Guess the rattle - strut top mount?

I've got a constant dull metallic rattle/vibration that seems to be coming from around the NS front footwell. It all but disappears when I've got a front passenger in the seat so my plan to have a listen whilst getting someone else to drive and sitting over there is no good.

Just done the tie rod ends, which were knackered, so it's not that. Got a bit of play in the NS inner tie rod, which will be replaced next, but I don;t think it's that.

Drop links are Meyle HD and maybe two years old. I'll be checking those next. On the one had it'd be great if they are the culprit as it's an easy fix, but equally will be disappointing given their reputation.

I've a horrible feeling it's the strut top mount bearing. This was replaced a few months back with a bearing and spring seat from Nordic. Annoyingly I went the cheap route as the plan was to sell the car soon after and it wasn't worth throwing money at. Had I made the decision to keep it a bit earlier I would have spent the extra on Volvo parts instead. The noise was evident within a few days after this was done but I couldn't tell if it was a new noise or pre-existing as there were that many rattles and clunks beforehand due to the knackered parts!

The point of this post is not so much what do you think the culprit may be, but rather, what's the best/easiest way to determine if the noise is coming from the top mount? Obviously I really don't want to have to strip the strut down again to check it, but if it's not the drop links and there's no other easy way to check then I guess I may have to.

I've not checked the suspension arm BJ yet. I suppose that could be a candidate too.

I too had a faint, intermittent and dull knocking from the front N/S suspension which started to become noticeable after Christmas.
This noise completely dissappeared when I had my springs replaced two months ago!

The only parts replaced were:

Front springs x2
Front spring seats or support plate (top hats) x2
front O/S shock dust boot (badly cracked) x2.
SUM calibration.

From past experience the spring support bearings make a grinding noise when worn and cause vague steering wander due to a resistence to correct self centering. They don't normally 'knock'!
However, the spring seat or Top hat, as they are more commonly known, can cause a chatter, knocking or if they are really bad, a thud or harsh knocking when driving over rough ground or subtle speed humps etc. The center portion normally starts to tear itself out of the rubber, causing unwanted movement in the strut assembly.

If you want to check the support bearings, raise the front of the car on jacks so the wheels are clear of the ground, with the engine off, ignition on, have a helper turn the steering lock to lock and you listen and feel the strut at the top. If you can feel it graunching and grinding, then the bearing is shot. If it's quiet, it's OK.

Top hat is more difficult, but if you've done the ARB links (common failure and cause of knocking at front end) then the only likely culprits are the support plate or the shock itself. Inner tie rods don't knock. They cause excess play in steering and may chatter if really badly worn.

On cars with 4C (V70R/S60R) and T5's with sport/comfort button, a SUM calibration will often sort out any subtle knocking providing the shocks are good.
Also a SUM update of the latest software and calibration will also cure a knocking shock, as it did in mine.

Great, thanks lee that's really useful. Know what you mean about the rubber top hat tearing as that's how the old one had gone, completely mullered and the strut and metal collar (that is moulded in to the rubber) where clattering about. Luckily it should be easy to tell if it's torn again as the strut moves noticeably out of position when it tears which can be seen from the engine bay. I don't think it's that anyway as this is a different noise.

Another thought was whether the star nut could have worked loose and if that would cause any movement inthe parts that could cause a knock. I don't have the proper tool for the star nut so I'd just tapped it around until it seemed tight enough.

THis is still an open case, but I have a suspect....

I was fitting poly subframe inserts and when I came to do the rear NS one I could see as soon as I removed the plate that the bush didn't look right. At first I thought it was deformed, the metal collar is oval shaped. Having done some googling it appears this is normal (no idea on the reason but the rear NS is different to the other 3). The rubber is definitely not right though, the gap where the poly insert is supposed to slide in to has partially closed up so I could not get the insert in for love nor money. So I guess the collar has started to rust and the rubber has expanded out closing the gap.

I'm going to have another look, maybe today. It's more or less the exact spot the noise seems to come from, and with a passenger the noise disappears so I can only guess that the extra weight on that side reduces movement between the shell and subframe. Apparently Volvo released a rubber O ring that sits between the shell and subframe for the S80 to address subframe rattles.

EDIT: Also, the noise became more pronounced when I fitted a poly bushed torque rod just over a week ago. If it is the subframe bush to blame, the vibrations from the engine/box will be getting fed in to the subframe from the torque rod and it stands to reason that it would exacerbate any rattling at the failed subframe bush.

Quote:

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Originally Posted by Gold 'N' Brown

THis is still an open case, but I have a suspect....

I was fitting poly subframe inserts and when I came to do the rear NS one I could see as soon as I removed the plate that the bush didn't look right. At first I thought it was deformed, the metal collar is oval shaped. Having done some googling it appears this is normal (no idea on the reason but the rear NS is different to the other 3). The rubber is definitely not right though, the gap where the poly insert is supposed to slide in to has partially closed up so I could not get the insert in for love nor money. So I guess the collar has started to rust and the rubber has expanded out closing the gap.

I'm going to have another look, maybe today. It's more or less the exact spot the noise seems to come from, and with a passenger the noise disappears so I can only guess that the extra weight on that side reduces movement between the shell and subframe. Apparently Volvo released a rubber O ring that sits between the shell and subframe for the S80 to address subframe rattles.

EDIT: Also, the noise became more pronounced when I fitted a poly bushed torque rod just over a week ago. If it is the subframe bush to blame, the vibrations from the engine/box will be getting fed in to the subframe from the torque rod and it stands to reason that it would exacerbate any rattling at the failed subframe bush.

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Sounds plausable to me fella.

MOT passed this morning. That's two years on the trot now, although not without some advisories. Tester pointed out that the NS balljoint has a small amount of play. He doesn't think it'll be causing my rattle but it's good to know as even once I've done this subframe bush the BJ could still be an issue afterwards, so I'll add it to my list to do.