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Posted: Sat Jan 15, 2011 2:35 pm
by the vegenator
Results from compression test that I performed this morning, engine warm:
#1- 300. #2- 225. #3- 410. #4- 410
Holy hell! The compression test done back in 2007 had better results (from what the shop told me). But these results explain a lot. Nowhere near the 425 to 493 psi ratings they should be showing.
The person helping me suggested pouring less than a teaspoon of motor oil in the cylinders and performing the test again - as a way to test for ring wear. Here are the results of that test:
#1- 440. #2- 350. #3- 425. #4- 475
My buddy said these higher compression results indicate that the rings are likely worn, since the oil fills in the gaps around the rings.
Car is disabled until I get some more answers. Could it be stuck rings? Something some kerosene could free up?
I was thinkin' a leak down test would be in order...
Posted: Sun Jan 16, 2011 3:54 am
by Fatmobile
I've never done a leakdown test but it sounds like so much more info can be gathered from it than a compression test.
Does seem like it's the rings though,
if it was a valve the oil wouldn't have reduced leaking.
I'd probably turn it over by hand to make sure it didn't hydrolock,
before I hit the starter,
if I put any fluid in the cylinders.
Posted: Sun Jan 16, 2011 10:25 am
by joat
can't hurt to try the "old penetrating oil in the cylinder " trick ...
let it sit for a couple of hours.
yes, spin the engine with the plugs out to clear the remaining oil before starting it.
leak down test can show if the rings are sealing all along the cylinder bore, or if its just loose at the top... (if it needs a rering or needs a rebore)
Posted: Sun Jan 16, 2011 11:40 am
by the vegenator
My mechanic friend mentioned the risk of hydrolocking, which is why we used a pretty miniscule amount of oil. I didn't turn over by hand in between each cylinder test. But I'll turn it over by hand to make sure it's good before putting injectors and lines back on.
In another thread, Hagar mentioned a homemade leak-down test tool:
A tester consist of a pressure regulator on the inlet ---and two Gauges with an orifice between them
Anyone made one of these before? A cheapo on ebay costs as much as $70 or $80 with shipping. The best I can do is go to napa and see if they laugh in my face when I ask to study theirs.
Kerosene in the cylinders - not a bad plan.
Let it soak for a few days,
turn crank bolt over by hand... Blow/suck it out?
Either do a cold compression test, or else let engine warm up first to test again...
I think I'm getting somewhere. It's amazing how liberated I felt to finally get some definitive that address all of my symptoms... Someone else here mentioned having bad compression in a couple of cylinders, but still getting 50 mpg. Doesn't make sense to me, since the motor would have to do more work and thus be less efficient....
I suspect pump issues too.
Wouldn't any normal person throw in the towel by now? Possible motor AND pump issues? I imagine so. But this is an obsession, healthy or not.
Posted: Sun Jan 16, 2011 11:58 am
by joat
with the injectors out, you can use the starter to spin the engine and blow the excess oil out safely.
crazy ? yeh, just like 99% of the rest of us on this board. ( it's nice to have company )
Gauge:
find a fitting to screw into the injector or glow plug hole, attach to a length of hose. put a T fitting at the end of that hose. put a gauge (0-150 PSI) into one of the free ports on the T fitting. attach an on / off valve to the last port and attach an air fitting to the end of everything.
rotate the engine to TDC for that piston, attach a compressor to the gauge contraption. open the valve to pressurize the cylinder. then close the valve.
read the gauge and see how long it holds pressure. then move the piston down and repeat. ( use the gear selector and park brake to hold the engine still) do the same for each cylinder and compare readings
if it leaks only at the top of the cylinders, the bore is tapered and you need a rebore.... if it leaks a lot all along the cylinder, the rings are done or you have a scratch in the cylinder wall.
Posted: Sun Jan 16, 2011 2:01 pm
by Fatmobile
There are plans online, for making your own leakdown tester cheaply.
Not sure where but I've seen them.
Easy to make.
Posted: Sun Jan 16, 2011 6:22 pm
by the vegenator
Turns out a fellow wingnut friend has a homemade one that I'll be borrowing. But yeah, it seems suuuper easy to make one. Using the regulator/gauge on the compressor, you would only need one gauge and regulator on the tester.
Hopefully I'll be back with results soon.
Posted: Wed Jan 19, 2011 1:53 am
by mtran
Re: Definitive answers? Re: Awful performance of my 85 VW Di
Posted: Sun Jan 30, 2011 10:45 am
by the vegenator
I dug up the original eBay description for my car that I had saved. ALL LIES. Or, what weren't lies were gross exaggerations. But I just re-discovered that the PO had the the cylinders bored .040 over, which doesn't leave me much room to fix the block up if the cylinders are out of spec.
Before I pull any engine or break anything down, I'd like to do the kerosene cylinder soak/clean out. Someone else suggested I could drain the oil and save it (only has 500 miles on it), leave the drain plug out, and watch for kerosene draining through the rings. Seems like an alright plan, but I'd worry that the kerosene would effectively degrease bearings and other components without standing oil to protect them.
Normally would you just drain the oil/kerosene leakage after the soak, refill and keep goin?
