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My crankcase ventilation modification


 
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granda
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Joined: 13 Nov 2006

PostPosted: Fri Dec 08, 2006 12:09 pm    Post subject: My crankcase ventilation modification Reply with quote

1990 4.0 automatic. Well that tiny tubing that runs from the valve cover to the intake manifold with the"metered orifice" in it clogged on me for the second time in 2 weeks, despite having removed the valve cover and cleaning it and the baffles and the snorkles inside. Today I replaced the stock tubing with 3/8" fuel line and the fittings on both ends with 3/8". Hopefully now it will not clog since there is a full 1/4"-5/16"(approx 6.5mm) I.D instead of the stock 2.6mm. Has anyone else done this? I saved all of the original parts in case I had to convert it back. Is it possible for my new setup to"overventilate"the crankcase?Total cost was about $6 so no big expense. I have searched other threads on this subject but have not read of anyone doing this. Great forum! Thanks.
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88WOWJ
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Joined: 12 Aug 2006
Location: Hinesville Ga

PostPosted: Sat Dec 09, 2006 7:56 am    Post subject: Ventilation Problems Reply with quote

I cant remember does the the 1990 use the same front vent tube as the
1988. Does your front tube cost about $60.00 bucks compared to the 1991. First of all, the back tube has a TSB that some dealers dont have access to. There is a larger tube and orfice and grommet per a TSB.
If you arent using it this may help. Secondly to clean the tube use carb or throttle cleaner on occassion. Spray the tube and the fitting in the intake.
How many miles do you have, you may have a lot of blowby.
_________________
1988 Wagoneer Limited XJ Tellico Tested
Rocklizards panels, Tomken rear bumper and front Tow brackets, Rocket air intake, 2 inch lift,
30x950x15, 1991 coolant system with electric fans, 8,000 mile marker winch
1991 Cherokee Limited
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granda
Member


Joined: 13 Nov 2006

PostPosted: Sat Dec 09, 2006 10:58 am    Post subject: Reply with quote

The dealership parts guy could not find a TSB concerning the rear CCV tube but said a new one of the original size is $16.00. I had soaked the old one in carb cleaner for over an hour and then blew it out with compressed air and thought I got it pretty clean but it clogged again in 2 weeks. I have no sign of blowby-no oil in the air filter box and the front tube from the valve cover to the airbox is clear. I am just hoping that my modification does not reduce the suction strength from the intake manifold so that it is no longer sufficient to pull the fumes from the crankcase. I have 167,000 miles on the engine and it seems to run fine. I am getting 16.2 mpg in combined in town/highway driving. Do you know what the orifice size is on the upgraded (TSB)ccv line is? Thanks.
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