I am having probs with a 2004 elantra. I just replaced the head gasket. The engine overheated and damaged the radiator and wharped the head. I had the head machined and replaced pump, timing belt, and thermostat. The compression is down about 30 psig in the #3 cylinder. I ran a leakdown test and got 50,50,70,and 8%, However the compression ranged from 180-210 psig which was better than I expected based on the leakdown test..
My scanner codes says PO341 cam sensor bank 1 . ALSO misfires 1,2,3,4. I am not sure what this tells me. I used a volt meter to measure voltage at the sensor. I got 2-3 volts while varying the rpm from near idle to about 3000 rpm. My books says voltage should range 2-5 volts. It hits 5 volts when the engine dies for a short time. Is this sensor messed up?

Also have problems with radiator fans. My fans don't run unless I turn on the a/c. Both will run. I replaced the temp sensor today to see if this possibly the problem. Does the ECM turn both fans on for the ac? Is this an ECM issue since both fans will run? I assume this rules out a relay problem.

What do I need to try next?

 

Oh boy..... ok first machining a warped head is dangerous. There is a spec to maximum warpage do you know what it was? are the timing marks on the chain to cam lined up correctly? Did you ck the shims on the buckets to make sure they are within spec? The shims are between the camshaft and the valve . If these are not within spec you are wasting your time. Sensor could be bad due to overheating. Cylinder leakage scares me cause most times when you warp a head you also eggshape a piston. Oil rings will be stuck to piston is one good indication and scarring in bore also. Both fans come on when a/c is on...thats correct. Radiator fan is controlled by pcm according to engine temp. alot of things you said worry me due to this isnt a plain engine . Clearances are everything . Is this a cvvt or non cvvt engine? You can tell by oil control valve on head.

 

The head was machined .005 inches. No valve work was needed. Required only pullling cams to machine. Put on new belt and am sure timing is correct.

I believe you are right about the pistons and rings. I squirted oil in the cylinder last night to test #3. It went from the 180 range back to the 210 range. This confirms at least the ring issue.

I bought a newer motor today that has 32M miles. I think this is the smarter route considering cost. The only concern I have now is about the ECM and the fan coming on. Is there a way to test this system out? I couldn't find anything online so far.

 

The way I test the system is to get the temp up to operating. Turn a/c off and put a cloth or a towel over front of car in front of condensor.Looking at current temp on my gds at actual coolant temp value the car will heat up to a specific range and fans will come on either low speed or high . Now you probably dont have a gds so you would have to do it another way. You could backprobe the coolant temp sensor and read voltage output and there is a conversion table to calculate that to temp. Or simply just run the vehicle without a/c on and inspect fans for proper cycle. Elantras didnt have alot of fan issues.Thermostates killed those engines. Change that thermostate every 30k miles.Now as for machining of the head on last engine.....I wouldnt have.Thats at spec and usually with a bad head ya get other bad things.