Groaning moose sound on cold startup

To each his own, and you may have your own constraints or limitations, but if it were me, and I was pulling the the subframe, you’d better believe I’d be doing all that has to be done in the front of that engine. I wouldn’t hesitate for one second to pull that radiator and stick a newly rebuilt harmonic balancer, water pump, power steering pump, and I’d be sending that radiator out to be tested and cleaned at a minimum. When you start talking about removing major components (in this case) like the subframe it readily lends itself to removing the radiator with minimal fuss. This in turn opens up all kinds of access to things that are normally a bitch to get to, and the workable space cannot be ignored. Unless you were to remove the engine at some point, you will never have that type of easy access again. I say do it all in one go and never revisit these subjects again.


My ‘88 has same noise, this should be an interesting thread. I think it is the engine oil cooler/ bypass but it isn’t something I think of until it does it, and then I am on my way somewhere.

Mine recently started doing something like this too. It sounds like a belt/bearing noise coming from the very front of the engine. By the time I get the bonnet open it’s almost stopped.

Its strange that it wasn’t there until maybe a month or two ago.

Not sure if this is helpful Greg but this lady noticed a noise coming from her car after running over a mattress. Took it to the dealer to investigate…image image


From Jaguar TSB JD03/84

There have been reports received of an engine noise on V12 engines described as a “groan” on initial start up when the engine is cold. This is a standard feature although it may not affect all engines. It is caused by the oil pump purging air out of the lubrication system which can enter the system after the engine has stopped.

It is not detrimental to the running/performance of the engine.



Thanks Doug- I knew I read the TSB somewhere. The sound must have been picked up by the trans. cooler lines which are clamped (I’m pretty sure) to the engine oil pan. No worries then- they ALL DO IT!

So V12 owners in Canada must get a lot of mooses showing up at their homes every morning?


Great: first, it was the Boeing Blade©, and now we have, Morning Moose Syndrome."


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So many possible tongue in cheek comments spring to mind

Meese. Pretty sure it’s meese.

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Moose. Single or plural.


Glad ya told me…:grimacing:

I have a similar noise on cold starts.
It comes a couple of minutes after it starts, but not always and with some variation in duration, from one to two minutes.
It’s more pronounced at idle, goes away as soon as I press the throttle, and comes back when I depress it. It seems to me that it’s related to the amount of vacuum.
I have concluded that it must be either the Rochester valve while the fuel tank is equalizing pressure, or air purging from the cooling system
Very elusive to pinpoint and it might be altogether a different thing.


My '83 had it, then it didn’t. Wasn’t documenting changes well enough to identify what made it go away. There have been suggestions that my recommendation to install a flushing tee in the heater hose to be used as a bleed port when filling the coolant system may have helped some cars get rid of that moose call.

I drove Prevost coaches for a few years part-time after I retired. One of my fellow drivers drove over a mattress, at night , on an Interstate highway. It wrapped itself around the “tag” axle, and, after a mile or so, caught fire. He saw the flames in the coaches mirrors, and stopped. (There were no passengers on board) The coach, just a couple of years old, burned to the ground, completely totalled.
From then on, all the other drivers called him “Fireball.” And he kept his job!

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The TSB says air being purged from oil. I wonder if it could be oil weight related? I did switch to 10/40W, not sure if that’s when my moose call started? Others here, long after an oil change, perhaps the 20/50 oil has broken down a bit in viscosity? Or even filter related? A brand new filter unclogged?

There is one old classic tool available on the market until today:

How’s that possible that most of the XJS owners (65+) are unable to recommend it…

There are different versions and probes with it. You can literally hear what is the condition of your bearings in water pump or alternator (my bet - rear alternator’s bearing)

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Oh this noise should be referred as the Bullwinkle syndrome