Towing my caravan recently I have had a jerking effect when braking hard or going down hills.
I think the caravan is braking too hard, then it pulls on the car dragging it back, then it brakes again when it catches up. I get this oscillating effect and it feels like I'm a learner again kangarooing the clutch.
Does anyone have any ideas what could be causing this?
It could be that the caravan brakes are not set up properly on the drums so when you apply the vehicle brakes, the caravan brakes are not responding causing the hitch damper to shunt into the rear of the towcar. I had this last year till I had the caravan serviced recently which has eliminated the jerking.
When did you last have the caravan serviced?
Could hitch damper which is the shock absorber inside the hitch. With hitch fully extended, push it in by hand until rubber bellows are fully compressed. It should go in smoothly but with a great amount of resistance. If it goes in easily then it needs replacing. New damper around £70, easy diy for those with some mechanical ability.
Could also be brakes as suggested. If caravan is old it's not unknown for brake lining to come unglued from shoe. When was it last serviced? If you have limited mechanical knowledge I'd book it in for a service. You can have just a chassis service for around £80 with parts & extra work like changing hitch damper at extra cost.
As for services I have only just bought the van, so the history I don't know. I am looking for someone to service the chassis/brakes as we speak. I've looked under the tow hitch and can see the damper and it moves quite easily I feel, and is probably not dampening enough.
Just unhitched and had a better look and the hitch can be pushed in quite quickly ( in 2 seconds) for full displacement.
Should I change it the shock absorber and then get the caravan serviced or get a mechanic to do all the work. I've always serviced my own cars so should have no issues doing it.
The shock absorber is called the damper and has a spring behind it which has to be restrained but not sure whether a special tool is required for this.
Servicing caravans can be a simple task but it's having the right tools for the job is the problem. For example, the 'one shot' centre spindle nut that holds the brake shoes in place has a massive torque of 300 nm. which only a professional torque wrench is capable for the job. A standard over the counter torque wrench is not sufficient so it's not cost effective to buy the tools you need to use just once a year (annual service).
Its all very straight forward to service. Greased the overun, adjusted the brake drums and also adjusted the ball nut to take up the slack in the brake centre rod. Did mine a couple of months ago. Also paid a mobile mechanic half hours labour to remove and check the drums whilst van was on axle stands and wheels off (no point paying labour for jacking the van up).
The only tip I would give is have someone pull the handbrake on slowly whilst you can see both wheels are spinning to make sure they slow at the same rate, adjust as necessary.
Damper was fine on mine, but it does sound like yours might have gone, though first make sure you have greased the overun, mine was bone dry and took 30 pumps with the grease gun.
If you have a hitch stabiliser check the front and back pads as they do wear (plus it might have been contaminated with grease at some point).
it will almost certainly be under adjusted brake shoes raise wheels and chock up from under the van on rear of brake drums is a arrow and theres a slot behind the slot is a star wheel use a small screwdriver and slowly turn in the direction of the arrow move each side by the same amount rotate the wheels at same time until you feel slight resistance then back off one notch, if damper feels too easy to push in it may well be dry of grease chances are grease nipples will be blocked either free off or replace nipples use ep2 lithium grease there will be 2 nipples easily accessible from the top of the hitch theres a further one underneath between the back of the tow hook and the hand brake linkage its quite hard to locate fill all with grease. depending on year of van you may not have one shot nuts if your hub has a castle nut with a split pin you can remove and clean bearings and re grease if you have one shot nuts best to leave well alone. On another important issue if you have no service history and you don't want to pay an engineer to service replace gas hose clips and regulator before use and give tyres a careful inspection if in doubt replace
------------- its our imperfections that makes us perfect
Basically the issue I was seeing was kind of to do with nose weigh but not, ball hitch or brake settings on the van.
It turned out that the caravan shell had some movement in its attachment to the chassis and thus there was physical movement/weight shift on the van when moving/braking.
The shift in weight caused the brakes to become applied earlier than requested in terms of the attachment of the van and car, and thus movement caused the oscillation. The nose weight changed in effect.
The fix was to better fix the shell to the van via strong fixings/long thick screws. The result was 10x better, although not perfect. The van is no longer a mobile unit and is sited at a fixed location.