Engine cranked in reverse during TB job — is there damage?

[crisp006]

Hi guys,

so I did my timing belt with my dad not long ago, and I didn’t think of it at the time as I (and it would now appear evident him too) lack much automotive knowledge, but now I’m wondering whether what we did whilst working on the timing belt could’ve damaged the internals of the engine.

When trying to line up the flywheel at TDC we found ourselves overshooting the mark (just a little) and then cranking the engine in reverse to get it to line up. I’d be eyeballing the flywheel TDC mark while he’d rotate the engine at the crank bolt with a breaker bar.

we had to do this a few times to get it to line up the first time we did it, but then did it a few times again when the flywheel mark would be off TDC after tightening the crank lock. And a few more times when the flywheel was off after tightening everything up.

overall I’d say we rotated it in reverse 20-25 times. However, the vast majority of that is accounted for by tiny adjustments (less than 5 degrees I’d say) after doing the initial larger adjustment in reverse because of overshooting the TDC mark (in which case we’d crank the engine in reverse by 10-15 degrees at most).

I know this probably sounds dumb (though I’m willing to bet I’m not the only one whose done this and that it’s much more common than one would think). Though I’ll say that I didn’t see any mention of this in the TB guides (though maybe it was thought it’s a given that one should not rotate an engine in reverse).

can anyone who is knowledgeable about these engines chime in? Am I overthinking this or is it likely serious (or minor) damage was caused? I read online elsewhere from a few sources that in general, one would have to crank an engine more than 3-4 revolutions in reverse to cause any problems. I assume that would be total, uninterrupted revolutions, not degrees of rotation in aggregate. Correct me if I’m wrong.

please feel to free to chime in guys.
Thanks.

the car is a 2000 Jetta TDI. ALH engine.

 

[Tdijarhead]

We’ve all done that, you’re fine. Did you turn the engine over by hand 3-4 times after the timing belt job was completed and were you able to reinsert all the indexing tools? Is the tensioner tab still in the slot?

 

[JB05]

I had to do this also. I turned back a quarter turn and then clockwise very slowly. No harm done.

 

[jmodge]

For this reason I made a crank lock out of a small piece of flywheel ring gear. It fits in the inspection hole and engages the flywheel teeth, no movement

 

[KLXD]

The only issue with rotating it in reverse at the crank is you would be loading the tensioner backwards and putting some slack on the tension side of the belt. Not a problem before replacing the belt but I wouldn't expect everything to line up perfectly for the final check if you do it. Prolly wouldn't be off by much since the cam is sorta sitting at dwell points and the pump doesn't load it a huge amount either but it's best to do it correctly.

I note that you're rotating by the crank bolt which is correct in spite of what various instructions say. Rotating using the pump or cam in the normal direction puts a big load on the belt and pulls slack out of the tensioner.

 

[tgray]

The TDI's can deal with reverse rotation but don't ever do this to the 1.8 gas turbo. I tried this once and bent a few valves as it jumps the timing belt and didn't realize it until I find no compression.

 

[crisp006]

We’ve all done that, you’re fine. Did you turn the engine over by hand 3-4 times after the timing belt job was completed and were you able to reinsert all the indexing tools? Is the tensioner tab still in the slot?

Yes, turned it over by hand 3-4 times. Tensioner tab is still in the slot. Didn’t reinsert all the indexing tools but checked the injection pump, #1 lobe position, vacuum pump side, and flywheel TDC and all was lined up.

 

[crisp006]

Thanks guys. Now I’ve just found out from my dad that he actually rotated it in reverse even more than I initially thought. To get the crank centred for the crank lock he also rotated it in reverse (by his estimation) up to a half or full turn a few times...

Now I’m more worried... obviously.

Do any of you know if more extended reverse rotation like described can cause damage to the engine? *to the oil pump or water pump, for example?*

If anyone else has any ideas feel free to chime in.

much appreciated.

 

[KLXD]

Pumps will be fine. The tensioner would get more load than usual as I splained but I don't see it getting hurt.

The IP rotating backwards would push the cage with the rollers to the full advanced position but I don't see that causing any problems. It gets moved to that position while it's running.

 

[crisp006]

Pumps will be fine. The tensioner would get more load than usual as I splained but I don't see it getting hurt.

The IP rotating backwards would push the cage with the rollers to the full advanced position but I don't see that causing any problems. It gets moved to that position while it's running.

Thanks! That’s good to know.

Im breathing a sigh of relief.

 

[Franko6]

I'm guessing me chiming in on an earlier request is really not necessary, but to fill out this picture...

1. We NEVER use a crank lock and 2. We INTENTIONALLY reverse rotation about 10-15 degrees when installing the timing belt.

The reason for the reversal: After pinning the injection pump and tightening one bolt, centering the pump sprocket in its adjustment slot, we use a 19mm 12 pt socket on 2 foot long extensions with a breaker bar to turn the crankshaft sprocket from the 15 degree BTDC position and turning the sprocket clockwise, pull all of the slack out of the belt between the injection pump and the crank sprocket. The objective is to have the belt become tight as the flywheel hits TDC. Also, for those not aware, there is a matching mark on the lower timing belt cover and a milled spot on the harmonic balancer which is the 'one man' way to find TDC very easily. The last piece installed for the TB is the cam sprocket. Hold the cam sprocket inside the belt and make sure the belt is between the shoulders of the TB tensioner. Then pull the crank to TDC position. Once the slack has been removed between the crank and inj pump, the cam sprocket will slip easily over the nose of the camshaft. If you check the timing mark on the harmonic balancer, and the mark came up short to the lower TB cover, skip a tooth CLOCKWISE on the injection pump sprocket and retighten. If it's past the mark, skip back.

If you set a timing belt without doing the mandatory 2 crankshaft rotations and attempt to start the engine, you are begging for trouble. The 1.8 engine is no different than the TDI so far as assuring correct position of the cam to the crank. If the engine rotates through two rotations of the crank without contact, then you have proven it is in 1 of 2 positions: in time or 180 degrees out of sync.

 

[crisp006]

I'm guessing me chiming in on an earlier request is really not necessary, but to fill out this picture...

1. We NEVER use a crank lock and 2. We INTENTIONALLY reverse rotation about 10-15 degrees when installing the timing belt.

The reason for the reversal: After pinning the injection pump and tightening one bolt, centering the pump sprocket in its adjustment slot, we use a 19mm 12 pt socket on 2 foot long extensions with a breaker bar to turn the crankshaft sprocket from the 15 degree BTDC position and turning the sprocket clockwise, pull all of the slack out of the belt between the injection pump and the crank sprocket. The objective is to have the belt become tight as the flywheel hits TDC. Also, for those not aware, there is a matching mark on the lower timing belt cover and a milled spot on the harmonic balancer which is the 'one man' way to find TDC very easily. The last piece installed for the TB is the cam sprocket. Hold the cam sprocket inside the belt and make sure the belt is between the shoulders of the TB tensioner. Then pull the crank to TDC position. Once the slack has been removed between the crank and inj pump, the cam sprocket will slip easily over the nose of the camshaft. If you check the timing mark on the harmonic balancer, and the mark came up short to the lower TB cover, skip a tooth CLOCKWISE on the injection pump sprocket and retighten. If it's past the mark, skip back.

If you set a timing belt without doing the mandatory 2 crankshaft rotations and attempt to start the engine, you are begging for trouble. The 1.8 engine is no different than the TDI so far as assuring correct position of the cam to the crank. If the engine rotates through two rotations of the crank without contact, then you have proven it is in 1 of 2 positions: in time or 180 degrees out of sync.

Timing was done properly. No issue there.

It sounds like I’m fine. Thanks for chiming in.