Groaning moose sound on cold startup

Hmmm. I’ve grown so accustomed to the sound I don’t notice any patterns, if any exist. I use both 10/40 and 20/50, and am 99% I’ve never had a clogged filter…so I don’t think those have any bearing.

Colder ambient temps might have some bearing. I’ll try to pay closer attention.


I have a stethoscope to listen, but i am quite apprehensive sticking it in the area with fans, belts and pulleys whirring around at 1000rpm! I assume my ears would not be yanked off, but i could easily damage something.

I don’t remember the noise when my car was in worse shape, when i first bought it after it sat unmaintained for 7+ years. Its only recently with it fully tuned up and several oil changes to get rid of the ugly oil. It seems most of us here who hear the moose call also maintain our V12’s religiously. Perhaps a top running V12 lets more air in after shutdown?

First, I do not think it has anything to do with the transmission cooler, as I have changed radiators, trans filter, and fluid with no difference. Ditto on oil filters. Also not HVAC.
It definitely is temperature related; didn’t occur during the summer, seems like 50f is when it is apparent. If really cold, no moan until engine has run for a few minutes, and longer time to occur and longer it lasts the colder it is.
Personal opinion is that it is the oil pressure regulator, as NA spec uses bypass oil cooling- when regulator opens, it directs flow through the oil cooler, which is rigidly mounted to the body and why some of you indicate that you feel it. I had some luck with a 3.3L Chrysler engine with a similar noise by grinding a groove in the regulator piston.

My guess is the sound is the vacuum canister having the atmospheric pressure air removed by the engine during start up. Check for leaks in your vacuum lines and the tank. May also indicate that the one way vale at the rear on the A bank is not in good shape.

Just a thought…

Over the years on various cars I’ve had luck curing fluid-movement noises by slight re-positioning or slight bending of hoses/pipes. Just a little tweak to change the flow characteristics can sometimes do the trick.


Gregmatic, can you post an audio file here of the sound, or does the new website not allow for those type? :confused:


Yes, same here.
It seems to me though that the noise comes from somewhere in left front wing area.

Doug, that is something to try- I also have had success with trans cooler lines and fuel lines that transfer fluid noises.
My problem is that I only remember the noise when it is occurring…

Left wing you say? Which one is it??? On LHD i guess??? Still going for alternator’s small bearing - that’s exactly what happens with temp drop if your alternator is on the way out…

Always experienced the same. To me the sound was center firewall and to the right hand side, firewall and dash.

I can actually hear the moose call more clearly inside the car than outside. When inside car, it sounds like it’s coming from right behind the instrument cluster (LHD), which is why I thought brake booster. But when i hop out of car and open hood, it sounds like lower part of car, slightly to left side.

It definitely doesn’t sound like bearings, so very much doubt it’s alternator. But you never know…maybe Lucas bearings are different. And vibration sounds CAN travel.

35f this morning and no sound whatsoever, had not been driven since Saturday. I hear it better in the car, sounds to the right side, which is why I initially thought HVAC or fuel rail/regulator- but have listened to those with a stethoscope and heard nothing.
It hasn’t changed in the 3 years that I have owned the car, and I replaced the alternator early on, and the a/c clutch more recently. Still did it when the a/c system was without a charge (and Greg removed his a/c if I recall). Power steering is quiet.

Considering the habits of UK_based Jag Lovers - have you replaced the alternator with the new one or second-hand???

Changed alt awhile back…same noise before and after…lower temp’s… continue until engine runs a little and then disappears… sounds like A440 on my piano tuner device.

Jaguar TSB says air purging in oil via oil pump. Why would that be worse when cold? Is it thicker oil?

Rebuilt Lucas, but doubt that it would have the exact same noise.

I would guess thicker oil. I run 20/50, might change or eliminate the noise to go thinner. Owners manual says 20-50 for above 32f if I recall.

I’m going to hazard a guess. I believe it’s a diaphragm noise from a vacuum or fuel line somewhere.