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#1
08-13-2006, 09:15 PM
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compression test
Hello all,
I did a compression test on the old Geo today and it wasn't good. Starting on the passenger side 70-120-160 cold pedal to the floor. I added oil and got 95-145-220 cold. I know that I have a valve problem how much of a ring problem do I have? What should a person do?  Replace the head or replace the motor. She seems to run ok, idles crappy. The odometer says 158,000. It's a '97 5 speed.Thanks, 
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#3
08-15-2006, 01:16 AM
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Re: compression test
I was able to replace the rings with the engine still in the car. I pulled the head and pan , pulled the pistons out and honed the cylinders replaced rings and had the head rebuilt. Put it all back together. Much improvement.
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#4
08-15-2006, 04:16 PM
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Re: compression test
Quote:
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#5
08-17-2006, 11:22 AM
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Re: compression test
Changing the rings while the engine is still in the car isn't too hard to do. Just make sure your cylinders are still perfectly round. If they aren't, your engine will barely run with the new rings in it. You'll have more blow by than you had before.
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#6
08-27-2006, 08:56 PM
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Re: compression test
Hey RockRemington !
It looks like I'm going to have to have the head done on my '93 Metro, too. 3 cylinder - 1.0 liter. Can you tell us what your total costs were? Head rebuilt - $ (Parts? Labor? Package deal?) Where - ? How long? Rings - ? Taking the head off scares the crap out of me !!! I have never undertaken such a job ! Is it a bastard? Need special tools ? If you could give us the story of it, that would help. You know, blow by blow description, things to look out for, problems encountered, all that stuff. It would help all of us folk who've never done such a thing before. DoctorBill
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#7
08-30-2006, 07:30 PM
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Re: compression test
It's a real adventure. Worse if it's your primary vehicle.
Things I learned ; you need a 6pt 8MM socket for the belt pulley; tap and die all the bolt holes and studs (to clean them out); very important...flush the hydraulic lifters, it will take a vice and right size socket to compress then and purge the old oil.Afterwords they should be springy. The shop will do it for you for extra charge. Remove the right side wheel, all belts. Remove the belt pulley, timing belt cover, timing belt, unbolt the head (need a 16 pt 10 MM 1/2 in drive socket) it's real tight. Unbolt the exhaust manifold, thats easy , and the top intake manifold, but to get to the bottom bolts on the intake I found it easier to lift the head and reach under it to get to the last intake stud nuts. The manifolds just swing away from the head. All vacuum lines stay connected. Pick up the head with one hand, take it to a machine shop. Cost me about $90 to service the head. HOWEVER I didn't purge the lifters and burnt a valve later so had to do over. Head gasket was $50 ...ripoff. Gasket kit is more but comes with pan gasket (if doing rings). Rings were under $20. Auto zone loans a cylinder hone. An old mechanic said to get the steal rings not chrome, they will seat easier. Check the cylinder bore for round. Pan drops off easy and pistons pull out the top. You need to get a Haynes Manual to check ware limits. For some reason my manual doesn't have it but a later manual at the auto parts did. I just read it at the book rack and didn't buy the book so I have forgotten what is was. I just checked it with a feeler gadge. I checked the oil pressure at the oil sender port and it was high so I didn't mess with the bearings. so, I put the rings in, head back on, torque to spec as per Haynes. Put a new timing belt on, reassemble. You have to pull the distributer so will have to re-time it. The book says replace the head bolts but I did not. I did re thread them. I have 50k miles on the rebuild and 250k on the car. I was real twitchy when I started. Not sure if I would get it back together. But now I have a lot of confidence. You might wont to replace the water pump while your at it. Mine went out 1000 miles latter. Also on my TBI there is a water jacket in the manifold with a freeze plug underneath. It's hard to get to so check it while you can. I replace it with a rubber expansion plug. I went to 1/4 drive sockets tools for fear of striping aluminum bolt holes. This is our second Metro, a sleepy driver crossed over and totaled out first one. It landed on the roof and my wife had to crawl out the window. You will bitch all the way but it's a real rush when it's over. Quote:
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#8
08-31-2006, 05:49 PM
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Re: compression test
Fantastic! Nice explanation!
I got my Cylinder Head off and took it in. See "That's the end of my '93 Metro....." for fixing the Cylinder Head and "NOT the end of my '93 metro...Life after death! RINGS" for replacing the rings. I am at the point right now of working on the rings. Got the tools and am trying to work up the courage to start on the bottom half of the job. So far it has been loosening bolts and nuts, etc., but now I have to go out there and cut some metal (Ridge-Reamer) and actually do something.... Scares me.....I am putting it off over and over. I'm wondering if the Piston Skirts and Connecting Rod bearings will be OK. Main Bearings could be going... Kind of like being tied to a tree and kicking an Ant's Nest at your feet! Whatever happens and I'm stuck with it. DoctorBill
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#9
08-31-2006, 09:43 PM
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Re: compression test
I had almost no ridge at 200K miles. Pistons came right out and I took down what little ridge there was with the cylinder hone. I had good oil pressure and figured I could replace the barrings later if I lost pressure. There is some stuff Plastigage. You remove a baring cap and baring ,put some Plastigage in it and re-torque it, then take it out and measure how much it has been squeezed flat. It comes with a paper scale. You can do this laying on your back under the car. Here is an Auto Zone page with instructions.
http://www.autozone.com/servlet/UiBr...3d8004a54e.jsp If you do need main barrings I think you will have to pull the block. I pulled my transmission out six months ago to install a new clutch. I believe it would be easier to take out the block seeing as the head is already off. I would attempt it because I have backup transportation and five acres of dirt to work on. And Kelly bluebook says my car is only worth $300 for trade in so not a big loss if I blow it. Quote:
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#10
08-31-2006, 10:20 PM
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Re: compression test
Man - I should go buy a cheap micrometer at Harbor-Freight!
See my latest post "NOT the end of my '93 metro...Life after death! RINGS" I sure wish I could relate how much of a ridge I am feeling. Like thin paper in thickness. Cellophane maybe....(?) I wonder if I should attempt to push the pistons out w/o Reaming The Ridges? Maybe I'm making too big a deal out of this Ridge-Reaming thing.... Once I got a look at the crankshaft....lord - so compacted. Hardly room in there to fart, let alone get at the rod bearings.  How do I push the pistons up and out without hurting something? What a mess. That RTV Sealer is all over the bottom of the block and the oil pan edge. It is going to be fun scraping that crap off clean! I will take pictures of the ring changing business when I get going on that... DoctorBill
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#11
08-31-2006, 11:15 PM
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Re: compression test
Digital calipers. Cut some pieces of paper to wrap around the crankshaft journals and tape them so you won't have tape glue on the crank. squirt ATF into the beads of the flex hone as you deglaze the cylinders. If the old rod bearings look pretty good, don't even look at the mains. Wash everything clean with detergent and warm water. Measure with the digital calipers ($20 at HF) and make sure you have the correct size rod bearings. Put the new rings into the clean bore and measure the ring end gap with a feeler gauge before you put them on the piston. Brake an old ring in half and use it to scratch the carbon out of the piston ring grooves. The old rings will be sharp so use gloves. Stagger the new ring gaps on the piston. Use this type of ring compressor so the pistons will push in easily without breaking a ring.
http://www.toolgopher.com/index.asp?...D&ProdID=16733 Don't let a rod bolt touch or scratch the crank as you push the piston down.
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#12
09-01-2006, 12:31 AM
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Re: compression test
I don't follow this..."Cut some pieces of paper to wrap around the crankshaft
journals and tape them so you won't have tape glue on the crank." What is this for? To keep them clean ? "Squirt ATF into the beads of the flex hone as you deglaze the cylinders." Good idea...I'll put it in a squirt bottle my wife has left over from Hair Dye. Why this...? I ordered rod bearings from Schucks...might they be wrong? "Measure with the digital calipers ($20 at HF) and make sure you have the correct size rod bearings." I have a non-digital calipers for Reloading Ammo - I'll use it. What if the gap is too tight or too loose on this issue? What do I do THEN ! ? "Put the new rings into the clean bore and measure the ring end gap with a feeler gauge before you put them on the piston." "Use this type of ring compressor so the pistons will push in easily without breaking a ring." Already bought one of those Ring Compressors from HF. Should be OK...no? Thanks for this information.... DoctorBill
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#13
09-01-2006, 10:08 AM
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Re: compression test
DOC;
I'll bet ATF would make a fine honing oil. Squirt bottle is a great idea. You probably got the right size bearings they come in standard and various oversizes (if the journals on the crank had been machined down then the difference is made up with larger bearings) use the calipers to measure the crank journal (us old guys who can still read analog do fine without digital instruments) use the plastigage to measure the completed assembly; it will help you verify you have the right setup so all will go as planned when you fire it up. Measure the ring endgap in the cylinder (push a new ring down into the cylinder with an upside down piston, get it down below where the "ridge" was). If the endgap is too small (tight) then you adjust it by removing the ring place a file in the slot then squeeze the ring so both surfaces contact the file and pull the ring away from the file, give it a stroke or two then reinsert into the cylinder and remeasure until you get the spec'ed endgap (you could play with one of the old rings to see how much material comes off from 1/2/3 file strokes before you work on the new ones). If the gap is too much from the start then your cylinder is worn beyond tolerance and you will need to consider having it bored (made oversize by a machine shop; this will also require an oversize piston and rings). From the posts others have made I would think this would be a very unlikely situation. Gloves are a good idea as the edges especially of the old rings will be sharp. To get the pistons and rings out you rotate the crank so the cylinder you are working on it at the bottom of the stroke; unbolt the rod bearing cap, rotate the crank to the top of the stroke (this will push the piston to the top of the cylinder) then get yourself a piece of dowel (an old broomstick works great) reach up from underneath, place the dowel into the bottom side of the piston then tap the dowel with a mallet and it will pop out (you may need to tap it fairly firmly (but it shouldn't require the kind of contact you used on the wheel bearings). Then as the book says repeat for the next cylinder. Your ring compressor should work fine. I have no idea what the reference to "tape glue on the crank" is all about. As far as washing things goes stay away from soap and water (think about it - your engine has SEPARATE lubrication and cooling systems and they are designed to stay that way) get yourself some cleaning solvent. It's the same stuff they use in parts washers at mechanic shops, around here I get it from the Chevron oil supplier. Just get yourself a new plastic gas can and go buy some, it does a pretty good job cutting the grease (it's no miracle and elbow grease is required) it doesn't have the fire danger gasoline does and you can let the crud settle into the bottom strain off the solvent and use it again. In addition you leave an oil based residue on the parts you clean not water so you avoid the potential rust issue. I'm looking forward to your post saying it's all back together and you took it for a test drive. You do realize you are obligated to take it for a test drive regardless of the time, muffler condition or irritation to others - right? Here's a link to an ad that got me laughing-it's in the same theme as your living will thing. http://www.ksl.com/?nid=218&ad=409318&cat=&lpid=1
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#14
09-01-2006, 11:14 AM
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Re: compression test
We know the piston will come out because it went in. The ring are the only thing that will catch on the ridge. Mine just came right out. The bottom of the ridge is more of a slope. Doesn't matter if you damage the old rings. Just don't damage the ring groves in the pistons. When you get them out brake a ring and use it to clean out the ring grooves. Sludge gets down in there.
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#15
09-06-2006, 04:25 AM
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Re: compression test
RockRemington obviosly has the neccasary experience to get the job completed successfully. I wouldn't spend $20 on a tool that I owned and could use. I like my $20 digital calipers because I don't have to put my reading glasses on to read the lines.
If you measure you won't need to spend the extra time useing plastiguage and increase your opportunity to get the new bearings dirty. Since you asked? Thirty-five years ago I used cleaning solvent to wash cylinder walls before learning that soap and water is more effective at accomplishing what you want to do. Solvent will leave a film on the cylinder walls where soap & water will not. The solvent on the cylinder walls is the same color as the solvent that washed off because it is contaminated. As RR said solvent breaks down oil and grease, that solvent film will breakdown some of the oil that you assemble the pistons with... not really significant but I found soap & water easier to work with, leaves cylinder walls cleaner and far less irritating to skin during regular use. Use a white paper towel to prove how clean it is. Wiping after solvent wash will make the towel grey from the cast iron and stone particles that remain. Rust can be prevented by WD-40 spray or a clean towel with clean motor oil. The reason I use strips of paper and tape is because it is the fastest way to protect the crank journals from getting covered with the grinding compound created during cylinder honing. Rags will not stop the grit from washing through. If the journals are not protected, some of the grit will get inside the oil hole in the journal and wash into the new bearings when you start the engine. Again not to worry too much as bearings are designed to let some dirt embed in them, like the score mark in your picture of the old bearing. Paper works better than tape alone that will leave glue that needs cleaning when removed. I realize you are working on dirt and that even a sterile assembly room has dust. Ring end gap is the most important factor when re-ringing an engine. Oversize rings can be filed to spec. Worn cylinders will not leave your new correct standard size rings with too little end gap. Too much gap will leave you with excessive blow-by. Yes you can get the wrong size rings or bearings. That is why you measure. You probably have the correct size parts. Size is your responsibility, not Schucks. RTV will seal the oil pan better than a cork gasket, won't seep vapor, or ever need to be re-tightened. If you use the cork, don't use RTV on the cork. Enjoy your experience, do it your way and be proud of you success! Last edited by JustSayGo; 09-06-2006 at 05:07 AM.
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