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Reasons behind white smoke emitted from exhaust?


I recently took my Renault Clio X Reg Auto along to local ATS to fix a rattling exhaust.
They replaced the brackets/clamps/mountings connecting front exhaust pipe to engine.

Days later exhaust rattle returned getting worse. Problems starting car, started Ok but not smooth and severe knocking noise, which settled after a couple minutes, when engine ran smoothly, although exhaust still knocking.

Day before I decided to take car back to ATS to sort out exhaust problems excessive amount of white smoke emitted from exhaust tail pipe. Noticed temperature gauge was reading high, stopped car to inspect coolant level which was low /reservoir empty, so topped it up and drove home.

Tested car today, coolant level ok, excessive white smoke still being emitted once engine warms up.

From researching on internet white smoke seems to indicate coolant/antifreeze getting into engine system due to head gasket problem.

Could ATS botched repair have caused problems or I have I been simply unlucky in that head gasket has failed??

Many thanks for help.

Too Badger
July 2009
Thanks John for advice

But I think I have managed to solve problem (at least temporarily), bought some K Seal Permanent coolant leak repair from local car shop for £9.99.

Put K Seal in radiator overflow, ran car on drive for 20 minutes for it to work, no need for draining coolant/anti-freeze etc, took car for long test run.

Hey presto, problem solved, no white smoke. From internet research this solution might only be temp fix, someone said might last for 6 - 12 months. But for 19 year old car, worth most probably less than it would cost to have gasket professionally replaced, it will do me.

Taking car back to ATS to exhaust sorted out.

Many thanks.

Toon Badger
July 2009
I'm trying to fathom out the connections exhaust rattle is one thing, and seems to be cured by new pipe mountings being fitted.
The exhaust rattle is back....why? If the engine is misfiring this could (just) cause the exhaust to knock as the engine isn't running smoothly.
White smoke, as you say, is steam or water vapour - caused by head gasket failure or simply that of a cold engine producing visible vapour on a cold day.
However - the coolant level isn't dropping now? In which case it isn't leaking - from the head or anywhere else. To check for head gasket failure, a 'proper' garage will do a 'sniff' test for you....a sample of the air above the coolant in the expansion bottle is passed through a blue liquid. If the liquid turns yellow, it has detected products of combustion - ie a blown head gasket. Naturally though, the smoke coming out of your tailpipe seems to be water vapour, but you say that you are not losing coolant? Somethings adrift somewhere!! I don't think you can blame ATS for this - more likely to be a coincidence.

July 2009

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