CA18DE Timing Belt Issues - Need Input

[80sKid]

Hi all, this issue is driving me nuts - any ideas?

I just finished rebuilding most of my CA18DE after an overheat (head work, valves, pistons, rings, bearings, etc.) When I replaced the upper timing belt cover, it seemed to be difficult to get into position like there was something interfering inside. I thought maybe the belt needed to go back a little farther on the cam sprockets and positioned it accordingly. The cover went on a little easier but still seemed like something was not correct as I don't remember feeling any interference upon removal. I checked and rechecked for anything that may be out of place but all was correct. Tensioner was locked into position and torqued to 19ft/lbs, belt was routed right and everything moved properly when the crank was turned by wrench. Since I couldn't find anything wrong I put it all back together and tested the engine.

It ran fine at idle so I tested it around town for a few days with no issues. For the last few days I've been breaking in the engine gradually with no issues. Then I noticed that at idle I could hear a very faint, repeating noise that sounds like the timing belt contacting something inside the upper cover. It comes once about every second. I took the cover off again to inspect but couldn't find any signs of timing belt dust or other wear. So I put it back together again but the sound was still there.

Finally today I had it out on the road again and the timing belt snapped! I can't figure out what the heck is interfering in there. I even read a thread here from a couple years ago where someone was missing the guide and crank sprocket cover which led to a similar problem. I have both of these pieces and everything else which belongs where it goes so this is making me insane. What's up with the upper cover and timing belt - anybody have this problem before? I want to solve it for certain before putting the new belt in.

[D_Stirls]

did the upper timing belt cover have the locating dows still in the head, quite often these go missing which means that the upper cover is missaligned

[80sKid]

Well, that must be what happened. I didn't catch it after bolting the head back in place, but now that I look closely the dowel on the right side just under the crank position sensor is missing. It probably fell out when the head was at the machine shop. It couldn't have been off by much considering the sensor has to align with the cover and the exhaust cam spline which is pretty tight clearance as it is. I guess even that tiny amount of play caused the belt to contact the web inside the cover? It's the only thing that isn't 100% so hopefully problem solved.

On a more grave note - this is an interference engine right? The timing marks on the cam sprockets are about 90 degrees clockwise past the alignment marks on the back cover. I hope this turns out to be a lucky position and the valvetrain didn't get whacked. Guess I'll find out soon enough...

[D_Stirls]

Yes a CA is an interference engine.
Isn't the a witness mark on the inside of the cover that showed where the belt was rubbing?

[themadscientist]

I've seen at least one CA and one RB survive a belt break. It's pure luck, though.

[bentvalves]

seems you know the importance of these two dowel pins mate (dstirls). why is it the modified CAS holder you offer only utilizes one of the two pins then?

[80sKid]

Well gentlemen (and ladies), I put a new timing belt in moments ago and tried starting her up while keeping my fingers crossed. Not even a cough. Checked compression and wasn't too surprised to find 195psi in #2 and #3, but absolutely zero in #1 and #4. I can picture just what happened and I'm sure you can too. It's the stuff nightmares are made of.

So, not the end of the world but certainly a s**t load of work to do over again.

It's still hard for me to believe that the one little missing dowel could have led to the timing belt failing. Seems like the cover couldn't have been out of place by half a millimeter even without it. By the way the belt was totally thrashed, not just snapped clean. It was shredded lengthwise down the middle about 12 inches, but who knows, could have just got chewed up by the sprockets after breaking.

Ah well, if you'll excuse me I need to devote the remainder of this fine evening drinking my sorrows into sweet oblivion. Sometimes luck don't be a lady. Back to the work bench!

[D_Stirls]

seems you know the importance of these two dowel pins mate (dstirls). why is it the modified CAS holder you offer only utilizes one of the two pins then?

There's a procedure when you fit them that centres the CAS, once again there have been 50+ sold in the past 3 years and there has never been an issue.
You never found what the issue was with your engine did you?

[D_Stirls]

Where was the belt rubbing?
The CA that i fixed that didn't have any dowels in it didn't have any marks on the belt at the cover had dropped ~6-7mm in that case. The only issue that engine had was the exhaust cam CAS locator snapped.

[boost_boy]

Well gentlemen (and ladies), I put a new timing belt in moments ago and tried starting her up while keeping my fingers crossed. Not even a cough. Checked compression and wasn't too surprised to find 195psi in #2 and #3, but absolutely zero in #1 and #4. I can picture just what happened and I'm sure you can too. It's the stuff nightmares are made of.

So, not the end of the world but certainly a s**t load of work to do over again.

It's still hard for me to believe that the one little missing dowel could have led to the timing belt failing. Seems like the cover couldn't have been out of place by half a millimeter even without it. By the way the belt was totally thrashed, not just snapped clean. It was shredded lengthwise down the middle about 12 inches, but who knows, could have just got chewed up by the sprockets after breaking.

Ah well, if you'll excuse me I need to devote the remainder of this fine evening drinking my sorrows into sweet oblivion. Sometimes luck don't be a lady. Back to the work bench!

Such a wicked lesson learned. You have some bent intake valves that will need to be addressed as that's what usually gets whacked when a belt breaks. Let me pass on some advice that I have been passing on for many-a-moon, if things don't seem right, don't take your car for a test spin to see if it'll get better because it won't. Sorry dude, but even if I had to do it over again, I'd be pissed and I actually can tear-off the head in less than an hour. Take your time, ask questions and remember "IF IT DOESN'T FIT, LET IT SIT"

[80sKid]

Yep, that's good advice. It's funny - I'm usually the one telling others the same thing but got caught up in the pressure to get a vehicle back on the road for some urgent business that week. That's what happens when you rush it, though. I'm not quite as fast as you - it took me about 3 hours to pull the head (about half an hour was spent organizing my garage, so not too bad I guess). Took way too much time on just those few bots which attach the coolant pipe and crankcase vent hose bracket to the intake manifold from underneath. Tight space & pain in the a**. Otherwise it went pretty well.

I double checked for evidence of contact inside the upper cover but still couldn't find anything obvious. I think next time I'll spray the interior with some white engine enamel so if it happens again there will be a clear mark if the belt touches anything.

So here's the damage: Two slightly bent intake valves on #1 and two very slightly bent exhaust valves on #4. I could barely see anything when examining the piston tops - just faint scratches (that was a big relief). Next week it's back to the machine shop for some new valves & hopefully she's back on the road.

[D_Stirls]

have you taken the bottom cover off? there wasn't a bolt or something dropped down there was there?

[80sKid]

No bolts rattling around; that was my first thought the very first time I heard that noise. That tight space at the bottom of the crank sprocket would be the perfect place for a bolt or something small to get lodged and rip up the belt for sure. I checked the entire belt path twice when the noise persisted and couldn't find anything that looked abnormal, except of course the missing dowel after you mentioned it. I even checked the alignment of the sprockets just to make sure that their angle of rotation wasn't half a degree off or something - causing the belt to walk forward - but they were perfectly straight.

I wonder if maybe the upper cover is warped? It sits perfectly flat on a gauging table, but if the internal webs are slightly off then maybe that's the cause. The original failure was due to an overheat so it might be worth replacing the cover just in case. We'll see what happens when I get it running again. If that noise is still there I'm really going to be thinking

[bentvalves]

something else needs sorting as the dowels only align the cover to the head, worst case scenario with 1 missing dowel is usually a worn cam/cas spline. dstirls, I sorted my issues after throwing a modified timing cover in the crash can. It used only one dowel pin to center it (factory cover uses 2) and after thousands of miles, sure as s*** it walks about and wears expensive parts.

[D_Stirls]

There is no way that if it is torqued up correctly that it'll move at all. I have done 6000+km's and there has been no wear on my CAS or exhaust key way; i have even posted up pictures of both for you to look at in the past and yet you still go on about it. So for the final time THERE IS NO ISSUE WITH THE GROWLY CAS BRACKET, my brother has sold over 50 with some cars having done over 20,000kms and there has been no issues.

You made up some back yard bracket by modifying that factory cast cover and you had issues. There has never been an issue with the billet machined bracket, and in fact plenty of others have done what you did by modding the factory cover and they never has an issue either so there is something up with YOUR car as NO other car has exhibited any symptoms

[bentvalves]

easy does it mate. maybe you could just write a program so the CNC will cut a batch that utilize both dowel pins already.

[D_Stirls]

there is no need as there has been no issue with the existing design over the past 3.5 years or 50+ units.