Wagon shakes when I apply break, vibrations that rattle cab Topic is solved

marcusantonus1 · Post by **marcusantonus1** » 23 Jun 2005, 19:48

1995 turbo wagon

Hello,
About a 3 weeks a posted a concern about the vibrations i get when i apply the break after driving the wagon for 30 mins or so. These vibrations occur off and on depending on when i break. Some suggested it may be the engine mount on top of the engine...well i switched that out and it still occurs. It has to be the break system, could it be pressure related? for example driving....then come to slow stop and then you can hear a build up of vibration come from the breaks. It doesnt seem like the rotors are warped or bad break wear and tear..but its got to be the breaks.

ps what should the wagon idle at? it just between 8-1000 rpm, kind of rough i think

thank you for your advice!

m

Guest · Post by **Guest** » 23 Jun 2005, 20:41

Even though I doubt this is the cause, I had the same problem with my 1999 S70. Turned out to be the notorius ETS, which I don't think would be the same deal with a '95. Just to be sure, check your RPM gauge when the car is shaking......is it staying constant or dropping as you shake?

Longman19 · Post by **Longman19** » 24 Jun 2005, 20:38

If your sure that its the brakes and that thier not warped then they could have developed hot spots on the rotors. Thats what the case was for my S70. They should appear as blackish-brown circles around your rotors.

marcusantonus1 · Post by **marcusantonus1** » 25 Jun 2005, 00:56

Hello,
I fogot to mention that the Rpms remain stable durning the influx of vibrations. I wil checkin into the rotors which it very well may be. But I recently switched the tires around and did not notice any spots. Any feed back on what RPM the car is supposed to idle at? Also, when i break the pedal remains stable...doesnt move up and down as it would when the rotors have been warped. Would the power booster or master cylinder have anything to do with it? Thanks for your feedback.

M

Post by **matthew1** » 25 Jun 2005, 01:02

You mentioned your wheels were just rotated. Volvos are sensitive to wheel lug torque. I'd take the wheels off and put them back on, torquing each lug to 81 lbs/feet in a crossing pattern. See if that does it.

marcusantonus1 · Post by **marcusantonus1** » 25 Jun 2005, 11:25

Hey,
Thanks for the response...the vibrations occured even before I switched the wheels around. So I am doubtful that its the torque on the nuts. Could it be a vaccum/pressure valve somewhere in the break network? Maybe it could be caused from a bad strut/spring in right rear wheel could have warped the rotor..I will definetly take another look. Have a great weekend guys!

thx
m

Post by **kelvin6** » 29 Jun 2005, 21:07

OMG! I have the same problem too. I just bought my Volvo 850 95 two days ago and just yesterday I felt that vibration, I know that my brakes are down to like 25%, but I didn't think they would produce such an effect.

I've noticed the vibration occurs when the car is at about 10 mph while braking. I've found a way around the problem, is to brake normally and the let speed fall to around 10 or less and 'pump' (about 2 times) the brake to stop.

The wheel nut solution is worth investigating, because I got the car back from a brake inspection, and obviously the wheel nuts were removed and put back in to place (and probably at the wrong spec).

marcusantonus1 · Post by **marcusantonus1** » 29 Jun 2005, 22:44

Hey,
I am so glad someone understands me!! Exactly how you stated it....I am thinking its the brake powerbooster or something. Because like you said it only happens once in a while around 5-10 mph and it stops when you pump breaks. Can some tell us what this is?

M

Post by **kelvin6** » 29 Jun 2005, 23:41

Tomorrow morning, i'm going to re-torque all the tires. The first time I felt that vibration scared the hell out of me, because it felt like the ABS kicked on until everything started to shake.

Im guessing we are dealing with something either too loose or too tight, because a vibration like that (my starts out with very little and suddenly builds up to heavy vibration). Resonance (Tacoma Bridge collapse?) is the key here. Now if the tire was too loose, its going to be obvious. If it was too tight, then we can begin to have resonance problems, lets say if we hit that natural resonance or the wheel, if it was too tight, the vibrations would be sent and amplified right into the car's body. I'm just guessing, it at least makes sense in my mind. After all, thats what torque specs are for right?

Guest · Post by **Guest** » 30 Jun 2005, 02:09

Hey, get away, me too. According to my service book this is quite normal! It says it's something to do with the abs. system just doing it's job!!? With me it just happens when I push quite hard, nothing too dramatic, just a mild shudering.