How does the water get in?

[Luditus]

Car is 206cc 1.6 auto 2002 reg.
I noticed being dumped into limp mode when underload on rainy days! Had just had gearbox overhauled and working well throughout summer, so was not too pleased to experience more gearbox problems. Then antipollution warning every startup, and tickover producing marked vibration at lower than usual revs, till eventually no power at takeoff (and in limp mode).
Suggested to friendly mechanic that he change plugs, renew airfilter and examine HT system. He reported back "All fixed" and produced a water soaked airfilter. "How did that get there?", I asked. "Do'nt know", he said, "but I got 2 pints out from the bottom of the filter box!". He'd examined all the pipe work and wheel arch fittings, which were fine. "So, in case I want to drive in the rain, could you drill some holes to let it all out?" - "No problem, I've already done that", he replied.
Well, it growls a little bit now, but the power is so much smoother, and no more limp-mode.
Now - how does the water get in? It might also help to know how the air gets into the wheel arch/inlet trumpet?
Curious,
Stuart

[GrandadMonkey]

If the air-filter housing lid is not refitted perfectly after renewing the air filter a gap is left through which water can enter when it rains.

It is a well known problem.

Extreme care has to be taken - the lid has to go on correctly and the screws all done up gradually and firmly to get a proper seal.

[Luditus]

Ah! Thanks for your response. That makes sense. The effect would be accumulative until the lower box is completely full, preventing a free flow of air. Got to add that I did also notice volumes of exhaust steam. So with my drilled holes mod, I will be okay until I drive through flood water! Doh!
Would some sealant around the filter lid be advisable, or not necessay if the job's done right?

[GrandadMonkey]

Not necessary if the correct filter element is used and the job is done right.

[Luditus]

Ha! Ha! Cracked it. Hope this helps others.
I had to drive through a large puddle (very slowly) - no problems until next day on start up - lumpy tickover - steamy exhaust. After a minute AOK and drove off fine. That evening started up - ICE ALERT followed by CATALYTIC CONVERTOR FAULT and flashing snow and sport mode lights, and the dreaded "limp mode".
As it had not rained since my last trip to the garage, I concluded that the water ingress was from the holes that my mechanic had drilled in the resonator box. Further more, this problem had been with me in the background from the day I aquired the vehicle over a year ago. Despite five different garages being told of the problem, it was evidently still there. The only recource was for me to do it myself. (Groan). I borrowed a friend's workshop and set about pulling the inlet system apart. It did'nt take long to find the fault.
At some time in the past the system had been incorrectly assembled, in so much as the forked support bracket for the resonator box was not located in the annular groove of the plastic elbow leading to the filter box. This prevented the rubber sealling ring from getting enough elbow lip to seal. I also found that the trumpet had come released from its velcro. (This is a very strong joint, and indicated to me that it had never been fitted.)
The car had only one previous owner with a full service history - all Peugeot Dealers! Sad.
Unfortunately, there is very little (if any) information available concerning the fitting of this bracket correctly to the pipe work, and I can understand how it could happen. A partial seal is made, but after a few miles the rubber ring will dislodge - and in comes the water.
Its a naff old design, and I believe that the so called resonator box was an after thought, and is really a holding sump for any road water spray reaching the trumpet.

[Capncol]

Thanks for the update