Moderator: volvite
won't tell you anything about valve stem sealsJimmy777 wrote:will the compression test tell me if the valve seals are gone? how about the scraped cylinders?
I am surprised Midas never suggested the compression test or the leakdown..
Interesting. Forgive me for the noob question... But what do I really need a compression test for? If the compression was low how would that eat up oil? I am guessing compression during explosion?eieio wrote:won't tell you anything about valve stem sealsJimmy777 wrote:will the compression test tell me if the valve seals are gone? how about the scraped cylinders?
I am surprised Midas never suggested the compression test or the leakdown..
valve stem seal issues are very rare
a compression test will tell how much (or little) compression you have
a leakdown test will show where the compression is being lost (piston/rings or valves, whether intake or exhaust)
just getting the spark plugs out to do these tests is quite time consuming, and a leakdown test even more so (may require front engine cover removal)
there are several other threads/topics on this problem
you might try a forum search for more info
if your cylinder walls, piston, and/or rings are damaged by converter debris, oil will go past the piston rings, and on into the combustion chamber, where it will be burnedJimmy777 wrote:Interesting. Forgive me for the noob question... But what do I really need a compression test for? If the compression was low how would that eat up oil? I am guessing compression during explosion?
I think the leak down test would be far more valuable?
is your "jug" a gallon?Jimmy777 wrote: I go through a jug of oil every 500 miles or so.
Please help....
3.78 litres - pretty sure its a gallon.eieio wrote:is your "jug" a gallon?Jimmy777 wrote: I go through a jug of oil every 500 miles or so.
Please help....
Will print this out and give to nissan dealer when I do the testssmj999smj wrote:These engine use the variable valve timing to accomplish EGR rather than a conventional EGR valve setup. It does this by cracking open the exhaust valve slightly during the intake stroke, which draws in exhaust gas directly from the exhaust manifold. If the converter is starting to break down, the catalyst substrate can be sucked into the combustion chamber during these EGR events, which will cause scoring to the cylinder walls...which leaks to poor compression and oil burning. This issue first cropped up on the 2002-2004 Altimas with the QR25DE engine. It's not quite as common on the VQ40DE, but it does occur sometimes. Compression and leakdown test, if needed, would help confirm this.
Some of you guys talk about changing the spark-plugs yourself but after looking at the post somewhere here (with colored pics and steps) i think its sort of involved...?CPLTECH wrote:From things said on this forum in the past, I get the impression that the cats do not like any misfires that go on inside this engine. It is for that reason I decided to replace the 100k mile spark plugs early and use injector cleaners.
Sounds to me like the cat substance got sucked into the cylinders due to their close proximity coupled with misfires.
I know that adding oil that often is an aggravation, but it only adds a half-cent per mile in cost until you decide what course to take.
Need to revise my math, I assumed it was a quart. Yes, that IS a lot of oil.Jimmy777 wrote:3.78 litres - pretty sure its a gallon.eieio wrote:is your "jug" a gallon?Jimmy777 wrote: I go through a jug of oil every 500 miles or so.
Please help....