Smoke test

Reason for this entry – unfortunately, when I ask the owners of the car to perform a smoke test or to entrust this procedure to the mechanic, mostly I receive the answer: it did not succeed to find the air intake places. Unfortunately not because there was no additional air intake, but because the test was performed incorrectly.


How to perform the smoke test?


An example on Youtube:

For a successful smoke test:
a) smoke has to be filled in the inlet manifold and the crankcase;
b) these smoke has to be “given the wish” to fill out the inlet manifold.


Step by step
1. To fill the smoke in the inlet manifold and the crankcase:
a) it is convenient to use a rubber glove:

b) hand opening of the glove put on the inlet of the inlet manifold, seal the connection; via one of the fingers (cut off the top of the “finger” to make it possible to connect it to the smoke pump) – start to blow the smoke in the inlet manifold;
c) for the smoke to fill the crankcase, open the oil refill cork;
d) fill the smoke and wait, till the smoke will start to flow out via the oil refill opening. Then close the cork.

2. The pressure in the inlet manifold should be high enough for the glove to be inflated. In such a situation, the smoke will try to “get out” of the inlet manifold and the crankcase;
a) be patient – the smoke certainly will not have filled all connecting pipes. At first, the air will flow out of the damaged place, smoke will appear later. If necessary, wait for 5 .. 10 minutes, till the smoke appears;
b) perform the test in a closed room. Even a little draft will blow the smoke away – it will be hard to indicate the exact spot, where the smoke has originated;
c) use high-quality local lighting, explore the connection spots of the connecting pipes of the inlet manifold and the location of them – during the test you have to know, where to look;
d) sometimes the airtightness defects appear only for the cold engine (in cold, the plastic and rubber become harder – the seal can fail). If necessary – coll down the engine, perform the test for a cold car; move all connections of the pipes.

If you see, that the glove slowly becomes “flat” – there is a leak somewhere. Search, until you manage to find it! Unfortunately, sometimes it is not an easy task, because even a tiny hole of 1mm diameter can cause serious Offset LTFT problems, the error messages regarding fuel mixture, misfires, etc.