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Old 04-24-2010, 09:23 PM   #1
Scooby Newbie
Member#: 217803
Join Date: Jul 2009
Chapter/Region: MAIC
Location: Northern Virginia
2003 WRX Wagon

Default Bent exhaust valves?

Hey guys, need some opinions:

Bought an '03 WRX with a blown engine at an auction, and got a replacement engine with 50k miles out of an '03 wrecked WRX. We have done the following:

Swapped over the intake and wiring harness. Used new intake gaskets. Changed the clutch (old one was toasted) Changed the plugs with NGK iridium. Installed the engine. Changed the oil using Purolator filter (same as OEM) and 5W-30 synthetic oil. Cranked engine which started after about 10-12 cranks. Engine had loud tapping/knocking noise from passenger side rear of engine (#3 cyl?) and very rough idle. Let run for 30 min. Had oil, coolant and exhaust leak. CEL on. Connected scanner and getting misfires on all 4 cylinders.

Fixed oil leak and coolant leak. Started car again and ran another 30 minutes. No change.

Added Heet and fresh gas. Ran for 30 minutes, no change.

With engine running I pulled the wire to coil on #3 cylinder. No changed in engine idle. Cylinder 3 is not contributing. Replaced #3 wire and pulled #1 wire to compare. Engine stumbled much worse. #1 is contributing to engine performance.

Thought I might have an ignition problem. Checked plug and coil pack on #3. both are OK

Did a compression test (cold engine). Cylinders 1,2,4 were all 150, #3 is zero. Thought the timing belt might be off. checked timing marks. Belt position seems OK. (did not check crank pulley position, only cam pulleys).

Pulled passenger side valve cover and checked valve clearance. Everything OK except for #3 exhaust valves. Clearance should be .025 mm. Clearance is .130 (about 5 times normal). This would account for the noise but not the zero compression.

Connected air compressor using Compression gauge hose with schrader valve removed. Checked #1 leak rate against #3 leak rate making sure I had the cylinder I was measuring at top dead center on compression stroke when measuring. #3 leaked down much much faster than #1.

Not sure what to do next. The shop manual says to bring the valve clearance into spec I need to pull the cam and replace the lifter buckets. 2003 wrx does not have shims. Doesn't make sense that only this cylinder would be that far off on both exhaust valves and not intake valves. The only thing I can think of is that the exhaust valves are bent which would keep the valve from closing all the way. This would account for the zero compression and the large valve clearance.

I really don't want to pull the head if I don't have to. Not sure what to do next. Is it possible that there is carbon or something on the exhaust valves keeping them from closing? Should I seafoam the engine? Is there anything else that could case these symptoms?

The cam gears on the passenger side are new (recently replaced by the seller). I'm thinking the timing belt jumped and the valves were bent as a result of the accident.

Again, don't really want to pull the head, any recommendations on what to do next?
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Old 04-24-2010, 10:56 PM   #2
Scooby Guru
Member#: 157348
Join Date: Aug 2007
Chapter/Region: NWIC
Location: Benghazi
1996 JNCO Jorts
Stonewashed Denim


Wirelessly posted (Phallic Tractor: BlackBerry9630/ Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/105)

Sounds like you've already identified the problem. You probably won't be able to fix it without removing the head, whatever the problem is.
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Old 04-25-2010, 12:05 PM   #3
Scooby Specialist
Member#: 151045
Join Date: Jun 2007
Location: NW Indiana
2013 Subaru STI


I doubt it's bent. You probably have a cracked exhaust valve on #3. Time for a teardown.
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Old 05-01-2010, 09:30 PM   #4
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Member#: 217803
Join Date: Jul 2009
Chapter/Region: MAIC
Location: Northern Virginia
2003 WRX Wagon


We're pulling the passenger side head and checking those exhaust valves. Other than replacing the valves on the #3 cylinder, is there anything we should do while we have the head off? If we already have the intake manifold and exhaust manifolds off, does it make sense to pull the other head (has good compression) or should we leave well enough alone on the driver side head?
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