When I accelerate, it feels like I am driving over humps

Thursday February 13 2020


By Paul Kaganzi

Hello Paul, my 1994 Toyota Land Cruiser Prado has been performing well but when I accelerate while driving on the highway nowadays, it feels like driving over humps on one side. My mechanic has checked the wheel hubs and changed two of them but the problem continues. We have replaced all the worn out suspension parts but the car continues to misbehave. Is it time to part ways?


Dear Joseph, get a tyre expert to examine the surface of the tyres for radial or lateral run out. This is extreme uneven wear of the tyre tread surface because this can cause wheel wobble or a sensation of hobbling as you drive faster on the highway. You may not see the tyre surface imperfections with a naked eye. You need a tyre specialist to use a special tool called a dial indicator to test for the run out.
Excessive run out can sometimes be seen by a very observant mechanic or tyre technician. This is common with tyres that have been damaged during an emergency braking incident or due to severe poor wheel alignment. The solution to this problem is immediate replacement of the damaged tyre(s) before they damage the wheel hub assemblies.

Why does my car lose power when I accelerate?
Hello Paul, my Mercedes Benz ML320 engine loses power when I accelerate and the check engine light is permanently on. The exhaust has a strong bad smell. We have failed to find the cause of this problem despite replacing the worn out spark plugs and fuel filter. Kindly advise what to check next. Francis

Dear Francis, the foul ammonia-like smell from your car exhaust, poor engine performance and check engine light are signs of damaged catalytic converters (CATS). To confirm this damage you can remove the exhaust pipe section with the CATS to check for loose melted or damaged honey comb structure. Replace with a Mercedes approved new part.


Why does my Audi Q7 have a rumbling noise?
Hello Paul, my Audi Q7 has a rumbling noise in the transmission when I take off. When I drive faster, it becomes quieter. Could it be a gearbox failure? My gears shift normally. Kawere

Dear Kawere, your Audi propeller shaft needs to be carefully examined for possible failure. The propeller shafts are notorious for failing rubber gaiters after 100,000kms. Consider replacing the propeller shaft and that problem will be sorted out. Gearbox failure would present symptoms such as rough, delayed or no gear shifts. Continuous use of a damaged propeller shaft can pause a risk of breaking into a half while you are driving fast. This can cause panic, under ride damage and possibly an accident.

How often should I change brake fluid?
Hello Paul, I read in one of your articles that brake fluid needs to be replaced every two to three years. But the brake fluid at the master cylinder of my car looks clean and I have never changed it. Kindly throw some more light.

Dear Allan, one of the factors why brake fluid ought to be renewed every two years is the tendency to build moisture content during use. Brake fluid is hygroscopic and attracts moisture as you operate the brake system. This moisture gradually makes the brake fluid corrosive and if kept for long will lead to corrosion damage of pistons, cylinders and brake lines.
While the brake fluid in the reservoir bottle may look clean, often we find brake fluid in the lines and cylinders mixed with dark after burn deposit and corrosion from the frequently heated brake system.

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