Have you ever had a customer come in and complain of a poor running engine? After diagnosing it you find engine misfire codes.
To narrow down the issue you do a compression test or cylinder leak down test.
Rocker arm dislodging with valve seat falling out. Now you have isolated a specific cylinder and confirmed cylinder leakage by the valves. You remove a valve cover only to find a rocker arm had fallen out of position. Your first thought may be to just reinstall the rocker and see what happens. You do this and it seems to run fine. You believe the problem is solved, or is it?
Well this is a lot more common than you think. It may be ok for two weeks or two months but it will be back. If you are lucky enough to not have a total failure the next time it comes back, you will probably remove the cylinder head and send it to a machine shop for inspection.
When they call you back they are probably going to tell you that a valve seat has come loose in the cylinder head. What happened was it moved down in it’s bore, it created a gap at the valve tip and this allowed the rocker to fall out of it’s location.
There are a number of reasons for rocker arm dislodging and some are more common than others, some things to consider are,
Something causing the valve to stick in the open position allowing a gap for the rocker to shoot out,
- Poor fuel
- Debris in oil
- Bent valve
- Valve seat coming loose and dislodging
A valve seat coming loose is probably the worst case and is very common in certain engines,
- 1991-1996 Ford 1.9
- 1997-2000 Ford 2.0
- 2002-2007 Chrysler 3.7
- 1999-2009 Chrysler 4.7
- 2003-2009 Chrysler 5.7
After removing the cylinder head this is what you might find. The seat is spinning and moving in and out of its bore and usually the valve spring pressure pulls it back in. Therefore at some point it will come all the way out and cause major damage.
This is repairable at most machine shops but they might recommend replacing all the valve seats as a precaution. For some reason the Intake valve seat is more of a problem than the exhaust. This issue is usually caused by insufficient crush between the valve seat and the machined hole to accept it.
This is what you might see after removing the cylinder head.
Some of the earlier 1.9 and 2.0 Ford engines had what they called powered metal inserts and they would actually break or just explode. When a valve seat comes out of it’s counter-bore, it shatters or explodes into tiny pieces from impact. As a result those pieces from the valve seat may get lodged in the intake or exhaust manifolds.
Other known problems could also be broken valve springs ( causing ticking or misfire ), overheated engines with stuck valves and old fuel issues.
Letting this go to long you could drop the Seat and possibly a Valve causing complete destruction of the engine. That is why analyzing what caused a problem before you try to fix it is so important. Broken or burned valves as well as worn or loose guides, cracked or loose seats and similar valve train damage is often the end result of a chain reaction of events. One problem leads to another and eventually a valve failure. So replacing parts without understanding what made them fail is no fix at all. Cooling problems in the engine itself can lead to valve sticking and burning if the operating temperature gets too high.
Some things that can make your engine run hot are,
- Low coolant
- Defective thermostat
- Weak water pump
- Radiator obstruction
- Defective cooling fan or fan switch
This, in turn, makes the valve stems swell which may cause them to gall or stick in their guides if there is not enough clearance. As a result if the valve sticks open, it can burn or be destroyed if it smacks the piston. Hence this can all be the result of the Rocker arm dislodging.