Tales of the Garage Mechanic

If you’re wondering why I haven’t been posting very much, it is because I’ve been fixing my vehicles. By that I mean all three of them.  I have a S-10, Firebird, and Camaro.  The S-10 is my daily driver and my wife drives the Firebird with the kids.  The Camaro mostly sits around because it needs some repairs and paint.  The S-10 has had a problematic clutch over the last few months.  It would squeak like a  door with dry hinges when the pedal was depressed and released.  The pedal also felt gritty and would stick when it got warmed up.  (It’s a hydraulic clutch and squeezing the hydraulic fluid heats it up.)  It also felt like the clutch wasn’t fully disengaging which is problematic as you might imagine.  It finally got so bad that I had to do something about it because it was almost underivable in stop and go traffic.  Luckily, the wife and kids were planning to go out of town for a week.  I figured I’d take advantage of this time to fix the truck and drive the Firebird to work instead.

Before I start talking about the clutch I’ll take a brief aside to explain the parts of the clutch.  The clutch on the S-10 (and most vehicles today) has hydraulic and mechanical sections.  I’ll talk about the mechanical section first.

The clutch assembly bolts onto a heavy metal disk called a flywheel.  Onto the flywheel bolts a piece called the pressure plate (pictured below).  In between the two is the clutch disk.  The pressure plate has a movable section (wide ring in the second picture) that presses on the clutch disk.  The “fingers” you see in the center of the picture below control the location and pressure of the movable part of the pressure plate.  If the fingers are pressed in, the movable section moves up and vice versa.  Since the pressure plate is attached to the flywheel, the clutch plate is squeezed between the two and rotates with them when there is nothing pushing on the “fingers”.  A part called a clutch release bearing moves these fingers by pressing on them when the clutch pedal is pushed.  The clutch release bearing is moved by either the clutch slave cylinder (green arrow in third pic) or a fork connected to the clutch slave cylinder depending on the design.  In the case of my S-10 there is a fork that the clutch slave cylinder pushes on to move the release bearing.

On to the hydraulic section….When the clutch pedal is depressed, a rod connected to a piston in the clutch master cylinder puts pressure on the hydraulic fluid in the system.  Since the fluid doesn’t compress, a piston in the slave cylinder moves which moves a rod. This rod moves the afore mentioned fork.

In case you were wondering, in the middle of the clutch disk is a splined hole that receives the input shaft of the transmission.

As you can see there are quite a few pieces that make up the clutch system of a vehicle.  Most of these parts are also inside a piece called a bell housing (red arrow in third pic) and requires removal of the transmission to access.  Fun fun!

Back to the story…I thought that the problem was a bad clutch release bearing.  I figured it was sticking giving me the issues mentioned above.  So, I tore into it and found that my diagnosis was wrong.  You might not be able to tell, but there are some pieces missing from the “fingers” in this first pic below.  See how they end  with a step down into thinner parts? It shouldn’t be that way.  Take a look at the fingers in the second picture below.  See how they extend in farther and even have a little curl to them?  All of that was gone because my clutch release bearing had been eating away the “fingers”.  I’m not sure why this happened though.  It’s possible the “fingers” were not properly hardened when made.  This was a cheap replacement clutch from AutoZone.  The circular stepped area was where the throwout bearing pressed on the fingers and if it had managed to make it all the way through I would have had no way to release the clutch.

So, I bought a new clutch, put it in, and took a short test drive around the neighborhood.  The clutch engages and disengages much higher now.  I figure the problem was fixed.  The next day, Friday, I took the truck to work and it turns out the squeaking, grabby pedal was still there.  So, I bring it back home and with the help of a friend determine it is the clutch slave cylinder.  Now, I have no idea why a metal piston riding inside of a plastic cylinder can sound like metal on metal squeaking but it does.  I ran by the parts store that night and picked up a replacement.  Luckily, it is on the outside of the bell housing so I don’t have to tear back into it.  I removed the old slave cylinder and put the new one in.  I then bled the system by myself and then went for a test drive.  At first all seemed well but then it seemed that the hydraulic system was getting air in it because the clutch pedal had a lot more play in it and engaged lower than when I started.  It also felt as if it wasn’t completely disengaging requiring more force to get into gear than it should.  I went back home, bled it again, and called it quits for the night.

I got up Saturday and test drove the truck.  It felt like the same thing was happening.  I returned home and removed the slave cylinder yet again.  On the end of the fitting on the hose from the master cylinder there is a flat topped, thick, o-ring.  I thought that perhaps something was wrong with it because it seemed like a little bit of air was seeping in somewhere.  I compared the new o-ring with the old one and the new one was 0.01″ thinner than the old one.  I thought that might be the problem so I swapped it out.  I took it for a test drive and the same thing, the truck is drivable but the pedal isn’t right.  I picked up a hand vacuum pump and bled it using that from the reservoir up top.  That seemed to help it some but the problem remained.  Oh well, I’ll have all week to mess with it.

On Monday I got up and took the Firebird to work (30 miles away) since the truck was having problems.  After work I went out to the car to go home only to discover that it won’t start.  It cranks over fine but won’t fire off.  This had happened the previous Thursday but it started and ran fine after a couple of minutes.  I thought it was weird but it started multiple times after that so I figured all was fine.  I was wrong.  I gave it about 10 minutes to decide to work but no luck.  Still wouldn’t start.  So, I start trying to diagnose it.  I notice that when I try to start the car I don’t hear the fuel pump run to prime the system.  So, I hop out to see if there is any fuel at the rail by depressing the Shrader valve.   Nope, no fuel.  Maybe it’s the fuse?  Check that and swap it with another.  Nope.  Maybe it’s the relay?  I swap that with the one from the AC.  Nope.   I tried waiting and starting again but it still wouldn’t run.  I called a friend who rode to my rescue and was able to take me home.

At this point I figured I was going to have to have it towed home which I wasn’t looking forward to because, as I mentioned before, I’m 30 miles away from home.  I decide that I’ll drive the truck into work the next day to see if the car will be kind and decide to start.  I get to work, hop in the car, and it starts the very first time.  Not wanting to look a gift horse in the mouth I drove the car home immediately.  Once I got home I tried to replicate the problem but had no luck.  I thought it might have been a heat issue so I let it soak in the sun all day long but couldn’t get the issue to reoccur.  Grrr…I can’t fix an issue that isn’t showing up.

FYI this is called an intermittent problem and can frustrate you and your mechanic to no end.  Though it can make them easy money since they charge for a diagnosis only to find nothing is wrong.

I had wanted to work on the Camaro some since the family was out of town.  Well, now since I had an unreliable car at home and the truck at work, I had plenty of time to work on it.  The Camaro had a sticking/dragging front brake caliper so I took both of them off to see which one it was.  I moved both of the caliper pistons by hand with a clamp and determined the driver’s side one was sticking.  I hoped that moving it by hand would free it up but a test drive showed that while it was better it still drug badly meaning I couldn’t drive it.  So, I hoped online to find out how much a rebuild kit for the caliper would be.  As it turns out a rebuild kit was $7 and a remanufactured one was $10.  This struck me as way too cheap but I wasn’t complaining.  I took the firebird up to the parts store and left it running to get a new caliper.

I returned home and replaced the caliper.  Yay, no more sticking.  On my test drive I went out of the neighborhood and took the car up to 50 mph.  I pressed the pedal to accelerate lightly and the car started shaking.  From previous experience, I knew that this meant that I had a cylinder that wasn’t working correctly and that it was probably due to an injector.  So, back home I return to fix yet another problem.  A mechanic’s stethoscope is great for an issue like this.  They’re like a regular stethoscope but instead of having whatever that cold thing is they place on your skin, it has a metal rod.  You can take the rod and place it against a fuel injector to hear it clicking.  I check out the injectors. I have 7 ones that sharply click and one that  has a dull click.  The dull click means that the injector isn’t working and is caused by you hearing the clicks of the injector next to it clicking through the intake manifold.   To double check, I pulled the connector off of the injector and note no change in rpm or idle quality.  Not really wanting to dig into this one I decide to smack the injector on the side a couple of times with the handle of my needle nose plies.  Problem fixed!  Idle quality improves and the engine is running smoother.  So yes, you can fix things by hitting them.  Testing via moderate and large acceleration tests showed all was working fine again.

The next day, Wednesday, I got a ride into work from another friend and retrieved the truck.  When I got home that day the Firebrid was starting fine so I wasn’t able to try to directly figure out what the problem was the easy way.  So, I turned to my factory service manual for the car to see if it could help.   The factory service manuals are great and so much better than the ones from Chilton or Haynes.   The factory service manuals can be picked up cheaply used from Ebay and I highly recommend you pick one up if you work on your vehicle.  The manuals have flow charts to solve problems in the form of “do this or that” and then ask a yes/no question.  Depending on if the answer is yes or no you goto another step or chart.  My manual has a “Car Cranks but Does Not Start” flow chart!  Perfect.  I follow through it and it leads me to another couple of charts.  I finally have an issue where the primped fuel pressure is lower than specified.  This left me with the possibility that it is the fuel pump or pressure regulator.  I followed the steps to check the regulator with a jerry rigged block off and eliminated it as a possibility.  All signs point toward the fuel pump.  I did some other checking but decided it was the fuel pump.

From the regular auto parts stores the fuel pump for the Firebird is a $375 part. Ouch.  From RockAuto.com thought it was much cheaper at $230.  I ordered it from there Friday and it got in yesterday.  The fuel pump is in the tank and on the Firebird requires removal of the rear end of the car to drop the tank.  I replaced the fuel pump and put it all back together.  It runs and has higher fuel pressure so hopefully the problem has been solved.   Here’s a pic of the old fuel pump assembly.  The arm on the left side is what moves your gas gauge.  As the fuel level changes the float moves the arm.

So, what was wrong with the pump?  A good question, let’s find out.  Despite the size of the fuel pump assembly, the actual pump is pretty small.  I extracted it from the assembly and mounted it in the vise to get it apart.

Once I got it apart I was able to check out the armature and brushed.  It appears that the brushes (green arrows) are worn with one being worn much more than the other.  I assume that it was barely touching when it was working and every so often would stop in the wrong place where it wouldn’t have a good connection.  I guess that’s what 170k miles will do.  Something, such as temperature change or vibration, probably moved it enough to start working again.

Here’s a picture of the top of the armature that shows where the brushed contact.  It looks pretty worn as well.

So, that’s what I’ve been up to for the last couple of weeks.  The truck’s clutch pedal?  It solved itself and has been fine for a week.  Odd but I’m not complaining!

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