Hello all,

I bought a 1991 740 TURBO with 137k on her. My first Volvo. So far I have put new tires on, new front pads and rotors, new gas fill door hinge, new front turn signal housing, new brake light relay, fuel pump relay, re-soldered the overdrive relay (no more dropping out of o/d for no reason!) new trunk supports and re-glued the headliner. It shook when braking so I did the fronts, and it was ok for a little while, now it is the same, shakes when braking. Can someone give me an idea of what the common problem is with these?

Thanks,
Mike

 

Did you inspect the rears to see if they might be the problem ?? Depending on how bad they might be you can see dull or rusty areas where the pads aren't hitting causing the pulse.

 

Check ball joints and tie rod ends.

 

jagtoes,

Will do, there is a little side to side or left to right play in the front when I grab the wheel and pull on it. Probably 1/4 to 1/2". Should just change all of that anyway. I did read about a brace, torque arm? that the bushings can go, on the front going from the frame to the control arm..I think. One on either side.

Kiss4aFrog,

I do need to do the rears, they don't look too bad though.It really feels like the shake comes from the front. The previous owner said it did not do this, started at probably 110k or so.

 

the 700/900's have a control rod to the control arm, this has a double-cone washer, and yes, if that wears you can get quite a lot of wobble in the front end. if you feel play in the front wheel when its jacked up and you grab it at 3 and 9 oclock, have someone else rock it back and forth, and 'feel' the tie-rod ends. there's both an outer (visible) tie rod end, and another behind the rubber bellows on the end of the steering rack.

this shaking, is it like throbbing fore-aft as you brake hard? when you did your brake job, did you replace the rotors too, or just the pads? my 92 740 turbo was prone to that until I replaced the rotors with Brembo, and the pads with PBR, and properly heat cycled them as part of the break-in process, once i did that, the brakes lasted for years of hard driving without any pulsing or throbbing.

 

pierce,

I did change the pads and rotors, always do them both. I have the Bendix dual piston calipers, no ABS. The transmission gear selector does shake as well when braking. I need to get under there and have a look see at the ball joints and tie rods while moving the wheel when jacked up.

Thanks,
Mike

 

One further item you may want to check is the rear u-joint of the driveshaft. A few years back my daughter called me complaining of the brakes in her 240 shaking when applied. When I checked it out I found that the rear u-joint had seized causing the whole car to shake when the brakes were applied. When I got similar shaking beginning on my own 240, I checked out the same u-joint and found it seized as well.

 

act1292,

The rear u-joint? Would this not just break, dropping the driveshaft? How did you determine it was seized? Just wondering...thanks for the reply.

 

I dropped the rear of the drive shaft by removing the 4 bolts that attach to the differential. Once disconnected, the u-joint should flex freely. My daughters wouldn't wouldn't flex at all. On my car it would flex but with noticeable stiffness.

It doesn't break since the rear u-joint usually has very little bend. Only when applying the brakes did the front of the differential dip ever so slightly introducing a bend in the joint causing the shuddering. I drove my daughter's car home 140 miles on the interstate and it was fine at 70mph. Only when brakes were applied did the car shake violently.

 

act1292,

I will have to check that out. I did read about a driveshaft bearing or similar, but thought the u joint would just fail like the one on my '78 C-10 did..lol. When I get the time I will check out the front end suspension and u joint and report my findings. Thanks for the reply.

Mike

 

My s90 is rwd but I had the brake shake as well. I found the front ball joints worn out first, now I've noticed the control arm bushings are worn. that's a definite brake shake issue.

 

the primary cause of throbbing or pulsing brakes is uneven deposits or wear on the rotors. some rotors are made from cheap steel that gets these deposits faster. we had constant problems with our 240 doing this, even with almost new rotors, you get them hot from one emergency stop from speed, and they can pick up these deposits.

sloppy ball joints & bushings make the symptoms worse.