| Author | Message | ||
     Chris Miller Prolific User Username: cjm51213 Post Number: 270 Registered: 5-2013 |
Hi Folks, If I turn the steering to the limit on either side, the power steering screeches. My first question is, "What causes this?" and my second question is, "How do I stop it?" Thanks for the help, Chris. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1320 Registered: 6-2006 |
The belt is probably loose or it is worn. Tighten or replace it. With power steering on lock ALWAYS let the wheel back an inch or two. The last bit isn't turning the wheels , it's just straining against everything else and overpressurising the system. | ||
| Bob Reynolds Prolific User Username: bobreynolds Post Number: 188 Registered: 8-2012 |
Yes, the belts are slipping. I had the same problem, I tightened the belts and it went away; only to return a few weeks later. I think I need to get new belts, as I don't think I can tighten them any further. It only does it when the engine is cold though. I know rubber contracts when it is heated, so I suspect the belts tighten up a bit when warm? | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1321 Registered: 6-2006 |
warm rubber grips more. Think about formula one tyres  | ||
| Chris Miller Prolific User Username: cjm51213 Post Number: 271 Registered: 5-2013 |
Hi Paul, When it squeals, I back off until it stops. If I understand what you're saying, it won't matter where I set the limits, assuming they are "settable", because the last tiny segment will always stop the wheels and not tell the power steering unit, so with a loose or worn belt, I'll get a squeal. Is there really no feedback to the power steering unit, like a pressure by-pass, when the wheels are at limit, or it is the case that the squeal is the result of loose/worn belt slippage simply being weaker of the two? Thanks for the help, Chris. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1322 Registered: 6-2006 |
it is the case that the squeal is the result of loose/worn belt slippage simply being weaker of the two? Yes If the belt is not slipping, at lock you will hear a different noise which is the fluid rushing through the relief valve. Not as loud as the belt screeching, but very audible. (Not good for your PAS system) If the force to open the valve is higher than the belts available friction the belt will slip and screech first (or much more loudly). When your belt isn't slipping and you lock the steering you will hear the fluid over pressurising , drop back a couple of inches and it will stop. | ||
| Chris Miller Prolific User Username: cjm51213 Post Number: 272 Registered: 5-2013 |
Hi Paul, Thanks very much for explaining that to me. I've never given it any thought before now, and what you say is perfectly clear and now obvious. Thanks for the help, Chris. | ||
| Jean-Pierre 'JP' Hilbert Experienced User Username: jphilbert Post Number: 12 Registered: 9-2013 |
Chris, is your suspension within specs? Toe-in seems to be off on your car, that's what was wrong on my car when I bought it (exactly the same symptoms as yours). With one sharp eye you can spot toe-in differences between L and R when the tires are supposed to be straight (steering wheel straight) , if in doubt pay a tire shop some money to adjust with the lasers....which brings us into caster-camber settings.... Post your findings! Suspension alignment is not rocket science, I did it, so can you. Call for advice on this frequency! | ||
| Bob uk Unregistered guest Posted From: 94.197.122.92 |
The pressure from the pump when the steering is not moving is connected to the return and the fluid goes round in circles at low pressure this saves on fuel and pump wear. When the steering wheel is moved the steering box valves open the pressure to the appropriate side of the ram. The more torque on the steering box input shaft the more the valve opens and the less the fluid is returned via the pressure to return section of the valve. At low speeds a lot of pressure is being used. once going faster the steering is lighter so the steering box input torque is less so less pressure is used and much more fluid travels back to the pump via the pressure to return bit of the valve. When on full lock and held against the stop the torque on the input shaft is high and therefore the valve is hard over and the pressure to return bit of the valve is shut. To stop the pressure exceeding the strength of the system the pump has an internal relief valve. I hardly use full lock I back up and take another bite. This saves strain on transmission tyres and steering. Sometimes there's no choice. Never hold the steering against the stops except at mot testing and no more than 1 second. The belts on my car are adjusted by moving the pas pump using a bar in a tube welded to the adjustor. It at the top and vertical. Do not lever between the pump and engine because the case which is the reservoir will bend and can cause the pump to leak where the case fits to the pump. Seen this a few times and fitted New pumps because of the damage. Look at the bottom of the vee groove in pulleys, if it is shinny the belt is riding to low and the pulley and/or the belt are worn. To change belts feed a loop over a fan blade then turn the fan a bit and feed the belt over the next blade. This works on all cars with cowlings around the fan. If the cowling fan blade gap is too small flex the cowling a bit, flex not bend. Some cars have a notch in the cowling to allow belt changes, Minis have a notch at 2 o'clock. On shadows use the 2 o'clock position working from the right-hand side of the car. Use a spring balance to check tension. If the belt slips still try talc power on the belt. Keep talc away from vents etc. Never overtighten belts it puts to much side load on brgs and brackets. I have seen a few water pumps and generators ruined by this. GM do a belt dressing spray which I have used but found it not very good. This may sound counter intuitive. A small amount of engine oil will quiten noisey belts, the oil softens the rubber surface a bit. Small means a squirt from the oil squirty can and not a pint chucked over the front of the engine. WD40 works but only lasts 40 minutes.  (Message approved by david_gore) |
