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#1 The strangest thing....
Posted: Fri Aug 11, 2017 9:32 pm
by 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.
#2 Re: The strangest thing....
Posted: Fri Aug 11, 2017 10:10 pm
by Durango2k
Vibrations, vibrations...
Carsten
#3 Re: The strangest thing....
Posted: Sat Aug 12, 2017 10:54 pm
by Series1 Stu
Durango2k wrote:Vibrations, vibrations...
Carsten
And also
Expansion, contraction, expansion, contraction
Regards
#4 Re: The strangest thing....
Posted: Sun Aug 13, 2017 7:45 am
by Durango2k
...which is the same but slower :-)
Carsten
#5 Re: The strangest thing....
Posted: Sun Aug 13, 2017 8:04 am
by 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
#6 Re: The strangest thing....
Posted: Sun Aug 13, 2017 10:37 am
by Heuer
Yes, there should be spring washers under the manifold nuts.
#7 Re: The strangest thing....
Posted: Sun Aug 13, 2017 11:24 am
by 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
#8 Re: The strangest thing....
Posted: Sun Aug 13, 2017 11:56 am
by 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.
#9 Re: The strangest thing....
Posted: Sun Aug 13, 2017 3:07 pm
by 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
#10 Re: The strangest thing....
Posted: Fri Aug 18, 2017 12:24 am
by 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.