Noise identification please!

[dowen]

Well after some years away from Jags I 've  got myself a 04 s type 2.5.

I must say I'm delighted! Much improved from a 2000 s I had some time ago.

The only problem, it doesn't happen very often, is a strange rumbling sound, seems to come from rear. It's a sort of pulsing noise almost like driving over rumble strips on the motorway. It's not in synk with wheel speed, road speed, or anything else I can think of! Seems to be pretty  consistent with 1 second intervals, goes on for 3 or 4 times and then stops! Could this be wheel bearings? I would appreciate some help.

[Mollbhan]

Hi, doesn't sound like a wheel bearing which would either get louder or disappear altogether on the corners depending which way the corner was going. I used to have a Hyundai that made a noise just like you describe, it would start quietly and build up till conversation would be impossible, only way to stop it would be to slow down to 40mph then accelerate again, the noise would be gone. My garage was completely stumped by it, I always thought it was some kind of tyre noise but never sussed it out.

[dowen]

Yes tyre noise, but not very loud! And about 3 or 4 pulses,  as something is resonating at a specific frequency. And then it stops.

I just want to sort it before it morphs into a serious issue.

Hope someone can give me a clue.

[Mark Five]

How old are the tyres? If the car had been standing for a long time before you bought it and/or they're around 10 years old then I'd change them. Otherwise try changing the fronts to the back and see if that helps.

[dowen]

A few years ago I had an old s type and experienced "tram lining " . No one could figure it out, I had back and front tracked, all bushes were good etc, etc.

You know what it was? Odd size profile tyres on the front! 45 and 40!

So,I'll swop tyres round. I'm a great believer  in Ocams razor!

Thanks, I'll let you know.

[JustBadly]

So you mean that when the engine is cold and you reach about 30mph there is a rhythmic rumble or growling from the centre/rear of the car and when warmed up it goes away? The transmission fluid is low (it's the gears resonating since the rpm should be higher).

[dowen]

Thanks, this had occurred to me! I'm  going to get atf changed, 80k, so it's about due. Temperature makes no difference, but next time It does it I'll change down, see what happens!

I'm tempted to do the atf change myself! I did it years ago on the older S with ford transmission, without issue, (but I'm older now)

[JustBadly]

Yes, when the engine is cold and gets up to 5th, force 4th or lower and it should go away. Last time I asked a garage for ATF change they wanted £630. If you can do it yourself I think you should.

[dowen]

£650. That's outrageous! All parts inc.atf,£90. Off eBay.

It's a simple enough job, it's just getting the car up high enough! And level.

I just can't trust garages,having worked in a couple, (I'm a retired auto electrician) the stuff that goes on is horrifying!

I'll wait till the sunny days com.