Heat Shields

[Mitchen]

How big of a job is replacing the heat shields on a m20b20? Mine have had it but I'm assuming the top part of the engine needs dismantling? One to leave for the mechanic?

[Bristol_Jer]

Do you mean the heat shields that protect the HT leads?

[Mitchen]

Yeah those silvery paper things

[aceifty]

Just take the exhaust manifold off and replace gaskets (heat shields)

Very simple job

[Grrrmachine]

Hahah, you must be joking: "just".

Expect a couple of the exhaust manifold studs to snap off. If you're lucky, they'll snap off proud of the head, so that you can weld a new nut on and draw them out. If not, you'll be taking the head off to drill them out, before fitting new studs in their place.

If you're not mechanically minded, leave this to a professional.

[aceifty]

I must be very lucky as iv never had exhaust manifold studs snap on me.

[Grrrmachine]

I had three snap on the last M20, and that was after two days of soaking in penetrating oil and with the engine out of the car.

[PeteE30Tourer]

Are these heat shields really necessary though? Mine disintegrated some time ago and the car is still running fine. I do have a new set, but I've heard these stories before of manifold studs snapping, so I'm leaving well alone.

[daimlerman]

Only very,very rusty exhaust studs snap,and the state of them can easily be seen.

What is far more likely to happen is for the manifold to warp and pull the end studs(cylinders 1 and 6)out of the head.
Head is alloy,studs are steel,so the studs are far stronger than the head.

In all my years of M20 ownership,I have NEVER had an exhaust stud snap on me,but I have had several pull out of the head.

My first M20 came wrapped in an '86 E28,bought in '94.....

[Mitchen]

Glad i haven't tried this now.. Hope this isnt a job I take to the garage expecting to pay £40 labour and then end up with a £500 bill because 'something was wrong with the engine'

[spook]

Just give em a good soaking in Oil mate, its a simple enough job.

[Topblag]

When I did the last one, I soaked the studs for a week in advance. Not one snapped. A great tip is to to use nothing more than a 3/8 ratchet and a six point socket on them if they are stuck, too long a bar and too much torque can lead to snapping them. Spanners are ok to use in my experience.

[Brianmoooore]

Are these heat shields really necessary though? Mine disintegrated some time ago and the car is still running fine. I do have a new set, but I've heard these stories before of manifold studs snapping, so I'm leaving well alone.

No, they're not strictly neccessary, and don't appear to have been fitted to some very late M40 engines.
They had broken up, and the remains removed on the red touring in my sig., which used to get to very high under bonnet temperatures when frequently used as a towing barge, and the leads on that were still as good as new when the car met its end.
If you do go to the trouble of removing the manifold, I'd recommend replacing all the nuts with new copper clad ones, replacing the studs, unless they are indistinguishable from new, checking the manifold flanges across a straight edge, and having it machined flat if there is any warping.

[pukar]

you could try a simple mod to smarten it up....take a look here...

http://www.e30zone.net/modules.php?name ... at+shields