The strangest thing....

[chrisfell]

....happened today.

Whilst out shopping (for another pot of paint as I'd been commanded to repaint a radiator that had scratches on it) I noticed my engine had started squeaking when cold and at low revs.

Warm, no squeaks. Cold and higher revs, no squeaks.

So back in the garage I waited until the engine was cool again, started it up and listened for where the squeaks were coming from. With a plastic tube I quickly identified the exhaust manifold as the source, where I found nearly half of the brass nuts were loose.

These nuts haven't been touched in years. The loosest were at each end of the engine, the tightest where the two manifolds meet.

All very puzzling.

[Durango2k]

Vibrations, vibrations...

Carsten

[Series1 Stu]

Vibrations, vibrations...

Carsten

And also

Expansion, contraction, expansion, contraction

Regards

[Durango2k]

...which is the same but slower :-)

Carsten

[Series1 Stu]

Ok Carsten, well observed.

Chris,
I assume the manifold nuts are brass but do you have spring washers under the nuts? I suggest you fit some if the studs are long enough, which they often aren't.

Regards

[Heuer]

Yes, there should be spring washers under the manifold nuts.

[Series1 Stu]

Back on one of my hobby horses.

Most fasteners should have spring washers fitted. Except for in places like cylinder head studs where the nuts are torqued down to give the requisite tension in the studs.

Regards

[chrisfell]

Everything is as it should be, all studs the correct length including those holding the dip stick clip and the alternator guard, spring washers under brass nuts. My fear is that they haven't come undone, but that the aluminium threads have become soft. I couldn't feel any softness when winding the nuts up again, but I fully expect to have to helicoil one or more of the threads in due course. I know the similar threads in the timing chest cover are already properly stripped, so a session with drills and taps and inserts is planned this winter.

[Series1 Stu]

It will be a better job than original if you fit helicoils. We always fit them in aluminium parts if they are considered service items. I suppose it's debatable whether manifold studs should ever need replacement but it is common to unscrew the stud instead of just the nut.

Part of the trouble is that the studs corrode with the presence of heat and moisture and the thread strength is reduced, then it strips.

Regards

[Hugo]

Sort of relevant - I had a coach develop a hydraulic leak where the pipe comes out of the master cylinder. It had been in there quite happily for about fifteen years then one day it decided to start leaking. Weird.