strange noise from front end of 406

[lawman27]

My V reg 406 HDI 90 has developed a strange noise which appears to come from the front drivers side although a passenger says front centre. The noise sounds like a soft thumping noise. What it reminds me of most is when I had a faulty exhaust rubber years ago and the exhaust was bumping gently underneath the car. I only get the noise when moving and it doesn't matter whether I am under load, coasting in gear, or freewheeling. Dipping the clutch doesn't change the noise at all.There is no vibration in the steering wheel, no warning lights and no change in performance, handling or braking. The noise seems to appear at about 20mph and disappear at about 60-70mph. These symptoms came on about a week or two after I had 2 new front tyres and have been going on for just over 2 weeks. They seem to be linked to wheel speed because if I change from 4th to 5th at steady speed, the frequency of the thumps reduces.
Finally, tonight I noticed a couple of times when I accelerated there seemed to be a slight 'stickiness' for a second as though something was catching and I had to overcome it before accelerating normally.

I have had it on jacks and the front wheels turn freely with no apparent play anywhere. I have 130,000miles on the clock and had the clutch replaced at 80,000ish. The clutch seems slightly jerky the first time I set off from cold but works fine and doesn't slip.

Has anyone got any ideas what it could be-I haven't a clue.

Many thanks

John

[steve_earwig]

I'm struggling to think of anything definitive to suggest

I'm not sure about this:

They seem to be linked to wheel speed because if I change from 4th to 5th at steady speed, the frequency of the thumps reduces.

Wheel speed, or engine speed?

I dunno, as the tyres are new check them for defects, check the wheel bolts too, engine mountings, crank pulley, aux belt for damage, hmm...

[PeterN]

I would first check the wheel bolts for tightness, if OK jack up each front wheel and rotate them slowly and look for any bumps in the tyre wall or tread, could be ply separation even though the tyres are new.

Peter

[Doggy]

I agree. It would also be worth swapping the spare for each wheel in turn until all are eliminated from your enquiries.

[PeterN]

Yep. even better.

[lawman27]

Thanks all,

I have checked the wheel bolts and they are very tight. I'll try changing wheels round at weekend. I am sure now that the noise is rotational in nature-on a quiet road tonight it sounded a lot like a washing machine on a slow wash.

Anyway, I'll try wheel swapping and see how we go.

Cheers,

John

[mjb]

securely chock the opposite wheels while you're changing them, and give them a spin. See if anything clunks while you're turning them by hand

[lawman27]

Well, I've had all the wheels and tyres swapped round and no difference. The tyre place cant find anything apparently wrong with steering or suspension. Could it be a transmission noise of some kind?

John

[PeterN]

I have just re read your original post and you said that the frequency of vibration changed when you change from 4th to 5th at a constant speed, that would suggest that its coming from the engine, I would check the crankshaft pulley, it may be disintegrating.

Peter

[lawman27]

I have just re read your original post and you said that the frequency of vibration changed when you change from 4th to 5th at a constant speed, that would suggest that its coming from the engine, I would check the crankshaft pulley, it may be disintegrating.

Peter

Thanks Peter,

I had the crankshaft pulley done about a year ago-it was making a hell of a rattling noise. The noise I have at the moment is (if you are old enough to remember this) almost exactly like the noise of an old twin tub washer on spin-like someone saying 'thub thub thub' in time with the engine. I've gone round my tyre and exhaust place and 2 garages now. My normal mechanics best guess is that it is a bearing on the input shaft to the gearbox (I think that's what he said). Anyway, its getting worse so I told him to order the bearing and will try to get it done weekend. Hopefully, I'll have good news next week. Otherwise I'll be back picking your brains again.

John

[PeterN]

Hi John

I well know the sound of a twin tub washing machine, in fact the first one we had was a Hoover single tub with a wringer on the top I used to repair them along with 405 line 1 channel TV's and wartime radio's, anyway I digress. It does sound strange, not the sort of noise I would expect a bearing to make although not impossible, but if it is the input bearing the noise should stop when you de-clutch.

Does this noise occur if you rev the engine when stationary or only when its under load? I would suggest DMF but I don't think yours has one. Next time you drive it try pushing the clutch out when the noise is there.

Peter

[lawman27]

Hi peter,

For some reason my last reply didn't post.

The input shaft bearing has made the car smoother and quieter and the stickiness on accelerating has gone. Just to try and eliminate things, I'll tell you what I have had done in the last year.
New brake shoes, wheel cylinders and pads.
Crankshaft pulley (but the garage didn't change the tensioner although I told them to-said it didn't need doing.
Both front wheel bearings
Drivers side engine mount-garage said passenger side was fine.
full exhaust
new front tyres.

Neither the tyre & exhaust place or my garage can find anything loose.
I have switched old rear tyres with new front tyres-no change.
Since I had the input shaft bearing done, I no longer think the noise is linked to engine speed. It seems to be purely a vibration linked to wheel speed, worst at 50mph. Dipping the clutch or putting it in neutral with foot off accelerator doesn't make a difference.
I am still convinced it is passenger side front wheel area. Tomorrow I am leaving it with my garage all day for investigation.

I will keep you all posted

[steve_earwig]

It could be a lot of things but at least that eliminates the crank bearing, which could screw up royally. It might not have helped jacking it up, it unloads the suspension and what's making the noise won't happen (hard to spin the wheels when they're on the ground...). I'm hoping they can find it so we can stop worrying about this and move on to the next crisis...

[PeterN]

The only thing I have ever had that caused apparant wheel vibration that wasn't the tyres was the inner driveshaft bearings on a Citroen CX, and then it only happened on a long run when the shafts got hot and the grease got thin, this was at a pretty high mileage though, probably around 200k.

Peter

[lawman27]

Well, I think we have eliminated everything but the recently replaced wheel bearing. I am going to take it back to the garage that did them and they will try replacing it. If there is a fault, they will try to get the cost back from the supplier.

I'll keep you posted.

John