cracked cylinder head
08-08-03, 10:14 PM
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cracked cylinder head
i know this is an rx7 forum, but this is the only place i can get info on the internet. i need to know if my starion has a cracked cylinder head. would it still run? it runs perfect until 4500 rpm, then it juss gets REAL loud from 4500 to redline, it has a ticking when its cold but goes away. what do you guys think?
08-09-03, 11:26 AM
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the ticking is probably the lifters (don't really know if they are called that in english but if anyone know what i mean you can translate it) that donest work properly when the oil is cold. The other problem i dont know, would need more info for that, maybe a soundclip?
08-10-03, 01:59 AM
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The most difficult thing to diagnose online is a problem where most of the info is related to the sound that a part is making. The second most difficult thing to diagnose is a piston engine problem in a Rotary engine forum.
To answer some of your questions, yes, it is possible that the engine will still run with a cracked head. It just depends on where the crack is. The ticking sound you hear is probably what Tobias said, the lifters, rods,or rocker arms. By rods, i mean the rods attached to the intake and exhaust valve. The lifter is pushed up and down by the cam shaft lobes, tilting the rocker arms, which open and close the valves. Been a while since I messed with a piston engine so bear with me. At idle, if you take your valve covers off, you should see that there isn't much oil circulating through there because the pressure isn't high enough. Also, you will hear the rocker arms and rods moving. If it is excessively loud or making a metal to metal clanking sound instead of a sort of hushed sound, you need to get the Haynes manual, Chiltons Manual, or Factory Service manual for that car, and it will show you how to check the torque on the nut holding the lifters in place. Having them too loose or too tight will cause what they call valve tapping. Something to do with the rod being aloud to drop too far and letting the valve slam shut. There should also be a measurement for the clearance between the rocker arm and the pushrod I think Again, its been years so I'm not 100% if that is the place you are measuring, but the books will have all that info.
For the cracked head, tell me this. Does the car smoke out of the exhuast while its running? If it is, what color is the smoke?
If you see blue smoke, then its burning oil. The cracked could be letting oil get into the combustion chamber.
If the smoke is white and thick (not a thin haze like steam) and smells sweet, its coolant. (It will smell like a brand new bottle of preston antifreeze. It is possible that there will be a strong coolant odor from the exhaust with no smoke.) The crack is letting coolant get past the head gasket. You need to fix this immediately. I've seen a several different vehicles (desiel, regular piston and rotary) with cracked blocks, heads or head gaskets where the coolant was leaking into the piston chamber and the owner didn't know. Coolant is corrosive and in each case, it was getting into the crank case and it damaged the crank shaft and bearings and caused the engine to seize up.
If you see black smoke, its running rich. It isn't a detrimental problem, but you aren't getting optimal gas mileage and it causes a little more carbon buildup than does usual operations. This isn't a big deal on pistons but it is on rotary engines.
While you have the valve cover off, inspect the heads for cracks, and check the oil, both on the dip stick and on the heads around the lifters. Your looking for milky white or tan coffee colored droplets in the oil. Its caused by coolant getting in the oil and you will know when you see it cause it looks like I said, Milk or coffee in the oil. It will be obvious because the oil and antifreeze don't mix.
If you can't find a crack, take the head(s) off, and take them to a machine shop that does magnaflux. They basically X-ray the heads to see if there are any cracks. Might cost $50 bucks I think, I'm not sure, but thats what I think the price was last time a friend of mine was talking about it. Call first to see what the price is and if they even offer that service.
Hope that was some help. Sorry its so long and sorry I don't know more about piston engines.
You should ditch these
and get these
To answer some of your questions, yes, it is possible that the engine will still run with a cracked head. It just depends on where the crack is. The ticking sound you hear is probably what Tobias said, the lifters, rods,or rocker arms. By rods, i mean the rods attached to the intake and exhaust valve. The lifter is pushed up and down by the cam shaft lobes, tilting the rocker arms, which open and close the valves. Been a while since I messed with a piston engine so bear with me. At idle, if you take your valve covers off, you should see that there isn't much oil circulating through there because the pressure isn't high enough. Also, you will hear the rocker arms and rods moving. If it is excessively loud or making a metal to metal clanking sound instead of a sort of hushed sound, you need to get the Haynes manual, Chiltons Manual, or Factory Service manual for that car, and it will show you how to check the torque on the nut holding the lifters in place. Having them too loose or too tight will cause what they call valve tapping. Something to do with the rod being aloud to drop too far and letting the valve slam shut. There should also be a measurement for the clearance between the rocker arm and the pushrod I think Again, its been years so I'm not 100% if that is the place you are measuring, but the books will have all that info.
For the cracked head, tell me this. Does the car smoke out of the exhuast while its running? If it is, what color is the smoke?
If you see blue smoke, then its burning oil. The cracked could be letting oil get into the combustion chamber.
If the smoke is white and thick (not a thin haze like steam) and smells sweet, its coolant. (It will smell like a brand new bottle of preston antifreeze. It is possible that there will be a strong coolant odor from the exhaust with no smoke.) The crack is letting coolant get past the head gasket. You need to fix this immediately. I've seen a several different vehicles (desiel, regular piston and rotary) with cracked blocks, heads or head gaskets where the coolant was leaking into the piston chamber and the owner didn't know. Coolant is corrosive and in each case, it was getting into the crank case and it damaged the crank shaft and bearings and caused the engine to seize up.
If you see black smoke, its running rich. It isn't a detrimental problem, but you aren't getting optimal gas mileage and it causes a little more carbon buildup than does usual operations. This isn't a big deal on pistons but it is on rotary engines.
While you have the valve cover off, inspect the heads for cracks, and check the oil, both on the dip stick and on the heads around the lifters. Your looking for milky white or tan coffee colored droplets in the oil. Its caused by coolant getting in the oil and you will know when you see it cause it looks like I said, Milk or coffee in the oil. It will be obvious because the oil and antifreeze don't mix.
If you can't find a crack, take the head(s) off, and take them to a machine shop that does magnaflux. They basically X-ray the heads to see if there are any cracks. Might cost $50 bucks I think, I'm not sure, but thats what I think the price was last time a friend of mine was talking about it. Call first to see what the price is and if they even offer that service.
Hope that was some help. Sorry its so long and sorry I don't know more about piston engines.
You should ditch these
and get these
08-12-03, 01:03 PM
#4
trying to build a racecar
Aside from the noise, if the car still builds boost ok and runs fine, then it may just be an exhaust leak. So I would check the exhaust system around the turbo before you rip the head off. But definitely check the oil for foaming (from coolant).
If you do a compression test, you might even be able to determine which cylinder is leaking... not that it would really change the outcome. You'd still have to pull the head.
Good luck
If you do a compression test, you might even be able to determine which cylinder is leaking... not that it would really change the outcome. You'd still have to pull the head.
Good luck
02-09-04, 10:07 PM
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I agree w/PROJECT84..check your dipstick for water droplets..(sign of head gasket failure)also check rad for bubbles or muddy contents
I used to fiddle w/piston engines but i graduated to rotaries....good luck
I used to fiddle w/piston engines but i graduated to rotaries....good luck
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