Boost leak testing and rings

[mwreed]

I originally posted this under Engine and Cylinder, but, no response. Maybe someone will see it here. I deleted the other post to keep things clean.

I've been trying to stabilize my by boost setting for a bit now. It will spike to 20, hover around 17-18, then go down to about 15-16. I've been getting about 11 counts of knock on average. I added fuel, but, it doesn't seem to be consistant, so, by researching (and knowing I should do it anyway), I did a boost leak test. It doesn't seem to want to hold and pressure. I had a different tester and it didn't seal well, so, I built a new one that seems to seal. I definately hear leakage thought the crankcase. My dipstick has popped out in the past. I know, not a good sign. I did the test before the turbo and at the TB, to remove the piping from the equation. I can hear sound in the valve cover from both locations and still cannot hold pressure. I blocked off the line to the MBC and while I had it on the turbo inlet, I blocked the PCV. I still had the noise. I did find that my FPR line was leaking and fixed it. So, I did a compression test last night when I got home from work. (25 miles) I got 150 accross the board. Not too bad, but, that was dry. I did the wet test and got 180-190 accross the board. I used a mobile 1 15W-? cap. I don't know if that makes a difference or not. Perhaps, a lot of oil??? From what it looks like, my rings are shot. I'm not surprised, but, would that cause me to not be able to hold any pressure? I have my regulator set to 20psi and as long as I hold the lever down on the air gun, it will send 20psi then gradually lower to 15psi. As soon as I let up, it goes right down to 0. I could be missing something here, but, I wanted to get some opinions.

I do have a little history on the engine too. It was transplanted with 750 miles on it from my first dsm to my current one. After I got it running, I was taking it down for emissions testing, and the oil cooler line burst, so I lost all my oil. I was not very pleased in the least. I fixed the line and filled it back up. I went down to get it registered and the my repair came apart. I fixed it and it held good this time. Seemed to be ok and then the oil pump seezed on my about a month or two later. It was a new front case with the rebuilt engine when I got it for my first car. Because of the oil leaks, I couldn't prove that it was the case or my oil issue. Needless to say, I ran into some problems. Timing belt jumped because of the oil pump, bent a valve or two, (found by leak down test) so I ended up replacing the head. Giving that information, I assume the rings a definately gone. I have the original engine sitting on a stand waiting for me to rebuild it. I just havn't had the money to do it yet. I still plan on doing it, hopefully soon.

After all of this information, my question is: Would bad rings cause me to not hold pressure at all durring a boost leak test or am I missing something else too? I wanted to do a leak down test last night too, but, ran out of time. I plan to do that and another boost leak test this weekend, when I have more time. Thoughs???

Mike

 

[BISHILVR]

I think you are missing something. Those rings are'nt that bad to be loosing pressure that quick when you are doing your boost leak test. Look elsewhere.

 

[mwreed]

Where else can I look? I had the tester connected to the TB. The only places I can figure is the TB itelf, the intake manifold or vacuum lines connected there. I plugged the PCV, and the BOV vacuum lines, so it's not leaking there. I gradually hear it start coming through the crankcase when I start filling. It's like it takes a sec or two before it starts leaking from the crankcase. I had testing before and spayed soapy water on the TB and the intake manifold in the past and came up with nothing. I didn't get a chance to do the test again this past weekend, as I hoped, but, maybe this week or weekend.

Mike

 

[ddavisaf]

Listen for leaks at your tailpipe. Spray soapy water over everything you're testing.
If you're hearing air at your tailpipe you've got a case of excessive crankcase pressure. Run a leakdown test, as it will help you pin point the problem better.
If you had a boost leak as bad as your test says, your car wouldn't make it to 15 psi. I would re-examine the tester to make sure your problem isn't there.

 

[Talesin]

Make sure your crank isn't at/near TDC. 2 and 3 have overlap (both valves open) at that point IIRC, so the air goes right in and right out. :b Just pull out a sparkplug, set a screwdriver in so you can watch piston movement, and turn the crank with a ratchet from behind the driver's side wheel well. Do NOT crank the car with the screwdriver sitting there. Get the piston to around halfway through its stroke, and one or the other valve should close, allowing you to boost test. :b

Alternately, just 'tap' the ignition once or twice for a half-second (after removing the boost leak tester!) and try again until it holds or starts leaking out somewhere else.

Also, as I understand it, 150 is damn near perfect for these pistons. At least, that's what my mechanic's told me.

 

[ddavisaf]

30° Above or Below TDC... I believe...

 

[mwreed]

Yeah, I wanted to do the leak down test the other night, but, I didn't have the time after doing the compression and boost leak test. I usually opt for my piece of cpvc for my TDC indicator instead of the screwdriver, but, I couldn't find it. I don't know if I will get a chance tonight, but, definately this weekend. I tested the boost leak testor before I put it on and it held as much pressure as I put in it. (about 15psi, the air compressor was set low) I just made this one the other day. Like I said, I know I have some air getting into the crankcase. I can hear it through the oil fill cap and the dipstick. Mostly I wanted to confirm that it wouldn't be the rings causing that much of a leak. I'll do the test and re-post my findings. Thanks for the replies.

Mike

 

[ddavisaf]

If you're hearing the air through the oil cap, chances are it's valve seals. Your compression and leakdown will tell you for sure.

 

[mwreed]

Good news... kinda.

I did another boost leak test, finally, and found that my injector seals are leaking. I know I put new seals and o-rings on the injectors when I installed them a year ago, but, apparently, they are not sealing properly. I ordered the kit from FIC so I can make sure they fit and are all new. I still haven't had the opportunity to do the leak down test. Need to do that too. Hopefully this weekend. I've been so busy lately.

Mike

 

[mwreed]

Timing belt shredded. No need to test on this engine anymore. We be building a new and improved engine / head.

Mike