Ask the Mechanic: Why is my car rusty again shortly after being repaired and painted?

Recently I took my car for a repaint. Although the garage did paint work repairs on it, within two months, all areas are rusty again. What should I do?


Hello JB, the rust repair may not have been repaired properly before painting the car. A rust repair paint job can fail if the kind of rust damage is not correctly identified and appropriately dealt with. There are three major types of rust; surface rust, scale rust and penetrating rust.

The three rust types have different causes, levels of penetration or damage as well as intensity or cost of repair. Surface rust is usually the result of a ding, scratch or small dents which are below the paint surface. This leaves the body panel exposed to rust formation. Surface rust is the easiest and cheapest to repair. If the little dents and dings are ignored, then it becomes scale rust.

This is more penetrative and noticeable when you begin to see small pits or bubbles on the exposed car panel. Scale rust is much more damaging and requires more aggressive repair protocols in order to avoid having to replace panels.

If scale rust is not arrested in time, it becomes penetrative rust which literally eats up the metal panels which it attacks. The affected body panels will develop holes and start to break into pieces.

The repair of penetrative rust is costlier and often involves replacement of panels and expensive rust treatment of irreplaceable panels before the paint process starts. I suggest you discuss with your paint job provider who should be able to identify what level of rust damage your car has in order to determine the appropriate repair procedure.


I have had this nagging AC leak that I cannot ignore anymore. How much will it cost to repair an AC leak in my car?


Hello Arnold, AC (Air conditioning) leaks can be a nuisance and sometimes difficult to trace. You need an experienced AC technician with the right leak testing tools to find the leak. The cost of AC leak repair will vary depending on where the leak is such as under the dashboard or in the engine bay and the kind of AC gas to be used.

A dashboard AC leak is more tedious because one has to dismantle the dashboard to access the leaking evaporator or AC pipe work. An engine bay AC leak is much easier to access and fix.

The cost will only go up if the leakage is on a component that has to be replaced. A simple leak repair costs Shs150,000.

However, replacement of leaking components such as the AC condenser will cost between Shs300,000 and Shs500,000 while an under the dashboard leak repair or replacement of the evaporator may cost up to Shs1.1m.

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