Groaning moose sound on cold startup

I’m trying to diagnose a sound that I’ve been having the last 6 months from the engine bay. Sounds like a moose far off in the distance. It’s a groaning/howling sound that is deep and medium to high pitched which slowly rises in pitch, then suddenly shoots down in pitch (like someone has shifted to the next gear) and then slowly rises higher in pitch , and keeps repeating this pattern for 10 seconds to 1 minute until it finally just fades away. It ONLY happens after first starting engine stone cold in the morning. And it seems to happen more on cold mornings.

I assumed it was belts or pump bearings, but I’ve recently ruled those out. The sound is influenced if I give it some RPMs, but it is indirectly related. Meaning, there’s a bit of a delay to the sound giving it rpms. If anything, the sound just gets louder, not different in pitch.

I thought it may be brake accumulator vacuum, but pressing brake pedal (to relieve pressure?) makes no difference.

The sound will also vibrate the chassis a wee bit. It is very hard to determine where the sound is coming from. It’s just the general engine vicinity, more on the left (drivers) side.

Reading archives, all I can think of is power steering pressure building up in the hoses/rack? What does this mean? BUT if i turn the steering wheel back and forth, it makes no difference to the sound.

I can’t think of anything else, except maybe coolant flow?

The sound does remind me of water pipes in a house making a howling sound, like from a home heating radiator.

Well, it would obviously have to be a moving part. I’m guessing one of the pulleys or the harmonic balancer maybe.

Could be hydraulics or air though… could it be coming from the transmission or evap/cold start valve something? Or the cooling fan (clutch)?
As long as it goes away when hot I‘d wait… but you seem to want perfection.

Hmm, reading the archives that indeed could be it. I get no howl or vibration after 1 minute warm up, and while driving even at high rpm.

Two things I’ve done over the last half year which could be contributing to the newish sound?

I changed oil weight from 20/50 to 10/40.

I think I over tightened alternator belt. It has no give.

Ill loosen belt a bit, and go back to 20/50 next oil change and see what happens?

And i don’t want perfection, ive just learned that fixing early symptoms prevent breakdowns
and major failures down the road

My 88 does same thing… sounds like a moose in heat…then goes away… could be steering pump…or?.. always does it

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Its just embarrassing, my neighbors think two mooses are doing it in my garage.

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Sage lessoned learned, an once of prevention is worth a pound of cure.

Okay that changes it :grimacing:
Yes the belts or balancer could be…

As part of my winter project, i am replacing power steering hoses. I also decided it prudent to buy a rebuilt p/s pump. I will mention then if the noise went away or not.

I believe that @DavetheLimey wrote about his investigation into this noise in his XJ-SC a while ago and concluded that it was transmission related. Both of our Jaguars with the 5.3L V12 and GM400 transmissions have a mild case of this noise sometimes after sitting for a few days.


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Hmmmm, that could be it too. I swear mine is from the engine bay not the TH400, but it could then be the transmission fluid going through the cooling lines to the radiator?

Now that I have a drain plug, I may try replacing trans fluid and see if that makes any difference at all.

Nice thing about Dave and I - we both have an 88, he is several years of experience up on me, and more of a perfectionist than me! :slight_smile:

Yes, I believe Dave concluded that the noise was due to transmission fluid and air moving around on start up but check the archives for his posts on the details.


Hi Paul, I spent a lot of time trying to track the source of the odd moaning sound. (Mostly out in the garage.) I would disconnect things one at a time, and then wait until the next start-up and listen. After a few weeks of searching, I started the car from cold one day, and found that the noise was very loud on the trans cooler lines going to the radiator. I guessed that convertor drain-back was responsible and learned to live with it.
Since then, I pulled my trans and it was rebuilt with all of the various bushings, seals etc replaced. I thought that the moan would go away, but no such luck.
Several months ago, someone posted a TSB on maybe A/C info- I don’t remember exactly- but added to this TSB was another paragraph describing a moaning noise on start-up that comes from the engine oil pump as it pressurises the galleries. How about that?
I use Castrol 20-50 in my car (Anybody remember Duckhams Oil?) and after sitting overnight, sometimes it will moan, and sometimes not. If this is the only moaning I have to listen to in my life, I’m ok with that.

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I checked all belts, and they
are fine. The moaning was there again for the first minute. Remember, mine also comes with a slight vibration you can feel in chassis. Did you have that too Dave?

But once i warmed up car, i took a good listen and there IS a slight metallic grinding/rattling sound at idle coming from water pump vicinity. I know the crank pulley is just below that.

Do harmonic balancers have a high failure rate in these cars? I am planning on pulling radiator next summer, is that the time to replace harmonic balancer? l’ll have subframe out in December. Or is that the time?

Both my V12 have had the morning moose call. If time permits I’ll find the Jaguar TSB that explains the noise and why it isn’t anything to worry about


Thanks, although reading archives, a lot of owners replaced harmonic balancer to rid themselves of start up noise. They never mentioned moose call, though.

Luckily balancer sounds doable with radiator in and subframe in. So i won’t proceed right now. If it ain’t broke…

And ok, ill admit I’m a perfectionist. I’ve been sick of my tank reading 1/2 when only 9/24 gallons have been consumed. So i drove 15 gallons of fuel (i average city 11mpg=165 miles. I also know that will put it just under tank sender opening so you don’t have a gas spill) and I proceeded today to bend float lever until the fuel gauge read 3/8 full. (It WAS reading 1/4)


Have you checked for nearby mooses?



Good one Wiggles. But, Greg have you checked for near by 89 XJSs? An even rarer possibility but who knows.

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Just to appease the neighbours, when you have moved the car out of the garage, get out of the car and close the doors saying ‘ now you moose behave while I’m gone’

Sometimes if the 88 sits a long while… especially on cool mornings…the power steering is stiff for a few seconds… however I can’t seem to relate the occasional sounds to the stiff steering… been this way a long time…had no problems