1968 Brakes pull hard to the right - front power discs, rear drums

[admin]

I'm finally getting my HCS on the road again after rebuilding the engine and transmission. And now the brakes pull hard to the right. If I brake slowly it definitely pulls right, but I can easily control it with the steering wheel. But if I slam on the brakes I have to really hang on tight to avoid being put into the curb to my right.

I have factory front discs (single caliper) and rear drums. I rebuilt both front and rear in Oct 2020; New front calipers & pads, new rubber lines front and back, new distribution block & proportioning valve, new master cylinder, new rear wheel cylinders, new rear drums and replaced all rear drum hardware. And finally a rebuilt power booster (Midland style). At that time the brakes worked fine. They weren't amazing and I felt like I just needed to bleed them better.

Since then I haven't had a chance to drive it much since I've been working on other things, including bodywork, paint, and rebuilding the engine & C4 transmission.

Since it pulls to the right, my thought is one of the right brakes isn't working properly. And I assume the front right disc since the fronts do the majority of braking.

My problem solving steps so far:

1. fluid levels in master cylinder are good. No visible leaks at master cylinder, proportioning valve or along the hard lines up front.
2. I jacked up the front and end had a helper push the brakes while I hand spun each tire. Both stop OK and very little pad drag. I can manually overpower the brakes if I really try turning the tire, but only when the car is shut off (power discs). When it's running I can't.
3. I had the car media blasted a while ago and there was still media in the wheels and brake areas, so I removed both calipers and pads to clean everything off really well. I checked the piston travel when the calipers where off (piece of wood in between the pads) and both seem to travel smoothly. They don't travel very far, but I don't think they're supposed to. Reinstalled the fronts and test drove. Still pulls hard to the right.
4. I pulled the rear tires and drums. Both drums were adjusted correctly (minimal dragging when rotating the tires by hand and I had to back the adjuster star off just a bit to get the drums off). The left side was dry as a bone with typical brake dust. The right side was a little oily. Both wheel cylinders appear dry with no visible leaks. So I'm wondering if the axle seal on the right side is leaking a little. So I cleaned the right side off with liberal brake cleaner, but ran out of time to put the wheels back on and test drive.

I've read pulling can also be due to either very poor wheel alignment or very worn front suspension pieces. To be honest, either of those is a possibility. Rebuilding the suspension was next on my list, but I had hoped to drive it a little bit before diving into that job.

Any other brake tests I should be doing?

 

[Ruppstang]

Did you replace the brake hoses to the calipers? They deteriorate from the inside out. May be there is reduced flow in one of them. Strange problem.

 

[admin]

Yes, I replaced all the rubber hoses.

 

[rvrtrash]

First, if the wheel cylinder looks dry, and you aren't loosing fluid, it does sound like you have an axle seal that might be leaking. Next, if everything in the front is as you say, I would check for play in the strut rod. It could also be a tie rod end or wheel bearings being loose, but usually you'll feel wobble while driving as well.

Steve

 

[Ruppstang]

I would try 2 or 3 emergency stops from 25 -30 mph. Then look at the skid patterns. Doing this may reset them. I would find a big parking lot and be ready to hang on to the wheel.

 

[admin]

I cleaned up the oil on the right rear drum/shoes and did a bit of test driving last night. Still the same issue (I didn't really expect cleaning off the little bit of oil to actually fix anything)

I was on the same page as you Marty and did some skid tests, but it was dark and I was alone, so I couldn't be very scientific about it. I will go out again on Fri when I have free time during the day and can see skid marks.

But one thing I'm confused about is that I can consistently get the left rear tire to lock up with an emergency stop at 20-25 MPH. If the left rear is the first wheel to engage the brakes, then the car pulling hard right makes no sense to me.

 

[admin]

I would check for play in the strut rod. It could also be a tie rod end or wheel bearings being loose, but usually you'll feel wobble while driving as well.

Thanks. Steve. I just went out and checked and the bushings are very hard and I can wiggle both strut rods by hand, so that's not good. I already have new strut rod bushings in the garage, so replacing them is my next step. Should be a quick 20 minute task (of course I just jinxed myself by saying that) I think I'll head out to the garage now and spray all the hardware down with penetrating fluid.