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Old timers collection of auto-repair nuggets of wisdom

4K views 8 replies 5 participants last post by  dovehunter 
#1 ·
A lot of them refer to older cars but there's also a lot of "I didn't know that!" info in there too...

http://www.misterfixit.com/autorepr.htm


"I had a funny noise under the hood of my 89 Taurus that no one could identify. It varied with engine speed but could not be localized, even by a Ford technician that I respect. Finally on a trip through Nebraska I had an occasion to take the car into a Ford garage in Scottsbluf . I asked if anyone there might know what I had been hearing, one of their young technicians came over and pulled off the alternator connector. The noise went away. He explained that when a diode fails the unbalance in the alternator magnetic circuit causes the whine. About 6 months later the alternator had to be replaced and of course the noise was gone."

"
During the 60's I worked as a mechanic while drag racing on the side. A friend who was somewhat new to mechanics decided to rebuild his motor. After the engine was reassembled he fired it up an it ran so smooth a nickel could be placed on the manifold upright. Throttling the motor it jumped to 9000 rpm's instantly. Sounded really good. Then he took it for a drive an came back saying he couldn't get over 30 mph..several of us mechanics took a look an we couldn't find anything wrong. New carbs..fuel flow was right..new manifold..new timing chain an the marks were right also. So we swapped distributors with a known good one - no difference.. Cutch an tranny were new too an adjusted properly leaving us baffled..finally one mechanic said hey check his compression. The compression was 60 pds not 160 pds. The funny part of this is we asked about how he put in the pistons an he said "I know its right cause I was sure to line up all the rings in a straight row facing the notch in the pistons"..lol..which of course you know they need to be staggered. We fixed it in short order an it ran great afterwards."
 
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#2 ·
...and more good stuff

It was about 3 above zero. Here in Webster in February that isn't too abnormal. We'd just finished a ten day vacation in Florida and my son was driving us home from the airport. The Buick was rolling along doing its normal smooth cruising at 60. As we pulled off the ramp the dash board lit up like a Christmas tree. "What's up?" "It stalled" "Well, start the **** thing and let's get home. I can't wait to get into that nice warm bed."

Trying to be the expert I reached over and turned the key. It didn't even hint at starting - just a weird uneven high speed cranking noise.

A quick call to 1-800-AAA-HELP got a friendly and warm hello. "The tow truck will be there in about twenty minutes." she said calmly. "Hang in there."
We waited nearly an hour. Suddenly from behind us we could faintly make out some flashing lights.Triple A had finally arrived.

...into my coveralls and dirty sneakers... It was time for some analysis and serious reading of the ever popular Buick Service Manual.

Sooo, how does one begin a diagnostic here?The first clue is uneven cranking speed. That means that the starter motor is seeing an uneven load in doing its job of turning the crankshaft and making the pistons go up and down. As the piston goes up on the compression stroke the starter motor sees an increase in the amount of force it takes to compress the fuel/air mixture in preparation for the firing of the ignition and the subsequent power stroke. Soooo, if the cranking speed varies wildly you can be pretty sure that the compression is not equal on all of the cylinders.
First step: do a compression test.

Sure enough the compression on two out of the six cylinders was well within range (you can find the range in the service manual that you got from the library). The remaining four cylinders were way below specification. Now there are a few possible causes for this. Basically, the cylinder is leaking the fuel/air mixture somewhere. It could be a blown piston and the leak is into the crankcase. It could be a blown head gasket and the leak is either into the atmosphere or into another adjacent cylinder. It could be a valve that is not seating correctly, either burned or possibly hanging so it doesn't close all the way, or it could be a bent valve also not allowing it to seat properly.

Now a long time ago I learned a trick from a fellow Ford mechanic. You see, if you could get air to flow back through the leak you could possibly identify the source of the leak and your diagnosis would be complete. So, what I did was to take a spark plug, break up the porcelain part so that all I had was the metal threaded piece. Then I brazed an air fitting onto the sparkplug body. When I was finished I had a way to thread an air fitting into the sparkplug hole and hook up my compressor to the fitting. Then I turned on the air. A bit of caution here. As the air pressure builds up in the cylinder, the piston will be forced down and the engine will rotate accordingly. Keep your hands clear of anything that may turn with the engine such as a fan blade on the older style engines or just an engine belt which might snip off a finger or two.

Well, when I did my experiment I found that there was air rushing out of the exhaust pipe. Think now, if that piston was just coming up on the exhaust stroke the exhaust valve would normally be open and one would expect to see air coming out of the exhaust pipe, right? So further work is required.
I removed a valve cover and turned the engine over by hand using the flywheel pulley bolt and a breaker bar. I turned it over until the intake valve opened and then closed and then turned the engine another 1/4 turn. That means that the piston is now on its way up on the compression stroke and both valves are closed. I verified that by watching the valves for that piston and seeing that they were indeed closed. Now I wedged the breaker bar against the frame so that the engine could not turn when I applied air pressure. I could still hear air coming from the exhaust system. There was no air coming back through the intake manifold. I could verify that by opening the throttle and inserting one end of a piece of hose into the throttle body and putting my ear near the other end. Quiet as a church. I then listened through the oil filler cap hole in the other valve cover to see if air was leaking out through the piston and into the crankcase. Also quiet.

My diagnosis was then confirmed with each of the other three low cylinders. Each of them was leaking through the exhaust port.

Soooo, what makes an otherwise smoothly operating motor suddenly stop dead on the expressway and exhibit the signs of bad exhaust valves? Well, if the camshaft to crankshaft timing suddenly changed drastically, the valves might be open when the pistons were at top dead center. How could that happen? If the timing gears and chain failed, that's how.

A quick check of the cam timing showed that my suspicion was correct. I turned the crankshaft until the timing mark came into view. As it approached I watched the valve sequence for the number one piston. If everything was timed correctly I would see one of two possible valve actions. If the piston were coming up on the compression stroke both valves would be closing. If it were coming up on the exhaust stroke, the exhaust valve would be closing and the intake valve opening. Neither was the case. The cam timing was off. With confidence that my diagnosis was correct I began the task of removing and replacing the timing gears and removing the cylinder heads to replace the bent valves.

I attacked the timing gears first. After about a half an hour's work I had removed the timing gear cover and saw the devastation. Buick, in all its wisdom, has supplied older motors with a nylon coated cam gear. After some time of running (the estimate is about 90K miles) the nylon starts to get brittle. The brittle nylon pieces break off and sit in the sludge at the bottom of the oil pan. Finally, after most of the nylon has broken off, the aluminum gear underneath the nylon begins to wear off, also settling at the bottom of the oil pan. Now I have a clue here for all of you who are wondering if you are about to go through all the pain and agony (and big bucks) of losing timing gears the hard way - along with your exhaust valves! Is there a predictor that warns the unwary Buick (and other GM products) that there is trouble? You bet! At your next oil and filter change try this. Get a clean coffee can and a clean piece of sheet or towel that you no longer want. Punch a hole in the oil filter that you've just removed. Let the oil drain out of the hole and into the coffee can through the clean cloth. If you see a lot of fine aluminum powder in the oil or on the rag you probably are a few miles from a timing gear failure. If you also see fine pieces of light green (Buick color) nylon in the filtrate - same message.

If you want further proof, put the oil drain plug back and pour a quart of kerosene into the oil filler hole. Leave the oil filler cap off. Then take an air hose and blow air down through the dipstick tube for about a minute. This will loosen up all the crud that has settled in the crankcase at the bottom of the oil pan. Drain the kerosene into a clean can and filter it through a clean cloth. You will be amazed at what you find! But if you find chunks of green nylon you know what to do!

Well, the timing gears were now replaced and it was time to see if the valves had been damaged by the traumatic failure of the timing gears. I had already done a compression test and knew that there was low compression on four of the cylinders. Next step was to remove the rocker arms for those cylinders and try the forced air trick. If the valves were bent the air would continue to rush out through the exhaust valves. Sure enough, air went easily out the exhaust ports. The valves were bent. It took another hour to get the cylinder heads off and examine the damage. I could see small indentations in the top of the pistons where the exhaust valves had hit them. A quick cleanup of the carbon with my Dremel got me down to clean aluminum. Inspection under a bright light told me that there was no serious damage to the pistons. I changed tools on the Dremel and ground and polished the small dings in the pistons to the point where they were hardly noticeable.

The Exhaust valves cost about six bucks each and the valve stem seals about a buck a valve, well worth it to prevent any oil seepage past the old hardened seals. About an hour later the system was ready to be cleaned up and the carbon and old gasket material removed. A scraper took the bulk of the heavy carbon off and the Dremel did the rest. While I was at it I used a stone in the Dremel and polished the ports, both intake and exhaust, to a bright finish with none of the factory casting flash that can cause poor dynamics of air flow both into and out of the cylinders.

With all surfaces cleaned and polished I was ready for re-assembly. That took another hour or two. I finally got up enough courage to crank it up. It started on the first crank and ran as smoothly as a new engine. I buttoned it up and ran it for an hour or so and then drained the oil to make sure that I had gotten all of the loose crud from the timing gears out of the system. I changed the oil filter and filled it with fresh oil and it has been running like a top ever since.

The total time for the job was about 12 hours spread over a few weeks. The total investment was about a hundred fifty dollars, valves, gears, gaskets etc. well worth the cost!
 
#6 ·
OK... many long years ago, a friend of mine called me & said. Could you help me get the rearend back in my car. Why sure I'm a good guy right? Here's the lay out: He had taken the bad rearend out of the 57 Chevy. & had another one by the car from a junkyard. So all we had to do was put it in & bolt everything up. Now here where the story gets good... All done, ready for the test drive. 4 Speed car, start up the small block that got a bunch of horses ready to race. 1st gear ready to and... away we go... backwards! I'd like to have a picture of our faces about then. Some'm wrong we say... try reverse, so... we did and.... forward we went! Holly smoke... now what did we do wrong?
 
#9 ·
My friend who got the rearend out of a van in the junk yard didn't think about the mounting. I can't remember... one was mounted on the bottom of the leaf springs & the other was mounted on top. Anyway we removed the rearend & cut off the mounts & welded them on the backside. Mounted the rearend back in the car & away we went in the correct direction...

I like to think I would have caught this if I had been with him when he went to the junkyard. It's history now...
 
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