Variations in timing belt procedure?

[sid_vicious]

Hi, I'm currently in the research phase, preparing to replace the water pump and related seals on my 97 Outback wagon. I've noticed a couple differences between my Haynes manual timing belt procedure and some links I've found to official Subaru literature.

 

The first thing I noticed is that this EndWrench procedure (http://endwrench.com/pdf/engine/FtTimingBeltReplaceF00.pdf) goes to great lengths to make sure that the camshaft sprockets are held in place with a special tool while the belt is off, because the left side cams are under tension when the timing marks are lined up. If they were left free, they would rotate and possibly cause damage because it's an interference engine. My Haynes manual did not say a word about this. What's the deal? I then found another EndWrench article that, like the Haynes manual, does not make any mention of holding the camshaft sprockets in place (http://endwrench.com/images/pdfs/TBeltEWWin05.pdf).

 

On top of all this, I did not see anything about bringing cylinder 1 to TDC in either of the EndWrench articles. This is one of the very first steps of the Haynes procedure.

 

Just when I thought I was ready to tear into it......can anyone help me out?

 

Andrew

[joelk]

Hi, I'm currently in the research phase, preparing to replace the water pump and related seals on my 97 Outback wagon. I've noticed a couple differences between my Haynes manual timing belt procedure and some links I've found to official Subaru literature.

 

The first thing I noticed is that this EndWrench procedure (http://endwrench.com/pdf/engine/FtTimingBeltReplaceF00.pdf) goes to great lengths to make sure that the camshaft sprockets are held in place with a special tool while the belt is off, because the left side cams are under tension when the timing marks are lined up. If they were left free, they would rotate and possibly cause damage because it's an interference engine. My Haynes manual did not say a word about this. What's the deal? I then found another EndWrench article that, like the Haynes manual, does not make any mention of holding the camshaft sprockets in place (http://endwrench.com/images/pdfs/TBeltEWWin05.pdf).

 

On top of all this, I did not see anything about bringing cylinder 1 to TDC in either of the EndWrench articles. This is one of the very first steps of the Haynes procedure.

 

Just when I thought I was ready to tear into it......can anyone help me out?

 

Andrew

 

I didn't have any trouble with the driver side cam turning on it's own with the belt off. Be careful when you are putting the belt back on and trying to get everything lined up, it won't take too much of a nudge to send it over the lobe. I just used a breaker bar and socket on the cam gear bolt, the weight of the breaker bar and a little caution was enough to keep it from turning.

 

Joel

[Storydude1]

Even if it does move, and a valve contacts a piston there will be no damage.

 

It's the 400Feet per second hammer blow that does in Interference engines.

 

When the motor is not spinning, the piston cannot come up and smack an extended valve. I would not try to turn it over past the stuck valve to re-align, but if it contacts it during the change, it's no big deal.

[later, Peter]

I think it was a Haynes book I was using while taking the head off of a 1972 Datsun (yeah, prior to Nissan) PU truck... I seem to remember that one step was left out... the step about blocking the timing chain tensioner... it became a MUCH bigger project after that.

 

Later,

Peter

[sid_vicious]

OK, thanks for the peace of mind. I knew the timing belt change procedure was a precise and delicate one, but I was pretty surprised by the language used in the first EndWrench article about how the camshaft sprockets must not be allowed to move at all.

 

Thanks again,

Andrew

 

 

Even if it does move, and a valve contacts a piston there will be no damage.

 

It's the 400Feet per second hammer blow that does in Interference engines.

 

When the motor is not spinning, the piston cannot come up and smack an extended valve. I would not try to turn it over past the stuck valve to re-align, but if it contacts it during the change, it's no big deal.

[idosubaru]

i just did this - not a bad job at all. the crank pulley was annoying (very hard to slide off)....but that's not necessary unless you want to do the oil pump seals which is a good idea. and the cam bolts are a serious PITA. i used strap wrenches and they did no good, just slipped and slipped. i will order the special tool now to loosen the cam bolts.

[joelk]

i just did this - not a bad job at all. the crank pulley was annoying (very hard to slide off)....but that's not necessary unless you want to do the oil pump seals which is a good idea. and the cam bolts are a serious PITA. i used strap wrenches and they did no good, just slipped and slipped. i will order the special tool now to loosen the cam bolts.

 

I had to take the driver's side cam gear off. I just broke the bolt loose when the old timing belt was still on and torqued it after I put the new belt on. I was holding on the crank pulley with my homemade tool. It went ok with that, didn't seem to put too much stress on anything. Although, having the right tool is certainly the better way to go.

 

I think you could also make a nice custom strap wrench using an old timing belt, that should hold a lot stronger than a smooth strap wrench.

 

Otherwise, yeah, doing the timing belt is not that bad. I think the only thing I found on the second car I did it was that putting the oil pump back on while the water pump was still off was a bit easier, a little more room to work.