Bad valve stem seal -- how to tell

http://www.fordforums.com/f655/5-0-uses-oil-rings-valve-stem-seals-how-tell-103279/#post1080284

Well, there are a couple of ways to tell. If you start the engine up
and it puffs out smoke, it's the valve seals because you are burning
the oil that has leaked past the seals when the engine was off. If you
slow down by downshifting and when you accelerate again, and it smokes,
it's valve seals. Why? Because when you deaccelerate by downshifting,
your throttle plates are closed and you have a lot of manifold vacuum.
That vaccum sucks in the oil past the valve seals. Then when you
accelerate, the increased air/fuel charge sucks it into the combustion
chamber and it is burned.
Unless the maintenance was completely ignored, I'd guess that it is
valve seals. They will deteriorate with age while a piston ring will
not.

I finally found the culprit

One month ago, my wife's car had a dead cylinder. It was cylinder #3. It passed all the usual tests: spark plug sparking, compression test showed 170psi across all cylinders, fuel injector ticking, presence of fuel injector signal. But it just didn't want to start.

Peering down the cylinder hole, I noticed a pool of oil on top of the piston. A leaking valve stem seal could put too much oil into they cylinder and foiled the proper mixture for combustion. So I replaced them and cylinder #3 was still dead.

I then wanted to double check the compression test figures. It showed 170psi for all cylinders. That was a good figure, but it measured only the peak compression and did not show there was enough compression at the right time. So I bought Harbor Freight Tool's leak down cylinder tester for $30.
   

But they showed minimal leakage.

I was desperate by this time. I decided to take a look at the fuel injector. Two years ago I replaced fuel injector for cylinder #3 because it went bad. So I was very doubtful that the fuel injector could go bad again within just 2 years. But I was desperate. 

Just for the record, it's possible to remove the fuel injector harness (fuel rail) without removing the intake plenum. You need to remove the bracket that secures the accelerator cable though. The bracket is secured by 1 bolt on the cylinder head and 2 studs on the intake plenum. Remove the bolt and twist open the studs with vice grips. Doing so will damage the studs. I replaced the studs with bolts. Good riddance since I hate dealing with studs in general. 

That's when I found the culprit. Compare cylinder 1 and 3's fuel injectors:

No wonder cylinder #3 was dead. The bad o-ring must had been leaking fuel into the cylinder.

It seemed that the replacement pintle cap I used was too wide. When securing the fuel injector into the harness, the smaller opening on the harness pushed the cap against the o-ring.

Fortunately I had spare pintle caps. It was a good thing I didn't cheapen out two years ago by ordering more than I needed. I trimmed the rim of one and installed it.

That's all it took to bring the cylinder operational again.

Installing and removing recessed valve keepers

Nissan Sentra GA16DE, as is the case with many other Japanese engines, have recessed valve. As such, a common valve spring compressor design like the one below won't work.

One tool that can work (or rather be made to work) with recessed valves is Leslie 36200.

To install the valve keepers, use it without the black attachment. Just position it on top of the valve keepers and push down. It has a strong magnet at the end so as you push down the valve spring retainer,  the magnet will capture the keepers. 

A valve spring retainer and valve keepers.

But as it was, its diameter was too big for the valve cylinder. So it needed to be filed. I didn't have a grinder so  it took me 3 hours while watching Pink Panther to file it down. Oh good times.

The yellow zip tie represented my target diameter. It was set to a slightly smaller diameter than the valve cylinder's.

 

I pushed the zip tie as far down as possible and marked places that were still thick.

1.5" was deep enough for GA16DE.

I don't have a picture of using it to remove the valve keepers, but here's one of me using the installation attachment. Just assemble the valve spring, retainer and keeper, and push down with the tool. Note that I was posing for the picture because I didn't take some while I was doing the actual installation. In a real installation picture, you should see an air compressor hose going into the cylinder or a string of nylon rope to float the valves up.

 

If you do not have enough power to push down the tool with your hand (awkward position, short stature, etc.), you can try pushing down the tool with your body weight as pictured above. Use a piece of wood to spread the pressure and push down. This works for the intake valves too which are positioned further inside the engine and may not allow you to push down effectively.

Water pump old vs new

From 1994 Sentra GA16DE 1.6L:

new vs old water pump. The old one had been on the car for 5 years and was leaking.

Brake pedal needs to be adjusted after master cylinder replacement

After replacing the master cylinder in my sis-in-law car, I found that the braking performance didn't improve much. The pedal still went to the floor and the wheel could not be locked up.

I consulted with my brother who was an actual certified mechanic. He suggested that that the brake pedal free play needed to be adjusted because of depth differences of the piston cap in master cylinders. At first I was skeptical. True, the replacement part was a remanufactured one; but was it really that different than the old one?
I measured and found that the freeplay distance was out of spec: 12.7 mm instead of 5 mm. But what could a 7.7 mm difference do to the braking performance?

After adjusting the freeplay distance, I found that I couldn't floor the pedal anymore. Although the wheels still won't lock up, the brake is now good enough for everyday usage. I attribute the inability of the brake to lock up the wheel to older (weaker) brake hose and moderate glazing on the front rotors and pads.

Replacing brake master cylinder

My sis-in-law's car, a 1993 Nissan Sentra, had not been maintained by its previous owner. Since its purchase two years ago, I have been doing incremental maintenance on it. The last one I did was a brake fluid change.

Apparently, the brake fluid had not been changed in a long time. After changing it, the brake pedal became soft, mushy and the pedal could go to the floor. The car became dangerous to drive. Even with pedal on the floor, the wheel would not lock up. Repeated bleeding didn't help.

Then I stumbled on an explanation somewhere in the Internet (I forgot to note the URL). The old brake fluid could have been saturated with water. It caused the rubber seal within master cylinder to swell. Because brake fluid (DOT3&4) is hygroscopic, when the fluid was changed it pruned the seal, leaving it wrinkly like your fingers when you have been swimming for too long.
This causes the master cylinder to have an internal leak: instead of forcing the fluid along the brake lines to the slave cylinders, the seal allows the fluid to leak past them to the unpressurised region.

Symptoms of a master cylinder with an internal leak:

• You can push the pedal to the floor with light continuous pressure even without the help of brake booster.
• The pedal slowly sinks to the floor under its own weight (by itself).

Since diagnosing brake failure cannot be done with 100% certainty, if you have one of the above symptoms and you cannot attribute it to anything else (leaky slave cylinders, leaky brake lines, weak brake hoses, various other kinds of external leak), you need to replace the brake master cylinder.

Special Tools & Parts:

• Replacement brake master cylinder. I got a rebuilt/remanufactured one for $60.
• Flare-Nut wrench (see picture to see the difference).
• Strong strings (optional. to help seat the reservoir in the new unit).
• Aluminium foil / plastic food wrap / plastic bag / any barrier suitable for containing brake fluid.
• Bench vise. Bench bleeding is much easier with one. Much much much easier.
  

Procedures:

• Lift car on all wheels with wheels off.
  
• You need some space around the brake master cylinder.

• So, start by clearing up the area surrounding it.

• Clean the area around master cylinder with brake part cleaner and wiping (physically). You want to get the area as clean as possible to prevent contaminant in your brake system. Use tooth brush (not the same one you used this morning) to clean tight spaces.
  

Do you know that brake part cleaner (Tetrachloroethylene) is a carcinogen? Do not let it drip to the floor. Do not let it free in the environment. I find an oil drain pan suitable to contain brake part cleaner liquid run-off. It's wide and short and can fit under various areas of the car. Don't use the same one as the one you use for engine oil. The chemical in the cleaner will render the oil unsuitable for recycling back as engine oil. It will force the recyclers to use it as fuel.

• With the master cylinder is still fastened to the brake booster, loosen the brake line nuts using flare-nut wrench. The reason you need to use flare-nut wrench is because they are made of soft material and tighten pretty tight (13-20N.m or 10-15 ft/lb). Don't open them, don't let fluid drip. Just loosen them and tighten loosely back with finger.

• Remove the master cylinder from the booster.

• Now that you can manoeuvre the master cylinder slightly, put aluminium foil or fluid barrier under and to the sides of it because next you'll be removing the brake lines. Put some towels (that's the white thing on top of the aluminium foil in the picture below) too so the caught fluid is not sloshing around on the barrier. When the brake lines are separated, they won't drip fluid, but the master cylinder will. So, put it in a plastic bag as you carry it over the car.
  

• Empty the master cylinder and reservoir of brake fluid.
  
• Mount the master cylinder on the bench vise.
  
• Remove the reservoir by moving it left and right while pulling it up. It's going be hard but it won't break as long as you are using your hand. The bench vise allows you to use both hands for pulling.
  
• Pry off the filter screen in the reservoir
• Clean the filter and the inside of the reservoir with brake part cleaner. Don't forget to do it above the drain pan to increase your karma. Afterwards, rinse with fresh brake fluid. Pour in some fluid into the reservoir, put on the cap and cover the ports with your fingers. Shake shake shake and let the fluid out. Repeat as necessary. Don't install the the filter yet, but clean it as well.

Here is a picture of the old and new master cylinders with the reservoir and metering valves removed.

• Install the reservoir, metering valves and the bench bleed plugs (the green plug screwed to the metering valves and ports in the picture below). If the plug does not fit well, do not use it because it won't help in eliminating air during bench bleeding. You need to be prepared for getting messy during the bench bleeding, or do a long painful re-bleed session on all wheels (good thing you already have the car up, right?)
  

Putting back the reservoir was hard for me as I was not powerful enough to press it in. So, I used a long piece of string to help convert torque to pressure. Make sure that the string form a wide band so the pressure will not damage the nylon reservoir.

• Install clear tubings from the plugs back to the reservoir. My green plugs takes 3/16" ID (internal diameter) tubings.
  
• Fill reservoir with fluid.
• Use a long screwdriver or a socket extension to push the piston repeatedly until you see no more air bubble. If there is a port without a plug (because it does not fit well), cover the port with your finger to prevent air being sucked in before releasing the pressure on the piston.
• Installation is the reverse of removal. Do not forget to put the master cylinder in a plastic bag during transport as it will be dripping fluid. Take your time in screwing in the brake line nuts. Do not cross-thread the master cylinder (the nut is soft, but the master cylinder is softer). Do not get panicky because the fluid is dripping. That's why you put the barrier underneath, right?
  

If you did a good bench bleeding, you don't have to do anything else beside putting the car down. Otherwise, go bleed the brake. Yes, new master cylinder means you can push the pedal to the floor without damaging the seal.

Make sure to test drive it and check for external leak.

Keep checking for five days for any fluid level drop in the reservoir and for external leak. Some leaks are very small. I found a very small leak on the third day on one of the the brake line nuts that was not there previously.

1994 nissan sentra fuel injector wierdness

We have two 1994 Nissan Sentra here, Put-Put and Pit-Pit. Put is 160K and Pit is 200K. They both still run strong but that is thanks to having 2 fuel injectors replaced.

It started last November when Pit's cylinder #1 fuel injector went bad. It was so unexpected because fuel injector rarely goes bad. I chalked it up to bad fuel filter. So I replaced the fuel injector and filter.

Then two weeks later, Put's cylinder #1 fuel injector also went bad. That was so surprising. What was the chance of two Sentras having bad fuel injector within weeks of each other. I can't blame it on gasoline because the other car, a 1991 Mazda Protege, was not experiencing any problem, and googling for the problem did not indicate that there was a widespread problem with Sentra's fuel injector. I replaced the fuel injector and filter.

The next day, Put's cylinder #3 fuel injector went bad. In less than 24 hours! I replaced it, and there is no more problem so far.

But last week, Pit's cylinder #4 fuel injector went dead again. By this time, I was so good at replacing Sentra's fuel injector, I did the whole thing from start to finish in under 30 minutes. For comparison purpose, the first time I did it I took 6 hours splitted across 2 days.