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Mechanical Assistance: Chassis Problems

Mechanics use a process of elimination to find faults which is how you should use the following information.  Carry out any of the checks you feel comfortable with, if you can't fix the fault you will  be able tell a mechanic what you have checked to help their diagnosis which could save you money.

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Free Mechanical Help
All the problems and possible solutions detailed below are provided by the experienced automotive mechanical engineers who carry out our vehicle inspections. The problems covered can be common to most vehicles but the list is by no means exhaustive. If your particular mechanical problem is not answered below ask our engineers for mechanical assistance here.

Creaking noise when turning the steering.

It is difficult to detect where the noise is coming from when this occurs and it can be a number of ailments that's responsible.

Dry or worn steering rack.
A worn or dry steering rack is a likely cause depending on the age of the vehicle in question. Wear is more likely on an older car, on a newer model a dry steering rack could be the result of steam cleaning if the hose was placed under the car but is unlikely.

Worn bottom ball joint.
On the underside of the hub is a ball joint that supports the hub along the vertical axis. This a wearing part and depending on the roads you generally travel on car wear quite quickly. For example if you have a driveway that is a little rough or a street that you travel on regularly with pot holes you hit from time to time the joint will wear relatively quickly. As it's a wearing part it is a fairly simple fix just remove and replace. It's not necessary to replace both sides if you are sure the noise is coming from one side however if you are unsure and as the parts are reasonably inexpensive it makes sense to replace them both.

Worn top suspension mounting bearing.
Some cars have a bearing fitted on the top of the strut which can be accessed from under the bonnet. This is a particular weakness in early Peugeot models (106,206,306, etc) and again is a inexpensive repair. However to carry out the replacement of the bearing the spring on the strut needs to be compressed with special equipment.

Knocking sound from rear under braking

Worn bump stop rubbers.
Positioned on the top of the rear swinging arm is a large rubber buffer which prevents the swinging arm from knocking on the chassis if the suspension is bottomed out. When braking the weight of the car shifts forward and as a result the rear becomes light allowing the suspension to chatter. If the rubbers are worn the arm will hit the chassis causing the knocking.

Knocking sound from the front of the car

Worn track rod ends
The adjustable track rods which as the name suggests are used for aligning the tracking are another wearing part which can cause knocking. This can easily checked by jacking up the suspect corner of the car and holding the wheel top and bottom. Use a pushing force to the top and a lifting force to the bottom. If the wheel feels loose and you can move it up and down without significant force its likely the rods are worn. Some movement can be caused by worn wheel bearings however this movement would be across the centre axis of the wheel as opposed to up and down movement.

No special equipment is required for replacing the track rod ends but you will need to measure or mark how much thread on the end of the old rod is exposed in order to fit the new one in the same position. Failure to do this will cause the the wheels to track out of line and cause veering and excess tyre wear.

Car veers under braking or whilst driving

Failed Suspension
When braking the weight of the vehicle is shifted towards the front end placing more pressure on the front suspension. If one side of the front suspension has failed the traction created on the road by the tyres will become uneven due to an uneven distribution of the weight over the front wheels causing the car to veer.

Failed brake calliper or uneven wear on brake pads
If one wheel is providing all the braking the car will try to pivot around that point. If you tried to balance the car on its nose supporting it from only one wheel the car would tip over towards the opposite side from which it is supported. The same effect can happen under braking with only one wheel, causing the rear of the car to try to rotate around the braking wheel cause it to steer from the rear.

Incorrect tyre pressures
A tyre which does not have enough pressure will cause the car to veer. A simple fix which is often over looked. If this was the case the veering would occur whilst driving normally as well as under braking. 

Dull low pitch whining or humming noise when driving.

Worn wheel bearings
Another wearing part on a car is the wheel bearings and can usually be changed with little expertise and a few basic tools. To check if the wheel bearings are the problem there are to things to do. Whilst driving in a safe place put the car out of gear and free wheel and let the engine idle to see if there is any change in the noise you are hearing. This will help rule out a drive shaft or gear box problem. If there is no change in the noise you will need to do a basic check on the wheel bearings.

Checking the wheel bearings
Take hold of each wheel in turn holding the tyre either side and try to twist the wheel back and forth. If you can feel any play that would for example feel like rocking a glass gently from side to side on a flat surface then the bearings are worn or loose. A temporary fix would be to remove the wheel and tighten the nut which secure the bearings however this may only work if the problem is caught early and the best way to deal with this as with most mechanical problems is to replace the faulty or failing part.

 Under inflated soft tyres.
As simple as it may seem, check your tyre pressures especially if they are new tyres with a lot of tread. Although this would be unlikely it can cause abnormal running noises and is a simple check worth doing.

Differential (rear wheel drive)
This can also be caused by the differential on rear wheel drive cars, very common in late 80's early 90's Nissans, and usually fixed with a Diff oil flush, or at worst a replacement of the Diff if the diff is badly worn..

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