Did a leak down test today to try and find my problem.

Cylinder #1: 90% loss, air blowing out of the next cylinder.

Cylinder #2: 20% loss, air coming out of dip stick tube when dipstick is removed.

Cylinder #3: 18% loss, air coming out of dip stick tube when dipstick is removed.

Cylinder #4: 80% loss, air coming out of dip stick tube when dipstick is removed and air
coming out of cylinder #2.

Usually when air is coming out of another cylinder it points to head gasket. The air out the dipstick tube is stumping me. But what i am thinking is with the tsb for the dipstick poping out being linked to the head gasket, that it would also be the cause for air out the dip stick too.

 

i guess so. that sucks. should've been nicer to it

 

It could be the piston rings being worn.That would make air come out of the dip stick.

 

if the blow-by isn't being exited somewhere for relief it has to go through the easiest way out .ex that dip stick

 

Ya, that's the other cause of air out the dip stick. But to have 3 rings all go mysteriously at the same time? When the problem started there was not sign of something wrong happening. No misses, no surges, nothing. I am stumped.

I just want to try and pinpoint the problem before i have to open her up.

 

dumb question. did you make sure the valves are closed at the time of said compression test?

if this is the case. your motor is fucked

 

I have same oil mystery as in your other thread. Car seems to run fine, even at WOT.

Can it be near death and run like a champ? You have me worried.

 

when running a leak down test, you just have to make sure the engine is at tdc. Not sure if the valves would all be closed in this position or not, but if that is the case then yes they were all closed.

If your talking actual compression test, the car passed the compression test.

 

the dipstip should pull vacuum right? if its out it sets a lean code

whats the car doing, running rough?

 

For each cylinder right???

 

Wow, okay, lots of stuff here.

First, when doing a leak down / differential pressure test, you have to have the engine at TDC on the compression stroke for the cylinder being tested. So yes, for each cylinder. That closes all the valves. If you are on TDC exhaust stroke, then both valves are actually open and you are letting all the air escape. You are going to need a wrench on the crank bolt to hold it still, because once you apply the pressure, the engine is going to try and turn.

A 20% loss through the rings is actually pretty normal. That is why the air exits the dipstick. That is perfectly normal.

If your compression test is okay, then your differential test should be similair.

 

If you have 80% leakage on a cylinder and the valves are closed and it coming out the dipstick your ringlands are probably cracked. What kind of setup have you been running ?

When you have the leakage tester hooked up and the shop air supplied can you spin the motor over freely ? This is out I knew Blown4Bangers motor was toast when I checked his out. I started on Cyl1 and just hooked up air and spun the motor over till it got tough to turn and forced it up to TDC to get a reading. Did the same on Cyls 2 and 3. When I got to Cyl4 I could easily turn the motor right up to and past TDC with the air supplied in the cylinder.

Have you done a compression test ?

 

This is a link to my first post about my problem, it also has the results of the compression test.

https://www.cobaltss.net/forums/show...ht=oil+problem

We set the motor to tdc and held the crank bolt in place when we ran the test. I don't think it has anything to do with the head of the car. if it was the intake valves are would be escaping the throttle body and if it was exhaust valves it would sound like its coming from the exhaust. It has to be bottom end, either the head gasket or the rings. The car had a bit of a funny idle but it went away very fast. It is blowing white smoke out the exhaust after its been running for a while.

I know i have to tear the motor apart, but to check rings you have to go in from the bottom. If i could avoid that, it would be great but if not i have no choice. I guess i just want to believe its head gasket. Might be another build coming.

Mods in my vbgarage. Cars has been running strong for over a year now with this setup

 

Sounds like a blown head gasket coupled with a blown ring land. Either way, your a fool if you don't put a new head gasket on, after installing pistons, so the problem will be solved either way.

 

Not being able to look at it in person its hard to say. But if I had to guess based on what ive read im with Blown on this. Sounds like you have a blown head gaskets and possibly some broken ring lands. 2.6" pulleys are scarey... nothing lasts forever. I would pull the head and oil pan... check out the head gasket and see if there are any obvious spots where coolant or compression is leaking through and pull the number 1 and 4 pistons to inspect the cylinder walls and ringlands.

 

#1 and #4 are hard places to blow the headgasket as the head doesn't move much at the edges during hard runs. If it had been the other way round I'd agree with you but he needs to make sure the test was done corectly as it sounds like there may be some confussion as to weather or not the valves were all closed.

 

Agreed... I wouldnt take anything apart unless I was 100% sure of the readings from both the compression and leakage tester.

You did rotate the engine and set EACH cylinder at TDC for the check right ? You didnt just run it at TDC #1 for all cyls ? Also are you sure you had them all on TDC Compression stroke ?

 

Well from what i was told tdc for 1 and 4 and tdc for 2 and 3 are the same. So we tested 1 and 4 at the same time then 2 and 3. I am assuming that a compressed stroke is when the piston is as high as it can go.

I can always run both tests again to be sure. I followed both sets of instructions very carefully the first time .

I can probably do the tests again tomorrow night, but won't be able to tear anything apart till the 26th. I will probably place and order for a head gasket and head stud kit tomorrow so it is here for the 26th. If i inspect the pistons and find broken rings then i will order a new set of pistons/sleeves.

 

There is the problem right there. You did not do the test correctly. So first thing you need to do is take whatever you think the problem is in your head and throw all of that garbage out. You can not make a diagnosis on a bad test.

While TDC is the same for 1 & 4, or 2 & 3, the TDC of one cylinder will be on the compression stroke while the TDC of the other will be on the exhaust stroke. Hence, one cylinder will test correctly while other will still have it's valves open. That is consistent with your results.

You need TDC compression stroke for each cylinder, like I said before. Here is how I would do it. Start at number 1. Have all the spark plugs for each cylinder removed. Hook up the gauge and just spin the engine by hand until you get compression. Then bring that to TDC (I am assuming you know how to locate TDC). Run the test. Then do each cylinder via the firing order, which if I remember correctly is 1-3-4-2. You should only have to rotate the engine 180 degrees each time.

Separately, if you have white smoke once the engine reaches operating temperture, that is a sign of coolant inside the combustion chamber, which is usually caused by a blown head gasket. So the next logical step is to do a leak-down test. Once you do the test correctly, you should expect to find the problem with the gasket. More then likely, that is your only problem. When you run your test, remove the coolant lines attached to the head. This will let you know if air is blowing out of them.

 

Alright, thanks. I will have to do this when i get back on the 25th though, just don't have time today anymore. I will post up the results when i get back.

 

This is what I ment when I asked if he had it on TDC for each cylinder, I should of specified on the compression stroke. Our motors are 4 stroke which basiclly means that that each cylinder fires once for ever two rotations of the crankshaft. You have your intake stroke (piston moving down and intake valves open pulling in the fuel and air), compression stroke (piston moving upward with all valves closed compressing the air fuel mixture), power stroke (all valves also closed and the spark plug ignites the the air fuel forcing the piston down), and exhaust stroke (piston moving up with the exhaust valves open pushing out the exhaust gases). This is a very basic explination of four stroke engine theory and I hope it helps.

 

White smoke is burning coolant. The headgasket is blown for sure. It'll only get worse if you keep driving, so park it before the cold coolant hits the pistons and cracks them.

Order a Cometic headgasket, Golden Eagle headstuds, and take the head to be resurfaced. Then bolt it all back up and you'll be running like a champ. This combo has worked great for me since I blew my headgasket.

 

Car has been parked since the problem arrived, thank goodness for a winter beater. I already ordered all those parts earlier today, but i am still going to run more tests to make sure the rings are facked before i put the new gasket in.

 

Any updates?

I seem to have the same issues, makes me sick to the stomach. I don't even want to test the engine.

I can't even see outside there is that much white smoke, if I sit and free rev in neutral. Sound like my headgasket/pistons?

I'm also running 3"CTI header/catless dp, into 3" Thermal catback.

2nd o2 sensor still plugged in like normal, never disabled with HPT.

Could this explain a lot of smoke? Possibly no engine damage?

 

i looked at ur compression #s and they looked really low cause mine hit 210 on all four
unless you did a dynamic compression test then it is ok