Exhaust sealing

[Tim Smith]

I have a leak from the exhaust where the primaries go into the 4 - 1. Gas is leaking around the edges of the primaries as this is just an interference fit. This creates noise, currently I'm at 101dB and want to get below 100dB if possible, but more significantly appears to be causing a misfire as well as the usual pops and bangs

 

I've had several goes at sealing it without luck so far. After reading that high temperature silicone was the way forward I bought some high temperature instant gasket stuff but this doesn't seem to work for long.

 

Anyone got any bright ideas? Is there a better type of silicone I could try? Is there a secret to getting the stuff to stay in the small gap between the collector and the primaries? Any advice or cunning plans much appreciated.

 

 

[Tony Whitley]

I spent ages faffing about until I bought a cheap exhaust expander off eBay and stretched the inside pipes to give a tight fit. They were as slack as a butchers before, you don't say how bad yours are.

[Tim Smith]

Mine aren't too bad, there's no rattling of the primaries in the collector, they just aren't gas tight. I'm concerned that if I get an expander I won't be able to get the collector on again as it's a bit of a struggle to get all 4 lined up at once.

[Mankee]

You could slacken the manifold nuts at the head to give yourself some wiggle room to get the collector on.

[Stationary M25 Traveller]

I used a smear of clear silicone sealant around each primary starting about 20mm from the end of each pipe (so the end of the pipes are clean).

 

Slacken the manifold nuts for more wiggle-ability.

 

Find and use the front mount (800-805mm from the rear one) to support the front of the can. If left unsupported, this is what stretches the collector holes and pulls the inlet out of the can.

[Myles]

I think you'll definitely want the correct high-temp sealant. Can't remember the model number of the stuff I use, but I did manage to find it at Halfords.

 

I'm still struggling with one of my cars - the eBay pipe-expander helped make removal/refittment a little easier (but still far from easy), but now the mikalor can't clamp the can on tight-enough to stop it twisting relative to the collector. Expanding it more (to ease fitment) will only bring me closer to needing sealant again...

[keybaud]

I used the Loctite 5920 high-temp sealant from Halfords. It works a treat.

 

Loctite 5920

 

Edited by - keybaud on 10 Jun 2014 13:27:34

[DaveMorris]

I thought that the idea of the expander was to expand the primaries that go INSIDE the 4-1 section, approx 30mm from the end, so that they feed in easily enough but then as they are fully pushed home you get to the slightly expanded section, which then seals more effectively (- or have I completely misunderstood the use of expanders ?)

Dave

[TomB]

I use that copper based Loctite product - but I wish it wasn't quite so orange, as it makes a right mess when it squeezes out of the join.