Timing Chain Problem.

[Les Henson]

Hope someone on here can help me please.

I just bought a 2000 model 1-litre Yaris, which was cheap - due to timing chain rattle. Engine ran fine at higher revs, but was erratic at idle and very difficult to start from cold.

Decided to replace the timing chain kit today and discovered that the exhaust cam was 1 tooth out anti-clockwise, so it had jumped (backwards) a tooth. Does anyone know if the engine can tolerate the chain being 1 tooth out without valve/piston contact. I could put it all back together and turn the key, but the amount of work involved in taking it all apart again and then removing the head as well seems too much to have to do.

Thanks for any help.

Les.

[Geoff Peace]

Hope someone on here can help me please.

I just bought a 2000 model 1-litre Yaris, which was cheap - due to timing chain rattle. Engine ran fine at higher revs, but was erratic at idle and very difficult to start from cold.

Decided to replace the timing chain kit today and discovered that the exhaust cam was 1 tooth out anti-clockwise, so it had jumped (backwards) a tooth. Does anyone know if the engine can tolerate the chain being 1 tooth out without valve/piston contact. I could put it all back together and turn the key, but the amount of work involved in taking it all apart again and then removing the head as well seems too much to have to do.

Thanks for any help.

Les.

What was the engine performance like when it was running one tooth out? A compression test and cylinder leakdown test will tell if there is any damage to the valves/pistons.

Regards Geoff Peace.

[Les Henson]

Performance was ok if the revs were above 2000 or so. Very difficult to start when cold and it would start on what seemed like 2 or 3 cylinders and the other/s would then come in. Once warm it would start ok, but was lumpy at tickover and the chain rattle is very loud. Apart from the exhaust cam being one tooth retarted, the chain is very slack and the tensioner is so far out that it's at a slight angle, so may come out completely. I could reset the the timing, but the excessive amount of slack in the chain may cause it to jump more than just the one tooth, which may then cause valve/piston contact (if that hasn't happened already), Last MOT the previous owner was told that the chain was rattly, but now it's above the engine noise, so quite bad. My gut feeling is that the engine is still ok, and I'm sorely tempted to reset the timing, fit the new kit, and the job will be ok. Just wondered if anyone might know the definitive answer. Some interference engines are ok with one tooth advanced or retarded, and the damage point is 2 or more.

Les.

[Madasafish]

You should be OK with one tooth out. The valve movement from TDC will be minimal.. and is unlikely to encroach much on the valve /piston clearances . You would find clearance will be built in for heat expansion so one tooth out should be fine... I have changed the chain on a 1.0 (2001) and got the timing out 1 tooth - but realised that after test rotation - with no damage.

[Les Henson]

Thanks Geoff and Madasfish :)

I'll be putting it back together tomorrow, so will post the results :)

Les.

[Geoff Peace]

You should be OK with one tooth out. The valve movement from TDC will be minimal.. and is unlikely to encroach much on the valve /piston clearances . You would find clearance will be built in for heat expansion so one tooth out should be fine... I have changed the chain on a 1.0 (2001) and got the timing out 1 tooth - but realised that after test rotation - with no damage.

I would agree with the above. I would go for it with the new parts etc. Please post your results, I for one would be interested.

Regards Geoff Peace.

[Les Henson]

Just finished and the jobs a good-un :)

Started 1st time on the key and runs perfectly.

Setting the timing was easy - due to the bright links on the chain, so the hardest part was removing the old sealant from the chain case/engine, which is murder - especially where it curves round the water pump.

The kit I bought was Blue Print, and contained the following - Exhaust cam sprocket, crank sprocket, Crank oil seal, both chain guides, chain tensioner, and chain. A bit expesive at £230 inc VAT, but the car is worth it.

Only 80k miles on the clock, so previous owners didn't service it I think.

Thanks for your help, guys - it saved me having to take the head off.

Les.

[Geoff Peace]

Just finished and the jobs a good-un :)

Started 1st time on the key and runs perfectly.

Setting the timing was easy - due to the bright links on the chain, so the hardest part was removing the old sealant from the chain case/engine, which is murder - especially where it curves round the water pump.

The kit I bought was Blue Print, and contained the following - Exhaust cam sprocket, crank sprocket, Crank oil seal, both chain guides, chain tensioner, and chain. A bit expesive at £230 inc VAT, but the car is worth it.

Only 80k miles on the clock, so previous owners didn't service it I think.

Thanks for your help, guys - it saved me having to take the head off.

Les.

Excellent result! It would seem the prevous owner neglected oil changes and may have used poor quality oil. Timing chains and tensioners last a long time anything up to 200k miles, but they must have good quality oil and changed regularly, otherwise the tensioner gives up, and you know the rest of the story.

Regards Geoff Peace.