Blowback

[GothicSunrader]

I’m getting blowback oil in my air filter. About a tablespoon after 300 miles of driving. I’ve recently changed my pcv valve.  Still does it.  1984 Nissan Sunrader (720 pickup chasis). 90,000 miles with recently rebuilt top end after head gasket blowing. Ideas?  Just live with it?   

[linda s]

No it might be something serious. Google oil blow back in air filter nissan z24. There are a bunch of possibilities and things you can try to locate the problem on the Nissan sites. Worse case scenario the head gasket wasn't done right. 

Linda S

[GothicSunrader]

So I’ve done the following with no improvement

1) changed PCV

2) engine oil flush and change with heavier weight oil

 

What to try next?  

 

[extech]

i would have a shop do a leakdown test on it. it will pinpoint rings, head gasket, or whatever. 

  if you pull the air into valve cover hose and put a dollar bill over the hole, with engine running the bill should be held to the cover. this will varify pcv system

  was the pcv specificly for your engine or generic

Edited April 7, 2022 by extech

[GothicSunrader]

The replaced pcv valve was just what it said that engine took on Amazon or parts geek, can’t remember. It was cheap though. 6 bucks. The one I replaced seemed like it was functioning. Made a sound when I shook it, just like the new replacement. But I changed it anyway, just to be sure. 
 

What do you think about putting a catch can in there so at least the blow-by oil doesn’t go to the air filter housing?

[WME]

Ive used a catch can before. Ended up with about 2/3 cup of fluid every 3000mi oil change. I don't know if the engine heat would boil off the water, but for sure it didn't get into the engine.

[fred heath]

Road draught tube. Won’t pass smog but will pull the blow back from the engine compartment.

[linda s]

Just in case a simple thing might work. The z24 will blow back if the oil is too full or if the oil cap is not on tight

Linda S

[GothicSunrader]

Thx all for the input.  My fear is that it is a harbinger for a major repair and I just don’t feel I can drop another $4k on a repair. So I’m  wanting to somehow fix it easily or limp along until it bites the dust, which could be years in a best case scenario. 
 

I’m thinking another engine oil flush followed by even heavier oil and some Lucas too.  Then maybe install a catch can so the blow-by at least doesn’t go to air filter housing. 

[thewanderlustking]

First off I wouldn’t bother with an  “engine or oil flush” as I haven’t seen a single shop in 25 years that still has one of the actual machines to do it.  There might still be one out there somewhere, but they went away for a reason. A simple cleaner, like BG sells, and an oil change are more than enough.  And even this is probably too much. 
 

A little oil on the air filter really isn’t even an issue UNLESS it is getting sucked into the engine airstream and causing pinking or detonation.   Engines are designed to handle some, hence the design of the PCV system. 
 

A new pcv valve also doesn’t mean it is good. Test it. Verify. It’s a cheaply made and very basic part. 
 

You can do a head gasket test super easily yourself. Autozone has a block test kit. It’s $30 or a free rental. They might charge you for a bottle of test fluid. Very easy to do. Watch a few videos. Since a head gasket has recently been done, this would be a good idea to do just to verify. 
 

But before you chase potentially imaginary issues, is the engine even running poorly???  If not, leave it alone!  At most, do your block test for some extra piece of mind. 
 

If you want to be paranoid, setup an inspection interval. Maybe every 1000 miles check or even change the air filter. Take a picture of the filter and your odometer. This would be a simple way to see if it gets worse. 

Edited April 9, 2022 by thewanderlustking

[GothicSunrader]

Thx, Wanderlustking.   That sure is a great, no BS answer. I like your style. (I suffer from a bit of wander lust me self). 
 

Regarding the engine flush.  I’m referring to the product you put in the oil, run the engine for 5-10 minutes. Then dump the oil. Supposed to clean passages and improve flow and “maybe” reduce blow-by.  Is that what you are referring to?  This doesn’t require equipment.  Some have advised it can take more than one time to make a difference.  
 

After the $5k of rebuild and new clutch two years ago, the engine is running great. I’m very happy with it. So my blow-by issues are not resulting in it running poorly. (BTW this last expenses is why I just don’t feel I can sink yet more into the project). 
 

No pinging or detonation. 
 

The PCV was changed and the new one made noise when shaking.  But so did the one I replaced.  So how to test if the PCV is working?  Any ideas here greatly appreciated.  I’m reluctant to just put in another, unless you’d give me good arguments why it’s a good idea.
 

I’ll do the block test you recommend. It’d actually give me a lot of peace of mind to see it turn out good since I recently dropped $5k on it.   That’s what I’m hoping at least. Then ignoring it might seem more prudent (which is actually my inclination here). 
 

I do check the air filter housing after each 300 mile gas up and dab the 1 or 2 tablespoons of oil that has accumulated. I change the air filter frequently too. 

Edited April 9, 2022 by GothicSunrader
Typo

[GothicSunrader]

LindaS:  Thx for the help. That is good input regarding oil cap and levels.  Always wise to check the easy stuff first.  
 
I think I’m good here unless for some reason the recommended capacities I’m operating under are wrong.  That’d be a hoot if that were the case, but a cheap (my kind of ) fix.  I recall it being 4.2 or 4.5 qts w oil filter. I don’t remember now but always just google it when needed. Dipstick on this rig is only marginally helpful.