cracked ring lands

[wild_maxx]

my compression droped badly so i took it in for a leakdown test. air was comming out of the oil filler cap so its getting by the rings and i am assuming that its also the ringlands. is wasnt leaking really bad but the compression went from 175ish on all 4 to 135ish on all four. can you still drive the car like this for a little bit or should i just pull the motor and start a fresh rebuild? there is no oil in the coolant or smoke out of the exhaust. so i dont think its a HG.

[fiznat]

If its coming out of the oil filter cap I'd say that the leak is in the valve seals, no?

[nissanfanatic]

No smoke at all?

IDK about you guys, but I compression test mine every 1k or if I mess up on something:p. other than that, if the car runs well and no smoke, its prolly fine....

You prolly just forgot to press the throttle to the floor.

How does the car drive? Why do you think ring lands are blown? What went wrong?

I agree fiz. Anyone ever notice if you remove the oil filler cap, air comes out, but if you put your thumb over the valvecover breather hose, there is suction???? Strange huh.

[wild_maxx]

thats what i asked them and they said rings. i thought valves were out of the intake mani or out the back of the exhaust. anyone know for sure?

ps. thanx for the quick response

[wild_maxx]

the test was done on a warm engine with WOT and bat. at 13.4 volts. i started out at 10 psi of boost and it ran great. a/f were about 11 -11.5 while in boost the just one day it felt extremely slow so i did some testing and found out the compression. the engine never overheated, it idles fine, doesnt smoke, oil level is still the same. i did change the oil after the compression test and it was black. did smell like gas tho.

[nissanfanatic]

Damn strange. Even stranger that all four went to 135. Sounds fishy. Most cars with a blown engine run like poop and smoke esp with busted ring lands.

[WDRacing]

I've had oil fumes ome out of the oil ap before...hence the need for the PCV valve and carnk case vent...thats just nromal ops as far I'm concerned. Especially with a FI motor. I never believe any shop, they are always in to make money...period dot. If you do a compression test right now, what are the readings?

WD

[DRIFTEADOR]

it sounds like it has more to do with cam timing/valves. at worst worn rings, even though at 135psi i'd think it would blow some blue smoke. broken ringlads would give you 0 compression at least in one cyl so youre ok to drive it.

[Frozen240]

I had three pistons with cracked ring lands and worn exhaust valve guides, with this combo my car left a blue vapour trail for at least three blocks!

I have a tough time believing that you have bad ring lands and aren't burning any oil.

[:: orion ::]

Even if you crack the top 2 ring lands, the oil control ring will still prevent oil from burning...all you'll get is blow-by.

- Brian

[HolyShiznit]

^^^ Umm ya.

I cracked ALL 4 ring lands AND the the lower ringlands on ALL 4 with my little 87 octane incident. Car did NOT smoke, however my catchcan was filled with oil. If you had cracked ringlands you should have enough compression to drive around but the car will just die on you and eventually not be able to turn over. This is what happened to me both times.

[wild_maxx]

well i did the compression test my self and the results were pretty clost to eachother. at the hightest it was 140 and the lowest was 135. they all were within 5 psi of eachother. i took off my intake and could see some oil residue on the turbo inlet. i do have the valve cover vent back into the intake pipe so thats where the oil is comming from. i will check around the motor more today and see if i have a leak somewhere else.