Welcome to BamfordRose and another question of the week. This week it’s a follow-up series to the DB9 Engine Tick and this week we can show the engine strip down and identify the problem.
So, if you’ve not seen it, please check out the previous videos on the DB9 Engine Tick which we link in the bio. It might be worthwhile seeing those videos and then coming back to this one.
Now you can see the engine laid out on the bench and here we’ve got pistons, con rods out and a couple of pictures of the block. You can see some of the liners. And actually, this engine cylinder liners all look really good. There’s still honing marks on the liners and it doesn’t look too bad at all.
As you can see here, we’ve got the borescope measuring the liner. We’re measuring its maximum size to check it’s within tolerance and we’re measuring to see if it’s perfectly round and it hasn’t worn oval. On this particular block, it’s all good, everything is fine. We’ve got none of the piston slap issue causing the tick.
If we just remind ourselves of the particular tick that this engine had, we’ll play it now. This sound as we can measure now is all to do with the small M bush, which is good news for this repair because it’s going to be the most minor of repairs needed.
Now we can see the piston pin in the small M bush in the con rod and look how we just put the piston pin into the small end and it just drops out onto the table straight away. At room temperature, this should be sort of an interference fit where it’s pretty difficult to get the pin into the bush to start with and gravity won’t allow the pin to fall out on the table, so immediately you can see that this is out of tolerance before taking any measurements.
The next thing we do is we’ve got the pin in the piston, so we can feel it is difficult… You’re not going to see this, appreciate this on the video. But we can feel either side of our fingers rocking the pin in the piston that there is some movement here. And again, you shouldn’t really be able to put the pin into the piston like we have done at room temperature, but it should be more of an interference fit. Separate from the borescope showing to us that the liner has not worn over creating piston slap.
More for your visual appreciation, we’ve put the piston inverted on the end of a connecting rod into the liner and now we can move it around the clock face and left and right, up and down. And if the liner had worn over, in the worst cases what happens is you physically can’t move the piston around in the liner. So, this is showing that it’s all to do with the small M bush ware.
The fix for this particular engine is to update with the small M bush that’s got the oil channel in, rebuild the engine, put it back together and everything is going to be good. So, for this particular DB9, it wasn’t a catastrophic rebuild necessary.
Next update will be the engine running in the car. Obviously, we’ll show the rebuild process. So, stay tuned to this series. Hope you like what you see. As always, please comment. It really helps us if you could subscribe and click the bell for notifications.