I have a used Neon motor for my 03 Neon, my oldest daughter overheated the original engine in, can you test the compression by spinning the engine over by hand?

Anyone ever do this?

Every time I have ever tested an engine with a compression gauge its always been on a running engine and I used the starter to spin it over.

I squirted a little oil down each spark plug hole then spun it over a few times then hooked up my compression gauge.

While turning by hand each cylinder reads only about 20-30 psi.

I have zero info on the engine except it came out of a wrecked car with 109,000 miles on it. Pooped the valve cover off and the valvetrain was VERY clean.

I know a engine just sitting for a few years with the valves open will rust the seats and valves so that could explain low compression but I also realize turning it by hand might not be a good way to judge it.

I have a decent gauge and will test it tomorrow on my running car to make sure there is no problem with the gauge.

Can you throw some jumper cables on the starter and spin it over?

ETA If turning it by hand I think you will lose most of the compression past the ring gaps.

Nope, the starter mounts to the bellhousing so I would have to remove it from the engine stand then mount a trans to it.

It would be a PITA.


I'm just wondering if someone has done this before.

On a Neon you need the transaxle bolted on by a few bolts. Since the starter bolts to the transaxle. No way to spin it fast enough without a starter.

NOW if you have a leak down tester, you can put each cylinder on TDC and perform a leak down test. You will need the tester and a small air compressor to perform the test. The leak down test is even more accurate than a compression test.


ETA: Amazon has a leak down tester for around $15, most of theirs are just over $30. Now Autozone may have one you can borrow.

Can you put an impact gun on the crank pulley and spin it that way?

you will need a leakdown tester,

air compressor, and knowledge of the firing order for that test..

You really need consistent fast rotation (starter) for the compression test to be accurate.

Yep a leakdown test would be best, I was tearing down the engine and thought about throwing my compression tester on it just to see what it would do.

Yea I tried that.

I've bought and installed a lot of used engines.

Never bothered to test compression.

In fact I've seen very few engines with compression problems.
I wouldn't worry about it
Especially if you saw the car it came from.

You'll not get accurate readings if you can't spin the engine at least 200-400 rpm

Came here to post something similar to this. Leak down test is what you seek for an engine on a stand.
also for good measure, cut open the oil filter and check for gold just to be sure there’s no spun bearings in the rotating assembly.

Thanks !! Thats exactly what I need to know.

And make sure you open the throttle plates when you test or they will all be incorrect.

The difference in reading is negligible.

I was able to get a decent leakdown tester and tested the engine , a Dodge Neon 2.0 SOHC.

Since I had the valve cover off I went ahead and just removed the rockers and shafts.

Tested at 100 psi input.

Readings:

Cyld # 1 was at  ~75 psi heard it leaking out the exhaust

Cyld # 2 was at  ~22 psi       "      leaking out the intake

Cyld # 3 was at  ~ 20 psi      "      leaking out the exhaust  

Cyld # 4 was at  ~ 25 psi      "       leaking out the intake

Also when I removed the water pump there was a big old blob of snot looking stuff that I assume is stop leak.



Will call the salvage yard in the am.

NO!

Good call, on to the next one.

Might want to see if they will refund some money to have the head rebuilt at a machine shop. I think you’d come out with a better job. Could even clean out the block and re-ring/bearing it.

Impact guns don't work like that

Picked up the THIRD used engine yesterday, will test it out in a little bit.

First engine had less than 5,000 miles on it but the guy who delivered it dropped it on the ground and broke one of the trans mounting tabs off., but the cylinders were full of mud and the cylinders were pitted real bad.

Second was the one that was the subject of this thread.

Third one, I shall see.

Well the third engine tested better but not as good as I hoped.

The valves are leaking on #2 3 and 4 but not too bad and a valve job should fix it along with a resurface.

So I pulled the head and will send it out to be checked.

I pulled the number one rod cap and looked at the bearing and it looks great.

Cylinder walls look ok as far as no obvious problems except for alot of carbon build up on top each piston so maybe hone and new rings.

I have no clue how many miles on it, the timing belt , waterpump and the head gasket have all been changed to aftermarket stuff.

The head gasket looked ok with no obvious problems.

I am tired of playing musical engines with the salvage yard and this one seems good enough and without major issues and I will probably just freshen it up.

At this point, you would have been better off rebuilding the engine that came out of it with all the time and effort put into fuck-fuck games with a salvage yard. Just have a trusted machine shop do the bore, crank and heads and order a rebuild kit with whatever size bearings the crank ground or polished to and bore honed to.

As long as the head isn't warped, it's fixable with a valve job and a shave of the gasket surface.

The original engine in the car is toast, my daughter was in traffic and it blew the upper radiator hose but by the time she was able to pull over and stop the engine died and would not spin over. You can turn it with a long breaker bar so its not locked solid.

I have did all kinds of issues with that original engine, its got like 250,000 miles on it, but it's always had a coolant leak that I could never find. It would do good except on REALLY hot days the the coolant would just disappear.  I changed the head gasket thinking it might have a small leak, did not fix, the heater core leaked a tiny bit so I changed that no change, the waterpump was stained just a tiny bit at the weep hole so I change that. Still the same problem. New radiator all new hoses ect.

I would check the coolant, my daughter would drive 45 minutes away and call me telling the car is running hot, so i go check it out and its like two gallons low. It would not do it all the time except only on REALLY hot days. As long as it was not the hottest days of the year it would not lose any coolant for months. But on a super hot day you could count on it to over heat. I  even tried ceramic block sealant as a last resort.

Crazy thing is there was never any coolant that I could find that was leaking out, only thing I can think of that the block had a hairline crack in the cylinder bore that would only open up when the engine reached a hotter than normal temp on a really hot day.

Worked with a guy that worked at an automotive machine shop for years and it just blew his mind because he had seen just about any overheating issue an engine had, I also was working at a Dodge dealership and it stumped everyone including the good techs.

So thats why I am wanting to start with another engine.