Exhaust Heat-Shield Above Backbox

[Lexus-IS]

Just noticed the left side thin heat-shield that sits above the back-box on each side of the exhaust has come loose. It seems to be freely sitting on top of the back-box. I couldnt see much access between the backbox and the heat-shield to be able to even attempt to fix it. If I jack up the car will the backbox stay low down and create more gap between the heat-shield and the back-box?

[johnatg]

No - it won't make any difference - except that you'll be able to get underneath - warning - DO NOT RELY ON JUST THE jack - USE AXLE STANDS OR SIMILAR.

You may be able to work around the silencer, or you may need to remove the silencer.

[Lexus-IS]

Oh. By the silencer do you mean the actual big bulky oval shaped back box? How is the heat shield attached does it slot into some sort of bolts pointing downwards and then nuts go and hold it in place. Anyone have any pics of where the mounting points are and how many there are?

[johnatg]

Yes the big oval things are the silencers.

I'm not sure what Lexus use. There are two common methods - one is where the panels are simply bolted to the floor - the bolts screw into tapped holes or captive nuts. This is probably what Lexus use. The other method is where there are plain studs protruding from the floor and the panels are held to them with starlock washers.

The panels have probably corroded around the fixing holes, so now you have big holes with rusty edges. You can usually effect a repair by using repair washers - they are about 3cm in diameter with a 6mm hole. That will cover the damage. Or you can make up a cross with perforated strip (perforstrip is one brand - accessory shops sell it or other brands) as big as required to extend beyond the damaged area. You may need new bolts and the repair washers as the holes in the perforated strip are quite big. You will probably need new starlock washers as they often break when you prise them off the studs.

[Farqui]

My rear heat shields are secured to stud's fixed into the floor. With washers and nuts to hold the shields in place. Adding a larger penny washer did the trick for me (the shield had corroded around the fixings).

[Texas]

Had this local corrosion of heat shield around fixing points on my Mondeo, I reckon it due to the reaction of dissimilar metals ( Aluminium & Steel) accelerated by the damp location. You can get a product called Isolation Paste to try and combat this but prob need to remove exhaust to do a proper job!

paul m.

 

[Lexus-IS]

3 hours ago, Farqui said:

My rear heat shields are secured to stud's fixed into the floor. With washers and nuts to hold the shields in place. Adding a larger penny washer did the trick for me (the shield had corroded around the fixings).

Did you fix yours yourself? Is there enough access to get to it?

[Farqui]

Yes, I was able to work around the muffler with either a spanner or a socket.

I may have jacked the car up a smidge to gain a bit more elbow room. But you should be able to check out the job without raising the car.

It's definitely worth a quick look to see if you can DIY.

[Britprius]

8 minutes ago, Farqui said:

Yes, I was able to work around the muffler with either a spanner or a socket.

I may have jacked the car up a smidge to gain a bit more elbow room. But you should be able to check out the job without raising the car.

It's definitely worth a quick look to see if you can DIY.

As Lee says there is room to work on the heat shield. Removing the two rubber hangers rear of the silencers will allow them to drop to give more clearance. The OEM nuts "8 mm socket size" holding the shield are made of a very soft material "probably zinc", and may break up or round off as you undo them. Replace them with steel nuts and a good coating of copperslip anti seize compound along with some penny washers for a lasting job.

John 

[samplify]

Reviving this thread - anyone know the thread pitch and size of nut I should use to secure the heatshield?

[steve2006]

Pretty sure M6 x 1