1998 S70 Intermittent vibration

Post by **Atis** » 30 Apr 2015, 02:09

Hello all,

I need some advice, how to go on with a really annoying vibration issue.
Symptoms:
-The chassis vibrates from ~70km/h (~45mph), the steering wheel not
-The severity of vibration changes within some kilometres
-During braking I can feel the pulsation in the brake force (not in the brake pedal), it is intermittent as well, so sometimes I cannot feel any pulsation
-Brake force pulsation and vibration is speed dependant
-I blamed the winter tyres, changed to new summer tyres with new rims, it got much better, but sometimes the vibration is still there, just the severity is lower
-Rear brake job was done ~5000km ago (new rotors, pads and e-brake pads)
-I have checked the suspension for any play, only found a really minor play at the right inner tie-rod.
-No strange noise from suspension when going over bumps

So I need some ideas what to check.

Post by **Atis** » 02 Jun 2015, 05:34

Bump

The vibration is still present and getting more annoying (I am not surprised that the car did not heal himself).
Yesterday on the highway I was driving out to a petrol station and for a fraction of second it was like one of the wheels was jammed. It was a sudden "hit of a back-holding" force. (I do not have any better description). The strange was that the car was not trying to go to left or right. So maybe it is driveline related...
Since than I have a bit of a fear...

Some additional symptoms:
-the vibration feels like the road is a bit uneven, although it is mirror flat
-I can hear a faint bearing noise (wheel speed dependent), which does not change by turning to right or left
-no typical CV symptoms as vibration during acceleration (inner) or clicking (outer); hard acceleration makes the vibration unnoticable

Could be a transmission failure? (manual 5 speed)

I would like to be really systematic, but I run out of ideas about what else and how to check.
Any advice is really-really highly recommended.

P.S: I have one month to fix it, after that we are moving back from Germany to Hungary with wife and two small kids, so it has to be reliable and safe till end of month.

Post by **JBC2565** » 02 Jun 2015, 07:32

Is it AWD??
I had a similar vibration and it turned out to be the middle u-joint in the propshaft. Also the front u-joint rubber collar was all beat up so front was bound to fail sooner or later.

volvooh · Post by **volvooh** » 02 Jun 2015, 08:49

Could be a tire and rotor issue.

Check for wheel balance, also if there is any broken belts.

Also check brake rotors for warping.

volvooh · Post by **volvooh** » 02 Jun 2015, 08:54

Also check your rims...a slightly bent rim will give you vibration at specific speeds as it throws off your tire balance.

Post by **Atis** » 02 Jun 2015, 13:43

No, it is a FWD. The tires and rims I would rule out as they are brand new, and the change from winter tires did not solved the issue, just made a bit improvement.
It is really not like an out of balance issue as driving with the same speed it comes for ~10 minutes and fades away (never complately).
I will change the tie rods and see how behaves.

Post by **scot850** » 02 Jun 2015, 16:44

Is the vibration felt through the seat of your pants? You say it is not felt through the steering. I was always told, if it was mostly felt through the seat it is more likely to be from the rear.

Jack the car up and check the rear brakes aren't sticking on. The rear calipers stick, the parking brake cables jam/stick (you may think it is working but may be stuck on one side) and parking brake shoes disintegrate in the rear drum or detach and cause vibration.

With the car jacked up, spin one rear wheel and check for rubbing/tightness in turning. If this is ok, try getting someone to slowly increase the pull on the parking brake lever while you turn the wheel and see if it is working, and that when they release it, the wheel turns ok. If it doesn't it is probably the cable on that side has jammed, or the parking brake shoe is damaged. Remove the rear rotor and check all is good.

While you are in there, check the condition of the rotor, particularly on the rear face for rust build up, check the pads and caliper piston(s) move properly and you have even wear on the pads.

Finally you could have slightly warped rear rotors.

Next thing to check is rear wheel balance, and that none of the tires are square from hitting a pothole. You can try swapping the front and rear tires on one side, drive and see if there is any change, then repeat with the other side.

Finally have a 4 wheel alignment done and have them check the rear suspension/axle bushes for wear.

Neil.