bunnspecial
Site Champ
- Joined
- May 20, 2021
- Posts
- 295
BunnSpecial's stupid moment of the day...or month.
So, a couple of things. After the rear axle refresh, I'd noticed two sounds when driving that were driving me bonkers-especially since I'd expected the suspension work to get rid of noise! Both were coming from the left rear wheel area, and I was concerned it was something not back together right.
The first was a metallic clinking sound. It honestly had me completely stumped. I couldn't reproduce it with the car stationary, and it didn't seem speed-dependent aside, again, from only happening with the car moving.
I actually had my(mechanic's) stethoscope out yesterday hunting for it, and I have to say that's a tool that will REALLY get you some funny looks.
I'd thought MAYBE it was something in the exhaust-either the pipe just rattling around or perhaps part of the resonator in one of the mufflers letting go. That didn't make a ton of sense, but the pitch of the sound was leading me in that direction. I couldn't see much, but figured I'd put the new rear hanger on I'd bought years ago but had never installed. The rear muffler hanger is a bit of a puzzle, but I got it out and realized that I was missing one of the two straps that surrounds the exhaust pipes in the new kit. Still, though, what was there fit the pipe better, so I changed out some insulating washers and parts of the bracket.
Second, I decided to pull the brake drum and just see if something strange was going on there. That was something I hadn't checked yet. This is the RH side brake(since I'm too lazy now to hunt down the LH side-it's the same although the parts are oriented a bit differently) but shows the basic set-up
I'll point out something key in this. As brake shoes wear in drum brakes, they "resting" position of the shoes needs to be adjusted to minimize the distance the shoes need to travel to engage the drum. Brakes that are out of adjustment will still work, but may need a "pump" on the pedal to bring the shoes into contact.
Modern drum brake designs on American cars-meaning basically anything American made in like the last 70+ years-have automatic adjusters that do this every time the car is put in reverse. These have their pluses and minuses, but mostly pluses.
The British are often ones to eschew new technology in things like this, so British cars retained manual adjustment on their drum brakes for quite a long time. The adjuster can be seen at the top at about 1:00. Basically the adjuster unit has a screw that has a 1/4" square drive on one end, and a "pyramid" on the other end. There are two plungers in this assembly also-one end is slotted to engage the shoe, and the other is sloped and rides against the pyramid of the adjuster screw. The brakes are adjusted by turning the adjuster screw, which as it is tightened forces the plungers and consequently the shoes further out. The pyramid gives four distinct "clicks"(that can be felt, not heard) or "flats" as the screw is turned one full rotation. The adjustment procedure is to turn the adjuster until the drum can't be turned by hand and then back off 1-2 flats. This is a fun adventure since after doing brake work, it often takes a few drives for the shoes to "seat" correctly, and they will need to be adjusted at least once. Also, adjustment is needed frequently on new shoes unless they're also paired with anew drum(or arced to fit the old drum, which no one does anymore) as they wear to match the radius of the drum.
In any case, I'd noticed my "flats" getting floppy/indistinct and sometimes my brakes going out of adjustment, so I opted to just drop new adjuster units in. That's all good and well except a new one behaves a bit differently than an old, well worn one. For one thing, on old ones, there's usually enough grease and corrosion that the plungers don't readily come out. On new ones, they will fall out with no provocation.
In installing this one, I dropped one of the plungers and couldn't find it. I ended up putting it back together with an old one.
When I pulled the durm today, there sat the shiny new plunger in the bottom of the drum. As I found, it's easy for the plungers to fall behind the shoes, and I suppose this is where it was.
The second noise still has me scratching my head. Basically it's a "slapping" sound not unlike a flat tire. I noticed its frequency was speed-dependent, and also I seemed to only notice it slowing down.
I asked on the MG forum, and the first answer said "Just a guess, but took at the emergency brake lever." By "lever" they meant the lever that sticks out of the brake backing plate. The e-brake cable pulls on this to apply the brake.
Basically, the suggestion was to see if the sound got better or went away if I pulled gently on the brake lever(the one in the cockpit). Sure enough, it did.
That's where I stop, though. I can pretty clearly see that the clearance between the lever and the wheel is tight. There's a scrape mark on the inside of the rim to show for this.
There's a couple of things going on here. One is that I lost the original clevis pin attaching the brake cable somewhere in all of this work, so I grabbed a generic trim-to-length one at the HW store. I may not have trimmed it enough, although I tried to do it in-situ with a die grinder today.
Otherwise, I'm just lost. While I was back there with the grinder, I chamfered several other areas, but still didn't fix the problem. I'll probably try painting it tomorrow to see if I can figure out where it's rubbing, but that's it. I'm still wondering if the issue is the clevis pin, but I'm not 100% positive.
As a side note, too, I bought my first compressor a few months ago, and it's one of the best things I've done for my garage. Air tools are great-they are so much less expensive and lighter than their electric equivalent, and often are more powerful than all but the biggest commercial grade ones. The die grinder I'm using was a $10 Harbor Freight special. Actual good quality ones are $50-100, but still a cheap consumer corded or cordless die grinder is that same price, and pro grade units are 2-3x that. Of course the downside(or maybe upside since my neighbors are beyond obnoxious) is that a pneumatic die grinder sounds vaguely like a dental drill.
Unfortunately, I WAY underspecced my compressor, so a better compressor is on my shopping list. I'm weighing two options. The one at the top of the list was a nice traditional cast iron 27 gallon unit from HF, but for a bit more Home Depot has a 30 gallon unit that looks somewhat better. Both are more traditional belt driven, oil lubed compressors. The cast iron tank of the HF should hopefully mean lower air temps, which is a big deal since I've found that water is a big problem in my small unit. At the same time, the HD unit is really appealing because it has a higher CFM rating(6.2 vs. 5.8 at 90psi). The HD Husky I'm comparing also runs at a 175 psi tank pressure vs. 150psi for the HF unit. Tank pressure goes both ways, since higher pressures give you more air capacity in a given tank size, but also raise air temperatures(so again water is an issue since the temperature drop will be more dramatic once the pressure is regulated down). The HD unit, though, above all is a lot quieter-77db(which is almost eerily quiet for a compressor) vs. 85db. I thin the Husky unit is winning.
So, a couple of things. After the rear axle refresh, I'd noticed two sounds when driving that were driving me bonkers-especially since I'd expected the suspension work to get rid of noise! Both were coming from the left rear wheel area, and I was concerned it was something not back together right.
The first was a metallic clinking sound. It honestly had me completely stumped. I couldn't reproduce it with the car stationary, and it didn't seem speed-dependent aside, again, from only happening with the car moving.
I actually had my(mechanic's) stethoscope out yesterday hunting for it, and I have to say that's a tool that will REALLY get you some funny looks.
I'd thought MAYBE it was something in the exhaust-either the pipe just rattling around or perhaps part of the resonator in one of the mufflers letting go. That didn't make a ton of sense, but the pitch of the sound was leading me in that direction. I couldn't see much, but figured I'd put the new rear hanger on I'd bought years ago but had never installed. The rear muffler hanger is a bit of a puzzle, but I got it out and realized that I was missing one of the two straps that surrounds the exhaust pipes in the new kit. Still, though, what was there fit the pipe better, so I changed out some insulating washers and parts of the bracket.
Second, I decided to pull the brake drum and just see if something strange was going on there. That was something I hadn't checked yet. This is the RH side brake(since I'm too lazy now to hunt down the LH side-it's the same although the parts are oriented a bit differently) but shows the basic set-up
I'll point out something key in this. As brake shoes wear in drum brakes, they "resting" position of the shoes needs to be adjusted to minimize the distance the shoes need to travel to engage the drum. Brakes that are out of adjustment will still work, but may need a "pump" on the pedal to bring the shoes into contact.
Modern drum brake designs on American cars-meaning basically anything American made in like the last 70+ years-have automatic adjusters that do this every time the car is put in reverse. These have their pluses and minuses, but mostly pluses.
The British are often ones to eschew new technology in things like this, so British cars retained manual adjustment on their drum brakes for quite a long time. The adjuster can be seen at the top at about 1:00. Basically the adjuster unit has a screw that has a 1/4" square drive on one end, and a "pyramid" on the other end. There are two plungers in this assembly also-one end is slotted to engage the shoe, and the other is sloped and rides against the pyramid of the adjuster screw. The brakes are adjusted by turning the adjuster screw, which as it is tightened forces the plungers and consequently the shoes further out. The pyramid gives four distinct "clicks"(that can be felt, not heard) or "flats" as the screw is turned one full rotation. The adjustment procedure is to turn the adjuster until the drum can't be turned by hand and then back off 1-2 flats. This is a fun adventure since after doing brake work, it often takes a few drives for the shoes to "seat" correctly, and they will need to be adjusted at least once. Also, adjustment is needed frequently on new shoes unless they're also paired with anew drum(or arced to fit the old drum, which no one does anymore) as they wear to match the radius of the drum.
In any case, I'd noticed my "flats" getting floppy/indistinct and sometimes my brakes going out of adjustment, so I opted to just drop new adjuster units in. That's all good and well except a new one behaves a bit differently than an old, well worn one. For one thing, on old ones, there's usually enough grease and corrosion that the plungers don't readily come out. On new ones, they will fall out with no provocation.
In installing this one, I dropped one of the plungers and couldn't find it. I ended up putting it back together with an old one.
When I pulled the durm today, there sat the shiny new plunger in the bottom of the drum. As I found, it's easy for the plungers to fall behind the shoes, and I suppose this is where it was.
The second noise still has me scratching my head. Basically it's a "slapping" sound not unlike a flat tire. I noticed its frequency was speed-dependent, and also I seemed to only notice it slowing down.
I asked on the MG forum, and the first answer said "Just a guess, but took at the emergency brake lever." By "lever" they meant the lever that sticks out of the brake backing plate. The e-brake cable pulls on this to apply the brake.
Basically, the suggestion was to see if the sound got better or went away if I pulled gently on the brake lever(the one in the cockpit). Sure enough, it did.
That's where I stop, though. I can pretty clearly see that the clearance between the lever and the wheel is tight. There's a scrape mark on the inside of the rim to show for this.
There's a couple of things going on here. One is that I lost the original clevis pin attaching the brake cable somewhere in all of this work, so I grabbed a generic trim-to-length one at the HW store. I may not have trimmed it enough, although I tried to do it in-situ with a die grinder today.
Otherwise, I'm just lost. While I was back there with the grinder, I chamfered several other areas, but still didn't fix the problem. I'll probably try painting it tomorrow to see if I can figure out where it's rubbing, but that's it. I'm still wondering if the issue is the clevis pin, but I'm not 100% positive.
As a side note, too, I bought my first compressor a few months ago, and it's one of the best things I've done for my garage. Air tools are great-they are so much less expensive and lighter than their electric equivalent, and often are more powerful than all but the biggest commercial grade ones. The die grinder I'm using was a $10 Harbor Freight special. Actual good quality ones are $50-100, but still a cheap consumer corded or cordless die grinder is that same price, and pro grade units are 2-3x that. Of course the downside(or maybe upside since my neighbors are beyond obnoxious) is that a pneumatic die grinder sounds vaguely like a dental drill.
Unfortunately, I WAY underspecced my compressor, so a better compressor is on my shopping list. I'm weighing two options. The one at the top of the list was a nice traditional cast iron 27 gallon unit from HF, but for a bit more Home Depot has a 30 gallon unit that looks somewhat better. Both are more traditional belt driven, oil lubed compressors. The cast iron tank of the HF should hopefully mean lower air temps, which is a big deal since I've found that water is a big problem in my small unit. At the same time, the HD unit is really appealing because it has a higher CFM rating(6.2 vs. 5.8 at 90psi). The HD Husky I'm comparing also runs at a 175 psi tank pressure vs. 150psi for the HF unit. Tank pressure goes both ways, since higher pressures give you more air capacity in a given tank size, but also raise air temperatures(so again water is an issue since the temperature drop will be more dramatic once the pressure is regulated down). The HD unit, though, above all is a lot quieter-77db(which is almost eerily quiet for a compressor) vs. 85db. I thin the Husky unit is winning.
