Here is a guide to what to look for when test driving a used 4x4:

Start the engine. It should idle smoothly between 700 and 900 rpm.

Warm up the engine. Have someone stand at the rear of the vehicle. Quickly push down the accelerator as far as it will go and then release it. There should not be excessive smoke from the exhaust. The engine should accelerate quickly and smoothly.
Black smoke? Diesels that smoke heavily under acceleration mean an over-rich fuel mixture. This causes turbocharger damage if left for more than a few hundred kilometres. Testing the exhaust gas temperatures is the best way to know if turbo damage has occurred. Extended temperatures over 750°C likely mean trouble and an expensive repair.
Blue smoke means oil in the combustion chambers and is likely caused by worn rings and valve guides. Repairs are expensive.

Listen to the exhaust for escaping exhaust gas from anywhere but the tail pipe. Do this by putting your shoe over the end on the tailpipe. This forces gas to escape from any leaks. Rust at the tail end of the exhaust is common and not serious, but rust in silencers is a more expensive problem. When the engine decelerates it should not smoke. If it does, it may mean worn valve guides.

Listen to the engine – does it clatter or are there any knocking sounds? Sounds like these can indicate worn bearings, cam chains, rockers, etc. If the engine ticks, it could mean a simple problem of valve clearances that require adjustment or worn hydraulic lifters. It is advisable to have an expert take a look and have a listen.

Check the air filter – an excessively dirty one will mean a poorly maintained vehicle.

Driving a 4x4 is different to driving a normal vehicle. Because of the complex transmission, and the heavy clutch and transmission backlash, smooth gear changes can be a little difficult to handle at first on some models.

Test the brakes. Drive at about 50 kph and when it is safe, push on the brake pedal until the vehicle comes to a halt. There should be no tendency to veer from straight-ahead. The brake pedal should not sink all the way to the floor. If it does, there could be fluid seepage inside the brake master cylinder or wheel cylinder which would require a brake system overhaul.

After driving for a few minutes, check the water temperature gauge. If it is equipped with an oil pressure gauge, check that also. Low oil pressure could mean worn engine bearings.

Take the vehicle onto the motorway and run it up to a reasonable speed. There should be no undue vibration. Vibration could mean a simple problem such as wheel balance, or, at worst, an unbalanced prop-shaft which could have caused gearbox bearing and oil seal failure. A quick inspection of the gearbox at the prop-shafts for oil leaks may reveal the source of the problem.

Test all gear ratios. Accelerate and decelerate sharply in all gears. Doing this may cause it to jump out of gear, a common problem with well used 4x4 transfer gearboxes.

Testing a 4x4 off-road is not easy. It is not fair to the owner to go crashing through axle deep mud to see if the vehicle can cope – especially if you are an inexperienced driver. The best way to do this is to look closely at the vehicle specifications and compare them with other vehicles. Ask other owners of the same type of vehicle for their comments. Do this and you will have a good idea of what you are buying in terms of performance.

Thanks for this info Andre.............or you could always buy a new Hummer!!

A brand new Hummer....the best 2nd hand car money can buy?

very good info Andre....thanks

Avan wrote:A brand new Hummer....the best 2nd hand car money can buy?

very good info Avan

Thanx for the info

thanks advan for the informations..