ok, i've been burning oil and smoking because of my 3rd cylinder. i just finished replacing the valve seals and did a leakdown test to find out what was causing the problem.

i tested the 3rd cylinder at TDC and there was only a 4% leak, which is pretty normal. all other cylinders are less than 5% at TDC.

so then i rotate the crank so that cylinders 1 and 4 are are TDC (piston 3 is at the bottom of the cylinder) and the leakdown is at 20% here. i tested cylinder 2 with the crank in this position and it was only 5% leak.

so what would cause 15% more leaking air with the piston at the bottom of the chamber? is this my rings? or my cylinder walls? or what? i can't tell where the leak is happening.

it's obviously not a valve or valve guide because at TDC the leakdown is fine. also, keep in mind that the engine has been sitting for 2-3 months and hasn't been started.

what do you guys think?


Modified by guedo148 at 4:53 PM 8/12/2008

 

anyone?

 

ima say it.s ur cylinder wall on cyl3. .is this ur stock motor and/or has this motor always been in ur possesion??

 

no, it's a mildly built N/A b-series that i put in last summer. i rebuilt the bottom end with new bearings, rings, and rehoned cylinder walls. i don't know why the walls on cylinder 3 would be messed up since i got the block rehoned. damn, i don't want to take it all apart again.

 

have u had ne ovaheatin probs befo afta the rehone??

 

it never overheated

just smoked some.. sometimes randomly, sometimes at high rpm. if i ran it hard then came to a stop, it would smoke when i started going again. i'd have to fill up the oil about a quart every 500 miles or so.

i had a b16 bottom end before i rebuilt the b18c1 and that was losing compression in cylinder 3 as well, so i thought it might be a valve or valve seal problem because i'm using the same head. but the valves seem fine.

 

bump for help

 

i kno it was rehoned but was it mic.d aftawards to make sure errything was tru to spec??

i jus dont see how it could be nething besides the wall becuz of that readin.

 

it was rehoned by a reputable machine shop so i expect they made sure everything was good.

20% leak doesn't seem that bad, if i just use a thicker oil will that stop or slow down the oil consumption? is there annything else i can do besides taking everything apart again?

 

20% leakage is horrible.

Why are you worried about leakdown at BDC??? Depending on cams/angle/etc, your intake or exhaust valve may be starting to open/close

It could still be a valve guide and/or seal.

A worn hardly ever shows on a leakdown, unless its so bad that your valve never sits right

 

i'm worried about leakdown at BDC because at TDC it's only 4% - same with all the other cylinders. but at BDC all cylinders are less than 5% but #3 is at 20%

i thought at BDC the valves were closed just like at TDC?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by guedo148 &raquo;</TD></TR><TR><TD CLASS="quote">i'm worried about leakdown at BDC because at TDC it's only 4% - same with all the other cylinders. but at BDC all cylinders are less than 5% but #3 is at 20%

i thought at BDC the valves were closed just like at TDC?</TD></TR></TABLE> They are not.

 

hmm. then why was cylinder 2 only at 3% leak at BDC?

so maybe replacing the valve seals fixed the problem. if i only have 4% leak at TDC in cyl.3 do you think i'm good?

guess i'll assemble the head and start it up to find out.

 

Because the EX valves were closed on #2 and IN open on #3? Do some homework on home a 4 stroke motor works. It will help you later on. I do leak-downs at BDC. I have the cams out or the adjusters full lose.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">Because the EX valves were closed on #2 and IN open on #3? Do some homework on home a 4 stroke motor works. It will help you later on. I do leak-downs at BDC. I have the cams out or the adjusters full lose.</TD></TR></TABLE>

there's only so much one can do...

 

i had the cams out while i did this test.

do you think i'm ok if i have good leakdown numbers at TDC in cylinder 3?

 

Then you have a taper , scores in the bottom of your sleeves. This is not rocket science, Something has a leak. Do your home work.Hard to see from here.
Let me ask you a question, are you happy with 20% leak at BDC? If yes you are good to go, If not figure out why.

 

i'm not happy with it burning oil and smoking. guess i'll have to take it apart.