Exhaust silencer heat shield

[sadako]

Greetings. I have just changed to using a magnex stainless. Upon taking off something is buzzing against the exhaust and the noise is driving me insane. It is coming from the drivers side and I think it is the head shield between the silencer and the car. The rear valence is also very close to the exiting pipes and i'm worried that it might touch when I am moving, i think i might hit it with a big hammer until it is not as close.

What would happen if I took this heat shield off completly. Would it make the boot hot? Would anything risk catching fire that I havnt thought about?

[andyj]

There are two heatshields I believe. A small one that comes off first and a larger underneath that, bolted to the underside of the boot. Magnex say remove all heatshields. I forgot to remove larger one but my Magnex went on fine with a gap still showing between silencer and heatshield, so didn't bother to take it all off again. It doesn't knock at all and the outlet pipes still come out straight at the back, without touching the rear valence.

I've noticed that even after use the rear silencer doesn't get anything like as hot as you'd expect. So I can understand why Magnex say OK to do away with both heatshields.

As you've realised you can adjust the upward tilt of the silencer and how far it sits from the boot floor by losening the joint between silencer and frontpipe, and pushing it up or down at that point.

[leewaring]

I'm with AndyJ, the exhaust sits there fine with heat shield in place.

Should be no trouble taking the heat shield off. Just dont keep any fruit in your boot

[j0nathan]

Hi there,

(warning - longish post)

I also have a Magnex fitted that buzzes. To date I have cured three causes of the buzzing noise:

1) Centre bracket mounting: When I fitted this component I did not take care with the distance between the bracket on the exhaust pipe and the fixed bracket below the car. Moving the mounting bracket on the exhaust to the rear cured the persistent buzzing from the bracket but induced a knocking noise under acceleration. The knock was caused by the engine rocking slightly under hard acceleration and the two brackets knocking against each other. Moving the bracket a further few millimetres to the rear of the car eliminated centre bracket problems.

2) Rear heat shield: The rear silencer rotates about the two rear silencer brackets either side of the car. It is possible to position the exhaust in such a way that it comes into gentle contact with the heat shield that sits directly above the silencer and protects the boot area from becoming too warm. It is especially important on the Mk1b that this area does not heat up too much since the air intake is positioned in the boot. In my opinion, despite what some people say, the exhaust does get bloody hot (I have the burn marks to prove it) and the heat is more than enough to raise the air temp in the boot by a few degrees - this would only become a real problem if you are sat idling for a while - and therefore removing the heatshield is not the best idea in the world. I cured the problem by leaving the heat shield in place but bending it out of the way with the aid of a suitable length bar and block of wood - fashion your own device to suit!!! Don't bend it too far though else it will contact the bodywork resulting in annoying buzz thus bringing your endeavours full circle.

3) Rear silencer mounting brackets: If, like myself, you have not replaced the exhaust mounting rubbers at the same time as the exhaust then they will have grown weak with age and may sag slightly. The angle on the silencer mounting brackets is greater than the angle on the standard Toyota exhaust silencer and the end of the bracket comes into contact with the mounting bracket on the car. The cure for this I believe is new exhaust mounting rubbers though I have yet to get round to this. In the meantime, wrap the end of the angle in Duct tape or better yet part of a bicycle inner tube - alternatively grind a centimetre or so off of the bit that comes into contact though this is entirely at your own risk....

My 2p. Hope this helps.

Regards,
Jon

[andyj]

Good points Jon. Real mystery though why your silencer gets hot ...mine really doesn't. Just come back from 40 mile trip and putting hand between silencer and heatshield ...it's just warm - not hot! Yes, other silencers I've had would be scalding hot (I've also been burnt that way).

Magnex's instructions say "Remove heat shield from boot floor and discard. (Note - on 1987 onwards vehicles remove both heat shields and discard)".

I'm really not sure there is a heat soak problem from Magnex without the shield?

[j0nathan]

Real mystery though why your silencer gets hot ...mine really doesn't. Just come back from 40 mile trip and putting hand between silencer and heatshield ...it's just warm - not hot! Yes, other silencers I've had would be scalding hot (I've also been burnt that way).

Hi Andy. I'll come clean - I write this whilst at work and with no car to reference to. My comment that the exhaust gets hot was general and I admit that the bits I have been burnt by are the exhaust pipes and not the silencer - I try not to make a habit of handling any recently running exhaust, silencer or other part, without wearing thick leather gardening gloves. I still wouldn't have thought that removing the heat shield would be necessary unless the exhaust silencer will not physically fit beneath the shield(s).

Magnex's instructions say "Remove heat shield from boot floor and discard. (Note - on 1987 onwards vehicles remove both heat shields and discard)".

Instructions? Read? Instructions are for wimps....

Jon

[crazylegs]

i have a magnex i fitted to my mk1a this summer.no problems at all.i have fitted one to another mk1 in the past again no problems.i think you need to loosen the bolts a bit and wiggle it (tech term) .you may find its just not sitting right, there is plenty of room between the box and heat shields.you could have knacked shields of course.

[andyj]

Cheers Jon and Crazylegs Kev. You're right leave on the big heatshield and simply jiggle the setting so it clears everything. In particular loosening that joint between the two sections allows you to move it up or down by inch or two ...clearing heatshield, rear valence, etc. No need for big hammers, I think!