2G Odd Compression Result

[spyderdrifter]

I'm posting this since currently, the search options seem to be broken and I can't search anything. Anyway, I ran a dry compression test just to get a basis of my engine's health. The results were as follows:

Cyl 1: 147 psi
Cyl 2: 143 psi
Cyl 3: 100 psi
Cyl 4: 150 psi

From there, you can all see the problem. But there's more. I didn't do a wet test, because I don't think cyl 3's reading is accurate. The other 3 cylinders are well within spec of one another, and they were higher than I had assumed they'd be, so I'm happy with those. However, while cranking the car over, cyl 3 would make a popping sound and wouldn't go above 100 psi. Every time yielded the same result with no variations. The only thing is I don't remember if the pop came before or after hitting 100 psi. I failed to note that. The car's power has been pretty good, but still at times it does kind of feel like it falls short. Not always, but on rare occasion. I don't know where this pop noise came from, and have no idea what could be causing it. The only idea I've been able to come up with, is if the pop happens right when it hits 100 psi, could one of the injector seals be popping and then re sealing? However, there's no leaking once it hits 100, and just simply won't go higher either. I'm a little lost on this one. The engine was warm as I had just returned fro ma test drive, and the only thing I forgot to do was open the throttle plate. Injectors were all unplugged and the plug wires were all pulled from the coils.

 

[iceguru1114]

That top ringland failure must be common on the OEM pistons. I had a set with the same exact problem some time back; the way it broke looked almost exactly the same to the one in your hand.

 

[1990TSIAWDTALON]

Diesel motor oil, particularly Rotella for diesel's, has more ZZDP (zink and phosphorous) for anti wear agents that have been taken out of conventional motor oils. I run it all the time, but it is very good for fresh built motors while they are wearing in bearings and rings (and on domestic motors, flat tappet cam lobes).
If the motor is running still, soak that puppy with some SeaFoam if you think that carbon has a role in this. Kill the engine with the stuff so it soaks. Let it soak a hour. Go out and get her started, then after she is able to idle, run some water (yes water) out of a bottle into a vacuum line and keep the motor from dying by revving it. When the water has all been sucked in, gun the crap out of the motor (the water will steam clean the combustion chamber and valves) and clear it out of all the junk the SeaFoam and water (steam cleaning) did. I learned to do this in the 70's, while I worked for a old mechanic that used to be in the Marines and he knew what he was doing. Usually, you end up with a black sooty spot where the exhaust exits so do it in the grass, not on your drive way. That always helps out the carbon by softening it and getting it to release then shoot out the exhaust.
Just an old timers trick that will help with carbon build up. If someone has already suggested this, I am sorry.
Also, have you done the leakdown with the valve cover off so you can hear and possibly SEE if any valve seals are leaking?
As always, just tryin to help.

 

[spyderdrifter]

Damn, wish you lived close enough to show me how to do that. I've never used seafoam, even though I got a can already that I never used. No, I haven't done a leakdown with the valve cover off. I had limited time when I did the leakdown on Saturday, I'll see if I can get my car back in to do another, and on all cylinders to be safe. If I do this seafoam cleaning, what would be the best vac line to use for the "steam clean"? Since that crap will destroy the oil (and filter), and need to be changed, is there anything else that'll need to be changed after all this? No one else has mentioned this so you're good, I'll take all the advice and help I can get.

 

[chrysler kid]

Yeah I've been using rotella for years in my 96 gst "married virgin car" (as in I bought the car from the original owner and I'm never selling it)

It's the colder time of the year up north, so t4 5w40 is about as thick as you want to run in the winter. T4 is conventional motor oil, t5 synthetic blend, t6 full synthetic. The brand is shell, Rotella is the product line name

They come in 3.9 quart jugs and it's 13.99 for the jug.

My camaro runs valvoline vr1 20w50 high zinc oil. It's had the same heavy cam shaft in it for over ten years and 60k miles.

You can buy the sea foam in a spray can with a nozzle that slips under a clamp. You don't have to attach a vacuum hose to a bottle.

I've never liked sea foam. Never seen a benefit. Get on YouTube and search sea foam test by Chris fix. He tests all of the cleaners on used lawn mowers and uses a small camera scope to view before and after.

If the compression is low enough the car will suffer other symptoms before death. The most obvious one to look for is blow by and the oil smelling like gas. So sniff the dip stick hole when you check your fluids. Too much gasoline past the rings and you can spin a bearing eventually

If it's a problem with the head, which is the most likely issue, you may not notice any issues at all besides crappy gas mileage. The spark plug on that cylinder should also look quite a bit different after several thousand miles if the problem is severe. I'm being generic but cars with eBay 16g turbos seem to suffer the same fate, toasted valves or toasted rings. It seems to be a very common trend on my project dsms

Picture of my cars since I spoke of them.

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[linksys42]

Also, have you done the leakdown with the valve cover off so you can hear and possibly SEE if any valve seals are leaking?
As always, just tryin to help.

A leak down test will not show leaking valve seals it will show leaking valve seats/valve. There is no reason to take the valve cover off to verify this all you have to do is listen for air escaping at the intake or the exhaust.

If its is a problem with the head, which is the most likely issue,

How do you figure it's a problem with the head after he posted his results of the leak down test on #3? If he didn't hear any air escaping past the intake valves or the exhaust valves but yet heard it coming out of the crankcase it does not point to the Head.

 

[1990TSIAWDTALON]

Damn, wish you lived close enough to show me how to do that. I've never used seafoam, even though I got a can already that I never used. No, I haven't done a leakdown with the valve cover off. I had limited time when I did the leakdown on Saturday, I'll see if I can get my car back in to do another, and on all cylinders to be safe. If I do this seafoam cleaning, what would be the best vac line to use for the "steam clean"? Since that crap will destroy the oil (and filter), and need to be changed, is there anything else that'll need to be changed after all this? No one else has mentioned this so you're good, I'll take all the advice and help I can get.

The way WE use it is simply pour it down the carb throat or in this case introduce it in a good vacuum line like the BOV line, not some little one. I let it suck it out of the can with the hose and keep it running until the end of the bottle then I choke it or turn it off and let it sit. Works best if engine was warm but doesn't have to be hot. I DO NOT put it in my oil for any reason, but I do use it to keep injectors clean on a normal car by running it in a half tank of gas, and yes it does work in these 2 situations. 40+ yrs of doing it. Saved my nephew a $300 injector cleaning by Midas and in "grandma's" car that never seen 40 mph for years, it made her car purr like a kitten when before it had a stumble at idle and some run on issues (hot carbon). Left a nasty black mark in my gravel drive for a few months. Just what I do.

 

[spyderdrifter]

So put the seafoam and water through the same vac line then right?

 

[joemamma]

do it in small amounts if u just let the hose sit in a cup of water the engine can die- also used to use atf in a similar manner

 

[1990TSIAWDTALON]

Yes. SeaFoam it first, let it die and soak. Then get it started, (may take a few tries since it has to flush out the stuff and get real gas in there).
After the SeaFoam treatment has cleared out (it will smoke, do not be alarmed, it will finally clear out), then introduce the water treatment to steam out the loosened carbon. That is what this procedure does, flushes out any carbon that can be loosened and cleaned away. Usually I have to do water a little at a time then hit the throttle to clear it out then repeat. I use a normal size water bottle, about 12-16 oz. Run the throttle good when done to get it idling nice and that is all you can do. It will not hurt anything, I don't know if it will help you but it is what I do for cars that have been bogged around town for years and they like it.
When you do this you will have to keep it running with your hand on the throttle, it won't idle and let you do any of this, just FYI.

 

[chrysler kid]

A leak down test will not show leaking valve seals it will show leaking valve seats/valve. There is no reason to take the valve cover off to verify this all you have to do is listen for air escaping at the intake or the exhaust.



How do you figure it's a problem with the head after he posted his results of the leak down test on #3? If he didn't hear any air escaping past the intake valves or the exhaust valves but yet heard it coming out of the crankcase it does not point to the Head.

Did you actually listen to what he said or did you just assume he said what you wanted to hear?

Well, I tried a different compression tester, and had the throttle plate open. All results were identical, except cyl 1 which rose to 152psi. Cyl 3 remained at 100psi. Ran a leak down on cyl 3 at tdc and it leaked (as we all figured). Only heard and felt air escaping througth the oil cap. No bubbles in the coolant, no air coming out the TB elbow, couldn't hear anything from the exhaust. The lowest of the other three cylinders was cyl 2 @ 140psi. Did the leakdown on it and it sealed good enough to turn the engine at 100psi.

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.

 

[linksys42]

Did you actually listen to what he said or did you just assume he said what you wanted to hear?

.

There is no other way to take what he said. He stated clearly that he did not hear air escaping past the intake valves or the exhaust valves only coming out of the oil cap/crankcase. That only points to one solution which I have already gone over.
And for the leak down test showing valve seals are bad, it won't. Good luck OP

 

[spyderdrifter]

Before anyone gets into an argument, I do appreciate everyone's advice. Before I decide to rip the engine open, I will do the seafoam cleaning with water. It'll have to wait until this weekend when I'm off work, and as long as the weather is good. After I do that, I'll update this accordingly and we'll go from there. You have all given great info, but hopefully only one of you is right, I don't want multiple problems, but as this is a DSM, it'll probably be more than one.

 

[chrysler kid]

I'm confused why you say sea foam with water. It should be a sea foam treatment, you don't add water. Is there another method?

And yes I think the problem could be carbon build up on the valve

 

[joemamma]

they are 2 seperate treatments either used is good but when use them back to back it is even better--u do not use them at the same time
seafom help to loosen it and remove carbor--the water acts like a steamcleaner also removing carbon

it is not seafom with water

 

[spyderdrifter]

So use the seafoam, and then clear it out before doing water?

 

[joemamma]

So use the seafoam, and then clear it out before doing water?

yes

 

[1990TSIAWDTALON]

Doug's got it!!
That is exactly right.

 

[chrysler kid]

Yeah I definitely don't like the water idea.

I definitely don't care for seafoam except for in the gas tank to clean the fuel system

It's so speculative, depending on the vacuum source you could be pouring everything into one cylinder. It's a liquid, it just doesn't turn into a vapor and disperse. It could literally pool down into one cylinder, and if the water did that...

 

[1990TSIAWDTALON]

It would turn to steam....
I have done this for 40 years and NEVER had a problem but I guess if you took a 2 liter bottle and somehow dumped it all in at once, well you would hydrolock it. I have hydrolocked a car before, this is no where close to anything like that. If you had a carbon or run-on problem, this would fix it most of the time as it gets rid of red hot embers of carbon in the combustion chamber. I have done dozens of cars and everytime, the owner was like, wow, it is so smooth now and actually shuts off when they turn the key off.
At idle, the pistons are moving up and down at around 13-16 times per second, give or take, so no time to "pool".

 

[spyderdrifter]

Got a decent update, I think anyway. I didn't do the seafoam yet. I did redo the leak down and it was good. Cyl 3 was in the moderate zone at 100psi and wouldn't hold more.

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The only difference from last time was that there was no air coming from the oil cap. So I wasn't satisfied that I couldn't even get the same results. I respun the engine and got all the way back to TDC on the compression stroke and pulled the o2 sensor off, and pulled out cyl 2 and 4 spark plugs. Still nothing, but I thought I felt air from the o2 bung, but wasn't positive. We hooked up a smoke machine to pump smoke through cyl 3. Smoke ended up pouring out the o2 bung.....

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....and cyl 2......

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So I'm thinking this is the issue. I will know for sure once I pull the head off, but that'll be once I get a new water pump and timing belt.

 

[chrysler kid]

At top dead center the exhaust valves are slightly open on cylinder 2, the intake valve on 3 are slightly open

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You'll notice less build up on the cylinder 2 exhaust valve as well in my photo. I have not been able to determine why that is, my project car has 180k miles.

I have several theories about it, but my project car also suffers from lower compression on cylinder 2. Results were 170-140-169-170 on my warm compression test

#2 has the shortest exhaust runner on the manifold, possibly causing higher combustion temps and more cause for detonation

 

[Diamond Star Werks]

Just put a small amount of oil in cylinder 3 and simply redo the compression test. If the numbers jump up significantly, your problem is the piston rings. If it stays about the same it is a valve seal issue. You don't need all these leak down tests and such. Simply compare dry and wet results. If dry and wet are the same it's the valves, if they are different by 20 psi or more then your rings are bad.+
+During compression obviously all 4 valves are closed, so the only two things in play are the valve/seats and the piston rings. Carbon builds up on the back of the valves, I have never seen carbon build up where the valve meets the head thousands of time per minute. I have seen deteriorated seats. Seafoam is a waste in time using it to try to increase compression numbers. Unless the car sat for a very long time and you suspect the rings are stuck.

 

[spyderdrifter]

Car sat under a tree for 2 years withput being started prior to me buying it....

 

[chrysler kid]

How many miles have you put on it so far. Have you had any problems blowing the dip stick out of the socket, or blowing oil oil of the oil cap under boost?

If it's not consuming excessive oil i wouldn't worry too hard about it. Check the timing belt and check the tensioner to pulley clearance and just use it as a daily driver till you can tear it down later

 

[linksys42]

If you have a weekend just pulled the head and do these two tests. These will tell you/give you a general idea if it's a lower end or upper end issue.

http://www.dsmtuners.com/threads/how-to-check-for-pinched-or-bad-rings.450572/

http://www.dsmtuners.com/threads/how-to-fluid-test-a-4g63-cylinder-head.420313/