duncan-uk Posted August 23, 2022 Share Posted August 23, 2022 This is an amalagamation of posts i found over the years Steering Older BMWs tend to use worm and sector steering which sits within a steering box at the end of the steering column. Even some fairly modern large BMWs do this as there are a lot of space and packaging advantages. Worm and sector feels less precise than rack and pinion and can suffer a lack of feel in the straight ahead position. For example the six cylinder E39 five series models use rack and pinion but the V8s use worm and sector, it's often been said the 528i is the best handling E39 as a result of this and it's superior weight distribution. Both systems have two end tie rods but worm and sector also has centre tie rod taking the place of the rack. One end of this centre tie rod is connected to the steering box and other to an idler arm. All current and most older BMWs have power assisted steering. The hydraulic pump is generally driven by a belt from a dedicated crankshaft pulley on older cars or by a common serpentine belt on modern engines. The power steering fluid is common Dexron II/III ATF. Steering Box - E28 1. E28 steering boxes - some play is necessary for them to work, but 2" is excessive. Before 'adjusting' the box: a. Is it moving around - the mounting bolts are a known weak spot on E28 and E24. Check this FIRST b. Is it the box - there is a universal in the shaft going to it - these have been known to fail c. If it IS the box - to really correct them - they've got to be removed and done on the bench. There are two adjustments. Problem is - if it IS out of adjustment - probably caused by a bearing going bad - which will continue to get worse. BMW lists in their common replacement parts catalogue a rebuilt box. Steering Fix - E28 A very common problem with the E28s (and 6 and 7s) is a loose steering. This car is supposed to be very precise, so if you have any slack in the steering something is wrong! Below are the things to do when your steering starts to loosen up. Starting with the cheapest. 1. There is a nut close to the floor in the cabin. This often gets loose. You can hear this rattle when you adjust the telescopic column. 2. The steering box is fixed with a bolt. This has a nasty habit of coming loose. If going on tracks make sure it is tight and apply some torque seal to be on the safe side. 3. The steering rack bushing wears out. The part is cheap, but it can be difficult to change, as it is a fairly tight press fit. Also there are two sizes. Before 0986 uses a 27 mm OD, the later a 24 mm. 4. The parallel bar. A doddle to change as long as you have a little 'fork' tool to release conical fittings. 5. The steering rods on both sides. Also easy to change, but requires wheel alignment afterwards. 6. The steering box! Can be checked by twisting the input shaft and watching the output shaft. Should be no, or very little slack. A repair kit exists for this, but you are better off getting a used one or sending it away for restoration. Steering Box Adjustment My 87 535is has a lot (3-4 inches) of play in the steering. All the linkages under the car appear to be tight. Where could this sloppiness be coming from? I noticed the steering box has some kind of adjustment on the top. What does this do? 3-4 inches-- Yow! Try the steering box. Large bolt locks the adjustment screw. Raise front off ground. Turn steering wheel full L or R. Note position of screw, and hold it with screwdriver while loosening nut with box wrench. Tighten screw until resistance is felt, then back off slightly and hold in that position while tightening nut. With front still raised and engine off, turn steering wheel over full L-R travel to ensure there is no binding. If there is, back off screw in increments of about 1/8 turn. Test drive. (See Note. Ed.) Reason for adjusting at full L or R is that most steering wear occurs at centre, with progressively less off-centre. If you adjust screw at centre, the steering will bind as you make turns. Reason for bind-test with engine off is so there is no steering boost, therefore easier to feel for binding. (Note: I use a slightly different method to set the steering box, the reason being that when you turn the Steering Wheel the Steering Box has a high spot at the straight ahead position, and a low spot when off centre. It is hard to adjust the Steering Box when it's off centre because you’re guessing at the amount to back off the Adjustment Screw. I prefer to adjust it in the straight Ahead Position, by tightening it slightly from the current setting. An explanation is below. If you turn the screw too much, then the steering (binds) becoming hard to turn around tight bends. The method I use is: The Steering Box has a Arrow on a plastic Collar (of the input shaft), this should be lined up with the Alignment Mark on the Casing - This is the Factory Straight Ahead Position, where your wheels actually point straight ahead. If this Plastic Collar is missing, you cannot find straight ahead position. Also the Alignment Mark is found from underneath the car. Now is the time to make sure your steering wheel is straight also. If not, unbolt it and adjust to get your Steering Wheel correct. If you now drive your car and your Steering Wheel isn't centred, your Wheel Alignment (tie-rods) need to be adjusted... time for a wheel alignment. If the Steering Universal Joint is worn, it has to be replaced and if you car has an Airbag, you can't do the adjustment - unless you know how to disable the Airbag. Ed.) Alignment BMW dealers use an alignment technique called KDS. This is very accurate and involves weighting the car down then mounting wheel plates to get the most repeatable results. It's expensive but perhaps cheaper than premature tyre wear caused by bad alignment. KDS is even more important if you're running 17" or larger wheels. As is often the case the BMW solution isn't the cheapest but is technically superior to a simple alignment at your local tyre vendor. Generally front camber isn't adjustable although you can retrofit upper strut mounts from an M car or buy fully adjustable mounts. On Models with the later Z axle there is a lot more to adjust on the rear axle, older systems need offset bushings for some adjustments. Steering Faults The steering tends to suffer wear and tear over the years but little else goes wrong. Worn tie rod ends or centre tie rod ends are often first noticeable as a judder under braking that can be mistaken for warped brake discs. The steering column joints are very reliable but on bigger engined cars (and especially E30 M3s converted to right hand drive) they can dry out so an oiling now and then is good preventative maintenance. Steering squeal can often be traced to a slack drive belt. Hard steering can be worn strut top bearings on extremely high mileage cars but can also be due to a blocked fluid reservoir filter. On older BMWs (E23, E24) they're replaceable but on most others you need to back flush or replace the reservoir in extreme cases. Many E36s had a new lower steering column fitted under warranty due to corrosion problems there was a recall for this. On E28 and E24 models the steering box support can break causing potentially serious problems, it wasn't really strong enough for the six series. Suspension Faults As with the steering general wear and tear are the main enemies. Shocks will last at least 100-140k before needing replacement. But rear shock mounts can fail sooner and cause a tinny rattle over low speed bumps, cheap to fix. On higher mileage cars the rear subframe mounts can fail after 10 years or so. Two rubber bushings hold the subframe to the car, not fun to change without the correct tool. Failed bushings make the back end of the car wander about, you can feel it when changing lane. Rattle, knocks or squeaks from either end can be traced to failing anti-roll bar links, around 11 GBP each as a rule. Another cause of knocking can be a failed trailing arm bushing; two are used to locate the front of each trailing arm to the subframe. A bad judder under braking or around 55mph could be worn front control arm bushings. Modified Suspension The factory produced many sports models and made M-Tech suspension available as an option on others. This is generally an excellent set-up that offers improved body control without undue harshness. For everyday use this is preferable to most of the harsher after market systems. I have this on my E30 318iS and can't fault it; it's 15mm lower than a normal E30. Lowering a BMW with semi-trailing arm rear suspension more than about 25mm will result in too much negative rear camber. Not only will this look odd but also you'll wear out the inner edges of the rear tyres quickly. A proper lowering kit for such a car will use offset rear bushings to cancel out some of the camber change. A kit from a supplier such as Alpina, AC Schnitzer or Dinan will include shocks with custom valving, springs, anti-roll bars and possibly bushings. This will have been track and road tested and will add value to the car. But expect to pay around 1000 GBP for an Alpina suspension kit. For 400ish you'll get a set of lowering springs and quality Bilstein dampers, not a bad option but it may be harsher. Anything cheaper is to be treated with caution. If you just lower the car by cutting the springs you can expect to bottom out the shocks fairly soon. If all you want to do is reduce understeer then fitting a stiffer rear anti-roll bar from a higher model (i.e. 325i bar in a 328i) is a cheap option. If you don't want to lower the car and are replacing worn shocks I'd suggest Boge Turbo Gas, not dear and they work well with the stock springs. I have them on my E36. For track use you can replace the suspension bushings with polyurethane equivalents, they transmit too much noise for road use though. Another common mod for E30s is to fit E30 M3 front control arm bushings to improve turn in. Older BMWs benefit from a front strut tower brace, I have one on my 635CSi (E28 Sparco bar fits). But on a modern BMW there is little to be gained by this, as the body is more rigid, I'd not waste money on one for an E30 or E36 road car unless I did a lot of track days. One exception is the front subframe cross brace, a lot of E36 318ti drivers say great things about this mod. I have a relatively low mileage 1988 M5 that is just beginning to show signs of front end shimmy... <my mechanic> tells me, I need to replace, "the left and right thrust arms and bushings, the left and right tie rods and the centre link. "Is a thrust arm also known as a control arm? Is there an upgrade option? Is upgrading necessary? Are the thrust arms/controls for an M5 the same for those for other E28s? The upper thrust arm and lower control arm together form the equivalent of an "A" arm or "wishbone". For example, the left front suspension looks like this from above: ^ | fwd (left front tire) [] ||----- (left, lower control arm) [] \ \ (left, upper thrust arm) The arms are called "upper" and "lower" because that's how they are oriented where they attach below the strut housing at the wheel. All the front end parts, including the bushings, for the E28 M5 are the same as any E28 535i. E28 (E24) Front End Rebuild Part Numbers Here's a list of the parts needed for a front end rebuild same parts as any E28 535i. The only upgrade option is to purchase correctly modified 750/850 thrust arm bushings (31 12 1 136 607 in place of stock 31 12 9 058 819 bushing). Quan Part Number Description Price ---- --------------- --------------- ------- 1 31 12 1 139 991 Left lower control arm $ 98.46 1 31 12 1 139 992 Right lower control arm 98.46 1 31 12 1 132 353 Left upper thrust arm 151.07 1 31 12 1 132 354 Right upper thrust arm 151.07 2 31 12 9 058 819 Bushing, upper thrust arm 36.43 2 32 21 1 135 666 Tie rod 36.39 1 32 21 1 136 450 Idler arm 34.09 1 32 21 1 129 014 Centre link 64.45 ------ Total $743.24 Notes: p/n 32 21 1 134 277 Drop arm $113.43 is not included because it doesn't wear like the other front end parts. Lower control arms include the bushings. Upper thrust arms do not include bushings, so they are listed as separate items above. Conquer the thru-bolt at the bushing. If yours is rusty, replace it. It's an M12 x 1.5 pitch x 77mm long. Loosen the bolt, although don't remove it yet. Leaving it in place makes it easier to loosen and to remove the ball joint. Without removing the brakes (unless you are an idiot like me and blew your wheel bearing, too 8^)), remove the 3 17mm bolts at the bottom of the strut tower. This will allow you to access the locking nut holding on the ball joint. It will also allow you to twist around the strut tower to give you adequate access to this nut. This was not intuitively obvious to me, and it ended up being very helpful once I figured it out. The original nut is the typical cotter-pin style that was made in the early 80's. The new one has the plastic insert. While the ball joint is still pressed in place, a 22mm socket on a 1/2-inch drive breaker bar or torque wrench works quite well. An offset box-end was recommended, but I found it to be unworkable. Once this nut is removed, the difficult work of removing the ball joint begins. On the driver's side, with a judicious amount of Rost-Off (liquid wrench to you yanks), a ball joint fork, the heat of a mapp gas torch (with a wet sock protecting the thrust arm joint's boot), and a large hammer applied strategically to one end of the lower control arm, it popped out. If you have to apply excessive force, you should support the bottom of this assembly since it isn't being supported by the strut tower (with those three bolts removed). I used my old wimpier floor jack to counter the forces of the blows on the lower control arm. On the passenger side, I cursed in three languages! 8^) But seriously, this one was a humdinger. The trick was to put the nut on the top of the ball joint so that it is held on by maybe a few threads. Then, put back those three bolts holding the assembly to the strut tower. They won't go in fully, because this nut will hit against the bottom of the strut tower. This is the key - I found that if you tighten these down, the strut tower presses the ball joint right out of the socket!!! Simplicity itself. Installation is the reverse of removal. Get your torque specs from your favourite manual. And follow Don E's advice about tightening the thru bolts with the car on the ground and you'll be all set. One side note: If you ever need to replace a wheel bearing, don't panic, as I did, if the inner race pops out of the new wheel bearing before you tap it onto the spindle. The solution to reinserting it is the following, thanks to our friend, Roland Freund: Remove the rear seal. Then remove the bearings, carefully, in its cage. Then slide the bearings around the race and reinsert it. Reinsert the seal, evenly. Fortunately, if the outer race comes out, you can insert it by simply placing it in the hub at an angle, and it slips in place. Also, another hint: To tap the new hub/bearing assembly onto the spindle, *don't* hit the hub or the outer race will surely pop out. Take the 1-13/16 (or 46mm) socket that you used to get the nut off, place it over the outer race, and tap away. Steering Slop First and least likely to cause steering slop is that the tie rods, center link and idler arm in the steering are exceedingly shot. I doubt this or the car would shimmy badly, but you may not feel that because of the second and or third problem. Second would be that the steering box itself is worn. Many times the power steering fluid isn't replace or is replaced with the wrong stuff. Our cars use ATF(Automatic Transmission Fluid) in the power steering. I have seen more than once a shop put in Power Steering Fluid in the power steering system. This is not good and causes the box and other parts to wear. A temp. fix would be to tighten the adjustment screw on the top of the box and that should eliminate some of the play. If you have a huge amount of play, this could be caused by the box. With this much play I doubt you would be able to feel if the steering arms where shimmying. The way to check to see how much play your box really has is to have a friend turn the steering wheel, only the amount of the play and see if the input to the box is moving. If so, is the output, or pitman arm moving. If not there is your problem. Third cause. This is also to do with the box and comes in now. The reason why I tell you to check to see if the input to the steering box is moving is because the steering column is actually 2 pieces. These are held together using a large nut, and that nut actually loosens over time. All you would have to do is tighten it up. Fourth and final. This is the worst and this should be check immediately. This is a grave situation which faces our cars. The mount that holds the steering box to the sub frame actually breaks!!! Yes I said breaks!! It slowly goes until it lets go all together and you loose all steering. BMW had a little known recall/suggested fix that the put out in the early '90s. There is one large long bolt that holds in the steering box. This bolt was inherently weak on the E28 and other cars. They have since upgraded the strength and have superseded the part number. If this is the problem on your car you will need to take it to an experienced mechanic who will be able to weld the brackets back on to the front subframe and reinforce them. Quote Link to comment Share on other sites More sharing options...
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