2.5L DOHC Interference question

turboleg · Post by **turboleg** » Sat Apr 25, 2009 12:03 am

Hey guys. I know this topic has probably been covered. Each time I search for key words I think will work well I get tons of posts that don't seem to answer my exact question.

So the car is a 98 Legacy Outback (2.5 DOHC) that all of the sudden died on the road. My friend had it towed to my work, it now resides in the factory machine shop awaiting me.

I figured the first thing I would check would be the timing. I pulled the two side covers to find that the two marks (double lines) on the left side head line up and the two marks on the right side line up. But the left and right heads don't line up at the same time. I know that this is an interference engine, but is this valve to valve, valve to piston, or both?

The reason I ask, is that it makes "some" sense to me that the belt may have jumped but in some magical fashion the cams seem to have preserved their position relative to one another. So if I looked at the cam pulley right, and the engine is a valve-valve interference I should be able to install a good timing belt and have this thing fire up. Sound right?

Sorry for my lack of knowledge...this happens to be my first DOHC catastrophy! I LOVE MY BC!!!!!!!

log1call · Post by **log1call** » Sat Apr 25, 2009 12:21 am

If the belt is still intact I doubt it caused the breakdown. Have you extracted trouble codes? Have you checked for spark and fuel?

turboleg · Post by **turboleg** » Sat Apr 25, 2009 12:33 am

Spark is good and fuel is spraying. I ran the OBDII scan and found no codes stored.

Thats when I turned my attention to the timing. Seems strange to me that the left and right sides don't line up at the same time.

Matt Monson · Post by **Matt Monson** » Sat Apr 25, 2009 1:13 am

Remove the timing belt and do a leakdown test. No guessing with a leakdown test.

turboleg · Post by **turboleg** » Sat Apr 25, 2009 1:22 am

Thanks Matt.

I'll give it a try

log1call · Post by **log1call** » Sat Apr 25, 2009 1:57 am

I'm not sure if you know but....
Those two lines, the double ones, they are meant to be together, that is as close as they can be, on both cams on any particular side. The single lines on each cam sprocket are meant to line up with the marks on the plastic cases. The double lines should be at the twelve and six positions of the cam sprockets and together.

turboleg · Post by **turboleg** » Sat Apr 25, 2009 2:39 am

Right. The issue is that when the double lines on the left side of the engine are aligned the ones on the right side are not. Likewise, when the right side double lines are aligned the left double lines are not. When I say that the double lines aren't lined up I mean there at least 1/4 cam rotation away from being lined up. Or in other words the right and left side heads nearly 90 degrees out of sink.

Bigest question is still, is this a valve-valve interference engine or a valve-piston interference. Valve-valve I might be ok with re-timing the engine...valve-piston, I'm pretty sure the valves will be toast.

Matt Monson · Post by **Matt Monson** » Sat Apr 25, 2009 3:09 am

It's both.

log1call · Post by **log1call** » Sat Apr 25, 2009 3:50 am

They are both, they will clash valves and piston.

turboleg · Post by **turboleg** » Sat Apr 25, 2009 2:08 pm

Thanks for the info guys.

I decided to come in on Saturday and do the leak down test on the engine to see where the valves stood. Having to retime the engine, I removed the center timing cover to find the source of the amazing timing belt "jump". I have to be honest...I have never seen this before.

Bonus Picture

Regardless he needs a new pulley. I'm going to order one from subaru, retime the engine and do the leakdown to see where we stand. Any suggestions?

PhyrraM · Post by **PhyrraM** » Sat Apr 25, 2009 2:52 pm

I could be wrong, but judging by the lack of a few spots of cleanliness or unless you took it out, the is no tensioner or tensioner idler to take up the belts slack either.

mexicanzero · Post by **mexicanzero** » Sat Apr 25, 2009 3:01 pm

i've seen that happen before
i'm assuming the other idlers are the same age as the one that blew up?
personally i'd change them all just in case. cuz if one failed whats to say the others arent going to 20k down the road when you're in the middle of nowhere with no cell reception.
happened to my buddy, he wasnt happy lol
theres a good company that makes the idlers cheap on ebay. i think PCI is the brand? anyways they are good quality i have them on my car and i wouldnt put just anything on my car. you can usually find a belt the 3 idlers and the tensioner for about 150$

-Alex

turboleg · Post by **turboleg** » Sat Apr 25, 2009 5:37 pm

Thanks guys. I've located a used one down the road. I am going to put it on and make sure I have compression and a tight seal. In that case I'll buy a brand new pulley set.

Thats a pretty good price for $150. Closest I found for the whole set was around $260.

Thanks

Matt Monson · Post by **Matt Monson** » Sun Apr 26, 2009 2:23 am

Why bother to reinstall the timing belt before you do the leakdown test? Do it now before you go to all that trouble.

Post by **Legacy777** » Mon Apr 27, 2009 6:13 pm

Similar thing happened to a girl's 91 turbo here in Houston. I ended up fixing it, not really knowing the specifics. It wasn't fun.

http://main.experiencetherave.com/subar ... ddedtbelt/

turboleg · Post by **turboleg** » Mon May 11, 2009 5:11 pm

Matt Monson wrote:Why bother to reinstall the timing belt before you do the leakdown test? Do it now before you go to all that trouble.

Technically, each cyclinder being tested should be at TDC while you run the leak down. Because we have said that there can be both valve-valve and valve-piston interference its easier for me to just put the timing belt on and lock in the position of the shafts. Since it doesn't take more than 5 minutes to put the belt on, I did it anyway.

I had to wait for the leak tester to arrive (decided to buy a nice new dual gage tester, since mine has developed a nice crack in the gage face). Before it arrived I put the timing belt on, got it all ready. The owner took it upon his self to turn the engine over. It fired like it had been running all along. Now the leak testers here. I can see how much the valves are F'ed.

Thanks guys.

irelyea0014 · Post by **irelyea0014** » Wed May 13, 2009 2:58 am

same EXACT thing happened to mine, but worse conclusion..... when the belt slacked, it got jammed in the cam pulleys, and shattered them..... in turn destroying the timing covers, cam seals, and electric cooling fans too..... this is how I bought it (98 GT)..... So I got some new pulleys, new seals, and a new belt, put it back together, and it's been sweet ever since.

turboleg · Post by **turboleg** » Thu May 14, 2009 3:03 pm

I really hope you have pictures of that!!!!!

Post em if you do.

Matt Monson · Post by **Matt Monson** » Thu May 14, 2009 3:15 pm

turboleg wrote:
Matt Monson wrote:Why bother to reinstall the timing belt before you do the leakdown test? Do it now before you go to all that trouble.
Technically, each cyclinder being tested should be at TDC while you run the leak down. Because we have said that there can be both valve-valve and valve-piston interference its easier for me to just put the timing belt on and lock in the position of the shafts. Since it doesn't take more than 5 minutes to put the belt on, I did it anyway.

There are a couple of other ways to determine TDC on these engines without the timing belt on. It's your car and it's up to you, but just want that pointed out for future readers who may not want to take the same approach you chose.

irelyea0014 · Post by **irelyea0014** » Fri May 15, 2009 4:01 am

turboleg wrote:I really hope you have pictures of that!!!!!

Post em if you do.

if you were referring to me, sadly I don't.... it was major destruction. I just today scored the second cooling fan, been driving without for 6 months.

turboleg · Post by **turboleg** » Fri May 15, 2009 3:11 pm

Matt,
I might be missing something. Since there is the posibility for valve-piston contact wouldn't you want to make sure the crank and cams are turning at the same time? I suppose I could rotate the cams so that the lobes aren't maxed out (or in other words all the valves would be closed). Rotate the crank from that point to get each cylinder to TDC. But then after testing how would I realign the cams to the crank safely without risking the chance that one piston is close enough to TDC to hit a valve? If it wasn't obvious I'm a noob to the DOHC.

PhyrraM · Post by **PhyrraM** » Fri May 15, 2009 3:30 pm

edit- I misread- garbage eliminated.

Matt Monson · Post by **Matt Monson** » Fri May 15, 2009 4:44 pm

turboleg wrote:Matt,
I might be missing something. Since there is the posibility for valve-piston contact wouldn't you want to make sure the crank and cams are turning at the same time? I suppose I could rotate the cams so that the lobes aren't maxed out (or in other words all the valves would be closed). Rotate the crank from that point to get each cylinder to TDC. But then after testing how would I realign the cams to the crank safely without risking the chance that one piston is close enough to TDC to hit a valve? If it wasn't obvious I'm a noob to the DOHC.

When you remove the timing belt (assuming you do it properly and not catastrophically like on this car) two of the cams are already closed. The other two are partly open and "loaded". Often they will snap shut on their own. If they don't, you can easily "release" them. Then all valves will be closed and it will be immpossible to damage anything.

On a failure like this, pretty much 100% of the time all the cams snap to the valves closed position once the rotation stops. As long as you spin the crank to the proper location for each test and know how far to spin it for the next cylinder you'll hit TDC with ZERO further risk to any valves.

Furthermore, if you have any doubt how far to spin the crank from your initial starting point, you can stick a long screwdriver or chopstick or whatever long device you prefer through the spark plug hole of the cylinder you wish to test and actually feel when it hits TDC and starts to drop back down.

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2.5L DOHC Interference question

2.5L DOHC Interference question