What to do with that rusting heat shield?
As good a sports car as Toyota made the Roadster it is by and large an accepted fact the build quality could and should have been better.
One of my personal pet hates, and I know others share it is the corrosion that seems endemic to our engine bay.
Two of the biggest most noticeable areas are the cylinder block which is made from aluminium and goes powdery (though some blocks are now sporting a vinyl coating to prevent this) and the exhaust manifold heat shield which rusts.
Last week I decided enough was enough and I would attempt rectify the latter of these.
Here you can see a picture of the problem area:
In order to remove the heat shield we need to remove a total of 4 bolts. The two shown on top of the heat shield and a further 2 that sits at the front of it. These are very difficult to see due to the proximity of the cross member and exhaust. You will need to work by feel but this is not particularly difficult. You will require a 12mm socket and a ratchet drive.
Here are the screws in question, rust, surely not?
You will also need to unplug the wiring harnesses for the 02 sensors which normally sit in the manifold and thread them the through the holes in the heat shield. In the picture above I have already removed these in order to check on my pre-cats (more on this later).
Suffice to say if you too decide to remove your 02 sensors you will need a 22m 02 socket as shown here, the slot is to clear the wires.
Unplug the sensor harness before attempting to unscrew the sensors or the wires will snag.
Here’s the heat shield removed…
And the naked manifold it covers.
Just for your benefit here’s the manifold with the 02 sensors in place so you can see how they fit.
Inspecting the Pre-cats
I mentioned earlier inspecting the pre-cats. As you may be aware there are a number of documented cases of the pre-cats (Catalytic converters) which sit in the bulges where the 02 sensors are located, collapsing with the inevitable result of blocked exhausts and engine failure. I’m not going to debate here the ultimate cause/effect theories surrounding this problem; however since we’re here it’s a good opportunity to inspect them.
Shine a torch into these holes and ensure that the honeycomb is still intact.
Unfortunately my camera refused on the day to take a useable shot of inside this hole. Here’s one courtesy of Beanie on Spyderchat:
You can see what the honeycomb should look like. My right hand cat looked like this. My left hand cat has signs of a hairline crack developing. I’m going to drop the main cat pipe this weekend and investigate further; I’ll write an article on this later on.
Suffice to say it’s advisable to keep an eye on these and if you only buy one tool make it the 02 sensor socket.
Here you can see my left and right 02 sensors, observe the white chalking build up. I’m not sure if this is good or bad.
And so back to that heat shield.
The first stage is to get rid of the rust, fortunately most of mine was just surface discolouration. Some wire wool soon got rid of that. Next I wiped the entire thing down with some Whites spirits and allowed this to dry naturally. This will ensure that there are no greasy or dirty areas left on the metal.
You’ve probably guessed by now that I’m going to paint the heat shield. To do this requires a serious paint that can cope with the extremely high temperatures that it’s going to experience.
My first intention was a trip to Halfords to find some Hammerite flat black barbecue paint. With a temperature rating of 650 degrees C I figured this should cope. Then in a moment of inspiration I found an old can of anthracite fire paint. This is intended for painting the exposed metal areas of gas fires and is also rated at 650 degrees. Reading the can closely revealed a suggested use for exhaust manifolds. I’m not convinced that it would hold up to use actually on the pipe but for the heat shield it should suffice.
As with any spray painting many light even coats will produce a far better result than a few heavy coats. Since the whole point of the exercise is to improve the looks and runners were not desirable I proceed to paint the heat shield over the course of two days. All in all I’d guess it had around 8-10 coats. Very light ones.
So here’s the end result.
And still half a can or more left of the paint.
While leaving this to totally dry for a day I decided to sort out the problem of those rusty bolts. Remember them?
Obviously these would spoil the end result, so off once more to Halfords I went (I should own shares in them) taking the old bolts with me.
The bolts are standard 8mm however they are 2 different lengths. In the end I bought a box of assorted black powder coated bolts, and a small pack of stainless 8mm washers, total cost of just over £5. Now you see why I should have shares in Halfords.
The two longer bolts were easy as the pack contained an exact match. The shorter ones required a little dexterity with the Dremel.
Here’s the end result.
Now just a simple matter of re-assembly
Here you can see the heat shield back in place:
And with the TRD rear brace back in place ready to go for a drive:
So how’s it holding up?
Well I’ve now done a couple of hundred miles with it in place and as expected the first few were a little smelly as the overspray that got onto the inside of the shield burnt off, and the top coat fully cured. But touch wood it’s still looking as good as the day I did it.
All in all a cheap mod at around £10, and a huge improvement. If only everything was this easy.