Blowby issue?

[88msftcomanche]

I think i may have a blowby issue on my hands and wondering if you guys could help me out. I have been trying to pin point a strange oil leak for a while and have checked almost everywere and seemed to find nothing. The other day i took the manche on a 15 min drive on the highway and stopped and when i did it smelled like oil..bad. so i opened the hood and noticed oil all around the oil cover area but not on the hood. I only notice the leak bad when at high rev's. I have an aftermarket breather on that seems like it could be a little loose and kind of $#!&ty really. I have a K&N cone filter so i l really don't have a place to plug in a good pcv hose. Should i just go back to stock air filter and hose or is there a better aftermarket breather i could buy that is better for highway use. Any input would be appreciated!! thanks guys :cheers:

[88msftcomanche]

have to start driving the comanche on the highway more often pretty soon and do not want to have to deal with this happening every time :dunno:

[Boots]

Do you have the little hose that goes from the back of the valve cover to the intake manifold?

If so, try cleaning it realy good. The plastic string stuff from a weed wacker works pretty good to break up the gunk.

[Eagle]

Are you saying that you have removed the air INLET hose from the stock air box the the valve cover, and installed a stand-up style breather cap directly on top of the valve cover?

 

That tube is the air INLET. It pulls clean air through the air filter INTO the engine. If you replaced it with a breather cap, it should also be functioning as an INLET. If you're getting oil pushed out of it, you do have a blowby problem. Part of it could be that the suction line (the very small tube off the back end of the valve cover, to the intake manifold) is clogged. However, if your rings are worn and the engine is generating a lot of blowby, even an open CCV tube probably can't keep up. If the blowby generates too much pressure in the crankcase for the CCV system to handle, the excess is forced out the inlet (reverse cycle), with however much oil fumes are in the mix.

 

Start by running a compression check.

[88msftcomanche]

Do you have the little hose that goes from the back of the valve cover to the intake manifold?

If so, try cleaning it realy good. The plastic string stuff from a weed wacker works pretty good to break up the gunk.

 

Yeah the back hose is connected, then of course i have my oil cap and then i have the aftermarket breather.

[88msftcomanche]

Are you saying that you have removed the air INLET hose from the stock air box the the valve cover, and installed a stand-up style breather cap directly on top of the valve cover?

 

That tube is the air INLET. It pulls clean air through the air filter INTO the engine. If you replaced it with a breather cap, it should also be functioning as an INLET. If you're getting oil pushed out of it, you do have a blowby problem. Part of it could be that the suction line (the very small tube off the back end of the valve cover, to the intake manifold) is clogged. However, if your rings are worn and the engine is generating a lot of blowby, even an open CCV tube probably can't keep up. If the blowby generates too much pressure in the crankcase for the CCV system to handle, the excess is forced out the inlet (reverse cycle), with however much oil fumes are in the mix.

 

Start by running a compression check.

 

Don't want to confuse anybody. I got the back hose connected, then got the oil cap of course and then i have an aftermarket breather that looks like a min cone filter near the front. Thanks eagle i will do this asap! :thumbsup:

[sinkrun]

Every early 4.0 I had did this even low mile motors I have even bought all new CCV tubes and lines. Nothing ever worked until I bought a newer 4.0 valve cover mines of a 2001 4.0 had to do a little adapting of the breather hoses this stopped 99% of my blowby. Reason is the older 4.0 valve covers have a bad baffle system in them the newer have a full length baffle. There are pics and write ups on here I will see If I still have the book marked.

[sinkrun]

Here ya go and you will be glad you did! http://www.naxja.org/forum/showthread.php?t=906582

[88msftcomanche]

Thanks alot sinkrun! :thumbsup: Ill check that out asap! :wrench:

[Exgrayxj]

Did something similiar on a 90 XJ. Eliminated most of the vacuum hoses, put a pcv valve in the rear hole, a twist in breather in the middle.

My rear hose, (the one that takes the place of a pcv valve) was clogged, and making excessive pressure in the engine, pushing oil out where ever it could, rear main, etc.

Just remember, there needs to be vacuum and a breather, and where the vacuum is needs to be restricted or baffled, or it will suck oil out of the motor. Check or Help, or Motormite(?) at the parts store vacuum is where care is needed.

Some thought required, not hard to do tho.

[88msftcomanche]

Thanks guys for all the help just waiting for the weather to get a little better and will work on doing the later xj swap i think. It will prob last longer and be more beneficial in the long run and who doesnt like new stuff

[sinkrun]

My cover was under $20.00 with shipping from ebay just make sure it comes with grommets inserts (if it the 97up) you will need them and the gasket to be from the same year xj and there not cheap but they do work well and can be reused no sealer needed.