XC90 pulls when braking... not the same story repeated

[willreed1]

Hello all,

I believe this is my first post on the site, although I do visit often for assistance on maintenance items and you all have been quite helpful. I have a situation that is baffling me and could use some assistance in troubleshooting. Importantly, I do nearly all of my own maintenance, have a well-stocked shop and nothing mechanical scares me off, so everything I state here is from a DIY mindset.

ISSUE: 2008 XC90 with 177k miles pulls to the right when braking. If you feather the brake it will still track mostly straight, but if you lay into the stop pedal, it drifts pretty hard and requires a steering correction. Seems straightforward thus far.

Backstory:
I've had the car for several years... always do preventative maintenance and it's never left us stranded. When looking at the car on the lift at 175k, noticed the LCA bushings were getting a bit worn and cracked, so time to replace. Tackled the project in an afternoon with new SKP parts from Rockauto, they went in fine. Immediately after, noticed car drifting to the right on braking. Went through several troubleshooting items to identify the problem:
- swapped L&R tires
- replaced flex brake lines to ensure nothing got pinched while hanging calipers
- figured the anti-roll bar end links and steering end links were on the edge with age, so replaced those also
- replaced right LCA again as a warranty part just in case the bushing was pressed in poorly
- removed brake pads and compressed calipers to ensure they were functioning and moving smoothly, bled brakes again. No visible difference in pads/rotors on the right hand side and I can tell that left side is applying significant pressure... I assume evenly.
None of the abovementioned fixes or trials changed things. Perhaps the steering is a bit more stiff, but still drifts right upon braking only.

INTERESTING THING:
here is the part that has me stumped. With an assistant, I had the car running whilst on the lift and put in gear at idle speed just to get the front wheels moving. When you hit the brake pedal, both front tires toe in, the driver's side most significantly. No weight on the chassis, nothing on the ground, but you can see clear toe-in movement and the idle speed will drop a bit with the steering wheel held straight. Put the car back on the ground again and just rapidly hit the brake while in Park, and the tires will again toe inward slightly, obviously less with the ground resistance.

The only other maybe related info is that I do have the warning light on for the anti-skid service that comes and goes... assumed it was the steering wheel sensor that I just haven't gotten to yet. Also, have noticed that steering feels slightly "lighter" when making hard right turn than hard left turn, almost as if the pivot point on the wheel is in a different location. Hard to describe, so I'll stick with a lighter wheel feel.

I'm desperately searching articles on steering, toe-in, and Servotronic issues, but every article tells me that my brakes are uneven and the suspension parts that I replaced need to be replaced. Graciously asking for some good help and thanks in advance.

[Capndirk]

I had that after all new front LCA bushings. Swapped out for better and different on the front LCA bushings with no change. Went after the rear bushings on the front LCA, and found one was poorly made in rubber casting. I had done a lot of researching, and found that the rear bushings on the front LCAs are usually the culprit.
First question is are they correctly installed at the correct angle per VIDA. but more than likely, the rear bushings aren't top quality. Mine are now all Poly and I'm very pleased, with the moose tracking straight down the road when braking.

[ggleavitt]

Was the mounting hardware re-used with your single-sided aftermarket LCA replacement? What torque/angle values were used on the hardware when mounting the new LCA ?

PNs for the mounting hardware (each side): Qty.2 PN 987456, Qty.1 PNs 999403, 985660.

[willreed1]

@ggleavit and @Capndirk: thanks for the responses. The same mounting hardware was used to reinstall - I was not aware these were single-use TTY bolts, but if so, they fit up fine and there did not seem to be any variable allowance on the installation for angle adjustment. I would estimate torque around 100 N-m based on my wrench... I have a torque guideline that has all M12 at 80 N-m unless otherwise specified and the LCA is not listed, and my wrench isn't exactly calibrated from what I've noticed (on the low side). I had an alignment done after the LCA install and the values came back within specification of their measurements. And for the record, the LCA were initially done as pair - I always do R&L side if I find a wear part. The pass side was again replaced single as a warranty item but the driver's side had <1000 miles.

[ggleavitt]

Veer and recover when brakes are applied or veer and no recovery when the brakes are applied?

[willreed1]

@ggleavitt - veer and no recovery when brakes are applied. It will continue to track right as long as brakes are applied, some recovery when brakes let off but takes a steering adjustment to fully correct.

[ggleavitt]

I'll stick my neck out and say there's some degree of space between the rear nut/bolt and the LCA rear bushing center barrel that's causing the steering geometry to shift under load and it stays that way so long as you have brake drag on the affected wheel. Another forum member had a similar story, he'll pipe in if he's around. Either bolt size or bushing, I would change the hardware out with new OE and try to do the tightening as per spec (I'll go hunt the values down). Consider another LCA manufacturer if hardware does not address your problem.

[willreed1]

Thanks ggleavitt, that was my next course of action... everything else seems to check out and problems occurred when the LCA was replaced... just wondering if the parts assembly is somehow off causing bad geometry. I'll pick up new LCA and bolts from the Volvo parts desk to install... just hate to throw new parts at a problem without knowing, but in this case I can't find anything else that would cause this bad of a pull. And unfortunately my old OE factory part is since gone so I can't compare new/old parts. Let me know those torque specs if you can find them. Thanks.

[xHeart]

Thanks ggleavitt, that was my next course of action... everything else seems to check out and problems occurred when the LCA was replaced... just wondering if the parts assembly is somehow off causing bad geometry. I'll pick up new LCA and bolts from the Volvo parts desk to install... just hate to throw new parts at a problem without knowing, but in this case I can't find anything else that would cause this bad of a pull. And unfortunately my old OE factory part is since gone so I can't compare new/old parts. Let me know those torque specs if you can find them. Thanks.

Unless someone says otherwise, the LCA bolts to the subframe are torqued at the ride height. I would also torque the ball joint nut to LCA at the same height.

[Capndirk]

I found the bushing orientation instructions in VIDA living in a backwater of my computer: Here it is:attachment=0]bushings.pdf[/attachment][/img]
The thing about the angle torquing spec is that it stretches bolts to an engineered extent. TTY is different in that they've stretched to an unrecoverable limit. Angle torque bolts can be re-used, with the peril being that they are near yield and may break. Volvo is in the business of selling parts and also encouraging dealers not to risk installation failures, so it recommends new fasteners. Many manufacturers, like MTU diesel, publish allowable elongation specs for angle torqueing used fasteners. It takes a leap of faith to re-angle torque used head bolts on a $125k engine!