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Snapped timing belt EJ253 AVLS


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06 Outback 2.5i EJ253 SOHC AVLS, 200k miles.  Did the HGs about 50-55k ago.  Had to replace a cracked head, replace worn piston rings, and pitted exhaust valves.

Compression test revealed 0 PSI on all cylinders.   Since this is a high mileage car, I don't want to be throwing endless amounts of time, money and effort on it.  I do want to get it back on the road though.

1st question-  What causes the timing belt to snap?  Belt was a Gates, had 70k and 6 years of use.  Short of the factory 105k or 105 months spec.  Belt has no obvious wear, missing teeth, cracks, etc.  Just a snapped. All idlers, tensioner, and WP were replaced 50k ago and were in good shape.  Engine turns over by hand now with a new belt installed, so I don't think anything is seized up.  Is there anything I should be on the look out for or just chalk it up to a bad belt?

2nd question-  I got a pick n pull motor last weekend. After bringing it home, I discovered it's got a bad rod bearing on #1.  The valves appear to still seal well (10% on a leakdown test, ~75psi on a hand cranked compression test), but the cam journals are in pretty rough shape (pictured).  What's the most cost effective approach here?  Are those valves still good?  Could I swap the valves over to my heads?  Have a machine shop repair the cam journals?  If I swap the valves over, should I pay the machine shop for another valve job or can I get good enough results if I lap them by hand?

20210927_223359_HDR.jpg

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the belt is a quality issue, and sadly, Gates has gone downhill in recent years - i wont use them anymore for timing.

Mitsuboshi is the OE supplier and preferred brand for timing belts on these cars.

Aisin for water pump, NSK or Koyo for idler pulley bearings, and NTN for the tensioner assembly. These are all OEM parts and what is recommended

 

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7 hours ago, jamesm113 said:

2nd question-  I got a pick n pull motor last weekend. After bringing it home, I discovered it's got a bad rod bearing on #1.  The valves appear to still seal well (10% on a leakdown test, ~75psi on a hand cranked compression test), but the cam journals are in pretty rough shape (pictured).  What's the most cost effective approach here?  Are those valves still good?  Could I swap the valves over to my heads?  Have a machine shop repair the cam journals?  If I swap the valves over, should I pay the machine shop for another valve job or can I get good enough results if I lap them by hand?

We have two pick-n-pull yards here, and why you'd want to do all that expensive and high-hassle messing with that head - rather than just returning it to them for an exchange - is beyond me.  Take it back and get one without the trashed journals.

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57 minutes ago, 1 Lucky Texan said:

The toothed idler is often the weakest link.

This is actually quite interesting.  Apparently the toothed idler suffers a much higher failure rate than the smooth ones, which is odd if you consider that it has the same bearings, and is spinning at exactly the same rate, as the smooth ones.  The only timing failure I've experienced to date was the toothed idler seizing, so it gets changed too when I change the belt.  My guess is that the constant engagement/disengagement of the teeth generates a lot of vibration that degrades the bearings faster than in the smooth idlers.

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I had replaced the idlers and WP during my HG job 4 years/50k ago.  Used koyo smooth idlers and an NSK toothed idler.  OEM water pump.  NSK toothed idler wasn't roller blade bearing bad, but was a little spun out.  Absolutely no wobble.  All other bearings were in good shape.  I had thought I had replaced the tensioner, but can't find the paperwork, so perhaps I didn't. It's an NTN and in good shape though.

As far as the junkyard motor - it's a 2 hour drive each way to the junkyard with no traffic and there's normally some of the worst traffic on earth between me and the yard.  Subarus that would fit my needs are very rare and I opted to not spend the extra $75 on the 60 day replacement warranty, so I'm stuck with the junkyard motor. 

Soo, yeah, it would be nice if I could at least use the valves from the junkyard motor

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We have Pick Your Parts here in southern california.  Pick Your Part doesn't have any warranty in CA unless you purchase the extended one: https://www.lkqpickyourpart.com/yard-rules/warranty/

 

In other news, I just called around some machine shops and got quotes for head work... $400 seems to be the going rate for a valve job.  Plus $75 a head for resurfacing.

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Photo of the carnage.  All but 4 intake valves were bent.  Junkyard valves seem to be in good shape, no pitting, some carbon deposits. Going to try lapping and testing to see if I can avoid a valve job at the machine shop.20211002_122051_HDR.thumb.jpg.50a3ff955aefc523655627085e86d987.jpg

Edited by jamesm113
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  • 2 weeks later...
  • 2 weeks later...

Got around to testing the heads and assembling them this week.

One of the intake valves was leaking when I did the acetone+compressed air test, so I took it back to the machine shop.

He said something along the lines of if he had known I would be testing them after he was done, he woulda done things differently.  He did say that once the motor "was fired up, they'd seal right up".  He's kinda one of those old school guys, so I don't know.  He has good reviews on Google & Yelp, and I've heard a few good things about him through my friends.

He lapped the valve that was leaking, I took the head back home and reassembled the motor, using the Fel Pro MLS gasket kit.

I did a leak down test, I was getting about 10-15% on every cylinder, which is higher than I would expect (I was getting 8-10% with the junkyard motor).  So I guess I'll find out after I install the motor if he's right about things "sealing right up".

Edited by jamesm113
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Pistons look pretty black and wet. I would be doing rings. NPR rings are cheap. DO NOT hone it. Just clean the pistons and install new rings. 

Machinist is correct - once the engine fires up the valves will lap themselves in pretty quickly. We will often drop in new valves and stem seals in cases like this and just do a light hand lap on them, resurface the head, inspect and stake any moving guides and send it. 

GD

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What did you end up doing about the scored rod?

2 hours ago, jamesm113 said:

The motor is back together now and I was planning on dropping it in tomorrow.  What causes the pistons to look black and wet?

I don't know if I'm missing something else with your move involved multiple engine/previous work scenario but oil blowing past the oil control rings.  Or a massively hosed PCV system but I doubt that's the case here. 

Good to know these lap in easy, I'll likely ever avoid doing another valve lap job but I've done it before and was (too) meticulous about it. 

On 9/30/2021 at 2:26 AM, jamesm113 said:

Belt was a Gates,

That's the issue. They might not be horrible but they have a higher failure rate.

On 9/30/2021 at 10:33 AM, ThosL said:

Are there any stress triggers on these? Running the engine too hard, sudden jerks back ups, etc.? Is there any way to know they are at risk as when these break it is tow truck city?

waiting too long to change the oil and low oil. 

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Yeah, my PCV valve was also 50k old...  I am replacing it with a new OEM PCV valve during this rebuild.

Car history - bought the car with 145k.  Noticed that it had a slight overheat condition going up hills, etc.  I never allowed it to go past 3/4 of the way up the temp gauge (~230F), but have no idea what the PO did.

While troubleshooting overheat condition, noticed HG's leaking oil externally.  Thought I should do HG as perhaps it was related.  Pulled motor and dropped the heads off.  The machine shop reported the exhaust valves were shot (pitted) and the driver head was cracked on one cylinder between the valve seats and spark plug hole. Also replaced the piston rings per GD's advice.  Replaced all driver head, exhaust valves, had valve job done, put the car back together, still was overheating.

Ultimately, I figured out the overheat issue 500 miles after the rebuild by doing a thoroflush brand chemical flush and replacing the radiator with a denso radiator.  I do not think the head gasket failure was contributing to overheating.

Fast forward 4 years and 50k miles, the gates timing belt failed, 12 valves bent.... rebuild #2 :banana: 

Car was running great before the belt failure.  No issues, just oil changes every 5k.

Edited by jamesm113
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Valve stem seals were replaced 50k ago with OEM parts.  Slipped guides - old cracked head a slipped exhaust valve guide, but that head was replaced.  None of the valves had a slipped guide when I checked them this time around.

Also noticed the two vent hoses from each valve cover were cracked and there was good amount of oily residue in the intake manifold.

So I guess PCV...

 

Thanks!

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