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Post by flyboy4613 on Nov 5, 2015 16:24:12 GMT -5
Car was idling high and stalling when idling for no apparent reason. I could not diagnose the problem myself and after fixing a vacuum leak in the intake manifold and adjusting the idle and throttle nothing seemed to fix it. Brought it into a mechanic and they ran a compression test right off the bat and found about 10 pounds of compression in the number one cylinder. No wonder there was no power and the idle was high!!!! Anyway the mechanic also did a leak down compression test and found that the leak was coming from the top of the engine. It's not showing any other symptoms of a head gasket leak so me and the mechanic are guessing it is a valve issue. The mechanic is asking for outrageous sums of money to fix this problem and I was wondering if anyone has had this problem or if anyone has tips on working on just valves.
Thank you for your help, I'm new to fixing cars and especially justy's having only acquired mine a couple of months ago and having very little time to work on it since.
Interesting note though, the Justy will get up to 70 mph on two cylinders. Found this out before I found out I had only been running on two cylinders.
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Post by sp0ngebob on Nov 5, 2015 17:23:09 GMT -5
the question is whats damaged. is it a valve head that got slammed by a piston? is it a valve being held open for some reason by an extremely tight lifter/rocker arm clearance?
assuming its the bent valve, just get a replacement cylinder head. less work than trying to get a valve, new guide, making sure the bowl is ok then putting it all together.
step 1: pull valve cover and check clearance and height of the valve stem relative to the other valves.
step 2: do a leakdown test again and this time listen if the air is coming out the intake or the oil cap
step3: tell what happened in steps 1 and 2
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Post by flyboy4613 on Nov 8, 2015 23:37:50 GMT -5
I pulled the valve cover and the number one cylinder's valves seem to have the same clearance and height as the other ones do. I disconnected the distributor and cranked the engine and all the valves seemed to move just fine. I haven't been able to get the tools for a leakdown compression test. Is there anything that I can do before I get those? Attached is a picture of the valves. I don't know if you can tell anything from it, I can't see any difference, I can get better pictures as needed. Thank You!!!!!!!
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Post by earthbounding on Nov 9, 2015 6:28:13 GMT -5
check/adjust the valve lash for each cylinder...
1) Set the cylinder to be adjusted to Top Dead Center of the compression stroke. 2) Insert the gage between the valve and rocker arm and write down the clearance. 3) with the gage still in place, adjust the clearance. Valve clearance:(engine cold) Intake valve: 0.13 - 17 mm (0.00 51 - 0.0067 in) Exhaust valve: 0.23 - 0.27 mm (0.0091 - 0.106 in) 3) Rotate the crankshaft a few turns and recheck the clearance.
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Post by certimafied on Nov 10, 2015 10:09:58 GMT -5
I would do the leak down test again, be sure its on TDC for cyl one compression stroke when its performed. The air can leak from the piston rings intake valves or exhaust valve. Its important to know what it is before tearing the engine down, a head job is a huge difference from doing the lower end as far as time and money goes. If you guys know for sure its a head issue, just out of curiosity I would want to watch the rocker arms while the engine is being rotated. From the picture you posted the rocker arms dont look bent and if the valves all have the same relative height your valves probably arent bent either but it would be pretty quick and easy to watch the movement of the valves in question. That and I think its cool to watch all that stuff move around in there . Were any of the valve clearances real tight when you initially checked?
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Post by sp0ngebob on Nov 11, 2015 18:27:01 GMT -5
if it has 0 or wicked low compression you can start it with the radiator cap off. if the water violently splashes around then its a blown head gasket where compression is leaking into the coolant system. otherwise its gotta be leaking into the oil or the rarest of which is a leak between cylinders. this would cause two holes to have low compression though.
Theres the outside chance that its a blown head gasket to the exterior of the engine but thats pretty rare unless you overheated it severely
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Post by coondog on Dec 29, 2015 16:01:21 GMT -5
to get 0psi on a cylinder there is obviously something letting air out as fast as it is going in. Some good advice added above, but the one thing I see being very possible is that a valve is missing a piece. I have a volvo in my bay right now that had no compression on a cylinder and I removed the head to find that the valve was missing a whole piece. Ill see if I can add a pic. The funny thing is that the piece that broke off, is nowhere in sight, and it did no cylinder damage...
But with 0 psi you can rule out a few things... rings-would have low compression, not 0. Other cylinders would have similar readings. valve seat crack- usually only misfires under load Camshaft problem-damage would be visible when removing valve cover
I had a newer jetta come in with a problem nobody could figure out, had 0 psi compression. I never got it to run during diagnostics, but no crazy noises turning it over. Passed a cylinder leakdown test It had a broken wristpin
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