jereli

So I re did my compression test with all spark plugs out and throttle fully open. Here are my results:

Cylinder 1- 30psi
Cylinder 2- 120psi ( first time I checked compression on this was about 150psi.. I couldn't thread the gauge hose in all the way this time it looks like the first couple threads on the head are damaged.. Maybe why I am getting 120psi this time.
Cylinder 3- 150-155psi
Cylinder 4- 140psi
Cylinder 5- 150psi
Cylinder 6- 140psi

How do I go about doing a leak down test? I will be buying a leak down tester tomorrow but do not know how to do it.

Thanks

james92toy

I don't really know the proper way to use one but this helped me confirm that i had a bent valve . This is what i did. Bought a cheap harborfrieght leak down tester.

Take off radiator cap.
Take off rubber boot to throttle body.
Take valve cover off on side that has bad compression .
Rotate motor till valves on bad cylinder closed (compression stroke)
Hook up leak down tester . Get some air flowing in there .
Open throttle body , listen for air . If you here air that means intake valve is bent and leaking .
Bubbles in radiator , head gasket leak.
Air coming out exhaust , bent exhaust valve.
Air coming out inside motor , bad piston , rings.

Or your valves could be out of adjustment and letting them leak.

jereli

How much air should I pump in there? And when I rotate to engine to the compression stroke on that cyclinder will all other cylinders be in compression stroke as well or will I have to rotate the engine for each cylinder?

Also, what do you guys think about those psi numbers I am getting on the other cylinders?

Thanks

nv4runner

The other cylinder numbers look okay. The leak down tester will have instructions about how much pressure to use. To do a leak down test on all of the cylinders you will have to turn the crankshaft to match up each cylinder with its compression stroke. As stated above, the easiest way is to watch the valves and stop when the valves for that cylinder are both closed. At the same time the valve covers are a bit of a pain to take off on these engines, so you might want to make yourself a gauge out of a coat hanger or a wooden dowel that you can stick in the spark plug hole to find TDC. If the leak down on that cylinder is horrible keep turning the crankshaft until it comes back to TDC (1 revolution of the crank) and try it again. You should also probably position your wrench/ratchet/breaker bar on the crankshaft so that it can't move in either direction while doing the leak down test. Otherwise the pressure could potentially turn the engine and you'd have to reset it.

jereli

So if I do this test with valve covers on where would I listen for air leak from the valves if the covers are on? Im guessing on driver side i can listen by removing oil fill cap but what about passenger side.

Also, you guys mention air coming out from the motor it would be a piston but where from the motor will I be listening for air?
Thanks

scope103

I would recommend a plastic straw instead of a coat hanger or wooden dowel to find TDC. If you accidentally mash it you won't hurt the piston/cylinder/head. Definitely don't use a screwdriver.

Supposedly, you listen at the dipstick tube (for leaking past the rings into the crankcase), the oil filler cap (for leaking past the valve guides), the exhaust (exhaust valves), and throttle body (intake valves). Remove the radiator cap to look for bubbles (I'm not sure how air would make it there; I would look for "surging" of the coolant level.)

jereli

So if its leaking on the passenger side valve will that also be heard from the oil fill cap?

millball

Valve leakage will be heard thru the throttle body if intake valve is leaking and thru exhaust pipe if exhaust valve is leaking. Leakage heard thru the oil filler would likely be from rings.
The valve cover should probably come off the side that has the weak cylinder so that the valve clearances can be checked/corrected. If It were mine, I would check and correct all valve clearances on both sides if it turns out that tight valves are the problem with your low cylinder.
You might end up having to do a valve grind.

jereli

Okay so I picked up a leakage tester... Cylinder one was leaking 55% which is moderate according to my gauge.. All other cylinders except for cylinder 2 were about 20% which is low on the gauge. Cylinder 2 I couldn't test since the threads got messed up so I will have to try and fix those threads.

I could not hear any air escaping from exhaust, intake, oil fill cap, or no bubbling in radiator but I did hear a lot of air escaping from the spark plug holes from cylinders 3, & 5. Most of the air was escaping from spark plug 5 hole. While the gauge was reading 55% leakage it would slowly climb to under 40% leakage.

millball

Where were you applying the air pressure when you heard the leaking from the #3 and #5 spark plug holes?

jereli

I was applying it to cylinder 1 where I had low compression through the spark plug hole.

millball

Sounds like your leak is at the # 1 intake valve and the leak was heard at the other cylinders on that bank because their intake valves may be open when #1 is on compression stroke. Can't totally rule out head gasket yet though.
You need to check the #1 intake valve clearance before proceding much further.

oldblue

i find sometimes its hard to hear or feel air coming out the tailpipe. i don't smoke anymore, but ill grab one from someone who does and light up a cigarette and blow smoke across the tailpipe and see if the smoke will blow rearward indicating a faulty exhaust valve/seat. i personally haven't seen a leak down test that has air coming out of another cylinders plug hole, not sure how that would even happen. read the directions carefully and try the test again and see what you come up with.

jereli

Yea I will need to remove the valve covers..I can still use the same plenum casket and valve cover gaskets right? I changed them about a week ago..

I am pretty sure I was doing it right..all other cylinders checked out okay. Found TDC on #1 pumped air and air leaked out of #3 and #5. I will check valve clearences once I get the covers off.

jereli

There wasn't much of instructions with the leakage tester. Harbor freight, probably cheap but looks like it will do the job.

oldblue

i just can't wrap my head around how air is coming out of another cylinders plug hole. are you hearing it, or feeling it? your ears can play tricks on you big time. grab a cigarette and a straw and blow smoke through the straw and across those plug holes and see if the smoke blows away from the holes. i HIGHLY doubt that is the case. when doing the leak down test on cyl #1 you do have it on top dead center COMPRESSION correct? even if you didn't and one of those valves was slap wide ass open, i still don't know how air could escape from those plug holes on another cylinder. i suspect you are hearing air pass through the exhaust manifold from a leaking exhaust valve on that cylinder. also, you shouldn't have to remove the valve covers to do the other cylinders. as stated, use something (i use a long 1/4" extension) through the spark plug hole and rotate engine until you find tdc. if leak down is 100%, rotate crank 180 back to tdc and see what you get.

scope103

Each to his own, but if you accidentally crank a piston into that extension, you won't even SEE the damage.

Intake valve stuck open (may just be too little valve clearance), air escapes cylinder into intake manifold, turns corner and enters the cylinders which are on the intake stroke (because the throttle plate is closed, where else would it go), and out the spark plug hole.

I've never heard it myself, but it doesn't seem too far fetched. I'd follow millball's suggestion (check clearance on #1 intake.) Especially look for TOO MUCH clearance, which might happen if the valve is stuck open (due to a bent valve, for instance)

oldblue

hey scope i am a ˟˟˟˟ing hillbilly so everyone needs to take any advice from me with a grain of salt hahaha

but i like using a 1/4" extension as it fits easily in the hole and i can use one long enough it wont fall into the cylinder, and i always have one handy in my toolbox. but yeah you got to be cautious the extension doesn't jam into anything and the piston loses that fight. i understand the air would enter the intake and could *possibly* end up going through another cylinders spark plug holes, but i would think it would find its way to the throttle body just as easy and faster with more volume.

maybe try re-installing the plugs on the other cylinders while you perform the leak down test.

jereli

yea i can actually feel the air coming out of the other cyclinder. i can plug up cylinder 5 spark plug hole with my finger and i hear less air escaping..when i remove my finger from hole 5 i can hear and feel the air flowing.


i haven't tried inserting spark plugs back in and then doing leak down test but i will try that.


after that i will remove the valve covers to check for valve clearance.

jereli

Okay so I just inserted the spark plugs back in on the passenger side and did leak down test on cylinder #1...I can definitely feel air coming out the exhaust pipe now.