I'm hoping this is it. I can't imagine why else I would be losing compression... The piston rings are new, and the head is fresh. I also threw in a new BMW head gasket and torqued my head bolts with care. Also the timing was dead on and the piston head for cylinder #1 was definitely TDC when I put the head on.
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With the work that has been done, extremely low compression will most likely be from a mis-timed cam or mis-adjusted valves. Either of which can result in the engine not firing.
Double check cam timing by rotating the crank with the harmonic balancer off until the mark on the crank hub aligns with the notch in the lower timing cover. Then see if the cam sprocket marks are aligned.The car makes it possible, but the driver makes it happen.
Jim Levie, Huntsville, ALComment
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Well, I adjusted valves and checked that timing is dead on - still no compression.
I guess my next step should be a leak down test. Anything else before I pull the head?Comment
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I haven't done a leak down test yet because now I have to price out and purchase a test kit as well as a decent air compressor.
Anyway, here are my dry/wet compression numbers. What might I glean from them? The car won't start so obviously I had to do this with the engine cold...
Cylinder #1 --30 psi dry - 51 psi wet
Cylinder #2 --29 psi dry - 35 psi wet
Cylinder #3 --29 psi dry - 45 psi wet
Cylinder #4 --107 psi dry - 127 psi wet
Cylinder #5 --35 psi dry - 56 psi wet
Cylinder #6 --15 psi dry - 40 psi wetComment
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Assuming that the rebuilt head is good enough and undamaged I'm sorry, but my money is also on mistimed cam or valves... I know, I know, you just re-re-timed them.
It's that or something odd must be happening and we have to ask odd questions:
Like, for instance, is the dowel pin in the cam still there and not bent or stepped (pn 07119942079)?
For a very, very rough check, can you turn the engine with the valve cover off, and when the distributor rotor is pointing at the contact for cylinder #1 are both the valves closed, or near enough closed?
Can you rent an air compressor and a rubber tipped air nozzle?
If you blow air into the cylinder via the spark plug hole at TDC compression you or a friend will be able to hear where it's coming out. Take the oil cap off, if it's coming out there it's rings or holes in the pistons (unlikely because the numbers come up wet); take off the air inlet tract and open the throttle; air out there means there's a stuck, broken or mistimed intake valve, out the exhaust ditto exhaust valve.
You have my sympathy, you may find that the answer comes to you as you're lying awake thinking about it. :yawn: Once I realized at 3 a.m. that the flywheel must have spun on the shaft...Sure enough! 'Course, that was a lawnmower...Comment
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Timing is correct. No doubt about it.
I'm going to borrow a friend's air compressor this weekend and do a leak down test. What baffles me is extremely low compression on all cylinders but #4.Comment
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With those compression numbers the leak down will be numbers will be horrible, but you should be able to tell whether the leakage is via the valves or cylinders.The car makes it possible, but the driver makes it happen.
Jim Levie, Huntsville, ALComment
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So I ordered an OTC Leak Down tester. This one:
It sucks that this beautiful thing just sits dormant.....
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Can anyone please give me a rundown on how to perform a leak down test? I've never done this before.
I'm really just trying to pinpoint where air is leaking from when my cylinder is at TDC...
Where exactly am I looking/listening for leaking? I have an automotive stethoscope if that helps....?Comment
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...part of me thinks my engine may have had some catasrophic failure on the highway while revving so high. Hence the broken rocker arm... Maybe my piston rods are bent?, or some rings flew off?, or my cark arm suddenly busted into little chunks?, or a gang of trolls found there way in there in an all out effort to bake my ass?.... Hey, I have to explore all possibilities, right?
I so Ronery... :(
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Eric is my friend. lol
So, basically:
If I hear leakage from the following it's the following:
Intake boot - Intake Valve
Muffler Tip - Exhaust Valve
Coolant Expansion Tank - Head Gasket
Dip Stick Hole - Pistons
It's all becoming clear. This was supposed to happen! I'm leeeearning...... lmaoLast edited by EyExR; 01-04-2013, 06:45 PM.Comment
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...."If I hear leakage from the following it's the following:
Intake boot - Intake Valve
Muffler Tip - Exhaust Valve
Coolant Expansion Tank - Head Gasket
Dip Stick Hole - Pistons
Yes, that's where you listen for air coming out.
I don't think you actually need the fancy dual gauge calibrated orifice rig for the trouble shooting you want to do.
Get one cylinder at a time to TDC compression, then set your rented compressor's output to some benign figure like 40 or 60 psi. Squirt the air into the cylinder as leakless-ly as possible. Listen for where the air is coming out.
The troll theory is unlikely (you'd be able to hear their beer-drinking songs) but something funky is going on if the valves and cam are timed correctly and 5 out 6 cylinders are stone dead.
One day I'll learn how to use the quote function...
Good luck, let us know the answer.Comment
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Well, I hooked up the leak down tester and I hear air escaping exclusively through the crank housing by listening to the oil dips stick hole...
I know I'm supposed to warm up the engine to do the test but the car won't start...
How can it be that all my pistons are shot at once??? The car was running and then came to a slow death off the highway. I broke a rocker arm... I had the head rebuilt, new gaskets and everything. And now I'm loosing compression right passed all but 1 piston ring. How the heck is that possible?
I know without a doubt I'm at TDC.
Is there a trick I can do to get my rings to seal so I can at least start the car and see if they seat correctly? Or am I shit outta luck??
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Did the shop that didn't replace the valve guides install any piston rings?Originally posted by EyExR View PostComment
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