Fixing a No-Crank Condition on an Automatic BMW 535i

My 1986 BMW 635 CSi has an automatic transmission and it recently failed to crank (turn over when I tried to energize the starter). Then, it would crank (and start) when I messed with the gearshift lever, and then it would fail to crank (and start) again.

The relevant parts of this car seem identical to a 1987 BMW 535i that I owned until recently, so what’s true for the 6-series is probably helpful to 5-series owners too.

The culprit was a loose connection. Wiring from the car runs to the gearshift selection unit via a plug, and if that plug is too loose, the car won’t start. It is difficult to push the plug in all the way, but it helps if you remove the ashtray and vertically pull the console up as high as it’ll go. Even a tiny bit of vertical movement can make the difference you need.

As part of troubleshooting the issue, I undid the plug completely and fed it out of the ashtray hole. The wires are long enough that I could plug it into a spare gearshift selector that I had handy. When I put that unit into Park or Neutral, the car started and otherwise it didn’t. This told me that the car’s wiring wasn’t the problem, and that the problem was the gearshift lever mechanism in the car, or the connection thereto.

The way the wiring works is interesting. A starter relay makes or breaks a connection in the main starting circuit. The gearshift lever basically intercepts the relay’s path to ground. The electrical plug to the gearshift lever has nine holes. The brown-and-black wire goes into the top center hole, the one with the bubble-shaped side as opposed to the smooth sides.

If you ground that wire, it has the same effect as putting a well-functioning gearshift lever into Park or Neutral. At least that’s a good short-term fix if you’re stranded.

If you need parts for any of this, I sell them, but perhaps all you need to do is make sure the plug is tight. Normally, it’s a very tight fit so it’s unusual for it to be loose.

Power steering blues

Power steering blues … I relate personally, and I gather many people do.

A friend of mine used to pour so much power steering fluid into her car that the price started to be a financial problem even if she could ignore that the leak was so massive that she was dripping power steering fluid all out over the roads while driving. She finally handed over the car to a junkyard for almost nothing, and the power steering leak was the main reason.

My own 735i has a massive power steering leak. I’ve just been ignoring it and driving it with the power steering inoperative. I gather many folks do that. Can you relate? It’s certainly good exercise.

But, having just spent literally all night messing with a problem on an E30 with the M20 engine, I’m now very familiar with that general geography of the car. The power steering pump, which is often the problem, seems to be a big, messy, black hunk of oil.

It’s intimidating, isn’t it?

And yet, on cars with the M20 engine (e.g,, 528e model) this part is relatively easy to access, and to remove and replace.

The pump is at the extreme bottom of the driver’s side of the engine compartment, and working from the bottom, it’s a relatively simple process to remove it. A key tip is to loosen the lines before loosening the bolts that attach the unit. If you have 12 mm, 13 mm and 19 mm wrenches, you’re off to a good start.

I sell good used original BMW power steering pumps, and I will refund your money and shipping if the part doesn’t work right when installed. You’re taking a chance on a unit that might have a year’s worth of life remaining, or another twenty years. I price the part so that the risk tends to be worth taking.

Sadly, the pump isn’t the only place that can leak. The steering rack can, too … and that’s a much bigger project.

BMW E34 5-Series 525i or 535i Front Cross-Bar

If you’re planning on dropping the engine and transmission, you’ll need to remove a big, sturdy cross bar that is rearward of the sub-frame. On each side of the car, the cross bar base is attached with a vertical long 18 mm bolt, and two 15 mm bolts.

Coaxing these loose can be very difficult, and I needed to resort to using penetrating oil and tapping the bolt heads with a hammer. Even then, in about half the cases, I still haven’t been able to loosen the large bolts, so I’m planning to use a large breaker bar.

BMW E34 5-Series 525i or 535i Front Hub-to-Steering Ball Joints

The front hub attaches to the steering rack mechanism with a ball joint at each end. The 17 mm nut was easy enough to remove, but even with a ball joint separator, and some hammering on the relevant steel part, I have been unable to separate the ball joint, in six out of six cases.

One thing that I know to be a no-no is to hit the bottom of the ball joint, in the direction that removing it would go. Such hammering, I’m told, doesn’t just damage the thread, but it makes the ball joint expand within the housing and makes it harder yet to remove.

BMW E34 5-Series 525i or 535i Front Hub-to-Subframe Rod

On the E30 (3-series) the front suspension base is part of the sub-frame. On the contemporary E34 (5-series), not so.

A large steel rod links the bottom of the front hub to the mounting point on the sub-frame.

If you are planning to remove the front suspension base or hub, or the sub-frame, you’ll probably have to remove the 19 mm nut and bolt that attaches the rod to the sub-frame. At the hub side, the rod has some flex, so I could use a small hammer to tap the rod away from sub-frame, after the 19 mm nut and bolt were removed.

The rearward-facing fastener is in close proximity to a welded steel structure that made it non-viable for me to get a socket into position there, so the socket went in front, and I used an open-ended wrench at the rear.

If the nut comes loose easily, life is good, but in one case out of six so far, it didn’t, and it was so tight that I couldn’t loosen it even with all of my upper body strength. Penetrating oil, and tapping the fastener with a hammer, was the next step. So far, even that hasn’t done the trick, so I’m investing in a long breaker bar, next.

BMW E34 5-Series 525i or 535i Front Brake Pad Wear Wire Loosening

If you’re planning a task that involves removal of the front hub, the wire for the front brake pad wear sensor will need to be undone.

As I recall, car manufacturers consider it unnecessary to have such a sensor at each front wheel since the driver side is likely to wear out approximately at the same rate as the passenger side, which is why it’s normal to see such a wire only on one side, not both.

By contrast, the ABS wires are on each side.

The sensor wire disappears into a plug in the inner wheel well well. Try to fight the temptation to cut the wire, and trace the wiring until you can find a place to unplug it. At this time, I have yet to find it myself, but I hope this write-up helps at least a little bit.

BMW E34 5-Series 525i or 535i Front Brake ABS Wire Loosening

If you’re planning a task that involves removal of the front hub, the ABS wire will need to be undone.

The wire runs from the hub to a rubber splash shield in the inner wheel well. The shield has a protruding rib so that I could grasp it firmly and twist it 90 degrees. It then came loose, and I could pull it towards me and see a electrical connection.

By pulling its ends clumsily in opposite directions, I managed to break the plug. By being more careful the second time, I still managed to break the plug. The 20-plus-year-old plastic seems pretty brittle which should probably not be surprising to me.

When I pulled very carefully, I was able to separate subsequent plug connections without additional damage.