940 knocking from underneath !!!

[besidetheseaside]

Hi Guys, Need your help again....... Knocking from underneath somewhere, seems to be middle of car ?? more often on braking or accelerating, had it on a ramp and could not find anything untoward, passed the MOT recently, might not do it for days then it will do it all day, really bad today, clunk, then double clunk then an almighty bang which feared me a bit. Exhaust is new, brakes have been re-furbed, been using a pry bar on suspension but no movement anywhere, bushes look a bit old but so is the car lol, just cannot pin it down........

Are there any places I should be looking at specifically, realise that this is absolutely impossible to diagnose but any help/pointers/advice would be gratefully received.

Booked in on my mates ramp for 6 so fingers crossed I find it then.

[griston64]

Could be propshaft. But if that I would've thought it would do it all the time

[360beast]

New exhaust could have been fitted in a way that when you brake the engine moves forwards on the mounts and knocks on something.

Check the calipers/carriers have been tightened properly.

[Sicnarf]

Its your brake discs that are bad. Check them inside and outside to see if there is damage.

[besidetheseaside]

So an hour on the 2 poster and here is what we found,

Propshaft center bearing shot, the rubber doughnut part is actually separated from the steel outer, 6-7mm of vertical and horizontal movement.

Rear gearbox mount worn ?? 5mm of vertical movement, not sure if that is within limits.

Gear lever rod linkage bolt is flopping about in the bracket, I have an auto gearbox.

Running from the front numbers 1 and 3 heat shields were loose and have now been secured.

Nut missing from exhaust to turbo manifold, new one fitted and all now secure.

Checked all brakes, calipers and brackets, all perfect.

I had a pry bar under there and found no movement in any bushes, track rod end rubbers are cracking, (noted on MOT) but no excessive movement.

So just about to order the centre bearing and will probably make up a bolt and spacer for the gear lever linkage.

Hopefully my car will soon be as quiet as the proverbial church mouse wearing velour slippers.

[griston64]

I now feel like the Lairds apprentice as I think I kind of got it right

[Laird Scooby]

Originally Posted by griston64

Could be propshaft. But if that I would've thought it would do it all the time

Would have been my first guess too Mark, centre bearing as they make a lot of noise.

Originally Posted by besidetheseaside

So an hour on the 2 poster and here is what we found,

Propshaft center bearing shot, the rubber doughnut part is actually separated from the steel outer, 6-7mm of vertical and horizontal movement.

Rear gearbox mount worn ?? 5mm of vertical movement, not sure if that is within limits.

Gear lever rod linkage bolt is flopping about in the bracket, I have an auto gearbox.

Second guess would have been gearbox mounts. There are two types, one is a square-ish block of rubber in a cradle with a single bolt to the back end of the box, easily found on fleabay.
Second sort has two "rubber cotton reels", these aren't available but if you turn the rubber pieces round (end to end, not rotate them) you can eliminate a fair bit of movement.

Prop centre bearings are fairly cheap and plentiful on fleabay as well but check the diameter of the prop where the bearing sits, there are two sizes and the cheap, plentiful one is also used by Transits, Sherpas, Land-Rovers and a whole list of others.
The other one is hard to find!
Either way, get one that comes complete with the bracket, when you fit it, take it for a test drive after. If you get any vibration, note what speed it occurs at.
Return to base, slacken the 4 bolts that secure the bracket to the floorpan by no more than 1/2 a turn.
Now take it for a short, gentle test drive so you just get up to the speed the vibration occurred then return to base and tighten the 4 bolts evenly, a little at a time in turn and retest. All should now be ok, if not, repeat.

Originally Posted by griston64

I now feel like the Lairds apprentice as I think I kind of got it right

Learning well, you are!

Certainly in the right area Mark and if you'd ever experienced a centre bearing that has detached itself from its rubber donut, i'm sure you'd have got there!

As for my third guess, are there any missing pedestrians?

[baggy798]

183265 is the part number for the center bearing. About £28. Made by SKF.

1340501 is the bearing carrier. About £117.
Ordered a Meyle carrier from ebay instead, £20.57. It was either that or Febi Bilstein.

1328900 is the gearbox mount. £50.64.

[Laird Scooby]

Complete prop centre bearing :

https://www.ebay.co.uk/itm/VOLVO-S90...-/232635958498



Gearbox mount :

https://www.ebay.co.uk/itm/Febi-Bils...-/192556749413



Much easier and cheaper than buying component parts and trying to assemble in the driveway!

[besidetheseaside]

Parts ordered from Parts Monster on eBay, had a lot off these guys recently and they always deliver on time with good prices and quality, both parts were just over £30.
I will make a bush and bolt set up for the gear lever linkage using stainless items.