BMW E31 850 Rolling Refurb - Our Shed

Date: 19.01.2022

It's been a year since Guido jumped in the deep end and bought the 1993 BMW 850CI. So far, so good?

We’ve had cause to play around a fair bit with the big E31 V12 Bimmer lately and so far it’s been going okay.

To recap, this is something we bought just on a year ago with 245,000km under its belt. Jimmy and the good folk at Southern BM in Moorabbin had got it up to speed with a whole bunch of repairs, plus a service, so it was a good runner at what was a bargain basement price for one of these. We’re talking $27,000 for a car that, back when it was new, was more like $220,000.

As with a lot of Euro models, the values tanked over time. I’m reasonably confident I bought at the bottom of the market, and the numbers attached to sales since then tend to back that up.

CS Free is a charger/booster unit

Now I got this in a good running state, not as a fully-restored unit. That and the fact it’s getting on in years and miles means there will always be little things to be attended to along the way.

Reading the assorted owner experiences with these has given me cause to be confident about the mechanicals, despite the significant mileage when I bought it – and now with a few thousand more under its belt.

The issues? Usually electrical. This is a complex machine for its day that seems to have at least two of everything. Plus it was a pioneer with multiplex wiring.

About six months ago, I decided to replace the batteries – yes, there are two, located in the boot. One is the size of a normal car battery, while the other would do justice to a good-sized truck. My reasoning was this gave us a fresh start and at least one of the two previous items was under suspicion.

Five-litre V12 fills the space

I went for the expensive and allegedly more robust option, a pair of gel units at close to $900. Frankly, I’m over lead-acid batteries.

These cars love their electricity. If you make the mistake of leaving them unlocked for long periods (as in a few days) – they’ll flatten the batteries fairly quickly, as the electrics, including a whole bunch of sensors, are still ‘live’ even though the car is switched off. Even when locked, they tend to ‘leak’ power at a substantial rate. You get about two weeks of idle time, max, before the thing needs help.

With something over 20 vehicles at home, a two-week sitting period is not unusual, so the obvious thing to do was fit a battery tender. I already had a few at home, but a new model came on the market that I was keen to try out.

It’s from Ctek, which coincidentally made my preferred existing unit, a CT5 or ‘Time to Go’. It’s a pretty straight-forward charger/tender that can be hooked up to most things and costs around $170.

The latest gadget is another step up again. What I actually wanted was something that would act as a combined charger/tender and booster battery. My reasoning was that things happen on long trips, and it’s good to have something to sling in the boot in case someone leaves the car unlocked overnight, or lights on, or whatever.

Many gizmos need powering

Ctek’s answer is a gadget called a CS Free. The charger side will work with anything from lithium through to lead-acid. The kicker is it has a very substantial lithium battery built in – rated at 130Ah, it’s got a bigger capacity than many full-sized car batteries. It can be recharged via mains, USB, and the power socket in your car.

This thing is a substantial size, about 25cm (10in) long, and weighs 1.4kg. Operation seems pretty idiot-proof, just plug and play. I’ve used it to jump-start a couple of cars, with no issues. The advice is to hook it up and give it up to 15 minutes to feed the car’s own battery, then hit the starter. So far, so good.

I’ve also been using it day-in day-out as a battery tender on the 850, and that side is working perfectly. Cost for the unit is substantial, at near enough to $500. I can live with that, given what it does.

Handle carefully, it looks expensive

Moving on, the latest wrinkle with the 850 has been the HVAC or heater control valve has gone to lunch. What that means is when the air-con (which works!) is switched on, you get the expected cold air one side and hot air the other. Hugely entertaining, but not good on a hot day.

America seems to be a remarkably good source of parts for this model – there is a substantial fleet of them over there – and there was in fact a choice of components from across the Pacific. A couple of hundred dollars later, and the bit has been landed here and promptly handed over to Rhys at my local workshop, RPM Auto Tech. It’s hidden under the cabin air filter on that side, and this was a good opportunity to shout the car a service.

Next mission? The interior trim is looking tired in places, so maybe it’s time to investigate what we can do to freshen it up.

Otherwise, with lockdown ending and good weather on the horizon, after an incredibly long and wet winter, it’s time to get out an enjoy the thing.

From Unique Cars 459, Nov 2021

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