Hybrid motor - timing belt broke - interference?

[jey]

Was driving home yesterday on the highway and all of a sudden the rpms dropped to 0, but there was no engine braking. Doh! Dumped it into neutral and coasted into a parking lot to evaluate.

After checking the oil to make sure it wasn't something completely catastrophic, I cranked it, and it freewheeled the crankshaft with no compression resistance. Got it towed home, haven't taken the timing belt cover off to look at it, but I'm pretty sure the timing belt broke.

This is a hybrid motor - EJ257 shortblock, with EJ25 SOHC heads from a 1st gen 2.5RS.

Is there ANY chance that this configuration is non-interference? If there is I'm going to slap on a new belt and do a compression test. But if we're 100% sure I've belt some valves I might as well pull the motor.

I'm thinking since it's SOHC there is no valve-to-valve collision. I'm wondering if the low-compression EJ257's pistons happen to be shaped in a way that prevents piston-to-valve collision too.

[mike-tracy]

The ej25x heads are all interference, sorry. There is a chance that the valves didn't come in contact, on one side, however.

[jey]

Is there an easier way for me to diagnose the valves than putting on a new timing belt and doing a compression test?

[ericem]

It's not that much work to put the timing belt on and do a compression test you can start it with all the covers and accessory belts off and even no crank pulley, but I would put it on.

You have to tear the front of the engine apart anyways. Depending on the rpm's you were at during the failure you could be perfectly fine.

[jey]

Yeah I was doing 70+ mph, I think that's at least 3500 rpm :lol:

[jey]

Took the cover and everything off this morning and it turns out that the Idler had just fallen out:

http://www.jeyping.com/idler.jpg

Bearings look pretty messed up too, I guess it seized?

Made some nice gashes in the timing belt cover, and ground up the timing belt as well.

[jey]

Looks like one of the other idlers got dinged up by the geared one banging around:

http://www.jeyping.com/idler2.jpg

Do I need to replace this one also??

[jey]

After some other research I decided to replace all the idlers. I pulled them and the bearings weren't all that smooth anymore.

Started to re-install and broke one of the water pump bolts :( I guess using a torque wrench for 7.4 lb-ft of torque was a horrible idea. Also forgot to install the gasket on the side of the pump. Ugh.

Owell, don't need a water pump to do a compression test. Guess I'll keep going, get the timing belt on and see what I can find.

[jey]

You all are right - I have 0 compression in all 4 cylinders.

So now what? I see 2 options so far:
1. Tear open the heads and replace the valves.
2. Find another set of SOHC EJ25 heads and swap...

Course, if the piston contacted the valves, is the piston damaged also?? This is starting to sound like a full blown rebuild...

[Huffer]

You're going to want to tear it down...

[superu]

sorry, i have nothing to add to your inquiry but am curious about your HC motor setup. How does EJ25 heads mated to an EJ257 block make hight compressions.. I thought it was EJ22 heads on an EJ25? Is it something in the 257 coding that makes it a different 2.5 liter block?

Junst curious since I'm a little interested in the frankenmotor high compression 2.2-2.5 hybrid...

thanks and best to you and your fix!






[b]This is a hybrid motor - EJ257 shortblock, with EJ25 SOHC heads from a 1st gen 2.5RS.

[jey]

The EJ257 actually lowers the compression - it's the block from the STi. I'm running a turbo through this motor.

[superu]

The EJ257 actually lowers the compression - it's the block from the STi. I'm running a turbo through this motor.


Ahhh, that makes sens... lower compression then boost.


Right on, thanks man!

[jey]

Ok, rebuilding the heads myself will be too much trouble and I'll probably screw it up anyway since I've never done it before. Found a good shop in my area (http://duffinengine.com/) so I think the plan is to pull the heads and take it to them. Guess I've got some dismantling to do tomorrow! We'll also find out how dinged the pistons are too I suppose.

[jey]

Didn't have an engine hoist, so I figured I'd try pulling the heads without lifting the motor. Nobody recommends doing it this way, but I don't know many people that have the SOHC heads in the Legacy either :) Legacy engine bay is bigger than the Impreza/Forester, and the SOHC heads are smaller than the DOHC heads that you usually find in the Legacy, so I felt adventuresome.

Success! It was unbelievably simple - unbolt the intake manifold, unbolt the exhaust manifold, take off the valve cover, 6 head bolts out.

http://www.jeyping.com/timing2.jpg

There was EXACTLY the right amount of room between the heads and the body for the head bolts to clear out of the block. It was almost as if Subaru designed it this way - in fact, why on earth DIDN'T they use the SOHC motor??

Bent valves:
http://www.jeyping.com/timing1.jpg

The collision left its mark on the pistons too:
http://www.jeyping.com/timing3.jpg

Is this damage going to be a problem??

[mike-tracy]

I see the valve reliefs on the piston, not any valve to piston contact.

[jey]

Sweet, thanks! I haven't stared at a piston in a while - didn't realize the reliefs looked quite like that :lol:

[jey]

It was actually scary how well one round of oven degreaser worked:

http://www.jeyping.com/timing6.jpg

I don't see any cracks so far, I think I'm good.

[Baddog]

Success! It was unbelievably simple - unbolt the intake manifold, unbolt the exhaust manifold, take off the valve cover, 6 head bolts out.



This was all after taking the timing belt cover off and the timing belt right?

I was going to go to a junkyard and tear apart their engine there just to see how the heads came off.

[jey]

Correct. Timing belt removal is easy too - remove radiator fans, remove coolant overflow tank, two tensioners take out the V-belts, unbolt the crank pulley, 2 bolts take off the A/C tensioner, and a few bolts for the timing belt cover.

The heads come off differently on the 2.2 - it's even easier and they're smaller. I think you don't even need to remove the valve covers.

So the question I have now is - should I put in fresh head gaskets while I have it all apart? The ones I have now have 68k miles on them...

[Baddog]

Thanks for the help. I have a 2.2.

I would put in new head gaskets while you're in there. I am one of those people. If you're in there you might as well do it.

I don't think you would need the heads resurfaced either. Since they have been done recently it sounds like.

[Zedhead]

I don't see any evidence of the valves colliding??
Head gaskets are ONE TIME USE!

Definately need a new set.


https://sl-i.net/FORUM/

[jey]

Those valves are bent, almost every single one, and the other side is worse - that picture is with the camshaft turned in the valves closed position, but there is significant gap and not forming a seal. If you angle it right you can see daylight shining through it :lol:

[Huffer]

port n polish time!

[elislider]

any shiny marks on the pistons or edges of the valves is a sign of contact. it doesnt take much!
good luck on your rebuild

[ouch1011]

I've pulled the heads that way once on a EJ25D. Its much easier than most people make it out to be, but not any easier than pulling the engine. Unless, of course, you have very limited space or no engine hoist.

And technically speaking, all gaskets are 1 time use unless otherwise noted. Head gaskets are pretty much always 1 time use.