Oil in The Turbo
#1
01-01-2010, 01:13 PM
Oil in The Turbo
While performing a thorough inspection on my Volvo 850, blobs of oil was found in the turbo. I was almost about to replace the turbo, but decided to perform additional inspection. A mechanic friend of mine performed compression test on all five cylinders. Cylinder # 3 has 20% leak around the piston. In other words, the crankcase is getting pressurized to a degree (higher). The PCV system is in good shape, and it does vent the pressure back to the inlet of the turbo.
Is it possible that the blow-by might be cause the oil (from the crankcase) to seep into the turbo via the PCV hose that is connected to the PTC valve?
I attached a pressure gauge to the PCV hose which connects to the PTC valve, and it does show positive pressure. I don’t know what the normal pressure reading should be when the blow by is within normal limits. Does anyone know what the normal pressure would be if the blow by is within normal limits?
My car is a 1996, Volvo 850 Turbo with 130K miles. Now I have to decide if I should replace the piston rings cylinder # 3. Yesterday I performed an oil change after using one of the BG oil products that is known to restore compression. How easy/hard is it to replace the piston rings? Can I drop the oil pan and reach the piston by disconnecting the rod from the crankshaft? Should I also replace the piston?
Is it possible that the blow-by might be cause the oil (from the crankcase) to seep into the turbo via the PCV hose that is connected to the PTC valve?
I attached a pressure gauge to the PCV hose which connects to the PTC valve, and it does show positive pressure. I don’t know what the normal pressure reading should be when the blow by is within normal limits. Does anyone know what the normal pressure would be if the blow by is within normal limits?
My car is a 1996, Volvo 850 Turbo with 130K miles. Now I have to decide if I should replace the piston rings cylinder # 3. Yesterday I performed an oil change after using one of the BG oil products that is known to restore compression. How easy/hard is it to replace the piston rings? Can I drop the oil pan and reach the piston by disconnecting the rod from the crankshaft? Should I also replace the piston?
#2
01-01-2010, 09:53 PM
Simply replacing piston rings isn't that easy. What was the actual compression of cylinder #3?
And yes, excessive blow- by will cause oil to get into the turbo, but with only 130k miles, I'm surprised to see that sort of engine problem, unless this car has been abused.
Anyhow, to replace rings, it's possible to do it with the engine in place... but it's not recommended. You have to remove the head, remove any ring ridge at the top of the cylinders, then measure the cylinder diameter. If it's within spec, you hone the cylinder walls and replace the rings on all cylinders. While you're in there, you should replace the rod bearings, as well. If the cylinder wall is out of spec, or has any scoring or other damage, you have to have the whole thing rebored to an oversize, then use new oversized pistons and rings.
And yes, excessive blow- by will cause oil to get into the turbo, but with only 130k miles, I'm surprised to see that sort of engine problem, unless this car has been abused.
Anyhow, to replace rings, it's possible to do it with the engine in place... but it's not recommended. You have to remove the head, remove any ring ridge at the top of the cylinders, then measure the cylinder diameter. If it's within spec, you hone the cylinder walls and replace the rings on all cylinders. While you're in there, you should replace the rod bearings, as well. If the cylinder wall is out of spec, or has any scoring or other damage, you have to have the whole thing rebored to an oversize, then use new oversized pistons and rings.
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