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Oil blows out CCV intake during operation

Oil blows out CCV intake during operation

Oil blows out CCV intake during operation

Hi, I've just completed the replacement of piston rings and valve seals on an 1988 Jeep Cherokee inline six. Reason for doing the above was an attempt to stop the crankcase oil from being blown out the air intake for the CCV system. The oil has been clogging the air filter and draining from the air filter box. I've checked all hoses for clogging and replaced the CCV 12mm outlet tube to no avail.
Any suggestions as to what is the cause and how to correct?

RE: Oil blows out CCV intake during operation


So, it sounds like excessive crankcase blowby?

Leaky valves will make it run poorly, but won't really affect crankcase blowby.

1. is the PCV valve clean and functioning, and is the vacuum *port* serving it open and unobstructed?

(does the apparant blowby increase a lot when the PCV valve is pulled from the valve cover?)

2. was there a baffle keeping oil splash away from the breather tube? Was anything changed to cause a *lot* more oil to be flowing and splashing around in the valve cover area?

3. How were the pistons and cylinders when you did this? did you re-bore it and fit new pistons, or just give it new rings? Worn ring grooves can prevent proper sealing. So can worn cylinder bores. Sloppy pistons (in the bore) could keep the rings from working properly.

(Please, I don't mean to insult you by throwing out these basics!)

3. You might have a "leakdown test" performed on the motor, to see if the rings are sealing well.


RE: Oil blows out CCV intake during operation

Thanks for the quick response Jay!      and no insult taken.....
1. This system doesn't use a PCV valve. (12mm tube is used to syphon off the gases, the larger tube(which is dumping the oil is used as an air intake(not)).
 No increase in blowby when this is pulled.

2. There is a baffle in the valve cover. It was cleaned with varsol,flushed and dried prior to reassembly. There was a small clear plastic perimeter gasket?(like clear wrap material) in this assembly which had disintegrated(was discarded).

3. Just new rings were installed. The cylinders and bore were not touched(honed only). I've done this procedure on 2 other vehicles with noticable improvement. This vehicle has been back in operation for 2 weeks and the oil is still new coloured. The previous 2 vehicles had oil blackening in the same time period which would suggest  blowby in the ring area.
As suggested, I'll check into the leakdown test.

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