Strange ABS Problems or something else?

[ldaggerl]

This is interesting as I have similar, if not the same issue with rear brakes locking up. When I first had the problem I did have the ABS light on, I ended up disconnecting the entire ABS module under the hood and no more ABS light and still the issue persisted. I then replace the front calipers, rotors and pads and upgraded to the larger calipers. It had some affect on the problem but didn't resolve it completely, it did seem to make it better and if after I start the truck, let it run for a while, that if I aggressively press the brake pedal a few times it seems to make the issue not occur. I think its related to the master cylinder or booster that is the problem, I have bubbling rust on the booster and I've seem the master cylinder spray bubbles out from the section between reservoir and the port. So they have issues and I have the parts to swap to hydroboost I just haven't had a dedicated weekend to do it.

 

[dmg92001]

By the way, Welcome to the GMT400 forum. Since you are fairly new here, you may have yet to
locate the download thread for the GM Service Manuals for your rig. If you don't already have these
on hand for personal reference use, then follow this link & give yourself an unfair advantage when
it comes to keeping your rig on the road: ('88+ FSM links) I just looked, you are in luck, for the '98
manuals are listed in the opening reply.

Thank you for all this information, I will definitely read up on the service manual for this truck.

"Copper paste"? Sounds like copper-based anti-seize to me, and that's ENTIRELY wrong for the application. The copper powder is essentially an abrasive on moving parts.

You need to clean that crap off, and replace it with a proper brake lube.

I applied sil-glyde brake grease when I did mine, so should I leave that then?

Idle changes, with brake use. Check all the vacuum tubes, hoses. There is a check valve.

I smoke tested the whole system, the only vacuum leak in my engine seems to be from the booster. The check valve was good, I smoked into the booster and it came into the cab when depressing the brakes (only very minorly)
I do plan to replace the brake booster eventually. I just haven't fully researched the process of how to disconnect the master and not have to bleed it again.

A method to confirm warped drums, is fine an area to get some speed then apply the park brake only slowly, be prepared to release, and see what reaction you have from drum , rear braking only. Do you experience any cyclic vibration , as it slows often you can feel the motion as if the wheels are oval instead of round.
A separate clunk at lower speed, sounds more like transmission, transfer case, suspension maybe, than brake related. Without visuals , that's best choice.

Everything kind of rattles, and I've never driven a known good pickup truck for a significant amount of time, so I can't quite discern what is bad, what is normal and what is just the road.

My drive shaft squeaks sometimes at low speeds, could this be a contributor?

The clunking didn't happen when I removed the ABS fuse, and it doesn't happen when the truck is cold, so hopefully that rules out the trans?

I just replaced all the shocks, and ball joints + tie rods are all solid, so I don't think suspension is it.

Thanks again to everyone for your help, I will be replacing the drums Thursday night (assuming they arrive in time)
I will keep you all updated

 

[GoToGuy]

I forgot the Sylglide, that's an excellent choice.

 

[Groosalugg]

"Copper paste"? Sounds like copper-based anti-seize to me, and that's ENTIRELY wrong for the application. The copper powder is essentially an abrasive on moving parts.

You need to clean that crap off, and replace it with a proper brake lube.

Like I said, I could do it wrong myself for free, but somehow not knowing too much, I fixed the blatantly obvious problem so called "professionals" didn't do right in the first place. I mean, after that many trips back, I was still left with a hard pull to the left, which is extremely dangerous for obvious reasons.

Then again, depending on who you ask, others disagree with you on the copper stuff. I personally don't care anymore if it's right or not. I had enough frustration with that whole ordeal all I care about is my brakes work awesome and I learned don't use the shops around here for anything that important because they're all idiots.

 

[GoToGuy]

If all else fails read the directions. Anti seize products are most often for threaded fasteners. Or pinned fasteners subjected to high heat , prevent corrosion. A graphite based antisieze is used in high heat Turbines.
Antiseize is not a grease type lubricant.

 

[dmg92001]

Ok, so I put on the *new* new passenger side drum and the clunking/skidding problem appears to be gone. I drove it for about 15 minutes and everything was smoother, both braking and driving.
I did not check if the pulling was still happening - I will update after I've done some more highway driving .
The drum that warped was Raybestos (if anyone cares) and it was about 1-2mm out of round when warm.
About a 1/2 cup of dust from the shoes fell out when I took the drum off, which seems like a lot considering its got maybe 500 miles on it.

My theory is that the ABS wheel signal codes were old, and the C0265 EBCM Relay Circuit code was from the battery cables being loose.

So far no new codes other than O2 sensors - which should go away now that I've sealed the hole before the cats.

Fingers crossed this was the solution, kind of annoying if it was such a simple problem but at the same time it'll be nice if it doesn't get more expensive to fix.

 

[dmg92001]

Okay, so after a bit more driving I still have no codes, no abs and no check engine light, still braking smoothly (maybe a little pedal pulsation but its barely noticeable).
I guess that drum was the whole problem?
Pulling when braking is significantly reduced, but this thing really likes to pull the wheel hard when there are ruts on the road, but I guess that's just how it is?
Replacing the booster soon and then I'll be happy with the brake system.

Thanks again to everyone for your help!
I will update if something changes.

 

[dmg92001]

Alright, well it started happening again but its not quite as bad.
I was driving around, stopping at a stop sign, and then suddenly the issue had started again.

I measured the temperatures at all the brakes and rotors after driving for a bit:
The rotors were about equal at 110F,
the driver side drum was 120F and the passenger side drum (the one which I just replaced because it was warped) was 160F
The rear brakehose, and cylinders are all new, but maybe one of them is causing it to stick (though I don't hear or feel anything)

I have one more new drum I could put on, but if something is causing them to warp then I don't want to put it on yet.
Seems unlikely that two new drums would warp on the same side by chance.

After it started, I thought maybe it was just slipping on the brake dust left over from before I changed the drum, opened it up and blew it all out.
And then bled both sides just as a last ditch effort, and noticed that the bleeder brake fluid stream from the side that keeps warping is a little less strong than the other.
But I could just be imagining it. It would really suck if I have to change the cylinder again because the leaf spring is so close to the backing plate I have to take it off just to get the cylinder off.

 

[Road Trip]

Alright, well it started happening again but its not quite as bad.
I was driving around, stopping at a stop sign, and then suddenly the issue had started again.

I measured the temperatures at all the brakes and rotors after driving for a bit:
The rotors were about equal at 110F,
the driver side drum was 120F and the passenger side drum (the one which I just replaced because it was warped) was 160F
The rear brakehose, and cylinders are all new, but maybe one of them is causing it to stick (though I don't hear or feel anything)

I have one more new drum I could put on, but if something is causing them to warp then I don't want to put it on yet.
Seems unlikely that two new drums would warp on the same side by chance.

After it started, I thought maybe it was just slipping on the brake dust left over from before I changed the drum, opened it up and blew it all out.
And then bled both sides just as a last ditch effort, and noticed that the bleeder brake fluid stream from the side that keeps warping is a little less strong than the other.
But I could just be imagining it. It would really suck if I have to change the cylinder again because the leaf spring is so close to the backing plate I have to take it off just to get the cylinder off.

Hello dmg92001,

Getting your drum brakes back to Day 1 'just popped off the assembly line goodness' can still be
done in 2024 -- but you are going to have to work a bit harder for this than we used to, back in
the day of plentiful, high quality (ie: meets factory runout specifications when you pick them up
off of the parts counter) brake drums.

Here's a couple of areas you could explore:

1) Your first new drum was way out spec. This was proven by your 'new new' drum acting
much better right from the get go. Seems that these days all the drums are made offshore and
then shipped over here, and finally distributed to warehouses or local parts stores. And as long
as the drums are shipped with the proper orientation respected (it's marked on the box) ...then
the drums will be close to circular when you install them.

On the other hand, IF the drums were shipped on their side, they will actually deform during shipping
just a few thousandths of an inch. Now they are slightly oval shaped. And when you adjust the new
shoes for a light drag, and you end up hearing 'Swish quiet Swish quiet' ? You can be pretty sure that
there will be some pulsation in the brake pedal afterwards. Whether or not if it's bad enough to rectifiy
depends upon the driver's preferences. And don't be surprised if the pedal pulsation worsens when the
brakes heat up to normal operational temps.

On the other hand, if you set your new shoes to a whisper drag on your new drums, and all you hear is
'Swissssssssssssssssh' when you turn the drum by hand, then you have much better odds of a equally
smooth brake pedal. (!) BTW, I base this on years of chasing after a properly smooth brake pedal, for
myself & others.

****

So the above explains why I am not surprised that 2 different new drums gave you 2 different levels of
smooth braking.

So what to do at this point? If it was me, now that you have run that drum through a few heat cycles,
I would take it to a brake machine shop that specializes in turning drums, and have them turn the drum
just enough to go from the oval shape back to a perfect circle. We have done this before, and when
you turn a new (green) drum this may or may not correct all the brake pedal nonsense.

But when we take new brake drums, put them on the vehicle, run them through a dozen / score of
heat cycles, and the pulsation shows up? NOW you take these 'seasoned' drums to the drum brake
machinist, they machine them back to a perfect circle, and afterwards you have something to work with
where you have a good chance that they will stay nice & pulsation-free for a long service life.

Q: Is it fair that we have to resort to this level of seasoning / final truing of brand new parts in order to
get OEM quality braking?

A: NO. But this is the workaround that I've been using over the years to get rid of pulsating brake pedals.
(Evidently I don't like pulsing pedals to the point where I'll do whatever it takes to get rid of it. :0)

Note: All of the above would explain why I was so happy to discover that the original drums on my truck
were still stock internal diameter. (never been turned) And that I found a brake specialty business that
was willing to just turn them enough to give me fresh friction surfaces. (Cost: $20/drum)

The good news is that A) they had never pulsated before the renewal, and B) they continued to not pulsate
after I redid the rear brakes. To this day. FWIW, here's a link to where I shared a few photos of the before/after
of my OEM drums: (Chore Truck rear drums refresh Note: See also reply #84 for the rest of the brake job story.)

2) As for your comment concerning different levels of hydraulic fluid activity at different brake positions? Instead of
getting into the weeds regarding aged flexible rubber brake lines, if they are of unknown vintage, go ahead and
replace them. They are both affordable, and they can clear up mysterious brake system symptoms by doing so.

And give the associated steel lines a careful visual inspection, and if there is any denting/creasing/flattening of the steel
line due to some previous undocumented incident, replace any hydraulic brake line that fails a close visual inspection.

****

That's all I got, so I'll stop here. The above is just brake troubleshooting food for thought.
No guarantees that what I discussed above will fix what you're experiencing, but it's what comes to
mind if we were neighbors and you just shared your story w/me.

Best of luck with this. And let us know what you discover down the road.

Safe travels --

 

[dmg92001]

And when you adjust the new shoes for a light drag, and you end up hearing 'Swish quiet Swish quiet' ? You can be pretty sure that
there will be some pulsation in the brake pedal afterwards.

I did notice this, and while I thought it was odd I didn't question it because I've never dealt with drum brakes before.

But when we take new brake drums, put them on the vehicle, run them through a dozen / score of
heat cycles, and the pulsation shows up? NOW you take these 'seasoned' drums to the drum brake
machinist, they machine them back to a perfect circle, and afterwards you have something where you have
a good chance that they will stay nice & smooth for a long service life.

This makes a lot of sense now, I guess I figured they would have been tempered at the factory... but it seems expecting quality parts these days is foolish.

Now to find someone around me who offers drum turning services...
I guess I will throw on the last new drum, and if it happens not to warp after driving on it a bit, I will leave it at that, and if it does
then I'll take the one I just took off have it turned, swap it out and return the other 2 that warped as defective (because frankly, they are)

I am very grateful for your thoughtful reply, I will continue to update.