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Possible blown motor help!!!

 
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Old 26 Feb 2018, 03:25 am
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Default Possible blown motor help!!!

I was racing one of my friends and I was flooring it to 6,000 rpm, I know it was so stupid, but the car just shut off, the oil light came on, and my oil pressure was zero. The car started back up but now when I go over 1500 rpm the car starts knocking in the top end. I know for sure itís the top end because I went under the car and it was louder at the top end than the bottom. Turbo motor. It idles fine. No knocks, rattles, misfires. 137,000 miles. Timing belt needed replacing but I know the timing belt is fine or else it wouldnít start. Any load below 1500 rpm does not make it louder. Strictly rpm makes the noise louder. Please help! Itís unusual for the motor to just turn itself off at 6k rpm and be kind of fine afterwards.
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Old 26 Feb 2018, 08:34 am
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Default Re: Possible blown motor help!!!

Remote diagnosis of noises is difficult. Be sure to run the car past an experienced engine guy, they can get a pretty good idea within in a minute of listening.

I've had engines where rod bearings wore enough that the piston would hit the cylinder head, this would account for top end noise.

My test for rod bearings is:

Hot engine

Bring RPM to the point where you hear noise ( usually the 1,500 you speak of ) .

Quickly snap the throttle open another 50 % then closed to idle, you do not need to go past 2,500 to 3,000 RPM. The goal is to quickly load then engine and see if the noise increases _sharply_ then goes away as the RPM drops from 3,000 to where the noise was first.

For rod bearings, higher load = more noise.

For other sources of noise, generally higher RPM = more noise regardless of load.

With large bearings clearances, oil squishes out and the rod bearing is no longer floating on a film of oil. This will allow the rod bearing to bang around.

The rod bearing insert is only 1/3 of the bearing system, the smooth / round surface of the crank shaft journal is another part. If the journal is damaged, rolling in another bearing won't help. The last 1/3 is the connecting rod, this keeps the bearing insert round and can be damaged by an old badly worn insert.
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Old 26 Feb 2018, 12:48 pm
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Default Re: Possible blown motor help!!!

Regardless of load my motor knocks in the top end. It canít be the rod bearings. Maybe I dropped or bent a valve?
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Old 26 Feb 2018, 01:13 pm
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Default Re: Possible blown motor help!!!

Oil pressure is the key. Do you have normal oil pressure now?

Spinning a rod journal will often allow it to really leak and that can drop your oil pressure. And even if the noise sounds like it's in the top of the engine, it could still be a rod in some circumstances.

If me, I'd likely start with a compression test. This will help you tell if it's a bad valve, plus it's easy to do. If compression looks okay, I'd like drop the oil pan which is fairly easy on a PT. Based on what's been said, my gut still tells me to think spun rod bearing.
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Old 26 Feb 2018, 02:30 pm
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Default Re: Possible blown motor help!!!

Another possibility is the bolts on the flexplate are loose and wrecked the plates on the torque converter.
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Old 26 Feb 2018, 04:19 pm
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Default Re: Possible blown motor help!!!

I wonder if a rocker slid out of place and is getting hammered by the camshaft. Pull the valve cover and have a look. Being these are 4 valve motors, losing a rocker on one valve won't affect idle quality.

If an exhaust rocker came off, this would make for a massive EGR effect at high RPM but still have a good idle due to lower exhaust flow, this could shut the engine down. I'm thinking the engine shut off first then no oil pressure from the non running engine.
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Last edited by 06_PB6_TOURING; 26 Feb 2018 at 06:34 pm.
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Old 26 Feb 2018, 05:16 pm
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Default Re: Possible blown motor help!!!

I believe that the PCM has been programmed to shut off the injectors on non-turbo at around 110 mph and on the Turbo about 120/130.
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Old 27 Feb 2018, 08:44 am
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Default Re: Possible blown motor help!!!

The speed / rev limiter should just start dropping injector pulses at top speed not do a total shutdown, that would be very unsafe. ( RE when speed drops, the pulses resume )
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Old 27 Feb 2018, 04:34 pm
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Default Re: Possible blown motor help!!!

I pulled the valve cover, no visible damage. The sound seems like it is coming from the camshafts. When I rev the motor up the sound gets faster and louder. I checked the plugs, they look fine. They are a little yellow white. I noticed more air is coming from the oil cap hole.
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Old 27 Feb 2018, 04:42 pm
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Default Re: Possible blown motor help!!!

Quote:
Originally Posted by 06_PB6_TOURING View Post
I wonder if a rocker slid out of place and is getting hammered by the camshaft. Pull the valve cover and have a look. Being these are 4 valve motors, losing a rocker on one valve won't affect idle quality.

If an exhaust rocker came off, this would make for a massive EGR effect at high RPM but still have a good idle due to lower exhaust flow, this could shut the engine down. I'm thinking the engine shut off first then no oil pressure from the non running engine.
It does sound like that’s possible based of the physical noise but I looked at the lifters and they look like they are all in place.

Last edited by kcabe1; 27 Feb 2018 at 04:44 pm.
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