85GT pulls left on braking (Page 1/1)
hobbywrench MAY 02, 12:50 PM
Chronic problem unsolved...On braking car pulls left. Car drives straight otherwise. The following has been done....rear right caliper just replaced with an AC Delco reman because that caliper e brake function had stopped. (car raised, e brake lever pulled up, driver side wheel locked, passenger side spun). Reman works. Still pulling. Couple years back replaced all rubber lines and disassemble/cleaned all calipers including new (orange) pin slider o-rings-no improvement. Also obtained all 4 brake disc temperatures after 3 separate 60 mph stops. Results uniform 225 F all four . All A arm bushings replaced couple years back. No contaminants on pads /discs AFAIK. Car stops ok. String alignment only. Have read all 6 pages of "brake" subject on search here. Can't recall If master cylinder ever replaced. Original owner. Use vacuum bleed. Car pulls lightly on light brake. Strongly on strong brake.

Any ideas? Thanks
olejoedad MAY 02, 02:22 PM
Recheck upper control arm bushings and long tube that the UCA mounts to.
theogre MAY 02, 03:50 PM
Check all suspension bushings including the rear and cradle.

Don't just look. Use small mirrors, bore scope, etc, so you see as much as you can on outside shells. Use a pry bar to look for loose/broke hardware etc.

You many need careful use of jacking or pry bar to unload/reload different parts. Warning: If done bad then you can die as car falls on you. Is not a job to do on dirt or cheap jack stands or anything that can lets the car move when prying anything or jacking a wheel.
Especially Front LCA is Never unloaded even jacked up because of spring loading. But careful use of jacking/prying can allow you to see when inner bushing is bad and allowing to steer under braking.
Other CA bushings can lie when jacked up so careful use by jacking/prying a wheel/bushing a bit can unload them too.
This may give you a better view to look at bushings outside shells. I've see many look ok to start but hide rust on the back that's hard to see.

If suspension has polly then polly can wear out and cause many problems and often never make noise.
Cradle polly doesn't wear out because doesn't move like others.

------------------
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(Jurassic Park)

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hobbywrench MAY 03, 09:51 AM
UCA tube...ID measure ? With telescoping gauge? If more than ? .005" ?wear....what to do, ream possible? Oversize shaft?


Rear cradle steer via worn bushings? Do not feel shift there on throttle?

So far verdict is not brake associated, but much more difficult fixes. Why no discussion on this problem here?

After A arm bushing replacement there was big improvement in chassis, but did not change out cradle bushings. All stock rubber bushings and inner bushing tubes worn and "belled. Mileage 134K.

[This message has been edited by hobbywrench (edited 05-03-2019).]

olejoedad MAY 03, 10:35 AM
I have seen the UCA mounting tube break free of the crossmember, allowing it to shift location during cornering and braking.
It's difficult to detect with the suspension hanging, support the LCA on a jackstand when checking.
hobbywrench MAY 03, 06:42 PM
Thanks, I will try to look at the tube. Went back thru records and the car has original brake master. A long run . Did notice a couple small rubber bits in reservoir after bleed. Maybe I should get a pro alignment and replace the master,
olejoedad MAY 03, 09:09 PM
Very doubtful a new master cylinder will fix your issue.
Are you sure the front brake circuit is properly bled?