Valve clearance adjustment
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From: Noddy on 20 Apr 2010 07:56 "John_H" <john4721(a)inbox.com> wrote in message news:vmkqs59sl5m57m3dg2p3o92oouijfea414(a)4ax.com... > Aww, come on. As you should know, the good ones usually end up being > the cheapest (and vice versa). :) That's certainly true, but you try getting the customer to see it that way :) > What the OP really needs is a mechanic who knows how to do a proper > compression test, and I've I've certainly come across more than a few > who didn't. ;-) Sounds like he has too. -- Regards, Noddy.
From: Jason James on 20 Apr 2010 10:57 "John_H" <john4721(a)inbox.com> wrote in message news:ib2rs5tti5fuahcdqajn4s8to83lau2ut2(a)4ax.com... > Jason James wrote: > >>Did you take the readings for each cylinder? Done with a >>compression gauge rated to 250 psi. Gauge either has a large tapered >>rubber >>knozzle to fit in the plug hole,..or a screwed fitting. Its imperative you >>hold open the throttle (wide-open) while someone cranks the engine for at >>least 8 revs. What were the figures? > > And you've forgotten one absolutely vital requirement... any idea what > it is? :) If you mean oil in the hole,...yes it can tell a story, but OTOH a comparitive test without oil will still tell a story,..actually, just killing the ignition, then cranking it, and listening to the starter will tell you ifthere are one or more dead cylinders. As each cylinder is cranked by the starter, it will either speed up for a sec if lower comp than the others or slow down indicating a good one, or close to aqua-lock :-) Jason
From: Milton on 20 Apr 2010 17:33 "Denis" <deniss.email(a)gmail.com> wrote in message news:95ea5de6-768e-4c7e-9df6-9d292277df4e(a)c20g2000prb.googlegroups.com... > Does anybody have any idea how much I'd be looking to pay for a valve > clearance adjustment around the Melbourne area? > > I have an 89 Nissan Pathfinder with the z24 engine, currently with bad > compression. > > Or could anybody recommend a cheap/good mechanic? > > cheers Cheap/Good? That's an oxymoron if ever I heard one. How do you know it has bad compression? Compression tests are on the whole, fairly useless at diagnosis. Ask your mechanic to do a "leak down" check and if he doesn't know how to do that, find one that does.
From: John_H on 21 Apr 2010 00:08 Jason James wrote: >"John_H" <john4721(a)inbox.com> wrote in message >news:ib2rs5tti5fuahcdqajn4s8to83lau2ut2(a)4ax.com... >> >> And you've forgotten one absolutely vital requirement... any idea what >> it is? :) > If you mean oil in the hole,...yes it can tell a story, but OTOH a >comparitive test without oil will still tell a story,..actually, just >killing the ignition, then cranking it, and listening to the starter will >tell you ifthere are one or more dead cylinders. As each cylinder is cranked >by the starter, it will either speed up for a sec if lower comp than the >others or slow down indicating a good one, or close to aqua-lock :-) Cranking over a cold engine with the ignition deactivated will certainly reveal the presence, or otherwise, of a serious compression loss. It's also something anyone with a bit of mechanical nous can easily do at home But back to testing with a gauge. To avoid spurious readings the engine needs to be at normal operating temperature. (And of course the spark plugs have to be removed from all cylinders and the battery also needs to in good condition and fully charged.) I've long lost count of the number of engines I've looked at that supposedly failed a compression test carried out by a "skilled" mechanic when there was nothing amiss other than the the way the test had been done (usually because they forgot, or else didn't bother, to run the engine up to temperature). Never had much faith in the oil bit myself -- it's supposed to verify whether compression is being lost past the rings. If it is, there are plenty of more reliable indications than a compression reading. IMHO a compression gauge is a useful tool for sussing out valve related problems... and very little else. -- John H
From: Jason James on 22 Apr 2010 14:40
"John_H" <john4721(a)inbox.com> wrote in message news:ih20t51fndaeagc0om46rknckjn07q2okq(a)4ax.com... > Scotty wrote: >> >>Blow by is through the rings or valve stem seals? > > Blow by is the combustion pressure (gas) that gets past the rings > (unless there happens to be a hole in a piston). Yes, a hole in the piston brings fast and total catastrophic failure of the engine,..due mostly because the compression stroke blows unburnt fuel/air into the crankcase via the hole.,..followed by a crankcase detonation once enough fuel is present. If detonation takes a while, the continuing pressure waves into the sump(from compression and combustion cycle), and oil-mist being shoved up into the cylinder,.via the piston-hole, ensures most of the sump-oil is pumped out without further ado :-) Jason |