Drivers intake Cam skipped 2 teeth

[FerGloyale]

Background.

08 WRX, 89K miles.  A few upgrades (GS intercooler, Perrin silicon intake tubes, bell-mount down-pipe, tuned, ) but basically a stock engine.

It was burning oil, smoking, so we pulled the heads to do rings and a HG job.  Engine looked good inside.  New oil pan, resealed oil pump with Subaru O-ring.

New Timing components went on with the reassembly.

Started up........ran smooth for 20~30 secs..............then bad, sudden sound and engine stopped.  Sounded like a bad sound from drivers side.

Pull timing covers....Drivers side Intake cam skipped 2 teeth behind all the rest...........Engine turns free, all Cams turn freely with belt off.  

When rotating the Drivers intake cam I can feel the valves resistance at 2 different points of rotation, like normal.  

Not sure what I'm gonna find inside when I pull valve cover, but I'm taking guesses.

Thoughts?

I'm not gonna sleep tonight I know it.

 

[el_freddo]

You’ll either find valves that “sit” lower than the rest (bent) or you’ll find nothing. 

I reckon two teeth out wouldn’t do anything nasty physically. But for engine operation it might just be enough to upset the apple cart. 

I can understand why you won’t sleep well tonight, but I reckon you’ll be fine. 

Cheers 

Bennie

[FerGloyale]

3 minutes ago, el_freddo said:

You’ll either find valves that “sit” lower than the rest (bent) or you’ll find nothing. 

I reckon two teeth out wouldn’t do anything nasty physically. But for engine operation it might just be enough to upset the apple cart. 

I can understand why you won’t sleep well tonight, but I reckon you’ll be fine. 

Cheers 

Bennie

Well....I'm hoping 2 teeth won't have bent valves, but WHY did the cam skip?  What caused the Cam to drag and what was that clunk, terrible sound, just before it stopped?

It was all brand new, Mitsuboshi belt, NTN tensioner, all new rollers, Waterpump, etc.......All Brand new OEM parts.

I'm hoping the cam isn't snapped.  It is one of those fully hollow Cams.  

We cranked engine 3 times for 20 secs a piece with no Crank sensor to prime oil pumpbefore firing it up.......Oil light went off so there was pressure from the pump, but wondering if the oiling to the head has some issue.

[idosubaru]

 

This shouldn’t matter but if it’s MT does it have the timing guide above the crank?

 

 

[GeneralDisorder]

Absolutely no reason to go in that far without doing forged pistons. Almost criminal not to in fact with how prevalent ring land failures are. That and a Killer-B pickup tube. 

But that's besides the point. Kinda sounds like a partially seized camshaft.

In my experience 2 teeth is borderline.  Sometimes you get bent intake valves, and sometimes you don't. 3 teeth is a guarantee on the dual cam engines. 

That said..... I have never had what you describe happen but if the DS intake cam should momentarily seize up the crank could pull enough slack to make the belt skip I'm sure.

GD

[FerGloyale]

26 minutes ago, idosubaru said:

 

This shouldn’t matter but if it’s MT does it have the timing guide above the crank?

 

 

It does.  It was in place, but not interfering.  I put a thin sheet of cardboard between it and the belt before I tighten it's bolts, so I can be sure there is space between it and the belt. 

And because it's a DOHC turbo motor, it has guides over both pass side and the drivers exhaust cams.

It doesn't have a guide over the drivers side intake cam.....but it has the extra small roller by the tensioner.  

Something must have caused the Cam to resist the rotation, and skip.  It didn't just randomly jump 2 teeth for no reason 30 secs after startup at idle.

[FerGloyale]

1 minute ago, GeneralDisorder said:

Absolutely no reason to go in that far without doing forged pistons. Almost criminal not to in fact with how prevalent ring land failures are. That and a Killer-B pickup tube. 

But that's besides the point. Kinda sounds like a partially seized camshaft.

In my experience 2 teeth is borderline.  Sometimes you get bent intake valves, and sometimes you don't. 3 teeth is a guarantee on the dual cam engines. 

That said..... I have never had what you describe happen but if the DS intake cam should momentarily seize up the crank could pull enough slack to make the belt skip I'm sure.

GD

Yeah, forged was discussed.  

Stock pistons looked great......no scratching or scoring.  Oil rings coked up but drain holes were open still.  

Pickup tube is the "new" design without the stupid clamp in the middle.  It's a one piece with it's support leg near the bottom. Got cleaned spotless and shiny in the hot tank, examined for cracks, none found.

As for the Cam.  It was 2 teeth.....all 3 other cams were timed perfect tot eh crank still.  So the intake valves opened later than they should.  Normally they open right as piston begins to go down for the "intake" stroke.  2 teeth late would mean it wouldn't open them until the piston was further down, but I think they will then be closed again before the piston is on it's way up again.  So I don't expect piston to Valve contact.  Now valve to valve with an open Exhaust valve? We will have to see.

I hate turbo cars.

[lmdew]

1+ I hate turbo cars.

I've worked on my son's 92 turbo but I'd never buy one.  NA for me.

[idosubaru]

11 hours ago, FerGloyale said:

WHY did the cam skip?  What caused the Cam to drag and what was that clunk, terrible sound, just before it stopped?

Were the heads disassembled, valve job?  Spring, guide issue?

Silly questions of the day: timing tensioner pin was pulled?

any chance it was off a tooth or so once it was rotated a couple times and settled?

 

4 hours ago, lmdew said:

1+ I hate turbo cars.

I've worked on my son's 92 turbo but I'd never buy one.  NA for me.

I avoid them as well. For the extra seats and kids a totaled Ascent would be worth a look, wish NA was an option on those. doubt I’ll see many of them any time soon anyway. 

[GeneralDisorder]

I LOVE turbo cars. Those fools bought me a dyno. All the money is in the turbo world and making more power. About 75% of our work is turbo cars. After you do a few hundred you get the process down. We turn them out like an assembly line. 

If we go in that far, we do forged pistons. Period. You can't judge the condition of the pistons visually. The ring landings can fail from fatigue at any time. It's a $hitty casting and the are weak. My cost on a JE set is like $450 and they come with rings. With that much labor on the line how does it pencil out to NOT have forged pistons and increase the value of the car when doing this invasive of a job? 

And the pickup tubes are $37 from Subaru - in stock. Not even worth cleaning or checking for cracks. Labor is $100+ per hour everywhere..... How much time can we spend on such a part? And why take the risk? I have several in my graveyard that are broken off at the flange. Killer-B or new Subaru. No way I'm reusing that junk. 

I still think you will find some kind of camshaft issue which isn't really a turbo thing per-se. Could happen to anything. I've seen broken cams, seized cams, and everything in between. Never happened in 20 seconds on a startup..... so I'm going to say either it's a freak component failure, or an assembly error/journal contamination, etc.

GD

[idosubaru]

2 minutes ago, GeneralDisorder said:

I LOVE turbo cars. Those fools bought me a dyno.

LOLOLOLOLOL

[FerGloyale]

2 hours ago, GeneralDisorder said:

I LOVE turbo cars. Those fools bought me a dyno. All the money is in the turbo world and making more power. About 75% of our work is turbo cars. After you do a few hundred you get the process down. We turn them out like an assembly line. 

If we go in that far, we do forged pistons. Period. You can't judge the condition of the pistons visually. The ring landings can fail from fatigue at any time. It's a $hitty casting and the are weak. My cost on a JE set is like $450 and they come with rings. With that much labor on the line how does it pencil out to NOT have forged pistons and increase the value of the car when doing this invasive of a job? 

And the pickup tubes are $37 from Subaru - in stock. Not even worth cleaning or checking for cracks. Labor is $100+ per hour everywhere..... How much time can we spend on such a part? And why take the risk? I have several in my graveyard that are broken off at the flange. Killer-B or new Subaru. No way I'm reusing that junk. 

I still think you will find some kind of camshaft issue which isn't really a turbo thing per-se. Could happen to anything. I've seen broken cams, seized cams, and everything in between. Never happened in 20 seconds on a startup..... so I'm going to say either it's a freak component failure, or an assembly error/journal contamination, etc.

GD

 

pickup tube went intot eh washer and came out clean.  Zero extra time used as opposed to new.  Anyhow.

The issue was a galled journal, receiving too little, or too dirty oil. Fed parallel to the screened banjo for AVCS, so that's not the problem.  2nd journal.  Weird thing is, 3rd journal, which is further down the line, was fine and beautiful and poured clean oil out when cam removed.  And the AVCS solenoid, and the ports it supplied had clean good oil in them too.  I am thinking the machine shop did not do a good job of cleaning out the journals after washer.  Dried up old soapy oil chunk sitting right there in that 2nd journal hole.

Anyhow.  Polishing the galled Cam.  Light emery cloth on the carrier and head journals.  I will check clearance with plastigauge before final assembly.  Was still freewheeling  not fully seize so should be OK.

I pulled banjos on the turbo and hte pass side AVCS, set all cams to closed, pulled spark plugs, and cranked engine 20 secs. at a time until all oil pumped out cam journals, and AVCS/turbo banjos.  Pumped the entrie contents of the oil pan out and all looked super clean by the end.

Compression test later will tell if valves are bent, but I don't think so......Clearance was right on i.e. no "low" valves.

****note****  This engine was the very first time using "lucas" engine assembly lube, green greasy sticky stuff in a bottle..  Usually use the more traditional black "sta-lube" stuff from a  tube.

Can't say it's the problem, but never had this issue before, and the lube didn't create the dirty crap in journal 2, so it can't be the whole issue.  But I have never, in 16 years of building engines had this happen to a Cam.  It's goin in the trash.  Or maybe in my wheeler gearbox....can't hurt in there.

[idosubaru]

glad you found it. I was wondering about the head work. Seemed like if it was touched it would be a candidate for suspicion .

so you cleaned up the scoring and replaced the cam?

[FerGloyale]

3 hours ago, idosubaru said:

glad you found it. I was wondering about the head work. Seemed like if it was touched it would be a candidate for suspicion .

so you cleaned up the scoring and replaced the cam?

Not yet.  Didn't get to the pressure test(leak down) yet to confirm valves are OK.  I think they are, but I'm gonna check. in the morning, and plasti-gauge the Cam/journal before final assembly.

I did decide to give to GD's advice a little, and pull the oil pan and inspect a more closely the pick up tube.

Again, I did not find any signs of crack, deterioration of brazing, or any signs of clogging.  When I unbolted the tube from the block, a large burble of oil dropped oit the bottom, as if a thumb had been lifted off the top of the straw......soooooo.......I think it was sealed and sucking well.

Glad I took the pan off, because even after pumping out oil through, and then draining the rest through the drain plug, when it came off, there was about 8~10 oz of "new" looking oil, but totally darkened and swirling with silty, gritty crud.  So good to get that all out of there.  In retrospect, maybe I could have done more to blast out ALLLL of the residual oil in the engine galleries.  I usually don't, I just cap all open oil ports during work, and fill with new oil on assembly.  15 years, never had a problem on startup like this.  

 

I do not think this customer will be buying a KillerBee oil pickup any time soon.......$185 dollars?   He said no thanks.  Literally millions of the stock EJ pickup tubes driving around just fine with no problems.  New OEM is only about $30.....so.....might be worth the peace of mind, but I do not think the pickup tube was at all involved with the Cam skip/seize issue. It was good to check though.  

I feel like plenty of shops would have just reset the Cam, fired it up again without even checking journals, oil pan, etc.....Might have run long enough second time to get down the road and get the shop paid.........not my way of doing it......I wanted to investigate every possibility before even trying to fire it again.

 

 

Edited October 2, 2019 by FerGloyale

[lmdew]

Good to know there are Great Mechanics out there that care and take the time to do it right.

[idosubaru]

thanks for the recap, obviously we hope it doesn’t happen but it’s fun to hear you diagnosing and figuring this stuff out as you go.

[FerGloyale]

1 hour ago, idosubaru said:

thanks for the recap, obviously we hope it doesn’t happen but it’s fun to hear you diagnosing and figuring this stuff out as you go.

 

Glad someones enjoying it. 

[el_freddo]

Im looking forward to hearing that it’s successfuly running and is returned to the happy owner without further issue. 

Cheers 

Bennie

[FerGloyale]

Car is up and running well.

Owner is taking it on a 100 mile drive today.

Moral of the story.....Fully clear ALL oil passages in the block of ANY old oil before startup of reassembled engine.

In this case, I left the "block prep" part of the process up to the owner, and he may not have cleared out the inside of the crankcase well after cleaning the block.  IDK.....Probably wont' ever fully know.

But for now, everything seems OK to go.