1993 Civic DX - Healthy cylinder compression readings? Hey, all. I've got a 1993 Civic DX with a D15B7. The car has 278,000 miles. I recently had the head resurfaced and changed out the head gasket (and all accompanying gaskets you'd normally change when doing so). Somewhere along the line the valves in cylinder #1 got stuck open or bent, so it's obviously reading a big fat goose egg when I do a compression test. I'm just going to replace all 4 valves in that cylinder. I did a compression test on the other cylinders as well. The readings for cylinders 2, 3 and 4 were all between 105-115 PSI with little or no drop off after 4 or 5 cranks. My question is: Are those acceptable results, considering the mileage of the engine? |
Re: 1993 Civic DX - Healthy cylinder compression readings? make sure you change the valve stem seals as well |
Re: 1993 Civic DX - Healthy cylinder compression readings? You did an invalid test. Keep cranking until the gauge stops climbing, probably 10 hits or more. I'd expect over 180 PSI. HTH |
Re: 1993 Civic DX - Healthy cylinder compression readings?
Originally Posted by ezone
(Post 4605733)
You did an invalid test. Keep cranking until the gauge stops climbing, probably 10 hits or more. I'd expect over 180 PSI. HTH |
Re: 1993 Civic DX - Healthy cylinder compression readings? Valve stem seals only control oil. They have nothing to do with compression. If your engine can only muster 105-115 PSI, I'd think your method is wrong, or your gauge is wrong, or the cam timing is off, or the rings are seriously worn.... Something is wrong...Good strong battery and good cranking speed? Did you do the compression test with ALL of the plugs out at the same time? Not doing so might explain low readings. A wet compression test may tell more about the condition of the rings. HTH |
Re: 1993 Civic DX - Healthy cylinder compression readings?
Originally Posted by ezone
(Post 4605757)
Valve stem seals only control oil. They have nothing to do with compression. If your engine can only muster 105-115 PSI, I'd think your method is wrong, or your gauge is wrong, or the cam timing is off, or the rings are seriously worn.... Something is wrong...Good strong battery and good cranking speed? Did you do the compression test with ALL of the plugs out at the same time? Not doing so might explain low readings. A wet compression test may tell more about the condition of the rings. HTH |
Re: 1993 Civic DX - Healthy cylinder compression readings? Ignition timing has absolutely nothing to do with compression. Cam timing has everything to do with compression. You are measuring the pumping ability of the engine. Adjust the valves and retry the compression test. Wet test and leakdown tests both have their own purposes. Use each for its intended purpose. At that mileage, I'd expect the rings to be significantly worn. If you tear the head off, that's the time to do the rings if you are going to. HTH |
Re: 1993 Civic DX - Healthy cylinder compression readings?
Originally Posted by ezone
(Post 4605816)
Ignition timing has absolutely nothing to do with compression. Cam timing has everything to do with compression. You are measuring the pumping ability of the engine. Adjust the valves and retry the compression test. Wet test and leakdown tests both have their own purposes. Use each for its intended purpose. At that mileage, I'd expect the rings to be significantly worn. If you tear the head off, that's the time to do the rings if you are going to. HTH |
Re: 1993 Civic DX - Healthy cylinder compression readings? good point that the rocker arm and/or camshaft assembly might not be seated into the head quite right, Did it do this on its own, or has it run bad ever since someone last had their fingers in it? None of that stuff should ever need to be messed with unless a human was in there and screwed it up. It wouldn't have "grown" to be screwed up without human intervention. All you need to do is run the valve adjustment, make sure they have proper (or adequate) clearance. Tight valves not only burn, they cause low compression for a while before they burn. HTH |
Re: 1993 Civic DX - Healthy cylinder compression readings?
Originally Posted by ezone
(Post 4605890)
Not a good point. Did it do this on its own, or has it run bad ever since someone last had their fingers in it? None of that stuff should ever need to be messed with unless a human was in there and screwed it up. It wouldn't have "grown" to be screwed up without human intervention. All you need to do is run the valve adjustment, make sure they have proper (or adequate) clearance. Tight valves not only burn, they cause low compression for a while before they burn. HTH |
Re: 1993 Civic DX - Healthy cylinder compression readings? My reading comprehension problem is showing again, huh? Here's a story for you: I have seen the guy that works next to me bend several valves while trying to reinstall the rocker shafts and stands on an engine similar to this. Didn't have the rockers all in the right places and tried to go ahead and run the bolts in, that forced the ends of the valves to bend outward as the rockers got mashed into place. Needless to say, it got the head pulled off and a pile of valves installed. Something else that is possible is setting the head down on something solid (workbench or floor) and bending whatever valves were open when the head came off. A leakdown check should tell where the leakage is going on that cylinder. Put it at TDC (all valves closed) and apply air pressure, see where the air is going: intake, exhaust, cooling system, or crankcase. |
Re: 1993 Civic DX - Healthy cylinder compression readings?
Originally Posted by ezone
(Post 4605905)
My reading comprehension problem is showing again, huh? Here's a story for you: I have seen the guy that works next to me bend several valves while trying to reinstall the rocker shafts and stands on an engine similar to this. Didn't have the rockers all in the right places and tried to go ahead and run the bolts in, that forced the ends of the valves to bend outward as the rockers got mashed into place. Needless to say, it got the head pulled off and a pile of valves installed. Something else that is possible is setting the head down on something solid (workbench or floor) and bending whatever valves were open when the head came off. A leakdown check should tell where the leakage is going on that cylinder. Put it at TDC (all valves closed) and apply air pressure, see where the air is going: intake, exhaust, cooling system, or crankcase. |
Re: 1993 Civic DX - Healthy cylinder compression readings? Dude, you don't need a leakdown tester. That's way too complicated for what you need at this point. All you need is to connect compressed air to the sparkplug hole. I use full line pressure, 170+ PSI. A real leakdown tester usually doesn't allow enough airflow to even locate a leak reliably. You know the reading is low, but you can't hear where it is going. This is why I use full pressure for this check. Many compression tester hoses will connect directly to a shop air line quick coupler (Milton brand "M" type coupler IIRC). Cylinder at TDC: Remove the Schrader (check valve) from the compression tester hose first, then screw the hose into the cylinder, connect the hose to an air line from a compressor. |
Re: 1993 Civic DX - Healthy cylinder compression readings?
Originally Posted by ezone
(Post 4605930)
Dude, you don't need a leakdown tester. That's way too complicated for what you need at this point. All you need is to connect compressed air to the sparkplug hole. I use full line pressure, 170+ PSI. A real leakdown tester usually doesn't allow enough airflow to even locate a leak reliably. You know the reading is low, but you can't hear where it is going. This is why I use full pressure for this check. Many compression tester hoses will connect directly to a shop air line quick coupler (Milton brand "M" type coupler IIRC). Cylinder at TDC: Remove the Schrader (check valve) from the compression tester hose first, then screw the hose into the cylinder, connect the hose to an air line from a compressor. |
Re: 1993 Civic DX - Healthy cylinder compression readings?
Originally Posted by Fragmare
(Post 4605940)
Ahh, I see what you mean. Just pump a bunch of air in there and listen for the "whistle", so to speak. With sufficient air pressure and flow you will be able to feel the air flowing out of the intake (throttle body or a vacuum hose), or the exhaust at the tailpipe---- if it is valves. BTW those valve stems are THIN. They do bend somewhat easily with enough pressure in the wrong direction. HTH |
Re: 1993 Civic DX - Healthy cylinder compression readings?
Originally Posted by ezone
(Post 4605941)
Well, I've never heard one whistle, but I guess you never know.... With sufficient air pressure and flow you will be able to feel the air flowing out of the intake (throttle body or a vacuum hose), or the exhaust at the tailpipe---- if it is valves. BTW those valve stems are THIN. They do bend somewhat easily with enough pressure in the wrong direction. HTH And, yea, I was noticing just how thin those stems really are when I was examining them with the rocker assembly out yesterday. No wonder they're so touchy. Thanks for all these tips, btw. Very useful info here! :) |
Re: 1993 Civic DX - Healthy cylinder compression readings?
Originally Posted by Fragmare
(Post 4605983)
How about the crankcase? Drain the oil and check for air coming from the oil drain or oil filter hole? Pop the breather vent hose off of the valve cover and use it. You would feel air movement from a small port or hose far more easily than a large gaping hole. Your nose hairs should be far more sensitive to air movement than your hand. (I know it sounds like a LOL, but I'm serious. Use it.) Note: There will always be leakage past the rings. There will always be air movement into the crankcase. Some is normal, you just have to do comparisons between the 4 cylinders to see if the bad one is excessive or significantly worse than the others. HTH |
Re: 1993 Civic DX - Healthy cylinder compression readings?
Originally Posted by ezone
(Post 4606009)
That would make zero sense. Pop the breather vent hose off of the valve cover and use it. You would feel air movement from a small port or hose far more easily than a large gaping hole. Your nose hairs should be far more sensitive to air movement than your hand. (I know it sounds like a LOL, but I'm serious. Use it.) Note: There will always be leakage past the rings. There will always be air movement into the crankcase. Some is normal, you just have to do comparisons between the 4 cylinders to see if the bad one is excessive or significantly worse than the others. HTH |
Re: 1993 Civic DX - Healthy cylinder compression readings?
Originally Posted by Fragmare
(Post 4606145)
do you recommend any particular kind of valve spring compressor? I'd imagine some fit better than others and some won't fit at all. Obviously, you would need one that fits. No opinion, I don't do that sort of work. It isn't worth my time and effort, and I don't have the tooling for it. I send that out to a reputable machine shop. They have all the necessary equipment to do valve work. HTH |
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