Timing off due to belt "jumping" on V8. Possible?

[shayk]

Here is the scenario. 2003 V8. I owned for 10 years before handing down to my son, who is out of state. Currently has about 260K.
My son was just informed by a mechanic that the timing belt jumped a tooth.


Full backstory
He had a thermostat problem when it was 95 deg and changed it, but put water back in. 6 Months later he took a trip north. It got down to 0 F. He forgot he refilled it with water. Drove it for a few miles after sitting in the cold and the temp gauge showed it was overheating, so he stopped. Realized what he had done. Got it in a garage and put a heater on it. Mechanic looked at it, found no problems, no cracks, but replaced the thermostat.
Son drove 700 miles home. Runs ok, but isn't running the same. Rough idle. Slightly down on power. Said if you didnt know the truck, you wouldnt notice it. CEL light was already on due to 02 sensor. He had the codes read (dont know the numbers) and that showed a misfire on at least 2 cylinders. Replaces plugs and wires, no improvement.
Took it to a mechanic that supposedly spent 20 yeas at a Toyota dealership. His theory is that when the coolant froze, the ice locked the water pump. When the truck was started, the locked water pump caused the belt to jump out of timing. (I assume this would have the be the crank sprocket where it actually jumped)
Compression check number were 200 for the cylinders on one side, and 130 for the cylinders on the other.
I 've replaced the T belt twice, last time around 230K
Mechanic claims he saw this once before. I find it hard to believe the truck could still run half decently.
Is it possible the belt jumped on the sprocket?

 

[Brian3676]

Here is the scenario. 2003 V8. I owned for 10 years before handing down to my son, who is out of state. Currently has about 260K.
My son was just informed by a mechanic that the timing belt jumped a tooth.


Full backstory
He had a thermostat problem when it was 95 deg and changed it, but put water back in. 6 Months later he took a trip north. It got down to 0 F. He forgot he refilled it with water. Drove it for a few miles after sitting in the cold and the temp gauge showed it was overheating, so he stopped. Realized what he had done. Got it in a garage and put a heater on it. Mechanic looked at it, found no problems, no cracks, but replaced the thermostat.
Son drove 700 miles home. Runs ok, but isn't running the same. Rough idle. Slightly down on power. Said if you didnt know the truck, you wouldnt notice it. CEL light was already on due to 02 sensor. He had the codes read (dont know the numbers) and that showed a misfire on at least 2 cylinders. Replaces plugs and wires, no improvement.
Took it to a mechanic that supposedly spent 20 yeas at a Toyota dealership. His theory is that when the coolant froze, the ice locked the water pump. When the truck was started, the locked water pump caused the belt to jump out of timing. (I assume this would have the be the crank sprocket where it actually jumped)
Compression check number were 200 for the cylinders on one side, and 130 for the cylinders on the other.
I 've replaced the T belt twice, last time around 230K
Mechanic claims he saw this once before. I find it hard to believe the truck could still run half decently.
Is it possible the belt jumped on the sprocket?

It's defiantly possible. Hard to believe it did not shred the belt though if the water pump was frozen. Intresting all cylinders one one side of the head have perfectly even low compression. With out further diag, I would say he is likley on the correct track. Hopefully if it is the case it did not bend valves too :-(

 

[shayk]

Hmmm. I was just looking through pictures of timing belt replacement threads. I forgot the water pump drive pulley doesn't have any teeth, the pump is driven by the smooth side of the belt. This theory is making a lot less sense........

 

[AuSeeker]

Here is the scenario. 2003 V8. I owned for 10 years before handing down to my son, who is out of state. Currently has about 260K.
My son was just informed by a mechanic that the timing belt jumped a tooth.


Full backstory
He had a thermostat problem when it was 95 deg and changed it, but put water back in. 6 Months later he took a trip north. It got down to 0 F. He forgot he refilled it with water. Drove it for a few miles after sitting in the cold and the temp gauge showed it was overheating, so he stopped. Realized what he had done. Got it in a garage and put a heater on it. Mechanic looked at it, found no problems, no cracks, but replaced the thermostat.
Son drove 700 miles home. Runs ok, but isn't running the same. Rough idle. Slightly down on power. Said if you didnt know the truck, you wouldnt notice it. CEL light was already on due to 02 sensor. He had the codes read (dont know the numbers) and that showed a misfire on at least 2 cylinders. Replaces plugs and wires, no improvement.
Took it to a mechanic that supposedly spent 20 yeas at a Toyota dealership. His theory is that when the coolant froze, the ice locked the water pump. When the truck was started, the locked water pump caused the belt to jump out of timing. (I assume this would have the be the crank sprocket where it actually jumped)
Compression check number were 200 for the cylinders on one side, and 130 for the cylinders on the other.
I 've replaced the T belt twice, last time around 230K
Mechanic claims he saw this once before. I find it hard to believe the truck could still run half decently.
Is it possible the belt jumped on the sprocket?

I would think if it jumped a tooth at the crank it would affect both banks the same, I'm thinking it somehow slipped at one cam to cause the banks to be so different in compression.

 

[Fern]

If a valve was partially open, wouldn't there be no compression at all and not affect all the cylinders equally.
I would think a head gasket blew since it was overheated would be more likely.
Maybe the water froze in the block pushing the head up stretching the head bolts causing the head gasket to leak.
And, how did the mechanic check for cracks without removing the head?

Just throwing ideas out there.

Or I could be totally wrong which has been the case before.

 

[AuSeeker]

If a valve was partially open, wouldn't there be no compression at all and not affect all the cylinders equally.
I would think a head gasket blew since it was overheated would be more likely.
Maybe the water froze in the block pushing the head up stretching the head bolts causing the head gasket to leak.
And, how did the mechanic check for cracks without removing the head?

Just throwing ideas out there.

Or I could be totally wrong which has been the case before.

If one of the cams slip just a tooth the valves wouldn't be opened at TDC, but it would cause the valves to close later on the compression stroke and thus not get as much compression.