How long before rebuilt engine rings seat? EDIT. Help a 1st time engine builder.

[brianao34]

Sorry to be the bearer of bad news, but that means the air is escaping into the crank case - usually means rings or a damaged piston.

Yea, I know, but you're always going to have leakage past the rings. And I forgot that the engine was dead cold when I did the test :/ oops.

[ForcedFirebird]

30% is a lot.

If you had the pistons at TDC and the air was escaping from the oil dipstick, the rings are toast in that cylinder.

[TobyB]

Yar, new motor <10% with Deves, <5% total seal.

...and a leakdown test isn't going to show up bad valve stem seals no matter....

I think the cylinder with 30% needs a borescope, and hope it's not a pin- meets- wall event.

t

[brianao34]

Well, after reading online about how inaccurate the Harbor Freight Leakdown tester is I feel a lot better, and it only tests at 15psi...

The project is on hold for now until I get moved into my new house at the end of the month, but I WILL be updated with a solution.

For now I'm just hoping the machinist that "went through" the head screwed up the valves seals or something simple.

[brianao34]

UPDATE
So I got a nice OTC cylinder leakdown tester for Christmas and retested my engine after warming it to operating temperature...
Everything was 5% or less! WOOOP! Giant sigh of relief.
So that just leaves the valve stem seals, and if it's loosing oil that fast it'd have to be something drastic like the machinist forgot a few...
:)

[jlevie]

A compression and leak down tests are essentially a test of the compression rings and the valves. The compression rings can seal even though the oil control rings have never seated, which is typically the result of a failure to cross hatch hone the cylinders or cylinders that are worn past the wear limit. Excessive oil burning can also be from worn valve guides and/or bad valve seals.

[TobyB]

ANd Harbor Freight is for things like hammers and pry bars,

not leakdown testers and torque wrenches!

t

[whodwho]

Unless I missed it, when do you notice it smokes?

You should be able to narrow it down by:
on accel - rings
on decel - stem seals
when leaving a light after idling - stem seals

5 qts of oil in 75 mi it should be smoking like a freight train if it is burning it!

[SmokeE30]

I've seen bad valve seals kill an m52 by burning up all the oil within a 175 mile trip, left full of oil, arrived and at destination very unhappy and siezed going up the driveway that's when it was discovered it burnt away all of its oil. This was on an engine that although was completely refreshed not rebuilt, sat for 4-5 months before it was put in the car and the valve seals dried out. Something to think about

[brianao34]

A compression and leak down tests are essentially a test of the compression rings and the valves. The compression rings can seal even though the oil control rings have never seated, which is typically the result of a failure to cross hatch hone the cylinders or cylinders that are worn past the wear limit. Excessive oil burning can also be from worn valve guides and/or bad valve seals.

Yea, I've heard that before, I'm thinking I'm just going to replace the valve seals before I tear the engine completely apart and hope for the best.

I've seen bad valve seals kill an m52 by burning up all the oil within a 175 mile trip, left full of oil, arrived and at destination very unhappy and siezed going up the driveway that's when it was discovered it burnt away all of its oil. This was on an engine that although was completely refreshed not rebuilt, sat for 4-5 months before it was put in the car and the valve seals dried out. Something to think about

That's a good point, the head did sit dry for probably 6 months before I had a chance to put the engine together. That sounds very feasible. Thanks.

[e30rapidic]

I had totally missed this thread before but after reading a few threads I'm saying valve seals. But are the valve seals even there to leak that much oil!?! wow

I totally rebuilt my S50 and it never smoked. I'm also one of those let it warm up and drive it hard (within reason) folks. Best of luck, hope you find a quick/easy/cheap(relatively) fix with this. I have my fingers crossed for you.

[brianao34]

I had totally missed this thread before but after reading a few threads I'm saying valve seals. But are the valve seals even there to leak that much oil!?! wow

I totally rebuilt my S50 and it never smoked. I'm also one of those let it warm up and drive it hard (within reason) folks. Best of luck, hope you find a quick/easy/cheap(relatively) fix with this. I have my fingers crossed for you.

Thanks man. Yea, it sucks but it is my first top to bottom rebuild so there were just too many variables to be flawless.

[brianao34]

ANd Harbor Freight is for things like hammers and pry bars,

not leakdown testers and torque wrenches!

t

Agreed, i bought that thing a long time ago while in college, the HF tester tests at 15psi...what a joke.

[brianao34]

Somebody put me out of my misery.

Finally finished up replacing the valve seals (my last ditch effort before tearing the pistons out)
And took it for a test drive last night, still smokes...
I'm not good with failure, especially when it comes to cars.

Here are the Cliffs for those not following:
- Completely rebuilt S50B30US
- Consumes approximately a quart every 10 miles
- No oil in coolant or vice versa
- Absolutely no leaks
- Compression tests good (don't remember numbers)
- Leakdown tests good (All cylinders 3-5%)
- Just replaced valve stem seals
- Barely smokes at idle, smokes like a train under full throttle
- Car pulls HARD


And here's my theories:
- There is so much oil left in the cylinders from burning so much oil that the compression and leakdown tests are skewed and the rings are really not seated
- Maybe just maybe the oil control rings are upside down. Haven't confirmed with Deve's Piston Rings yet, but I assume they have a right-side up

But it's looking like the pistons have to come out...
Sucks, hard. I just want to drive my car again (been almost a year since I pulled the M20) and I'm stuck driving my little brother's Sentra...

Any help is appreciated, usually all the east stuff like installing air filters and changing your oil is documented left and right, but the more technical stuff is hard to find. I guess the people that rebuild engines all day and master mechanics aren't usually forum-goers. :/

[whodwho]

Unless I missed it, when do you notice it smokes?

You should be able to narrow it down by:
on accel - rings
on decel - stem seals
when leaving a light after idling - stem seals

5 qts of oil in 75 mi it should be smoking like a freight train if it is burning it!

Somebody put me out of my misery.

Finally finished up replacing the valve seals (my last ditch effort before tearing the pistons out)

- Barely smokes at idle, smokes like a train under full throttle
:/

You must of missed my post ;)