How big a drain hole in new silencer?

MissMoppet · 14th January 2020, 14:02

There is frequent mention that it may be helpful to "drill a small hole" in any new silencer presumably at the lowest point. So two obvious questions: if it's so beneficial why don't the exhaust makers supply it ready drilled? (OK if it does prolong the life, then they'd last longer but reduce sales . . .).
And how big? 5mm? Too big and presumably it would blow.

Comments awaited.

Mark Murphy · 14th January 2020, 15:58

I would drill a 3mm hole anywhere on the lowest point, then put in a self tapper screw, so it can drain when you want, and not blow.

Blink · 14th January 2020, 16:25

I found water collected in the pipe bend leading to rear silencer. It wasn't in the silencer itself.

roverbarmy · 14th January 2020, 18:15

Quote:

Originally Posted by Mark Murphy

I would drill a 3mm hole anywhere on the lowest point, then put in a self tapper screw, so it can drain when you want, and not blow.

I had a 3mm hole in my old car and you couldn't detect any extra noise but the condensed water would definitely drain away. After drilling the hole, I applied a decent amount of silver hammerite so that it wouldn't rust (inside or out). I popped a self tapper in at MOT time.

COLVERT · 14th January 2020, 18:42

3 mm is fine and will do what you want it to but you don't need the hole in the diesel exhaust.

They don't rust away like the petrol exhausts do. They have a coating from the diesel oil.----

14th January 2020, 14:02	#1
MissMoppet Posted a thing or two R 75 Tourer diesel Conny 2002, V6 Conny saloon petrol 2003 Join Date: Mar 2013 Location: Taunton Posts: 1,125 Thanks: 212 Thanked 406 Times in 223 Posts	How big a drain hole in new silencer? There is frequent mention that it may be helpful to "drill a small hole" in any new silencer presumably at the lowest point. So two obvious questions: if it's so beneficial why don't the exhaust makers supply it ready drilled? (OK if it does prolong the life, then they'd last longer but reduce sales . . .). And how big? 5mm? Too big and presumably it would blow. Comments awaited. __________________ Rover 75 Tourer Conny 2002 remapped 160 auto, R75 V6 2.5L auto Connoisseur 2003

14th January 2020, 15:58	#2
Mark Murphy Regular poster Rover 75, and Mg zt 1.8T Join Date: Aug 2019 Location: Huntingdon Posts: 92 Thanks: 302 Thanked 23 Times in 22 Posts	I would drill a 3mm hole anywhere on the lowest point, then put in a self tapper screw, so it can drain when you want, and not blow.

14th January 2020, 16:25	#3
Blink Posted a thing or two Rover 75 Saloon Join Date: Apr 2019 Location: Under the car Posts: 1,840 Thanks: 210 Thanked 244 Times in 221 Posts	I found water collected in the pipe bend leading to rear silencer. It wasn't in the silencer itself.

14th January 2020, 18:42	#5
COLVERT This is my second home R75 Saloon. Join Date: Feb 2009 Location: France/or Devon. Posts: 14,003 Thanks: 3,851 Thanked 2,167 Times in 1,816 Posts	3 mm is fine and will do what you want it to but you don't need the hole in the diesel exhaust. They don't rust away like the petrol exhausts do. They have a coating from the diesel oil.----