There are days when the sun is shining, Mowgli is purring along a busy road, meandering along the south of Spain and all is good in the world. All of a sudden, the engine stalls as you decelerate for a roundabout, a rolling bump start, left foot braking, right foot holding the revs on the engine and all while looking for a safe point to pull over and fix the problem. The instant it snaps, the inconvenience of a Unimog broken throttle cable becomes apparent. Once you have pulled over and diagnosed the cause, you’ll quickly find a broken throttle cable is not an easy road side fix.
The inconvenience of a Unimog broken throttle cable
Having left Gibraltar in the morning we were heading inland to visit Ronda for a photo assignment before heading to nearby Malaga to meet visiting family. The roads were busy; Spanish drivers are sensible on the road but are also impatient, drive fast and give little room for manoeuvres. As we approached a busy roundabout, I depressed the clutch, foot off the accelerator and the Unimog engine stalled. I let the clutch out to bump start the engine, still decelerating. As I dipped the clutch and without applying the accelerator the engine stalled again! The junction was fast approaching, well Mowgli fast, so slowly in reality. I repeated the rolling start and used my left foot to clutch, find the neutral gear and then brake, while holding the revs up by my right foot. We got through the junction and I looked for a safe place to pull over.
It didn’t take long to discover the throttle cable had snapped. It’s a single core stainless steel wire, housed in a protected wire and plastic covering. One end is fixed to the throttle linkage on the engine and the other to a control knob on the floor by the gear stick. The only way to get to the throttle linkage is to remove the engine cover from inside the cab, unless you can lift the cab. We don’t have that luxury on Mowgli so I opened up the engine cover in the cab. I had limited access to the throttle linkage and cable end.
No problem I thought, certain that Mercedes would have designed the cable so that the wire could be replaced. I carry some wire, so I set about dismantling the broken throttle cable. Once I got the cable off I saw it was a manufactured component and doesn’t break down further to allow a wire replacement. Even in a fully fitted workshop I’m not sure I could re-engineer this component to allow a wire replacement, never mind sitting in a field next to a busy road. Time for a cup of tea and a ponder.
It’s Sunday and the nearest campsite is 20 kms away on a busy road with umpteen roundabouts and junctions. I considered ways of jury rigging the throttle arm linkage. It has a spring attached which pulls the throttle into the off position; the wire counteracts the spring to hold a minimum throttle setting. Without the wire, the spring sets the throttle linkage to a closed position and the engines stops. It’s not easy to work in this space; there’s enough room through the hatch to get one hand in. From the ground, my arms are just not long enough to reach the side of the engine. So it’s a fiddly space to tinker in.
We needed to get off our makeshift camper stop and get to a campsite so I rigged up a temporary bush repair. I have a selection of long springs in my spares box; using a longer spring, I stretched it so it would not push the throttle back to the closed position. I managed to get it to sit at around 1500 RPM. I could accelerate and when I took my foot off the accelerator it returned to 1500 RPMish….
With this temporary fix in place we drove carefully to the nearest campsite; it was a little easier than before the repair but I wasn’t confident of driving too far with this temporary set up.
We pulled up at a campsite, knowing that we probably needed an address for a new part to be shipped out by Atkinson Vos. The south of Spain at this time of year is busy with long staying camper homes all crammed in together. This was our home until a new part arrived. Our photo assignment was postponed, we rearranged our family to stay in hotels nearer to us and we also had to hire a car. While we awaited the new part, we busied ourselves in Andalucia.
The part arrived (great service from Atkinson Vos as always) and has now been refitted. I’d recommend that if you’re overlanding and expect to go to remote places then carry a spare throttle cable. They are impossible to repair and any temporary solution makes driving difficult. Replacing the complete cable assemble is a relatively easy job if you can get your hand down the side of the engine block.
So after 10 days sitting on a campsite, we’re ready to roll again. But let’s just say a broken throttle cable can be a very, very inconvenient if you don’t carry a spare.