Monday, April 24, 2006

Blow by on an Aging 4.0L

4.0 oil blow by problem
Engine repair problem

A common problem with aging 4.0L's is excessive oil blow by. On some engines oil blow by is a sign of a trashed engine, but in many cases a Jeep 4.0L has a lot of life left even after oil starts to appear in the air filter.

My 1991 Jeep Cherokee Laredo has over 250000 miles on it and is still going strong. I have eliminated the factory air box on this Jeep so I had to design a different collection system for the blow by. I routed a tube form the top of the valve cover to an old brake fluid bottle to catch the drips. There is a small hole drilled in the bottle to vent excess vapors. The oil in the bottom of the bottle acts as a filter for any air that is drawn in. I also enlarged the orifice in the vacuum line from the valve cover to the intake.

On our 1988 4.0 we added an old oil bottle for a catch can and enlarged the tubing for the vacuum line. Also we replaced the orifice in the valve cover grommet with a quarter inch plastic tube.

Or you can cure the whole problem completely by replacing your aging engine with a new stroker motor from Titan engines like I did on my Rally Jeep.



Anonymous Alex said...

I have a 1988 Jeep Cherokee laredo like yours, and I am having many overheating problems still perplexed by why after I have cleaned out the entire system from rust over the years. Now there might be a problem with the water pump not pumping the water through or I have a bad radiator. If you know anything please late me know. is how you can reach me

4:48 PM  
Anonymous Alex said...

Hey, I don't know if my last comment went through, but I can still be reached at
I was also wondering how you got titan engine in your jeep and how much did it cost.

4:53 PM  
Anonymous Anonymous said...

I did this process as stated but now i have smoke coming in the cabin? do i need oil in the can to prevent this?

2:55 PM  

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