andystart

I just swapped a ZC DOHC into my 88 CRX two weeks ago. I have some blue smoke coming out of the tailpipe, mostly on acceleration.

I had a compression test done, thinking it was probably piston rings or maybe head gasket and every cylinder came out at 175 which I believe is OK. If the oil rings are shot, wouldn't that show up as a poor compression test?

Ideas on what to do next? I did the compression test after searching here and finding that the two most common problems are valve seals and rings.

Thanks

Jurassic Four

Are you shure it is blue? That is definatly oil, which would signify pistion rings. Or a head gasket possibly. But that would cause low compression also. 175 is almost perfect.

LSVTEC 91 Civic

A bad oil control ring will burn oil, as well as a bad valve seal... but both of them won't show up in a compression test. Pull your plugs out and see how they look...

92integra_gs

yea definitely oil burning...

yoursupinehead

do a dry and a wet leak down test, that will tell you where it is coming from

HonduHHerB

have you check to see if running rich? Blue smoke indicates fuel

vtecn8ive

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HonduHHerB &raquo;</TD></TR><TR><TD CLASS="quote">have you check to see if running rich? Blue smoke indicates fuel</TD></TR></TABLE>

Blue=oil
White=coolant
Black=fuel

mrspeaker

Pull your plugs and see if they're covered with oil..
It might be ur vavle seals

StorminMatt

A bad oil control ring alone will not show up on a compresion test. But it is highly unlikely that an oil control ring would be worn to uselessness while the compression rings are still good. So if you are burning oil and have a good compression test, the valve stem seals are likely to blame. This is particularly the case on swapped motors, whose valve stem seals tend to go bad while sitting for long periods of time at salvage yards or importers.

89hbcivicguy

oil rings for sure.....i had the same problem with my crx si.......blue smoke is oil.....and if its valve seals it will only smoke on start up till the rubber gromets get warm and expand...........definately oil rings.....and oil rings wont affect compression

StorminMatt

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 89hbcivicguy &raquo;</TD></TR><TR><TD CLASS="quote">definately oil rings.....and oil rings wont affect compression</TD></TR></TABLE>

But as I said, good compression rings and bad oil rings is a very unlikely combination.

andystart

Thanks all for the feedback.
I'll get the leakdown test done and plan on replacing the valve seals at least.

If I have to take the motor apart to replace the oil rings, I'll replace the pitsons, rods and rings - that way I'll be ready for a turbo when the time comes. I was just hoping I didn't have to do that now.

Thanks again

drussell4801

squirt some oil into the cylinder and then do a leakdown test. The oil will seal the rings to the cylinder wall during your test. If it leaks then you know its in the valve train.

andystart

Hmmmm.

If I understand this correctly, working down from the top of the piston, there are two compression rings then the oil ring at the bottom. Won't it be the quality of the compression rings that respond to the compressed air in the leak-down test? i.e. if the compression rings are in good shape, no compressed air will leak by them.

What the leak-down test will do is identify if there are problems with intake or exhaust valves and which of those it is. If the test shows no leakage through the valves, then the blue smoke must be from worn oil rings. Is that right?

I did have another thought. Can too much oil cause the blue smoke? When the motor was swapped, I put 5 quarts of synthetic oil in which is about 1 pint too much.

Any more thoughts?

crx_88_si

no. if the VALVE STEMS are bad then oil will leak past those into the area right behind the valve. (intake OR exhaust).

if an intake valve stem is bad it will pull the oil into the combustion chamber w/ the air/fuel

if an exhaust stem is bad it will put oil in direct path of the exhaust when the valve opens, then it will burn the oil.

a compression test wouldnt show this cuz the valve are probably sealing in the valve seats properly.

i got bored at work.. here.. red marks = where valve stem seals are.



Modified by crx_88_si at 1:03 PM 10/15/2004