accessory drive belts, then see if one is powering just the AC compressor.

When the steering wheel is turned all the way to the stop, the relief valve does open but the pump is still working very hard.

When checking the condition of the accessory drive belts, check the ribbed underside to make sure it is not glazed or has chunks missing from the ribs. Also make sure that the belt is properly tensioned.

It's a 14 year old car - when was the last time you changed the fan belt singular (serpentine) or belts plural (old school V-belts)? It is (or they are) probably overdue to be changed, and are glazed and slipping.

If it still acts up with a fresh belt and it's a one-belt multi-rib serpentine system, the spring in the automatic tensioner takeup pulley may be bad and it's not getting the belt tight enough. Or you don't have the tension set properly on a car that does it by hand.

The relief valve pops on the PS pump at hard-lock, but it is still working at maximum output - the pressure has to go high enough to pop the relief, and that only throttles the system pressure back 50 PSI or so while it's bypassing. The relief valve doesn't close again until you ease off on the steering wheel, and the system pressure drops down to the normal unloaded state.

When your hands are off the wheel is when the system is at minimum pressure. The spool valve in the steering box is bypassing the fluid right back to the pump, and keeping the pressure low.

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Good question, and I have no idea, since it's not actually _our_ car (though we've been offered it for free if we want it). I suspect the answer is "last time it broke". Visually, the belts [there are at least two] seem OK and the tensions is about what I'd expect.

Thanks. I was visualizing the system differently.

There are at least two belts, but it's a bit difficult to see which one goes where. I'll have a closer look this weekend.

By ribs you mean what I would call teeth?

======== You should be able to get an inexpensive click type belt tension gauge at NAPA to check belt tension. You might be surprised to see how far they can be off when actually checked. Correct tension is in the manual:

I bought the Burroughs belt tension gauge on eBay and every time I check it is difficult for me to believe that the correct belt tension on the Camry is 120 pounds - seems awfully tight, but I've found that figure listed in three different places in the Factory Service Manual and also checked the calibration of the gauge - it is correct. My guess is that the belt when loose vibrates a lot between the pulleys actually accelerating bearing wear, whereas when correctly tensioned, as the engine revs increase the belt stays straight. This isn't really a factor with the short power steering belt, but the principle is the same. With the factory belt, used, it had to go all the way to the end of the adjustment slot to get the correct tension - eighty pounds IIRC.

There are 3 types of rubber belts used in automotive applications. The type most people probably are familiar with is called a V-belt, and if you were to cut the belt and look at the end, the profile looks roughly like a V with a flat top and bottom, or an inverted pyramid with the pointy end cut off. The sides of the belt should fit tightly with the inner sides of the pulley, and that contact is what drives the accessories.

The second type of belt is called a ribbed belt, and if you cut the belt and looked at the end, you would see a series of grooves or ribs on the under-side of the belt, almost like treads on a tire that mate with grooves in the pulleys, and it is the groove - to - groove contact that drives the accessories. A ribbed belt is usually used for serpentine belts, where 1 long belt drives everything on the front of the engine.

The third type of belt is a cogged or toothed belt, most often used for timing belts. The teeth in the belt fit in teeth in pulleys to provide precise timing and do not allow for any slippage.

This link

has pictures of the types of belts, from left - to - right, V-belt, a cogged V-belt (a cross between a V-belt and a toothed belt), a ribbed-belt, and a toothed belt.

ISTR our geometrical friends call that a "frustum of a pyramid". Inverted, as you say. Something to do with zombie languages[*]. :-)

[* : my coining -- "dead" languages that won't stay dead]

You must have a phenomenal memory to remember a term like "frustom"

OTOH, I can barely keep my children and pets' names straight. When it is time to call them, it is Caseymarktigermatthewsarahshadowgizzie.

*heh* Partly the oddity of the word, partly my memory being a bit like flypaper -- it picks up the intellectual counterparts of dead insects. FWIW for decades I actually misremembered it as "frustrum", only fixing it as "frustum" on checking for the post cited above. (Yes, I check such facts. Sad, wot? )

Good idea: use the same name for all. Like car makers who tag a long series of different models with the same monicker.

I agree with Sherlock Holmes' hypothesis that the human brain has a finite capacity, and I'm afraid I've reached capacity with obscure tidbits about mechanical devices. I still can't remember the difference between a bogie and an eagle and a hook and a slice.

LOL! How true!