Smoke from left rear wheel well?

[lanceh007]

Hey everyone, I have something I hope you can help me with.
Over the past month, whenever I drive my car ('81 corvette) for about 20 minutes or longer, smoke starts billowing out of the left rear wheel well. It's very white, thick smoke and it looks like it's coming from the brake/caliper area. The caliper looks fine (as far as I can tell), it's not leaking any fluid and there is no residue anywhere. I've tried replacing the rotor and brake pads. I've also completely backed off the parking brake shoes (thinking that they might be sticking), so now I'm pretty sure that they can't even come into contact with the rotor hub (even with the parking brake fully engaged). So I don't think it's the parking brake causing this.


Today I took it down to the mechanic's shop and we used one of the laser temp gauges and found out that the left rear rotor was 115ºF while the right one was only 85ºF. So it seems like it's got to have something to do with the brakes, especially if that rotor is so much hotter.


Today I also jacked up the car and took off the rear wheels. I started it up and let it run in drive, allowing the rotor assembly to spin. I let it run for about 15 minutes that way, yet there was no smoke whatsoever, and the rotors felt the same temp. The brake caliper also looked like it completely released from the rotor (after pushing the brake pedal and releasing it), so I don't think the caliper is causing the pads to stick to the rotor...but who knows what it does with the wheels on? I just can't figure out what's going on...and I don't have any money left to take it to the mechanic (it's great being a poor college student!)


I was just hoping some of you might have some tips or ideas on what's going on and how I could fix this? Thanks!

 

[Stingray6974]

Hi Lance,

One possibility is a brake hose coming apart inside not allowing the brakes to fully release after applying. Have you checked for excessive play in the wheel bearings?

Mike

 

[bradfordsvettes]

Hi Lance,

One possibility is a brake hose coming apart inside not allowing the brakes to fully release after applying. Have you checked for excessive play in the wheel bearings?

Mike

Mike has a good point brake hoses fail internally and won't act up till they have been applied a few times and don't release fairly common faiure also check out the bearings but suspect the hose probably a good idea to replace all of them Steve

 

[lanceh007]

Thanks for the tips! Those sound like very good possibilities. So how could I check the wheel bearing to see if it's the problem?

Also, how hard is it to replace all of the brake lines? Do the lines cost very much and are there any special tools I would need in replacing them?

 

[Ripp 73]

I would expect to spend about $50 for the rubber brake lines. I know thats two weeks worth of grocerys for us college kids, but the brakes are one thing on the car that have to work. Doesn't matter how well the car runs, it has got to stop. How does your brake pedal feel when you press on it. Does it go all the way to the floor or does it have a quick toe touch feel?

 

[Stingray6974]

Lance,

With the wheel off the ground grab it at 9 & 3 o'clock and twist it back and forth. You should feel a little play. To check for stub axle wear push in hard at the 12 o'clock position.



Mike

 

[bradfordsvettes]

lines are about 20 dollars each front and rear the wheel bearings can be given a cave man check by rocking them when jacked up at 12+6 o clock and and 9 and 3 o clock should be very little movment in either position Steve

 

[74bigblock]

Ehhh.... just tape it. It will be fine.

 

[lanceh007]

Say, what kind of tape is it that you use there? I need to get me some of that!

That's not a bad price at all for the new brake lines; I think I can manage that.

Now how about installing the new lines? Do they run through the frame? How hard would it be to run new lines and get them installed?

I'm going to check the bearing tomorrow through your advice. I think I'll compare it to the other wheel and see if it has any more play.

I really appreciate your replies! I felt like I had no where to turn there for a while, you are all life savers!

 

[74bigblock]

, you are all life savers!

... Except me... I'm the comic relief.

 

[lanceh007]

How does your brake pedal feel when you press on it. Does it go all the way to the floor or does it have a quick toe touch feel?

That's been one of my problems lately. I've never really had a good brake pedal feel. I've always suspected the brake booster (as I've gone through quite a few master cylinders). I had never thought it to be the lines; so after all these problems, the lines may truly be the culprit. Also, I had a new caliper installed lately (The right rear) because the old one was leaky. The mechanic spent over two hours bleeding the system and charge me $190 just to change the caliper and bleed it (that's not including the new caliper!) No one has ever had much luck bleeding the brakes either, so I'm starting to think that the brake lines could truly be causing all this.

 

[Evolution1980]

I'm gonna put my money on the wheel bearing. Why? Because my driver-rear exhibited the exact same thing. Had to have it replaced, but I don't remember the cost. I don't think it's exactly a cheap fix though because "I think" the bearing is pressed into the hub and not just a bolt-on.
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Your braking problem is likely an entirely different issue and likely going to a moderate-to-expensive fix if you want to really fix it. By "really fix it", I mean that it ALL gets replaced. The OEM calipers on the later C3's were garbage. There's a reason GM didn't use them for very long. They are lip-seal calipers and because of their design, it's easy to get the the pistons cocked at an angle inside the bore, and once that happens, you're screwed. They'll leak forever and you can't really fix it without a rebuild. But even the rebuilds are only so-so quality in my opinion.

As to your soft pedal, that could be any number of things. Unless you can actually see a line bulging, it's going to be process of elimination. You might simply have a bad proportioning valve, which was one of my problems causing a soft pedal. I think they are about $75 from MidAmerica (a CAC sponsor!). The problem with replacing the proportioning valve is that if your brake lines are in questionable condition, you could easily twist/tweak/crease/break a line trying to remove the line fittings from the valve.

The worst case/best case scenario is that you have to replace the entire system piece by piece or all at once, such as I did. Just after CruiseFest 2004, I purchased the entire patented O-ring caliper brake kit from VB&P (another CAC sponsor!). Set me back in the $900 range, minus the $160 I got back for my caliper cores. Add in the proportioning valve at $75 and I have EVERYTHING brand new. Master cylinder, proportioning valve, stainless steel braided lines, calipers, and pads.
Worst case...because it's the most expensive option.
Best case...because you have the best and all new components that will likely last longer than the car.

And since I was redoing the entire brake system, I threw in a line-lock setup just for grins...I developed a little bit of an addiction at CruiseFest '04, so figured, Ahh, what's another $100 at this point for a little fun factor???"
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...be careful driving on that bad wheel bearing. It's gets too too bad, you could drive your wheel right off the car! In case (Stingray6974) Mike's suggestion was a little unclear, allow me to elaborate. Put the rear of the car up. Put your hands at 12 and 6 o'clock. Push in at 12 and pull out at 6. Basically, wiggle the wheel back and forth, top to bottom as if you were trying to break it free of the spindle. If there's more than 1/8" play, you've got a bad bearing.
Another test is, with the rear end still up in the air, put the car in gear and let it idle. Put your ear near the center of the rim and just listen. With a bad bearing, you'll hear a faint sst-sst-sst-sst-sst sound. If not, have someone slowly take the speed up to about 40mph and hold it there. See if you hear anything then. If you're not sure, go to the other side and listen there. Then go back to the suspected side and listen again.

...this is all personal experience with my own car(s)...

post-edit.... the passenger-rear caliper is usually the hardest and longest to bleed because it's the furthest from the master cylinder.

 

[WayneLBurnham]

Man, Evo80 has it dead on - worry about the BEARING!

Someone else mentioned the same thing earlier too...

As someone who had the driver rear outter axle stub melt off and depart with all that silly wheel type stuff at 80 two feet off a magnet wall I am PARANOID of that ever happening again. Amazingly, these silly things can DRIVE without a wheel! More amazingly is I didn't get killed or much, much worse, cause any significant damage to The Car I Serve! other than some paint and the wheel parts. (I still paid a multi-thousand amount having it all repaired professional out of fear I had damaged my exhorbitantly expensive Tom's Differential's center section - but that was my own stupidity.)

From that day forward I get the rear bearings repacked every 10K and inspected every 3. I am constantly touching all four wheels after a good run to see if any are warm. One of my less-than-blue-sky upgrades planned is a bearing temp system to warn me of this, whether just regular temp senders or a set of IR temp lasers is still up in the air. Without the mobile cooling of diff fluid like on a dead axle primitive-mobile, those bearings (my inner seized) only have that relatively small amount of high temp grease to stop them from seizing and melting the axle stub like butter on a lathe.

The brakes I REALLY ditto on. In the 85-90K I've put on this thing I have had in in for brakes at least 10 times in two shops, replaced 6 rotors, 8 calipers, 7 master cylinders, the prop valve and braided hoses and near end metal lines. Only when I rebuilt my newish Oring calipers all at once and did the prop valve did I finally get decent brakes. Do it all at once and switch to the VBP Oring system. BTW, the braided SS rear lines made a real difference. They are higher but increase braking power and durability over the rubber ones. as they don't flex.