Jeep Wrangler Forum banner
  • Hey everyone! Enter your ride HERE to be a part of September's Ride of the Month Challenge!
1 - 5 of 5 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Hi All, I have posted before and thanks for all the help and advice.....

My post today is about oil blow-by and the causes. The Jeep I am working on is my sons 1991 Wrangler 2.5 with 120K.

I suspected some blow-by when I noticed some oil escaping the top vent tube and hitting the air filter. I figured this was due to a PCV or what I now know as a CVV valve on the side of the valve cover.

In the meantime, I took the Jeep to a well respected specialty shop in my area to have all the fluids changed out....front/rear differential, Tcase, engine...so forth.

My concerns were not major.....just something I was going to address soon. Then, since the shop service, the blow-by seemed to be a much bigger issue. I took the front/side CVV valve and hose off and noticed oil was in the line to the intake....I also noticed oil blowing out the fill cap. This was all over a month a maybe two hundred miles. This jeep is in my garage and not used much since my son went back to college.

I checked the dipstick and the oil level is about 3/4 of an inch above the top mark for safe....so I am thinking it has too much oil. I checked the receipt and it lists 4 quarts of oil and 1 quart of Lucas treatment which I authorized. I looked up the oil capacity which states 4 quarts......so the shop put in 4 quarts of oil + 1 quart of Lucas for a total of 5 quarts.

Could this be my issue? Would too much oil push too much into the valve cover and then start to fill the CVV tubes? Also, would overfilling the engine with oil damage the motor?

I know that most blow-by issues are the venting or worn rings....however I thought that worn rings would also include smoke from the motor and other symptoms which I do not have.

Thanks for any thoughts you may have on this.

Mike
 

·
Premium Member
Joined
·
10,093 Posts
If there is too much oil in yes it will push into the CCV system. They may have put 5 quarts in a 4 qt engine. I would drop by there and have them remove the extra oil and it should go back to normal. The CCV just vents vapors supposedly but they are hot oil vapors that cool on their way to the intake to be burned. When they cool youget an oily residue which sometimes is mmistaken for the engine sending oil to the intake. Asthe engine wears you may get more noticeable residue. It is normal to get some but a lot is an indication of a worn engine or in your case too much oil. Clean what you can andd you should be good to go when the excess oil is removed.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #3 ·
I went to NAPA today to pick up a new CVV valve.....they did not have one and after looking, did not see a supplier to order one. Any suggestions on where to buy one and if not, can I service this one? I am still not clear on how the difference between a CVV and PCV and if I can restore this one.

Thanks.

Mike
 

·
Premium Member
Joined
·
10,093 Posts
OK the CCV is just an opening in the valve cover not an active PCV valve. The attached is from the FSM and it explains the purpose. I would imagine since the size of the opening is fixed you should be able to clean it out with some solvent and blow out with compressed air. I can't find one for sale. But I did find an article with a fix here is the link.

Found a fix for 80s to 90s 4.0L Jeeps with CCV - Bob Is The Oil Guy
 

Attachments

·
Registered
Joined
·
4,917 Posts
mscanon99 said:
I went to NAPA today to pick up a new CVV valve.....they did not have one and after looking, did not see a supplier to order one. Any suggestions on where to buy one and if not, can I service this one? I am still not clear on how the difference between a CVV and PCV and if I can restore this one.

Thanks.

Mike
CrankCase Ventilation (CCV) does not have a check valve. It allows the crankcase (where the oil lives) to ventilate at all times.

Positive Crankcase Ventilation (PCV) has a check valve, and only allows crankcase ventilation under positive pressure.

The ccv can be cleaned with carb type cleaner and a paperclip. The pcv should be replaced at regular intervals.

Too much oil will certainly show more blowby as the pressure is increased in the crankcase. If your rings are just starting to blowby, you may not notice an increase in oil burnoff by smoke. Check at cold startup for blue smoke, best sign of rings or valve stem seals being comprimised.

Overfilling can hurt an engine, but I have seen em run with 2xs the oil capacity in them (oh those dealer lube kids, lmao). Depends on the motor, but you should be fine.
 
1 - 5 of 5 Posts
Top