I bought a wrecking yard M10 engine to put in my E21. I'm 2.5 weeks into the 30 warranty period (driving 200 miles to give the engine back). I have no idea how long the engine was sitting.
It's now on an engine stand, flywheel on the crank, and a starter motor mounted to spin the engine.
The engine generates about 55 psi oil pressure on fresh Castrol 20w-50 and a new filter at starter motor speeds (no spark plugs).
I tried running a leak down test before I got the starter mounted, but I didn't trust the results from the HF gauge set I got (#1-45%, #2-20%, #3-40%, #4-50%) on the initial tests before I got the engine spinning. The HF gauge only uses 15psi or so cylinder pressure. I noticed the most air noise from the intake manifold and crank case. I'll get back to run another test after I get the compression issue below.
I then decided to go back to something simpler and run a compression test now that the engine can be spun fast enough. The first pass, my gauge read 30 psi or so on all the cylinders. No measurable difference wet or dry. Thinking that didn't make sense, I got ahold of another gauge, and when I ran a second pass, I read about 40psi or so.
I ran a couple more passes, and the pressure seemed to go up each time. The last pass was around around 90 psi. I'm going to run the engine longer and see if those numbers will come up more, and run another leak down test with a gauge that uses higher pressure.
Is this an explainable phenomena? Were the rings and valves not sealing correctly because they've been sitting, and now that I've spun the engine for a couple of minutes and with oil in place, they're functioning better?
Any insight is greatly appreciated.
I've had one experience with wrecking yard engines and it had issues. Regardless, those numbers aren't so promising.
What did the plugs look like when pulled? Color, moist with oil, etc?
04M3 TiAg 69k slick-top 3 pedal
99M3 Cosmos 61k S50B32 euro 6Spd
88M3 AW 43k miles Project FS
WTB: 3.5" Eurosport/Conforti CAI
It's incredibly difficult to judge a salvage yard engine, before it's installed. Leak down is your best bet, but even that is unreliable, when the motor hasn't run recently.
I would say, though, that I've never ever heard of a 30-day warranty on a junkyard motor. Three months is the very shortest I've ever known, six months or more is common.
On something as old as an M10, I think you're going to be pretty much taking your chances, if you buy it anywhere but from a BMW enthusiast.....and even then, sometimes, huh, MauiM3Mania?
Chris Powell
Racer and Instructor since, well. decades, ok?
Master Auto Tech, owner of German Motors of Aberdeen
BMWCCA 274412
German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471
04M3 TiAg 69k slick-top 3 pedal
99M3 Cosmos 61k S50B32 euro 6Spd
88M3 AW 43k miles Project FS
WTB: 3.5" Eurosport/Conforti CAI
I've been in conversation with the junk yard about bringing the engine back (200 mi. drive) this weekend. They were not my first choice, the other place I tried had the early 320i M10 that has the injectors in the manifold, not the head. The next closest source is 750 mi away.
The plugs were black and shiny but not wet. Put a borescope down the spark plug holes and the piston tops were black, but the honing cross-hatch marks are still visible on the cylinder walls, no rust.
Sunday night I rotated the engine so that the exhaust ports were turned up enough to hold liquid and sprayed some brake cleaner in the exhaust ports figuring it would evaporate eventually anyway. When I did a comp. test on #1 Monday morning, the reading was up to 120. Rings freeing up?
This morning, I sprayed some penetrating oil/Kano Kreen down the bores and have turned it over by hand a few times, and with the starter.
Haven't run another full test yet. Will do that this evening.
The last compression test I ran showed: #1-120, #2-90, #3-80, #4-70.
I talked to the guy at the yard, and he said something similar, that the numbers are meaningless until the engine has been in the car and running for a couple of hours, especially since it's been sitting for several months. Sounds hokey to me, but then they have my $, and would only give me "store credit" if I turned the engine back. I acted based on my assumptions of what I should have looked at the Yelp reviews first.
It's interesting, though that pressurizing the cylinders for a leak test shows the loudest leakage coming from the exhaust valve, seeming to be pretty consistent across all cylinders, even with the compression differences. At the same time, if I tilt the engine so that the exhaust ports are up, and spray some brake cleaner in them when the valves are closed, it doesn't drain past the valve into the cylinder.
One thing that gives me hope is that the oil pressure is 55 psi when I spin the engine with a starter. At least the bottom end is hopefully in decent shape.
"Good judgment comes from experience, experience comes from bad judgement..."
Last edited by txzaphod; 03-19-2017 at 12:22 PM.
Do you have fuel delivery disconnected for your compression testing? Because those numbers look exactly like an engine that has fuel being delivered, and was tested from front to back. (Fuel washes away compression; test with no fuel being delivered; a half teaspoon of oil in each cylinder will restore the compression that fuel washed away)
Chris Powell
Racer and Instructor since, well. decades, ok?
Master Auto Tech, owner of German Motors of Aberdeen
BMWCCA 274412
German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471
Sitting a few months shouldn't have harmed it all unless unprotected against the weather.
An engine this old from wrecker is at best a crap shoot. Even if turns out a bit tired, which it likely is, exchanging it for another mystery motor might be an exercise in futility.
All these tests on a stand aren't telling you much and consuming enough time to put the engine into the car(how hard on an E21?) and actually fire it up. Once oil is circulating at pressure and it's been through a few heat cycles you'll know what you've got.
I say plug it into the car and roll the dice. Good luck
If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue
Well, I just learned this right here and now. Thanks for that, Chris! BTW, Tool will be on it's way today. Yesterday my family and I were dealing with a rather ugly situation; a good friend with a problem that wasn't sure his problem needed immediate, long-term hospitalization. He was in no condition to drive, so we had to get him to where he needed to be. I'm still trying to figure out what to do with his car. We live in a condo (2 parking spaces per condo), and it sounds like 1 or more of his connecting rod bearings are about to go.
If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue
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