Is it time for a rebuild? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

samdamanzo · 01-04-2016, 01:02 PM

I bought an s14 about a month ago, test drive drove fine, the first few days it drove great, and then it started leaking oil out of the breather valve. I figured it was just the oil catch can was full because PO told me it had been over filled with oil a little bit. It really started to leak so I took it to a buddies, did a compression test, and cylinder 2 had 100 psi, then 70 psi, then 30, then 0. Absolutely no compression and then I pulled the oil cap on the valve cover and it had blow by. The car also was spitting out white exhuast right before I pulled up to my buddies. The weird thing is the car never felt like it lost power on the road, which is what I'm so confused about.

Kingtal0n · 01-04-2016, 01:51 PM

air coming out of the valve cover is normal on the running engine.

You need to make sure 100% beyond reasonable doubt that there is no compression. Your test might have been a failing compression tester.

Repeat the test with a known good tester. Then try to find out where the compression is going. White smoke and bubbles from the radiator indicates head gasket.

samdamanzo · 01-04-2016, 01:53 PM

There was smoke from burning oil in the valve cover not just air, and the spark plug had oil on the bottom of it(the cylinder with our conpression).

Kingtal0n · 01-04-2016, 06:27 PM

Diagnostic procedure is,

1. compression test (If you dont know how, ask someone will help)
2. audible/visual inspection on running engine like you have been doing, good job. Oil on plugs is a bad sign, but it could come from the valvecover gasket so be sure that it is indeed coming from within the cylinder which indicates a broken piston/ ring problem.

Oil vapors from the valve cover is also not necessarily a "bad engine" diagnosis, there are other ways you can get an oil vapor such as PCV blockage or incorrect PCV routing. This is part of visual inspection. If you need a PCV diagram you can ask I have a few.

3. leakdown test, requires air compressor. You only do this after exhausting other options because it can be inconclusive if you do not have experience.

Start there...

samdamanzo · 01-05-2016, 07:34 PM

Can you link the pcv diagram? I took a look at one and it has a breather filter (out of the catch can I believe?) Instead of routing it back into the intake.

samdamanzo · 01-05-2016, 07:36 PM

The buddy I took it to almost immediately said it was a ring land or ring or something inside the piston, but I wanted to make sure before I start pulling it apart. He is a trained mechanic so I'm assuming he's probably right.

SoundEfx · 01-07-2016, 10:00 AM

If I'm not mistaken, white smoke is burning coolant and blue is burning oil. So I would think that if your ring lands are bad, you would get more blue smoke than white.

Other pros on here should chime in with more info though.

Kingtal0n · 01-09-2016, 06:10 PM

Here is the OEM routing for PCV on every OEM engine (almost) ever made, that came factory with a turbocharger

The port you see on the right side can be anywhere on the engine, but on sr20det it is on the valve cover. So think of that port as the top port on the turbo side of your engine.

The valve on the left labelled "Pcv valve" is on the other side of the valve cover, attached to the intake manifold.

Do not use a catch can (yet). first diagnose and use the OEM route. You might have a bad pcv valve for example, that will sure simulate bad rings. Would suck to tear an engine down over a $8 check valve right? So identify and properly diagnose, do those things I listed, take your time.

jr_ss · 01-10-2016, 11:57 AM

The suction of the intake pulls air out of the crank case, it does not feed the crankcase, as you have depicted in your fancy drawing.

Kingtal0n · 01-11-2016, 01:51 PM

Quote:

Originally Posted by jr_ss

The suction of the intake pulls air out of the crank case, it does not feed the crankcase, as you have depicted in your fancy drawing.

depends on boost or off boost. during cruise/idle the airflow in the drawing is depicted. It does indeed supply the crankcase, lest the crankcase vacuum escalate to the point of oil seal failure or deprived oil pump. The factory also uses a restrictor in this line for maintaining a somewhat consistent vacuum signal.

more discussion
http://www.performanceboats.com/gn7-...um-pump-3.html

Quote:

Originally Posted by GearHead

Vacuum is good and it helps keep the boat and/or car stay cleaner. I believe Bob and Bob have covered the subject pretty well. If one looks back at the Grumpy Jenkins study, he said one of the best performing pans was one with a large box style sump to let the oil sling away from the crankshaft. I have used this theory in several competition eliminator engines that mandated wet sump pans with good outcome. Now as has been mentioned, the dry sump has better oil control, but turning all those pump stages does not come without some power losses due to turning the pump.

Dry sump is best all around in oil control and the amount of vacuum one can pull. It is generally worth 40 to 70 HP on a decent machine. Comparing with a bad design it can be worth more. One can pull 20+ inches of vacuum as you are just pulling against atmosphere.

A big wet sump pan and vacuum pump are much cheaper. However one cannot pull the same amount of vacuum as the dry sump because in the wet sump you are pulling against the oil pump and too much vacuum can cause oil pump cavitation.... aereate the oil and damage bearings and crankshaft. With a better oil pump, the more vacuum one can run. Typically I have kept the vacuum to a maximum of 13" in a wet sump. However, the first 5 to 8 inches have the largest gain. As mentioned, oil pan and ring drag do affect the actual power, but pretty well one can see a 20 to 40 hp gain with just the vacuum pump and generally more in the 10 hp range with an evac system.

I made a more detailed post about this discussion, here
http://zilvia.net/f/showpost.php?p=5736274&postcount=4

01-04-2016, 01:02 PM	#1
samdamanzo Join Date: Dec 2012 Location: Georgia Age: 24 Posts: 15 Trader Rating: (0) Feedback Score: 0 reviews	Is it time for a rebuild? I bought an s14 about a month ago, test drive drove fine, the first few days it drove great, and then it started leaking oil out of the breather valve. I figured it was just the oil catch can was full because PO told me it had been over filled with oil a little bit. It really started to leak so I took it to a buddies, did a compression test, and cylinder 2 had 100 psi, then 70 psi, then 30, then 0. Absolutely no compression and then I pulled the oil cap on the valve cover and it had blow by. The car also was spitting out white exhuast right before I pulled up to my buddies. The weird thing is the car never felt like it lost power on the road, which is what I'm so confused about.

01-04-2016, 01:51 PM	#2
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	air coming out of the valve cover is normal on the running engine. You need to make sure 100% beyond reasonable doubt that there is no compression. Your test might have been a failing compression tester. Repeat the test with a known good tester. Then try to find out where the compression is going. White smoke and bubbles from the radiator indicates head gasket. __________________ 5.3/4l80e/turbo 240sx playthrough: https://tinyurl.com/turbo240

01-04-2016, 06:27 PM	#4
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	Diagnostic procedure is, 1. compression test (If you dont know how, ask someone will help) 2. audible/visual inspection on running engine like you have been doing, good job. Oil on plugs is a bad sign, but it could come from the valvecover gasket so be sure that it is indeed coming from within the cylinder which indicates a broken piston/ ring problem. Oil vapors from the valve cover is also not necessarily a "bad engine" diagnosis, there are other ways you can get an oil vapor such as PCV blockage or incorrect PCV routing. This is part of visual inspection. If you need a PCV diagram you can ask I have a few. 3. leakdown test, requires air compressor. You only do this after exhausting other options because it can be inconclusive if you do not have experience. Start there... __________________ 5.3/4l80e/turbo 240sx playthrough: https://tinyurl.com/turbo240

01-07-2016, 10:00 AM	#7
SoundEfx Zilvia FREAK! Join Date: Aug 2015 Location: WA Posts: 1,230 Trader Rating: (1) Feedback Score: 1 reviews	If I'm not mistaken, white smoke is burning coolant and blue is burning oil. So I would think that if your ring lands are bad, you would get more blue smoke than white. Other pros on here should chime in with more info though. __________________

01-09-2016, 06:10 PM	#8
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	Here is the OEM routing for PCV on every OEM engine (almost) ever made, that came factory with a turbocharger The port you see on the right side can be anywhere on the engine, but on sr20det it is on the valve cover. So think of that port as the top port on the turbo side of your engine. The valve on the left labelled "Pcv valve" is on the other side of the valve cover, attached to the intake manifold. Do not use a catch can (yet). first diagnose and use the OEM route. You might have a bad pcv valve for example, that will sure simulate bad rings. Would suck to tear an engine down over a $8 check valve right? So identify and properly diagnose, do those things I listed, take your time. __________________ 5.3/4l80e/turbo 240sx playthrough: https://tinyurl.com/turbo240

01-04-2016, 01:53 PM	#3
samdamanzo Join Date: Dec 2012 Location: Georgia Age: 24 Posts: 15 Trader Rating: (0) Feedback Score: 0 reviews	There was smoke from burning oil in the valve cover not just air, and the spark plug had oil on the bottom of it(the cylinder with our conpression).

01-05-2016, 07:34 PM	#5
samdamanzo Join Date: Dec 2012 Location: Georgia Age: 24 Posts: 15 Trader Rating: (0) Feedback Score: 0 reviews	Can you link the pcv diagram? I took a look at one and it has a breather filter (out of the catch can I believe?) Instead of routing it back into the intake.

01-05-2016, 07:36 PM	#6
samdamanzo Join Date: Dec 2012 Location: Georgia Age: 24 Posts: 15 Trader Rating: (0) Feedback Score: 0 reviews	The buddy I took it to almost immediately said it was a ring land or ring or something inside the piston, but I wanted to make sure before I start pulling it apart. He is a trained mechanic so I'm assuming he's probably right.

01-10-2016, 11:57 AM	#9
jr_ss Post Whore! Join Date: Dec 2005 Location: Pa Posts: 6,056 Trader Rating: (34) Feedback Score: 34 reviews	The suction of the intake pulls air out of the crank case, it does not feed the crankcase, as you have depicted in your fancy drawing. __________________ My SR20VET

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode